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 f<sub>k</sub> nonnegative integers less than b (the significand digits)</pre>
1575 A floating-point number (x) is defined by the following model:
1578 x = s b<sup>e</sup> (Sum) f<sub>k</sub> b<sup>-k</sup> , emin <= e <= emax
1582 In addition to normalized floating-point numbers ( f<sub>1</sub> > 0 if x != 0), floating types may be
1583 able to contain other kinds of floating-point numbers, such as subnormal floating-point
1584 numbers (x != 0, e = emin , f<sub>1</sub> = 0) and unnormalized floating-point numbers (x != 0,
1585 e > emin , f<sub>1</sub> = 0), and values that are not floating-point numbers, such as infinities and
1586 NaNs. A NaN is an encoding signifying Not-a-Number. A quiet NaN propagates
1587 through almost every arithmetic operation without raising a floating-point exception; a
1588 signaling NaN generally raises a floating-point exception when occurring as an
1592 arithmetic operand.<sup><a href="#note17"><b>17)</b></a></sup>
1594 An implementation may give zero and non-numeric values (such as infinities and NaNs) a
1595 sign or may leave them unsigned. Wherever such values are unsigned, any requirement
1596 in this International Standard to retrieve the sign shall produce an unspecified sign, and
1597 any requirement to set the sign shall be ignored.
1599 The accuracy of the floating-point operations (+, -, *, /) and of the library functions in
1600 <a href="#7.12"><math.h></a> and <a href="#7.3"><complex.h></a> that return floating-point results is implementation-
1601 defined, as is the accuracy of the conversion between floating-point internal
1602 representations and string representations performed by the library functions in
1603 <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
1604 accuracy is unknown.
1606 All integer values in the <a href="#7.7"><float.h></a> header, except FLT_ROUNDS, shall be constant
1607 expressions suitable for use in #if preprocessing directives; all floating values shall be
1608 constant expressions. All except DECIMAL_DIG, FLT_EVAL_METHOD, FLT_RADIX,
1609 and FLT_ROUNDS have separate names for all three floating-point types. The floating-point
1610 model representation is provided for all values except FLT_EVAL_METHOD and
1613 The rounding mode for floating-point addition is characterized by the implementation-
1614 defined value of FLT_ROUNDS:<sup><a href="#note18"><b>18)</b></a></sup>
1619 2 toward positive infinity
1620 3 toward negative infinity</pre>
1621 All other values for FLT_ROUNDS characterize implementation-defined rounding
1624 Except for assignment and cast (which remove all extra range and precision), the values
1625 of operations with floating operands and values subject to the usual arithmetic
1626 conversions and of floating constants are evaluated to a format whose range and precision
1627 may be greater than required by the type. The use of evaluation formats is characterized
1628 by the implementation-defined value of FLT_EVAL_METHOD:<sup><a href="#note19"><b>19)</b></a></sup>
1635 0 evaluate all operations and constants just to the range and precision of the
1637 1 evaluate operations and constants of type float and double to the
1638 range and precision of the double type, evaluate long double
1639 operations and constants to the range and precision of the long double
1641 2 evaluate all operations and constants to the range and precision of the
1642 long double type.</pre>
1643 All other negative values for FLT_EVAL_METHOD characterize implementation-defined
1646 The values given in the following list shall be replaced by constant expressions with
1647 implementation-defined values that are greater or equal in magnitude (absolute value) to
1648 those shown, with the same sign:
1650 <li> radix of exponent representation, b
1651 <pre> FLT_RADIX 2</pre>
1652 <li> number of base-FLT_RADIX digits in the floating-point significand, p
1656 <li> number of decimal digits, n, such that any floating-point number in the widest
1657 supported floating type with pmax radix b digits can be rounded to a floating-point
1658 number with n decimal digits and back again without change to the value,
1660 { pmax log10 b if b is a power of 10
1662 { [^1 + pmax log10 b^] otherwise</pre>
1663 <pre> DECIMAL_DIG 10</pre>
1664 <li> number of decimal digits, q, such that any floating-point number with q decimal digits
1665 can be rounded into a floating-point number with p radix b digits and back again
1666 without change to the q decimal digits,
1673 { p log10 b if b is a power of 10
1675 { [_( p - 1) log10 b_] otherwise</pre>
1679 <li> minimum negative integer such that FLT_RADIX raised to one less than that power is
1680 a normalized floating-point number, emin
1684 <li> minimum negative integer such that 10 raised to that power is in the range of
1685 normalized floating-point numbers, [^log10 b<sup>emin -1</sup>^]
1686 <pre> FLT_MIN_10_EXP -37
1688 LDBL_MIN_10_EXP -37</pre>
1689 <li> maximum integer such that FLT_RADIX raised to one less than that power is a
1690 representable finite floating-point number, emax
1694 <li> maximum integer such that 10 raised to that power is in the range of representable
1695 finite floating-point numbers, [_log10 ((1 - b<sup>-p</sup>)b<sup>emax</sup>)_]
1696 <pre> FLT_MAX_10_EXP +37
1698 LDBL_MAX_10_EXP +37</pre>
1701 The values given in the following list shall be replaced by constant expressions with
1702 implementation-defined values that are greater than or equal to those shown:
1704 <li> maximum representable finite floating-point number, (1 - b<sup>-p</sup>)b<sup>emax</sup>
1707 LDBL_MAX 1E+37</pre>
1710 The values given in the following list shall be replaced by constant expressions with
1711 implementation-defined (positive) values that are less than or equal to those shown:
1713 <li> the difference between 1 and the least value greater than 1 that is representable in the
1714 given floating point type, b<sup>1-p</sup>
1716 <pre> FLT_EPSILON 1E-5
1718 LDBL_EPSILON 1E-9</pre>
1719 <li> minimum normalized positive floating-point number, b<sup>emin -1</sup>
1722 LDBL_MIN 1E-37</pre>
1724 Recommended practice
1726 Conversion from (at least) double to decimal with DECIMAL_DIG digits and back
1727 should be the identity function.
1729 EXAMPLE 1 The following describes an artificial floating-point representation that meets the minimum
1730 requirements of this International Standard, and the appropriate values in a <a href="#7.7"><float.h></a> header for type
1734 x = s 16<sup>e</sup> (Sum) f<sub>k</sub> 16<sup>-k</sup> , -31 <= e <= +32
1740 FLT_EPSILON 9.53674316E-07F
1743 FLT_MIN 2.93873588E-39F
1746 FLT_MAX 3.40282347E+38F
1747 FLT_MAX_10_EXP +38</pre>
1750 EXAMPLE 2 The following describes floating-point representations that also meet the requirements for
1751 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
1752 <a href="#7.7"><float.h></a> header for types float and double:
1755 xf = s 2<sup>e</sup> (Sum) f<sub>k</sub> 2<sup>-k</sup> , -125 <= e <= +128
1760 xd = s 2<sup>e</sup> (Sum) f<sub>k</sub> 2<sup>-k</sup> , -1021 <= e <= +1024
1768 FLT_EPSILON 1.19209290E-07F // decimal constant
1769 FLT_EPSILON 0X1P-23F // hex constant</pre>
1776 FLT_MIN 1.17549435E-38F // decimal constant
1777 FLT_MIN 0X1P-126F // hex constant
1780 FLT_MAX 3.40282347E+38F // decimal constant
1781 FLT_MAX 0X1.fffffeP127F // hex constant
1784 DBL_EPSILON 2.2204460492503131E-16 // decimal constant
1785 DBL_EPSILON 0X1P-52 // hex constant
1788 DBL_MIN 2.2250738585072014E-308 // decimal constant
1789 DBL_MIN 0X1P-1022 // hex constant
1792 DBL_MAX 1.7976931348623157E+308 // decimal constant
1793 DBL_MAX 0X1.fffffffffffffP1023 // hex constant
1794 DBL_MAX_10_EXP +308</pre>
1795 If a type wider than double were supported, then DECIMAL_DIG would be greater than 17. For
1796 example, if the widest type were to use the minimal-width IEC 60559 double-extended format (64 bits of
1797 precision), then DECIMAL_DIG would be 21.
1799 <p><b> Forward references</b>: conditional inclusion (<a href="#6.10.1">6.10.1</a>), complex arithmetic
1800 <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>
1801 (<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>
1802 (<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>).
1806 <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
1807 does not require the floating-point arithmetic of the implementation to be identical.
1809 <p><small><a name="note17" href="#note17">17)</a> IEC 60559:1989 specifies quiet and signaling NaNs. For implementations that do not support
1810 IEC 60559:1989, the terms quiet NaN and signaling NaN are intended to apply to encodings with
1813 <p><small><a name="note18" href="#note18">18)</a> Evaluation of FLT_ROUNDS correctly reflects any execution-time change of rounding mode through
1814 the function fesetround in <a href="#7.6"><fenv.h></a>.
1816 <p><small><a name="note19" href="#note19">19)</a> The evaluation method determines evaluation formats of expressions involving all floating types, not
1817 just real types. For example, if FLT_EVAL_METHOD is 1, then the product of two float
1818 _Complex operands is represented in the double _Complex format, and its parts are evaluated to
1821 <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
1822 limits are one less than shown here.
1825 <h2><a name="6" href="#6">6. Language</a></h2>
1827 <h3><a name="6.1" href="#6.1">6.1 Notation</a></h3>
1829 In the syntax notation used in this clause, syntactic categories (nonterminals) are
1830 indicated by italic type, and literal words and character set members (terminals) by bold
1831 type. A colon (:) following a nonterminal introduces its definition. Alternative
1832 definitions are listed on separate lines, except when prefaced by the words ''one of''. An
1833 optional symbol is indicated by the subscript ''opt'', so that
1835 { expressionopt }</pre>
1836 indicates an optional expression enclosed in braces.
1838 When syntactic categories are referred to in the main text, they are not italicized and
1839 words are separated by spaces instead of hyphens.
1841 A summary of the language syntax is given in <a href="#A">annex A</a>.
1843 <h3><a name="6.2" href="#6.2">6.2 Concepts</a></h3>
1845 <h4><a name="6.2.1" href="#6.2.1">6.2.1 Scopes of identifiers</a></h4>
1847 An identifier can denote an object; a function; a tag or a member of a structure, union, or
1848 enumeration; a typedef name; a label name; a macro name; or a macro parameter. The
1849 same identifier can denote different entities at different points in the program. A member
1850 of an enumeration is called an enumeration constant. Macro names and macro
1851 parameters are not considered further here, because prior to the semantic phase of
1852 program translation any occurrences of macro names in the source file are replaced by the
1853 preprocessing token sequences that constitute their macro definitions.
1855 For each different entity that an identifier designates, the identifier is visible (i.e., can be
1856 used) only within a region of program text called its scope. Different entities designated
1857 by the same identifier either have different scopes, or are in different name spaces. There
1858 are four kinds of scopes: function, file, block, and function prototype. (A function
1859 prototype is a declaration of a function that declares the types of its parameters.)
1861 A label name is the only kind of identifier that has function scope. It can be used (in a
1862 goto statement) anywhere in the function in which it appears, and is declared implicitly
1863 by its syntactic appearance (followed by a : and a statement).
1865 Every other identifier has scope determined by the placement of its declaration (in a
1866 declarator or type specifier). If the declarator or type specifier that declares the identifier
1867 appears outside of any block or list of parameters, the identifier has file scope, which
1868 terminates at the end of the translation unit. If the declarator or type specifier that
1869 declares the identifier appears inside a block or within the list of parameter declarations in
1870 a function definition, the identifier has block scope, which terminates at the end of the
1871 associated block. If the declarator or type specifier that declares the identifier appears
1873 within the list of parameter declarations in a function prototype (not part of a function
1874 definition), the identifier has function prototype scope, which terminates at the end of the
1875 function declarator. If an identifier designates two different entities in the same name
1876 space, the scopes might overlap. If so, the scope of one entity (the inner scope) will be a
1877 strict subset of the scope of the other entity (the outer scope). Within the inner scope, the
1878 identifier designates the entity declared in the inner scope; the entity declared in the outer
1879 scope is hidden (and not visible) within the inner scope.
1881 Unless explicitly stated otherwise, where this International Standard uses the term
1882 ''identifier'' to refer to some entity (as opposed to the syntactic construct), it refers to the
1883 entity in the relevant name space whose declaration is visible at the point the identifier
1886 Two identifiers have the same scope if and only if their scopes terminate at the same
1889 Structure, union, and enumeration tags have scope that begins just after the appearance of
1890 the tag in a type specifier that declares the tag. Each enumeration constant has scope that
1891 begins just after the appearance of its defining enumerator in an enumerator list. Any
1892 other identifier has scope that begins just after the completion of its declarator.
1893 <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
1894 (<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>),
1895 source file inclusion (<a href="#6.10.2">6.10.2</a>), statements (<a href="#6.8">6.8</a>).
1897 <h4><a name="6.2.2" href="#6.2.2">6.2.2 Linkages of identifiers</a></h4>
1899 An identifier declared in different scopes or in the same scope more than once can be
1900 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
1901 three kinds of linkage: external, internal, and none.
1903 In the set of translation units and libraries that constitutes an entire program, each
1904 declaration of a particular identifier with external linkage denotes the same object or
1905 function. Within one translation unit, each declaration of an identifier with internal
1906 linkage denotes the same object or function. Each declaration of an identifier with no
1907 linkage denotes a unique entity.
1909 If the declaration of a file scope identifier for an object or a function contains the storage-
1910 class specifier static, the identifier has internal linkage.<sup><a href="#note22"><b>22)</b></a></sup>
1912 For an identifier declared with the storage-class specifier extern in a scope in which a
1917 prior declaration of that identifier is visible,<sup><a href="#note23"><b>23)</b></a></sup> if the prior declaration specifies internal or
1918 external linkage, the linkage of the identifier at the later declaration is the same as the
1919 linkage specified at the prior declaration. If no prior declaration is visible, or if the prior
1920 declaration specifies no linkage, then the identifier has external linkage.
1922 If the declaration of an identifier for a function has no storage-class specifier, its linkage
1923 is determined exactly as if it were declared with the storage-class specifier extern. If
1924 the declaration of an identifier for an object has file scope and no storage-class specifier,
1925 its linkage is external.
1927 The following identifiers have no linkage: an identifier declared to be anything other than
1928 an object or a function; an identifier declared to be a function parameter; a block scope
1929 identifier for an object declared without the storage-class specifier extern.
1931 If, within a translation unit, the same identifier appears with both internal and external
1932 linkage, the behavior is undefined.
1933 <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>),
1934 statements (<a href="#6.8">6.8</a>).
1937 <p><small><a name="note21" href="#note21">21)</a> There is no linkage between different identifiers.
1939 <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
1940 <a href="#6.7.1">6.7.1</a>.
1942 <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.
1945 <h4><a name="6.2.3" href="#6.2.3">6.2.3 Name spaces of identifiers</a></h4>
1947 If more than one declaration of a particular identifier is visible at any point in a
1948 translation unit, the syntactic context disambiguates uses that refer to different entities.
1949 Thus, there are separate name spaces for various categories of identifiers, as follows:
1951 <li> label names (disambiguated by the syntax of the label declaration and use);
1952 <li> the tags of structures, unions, and enumerations (disambiguated by following any<sup><a href="#note24"><b>24)</b></a></sup>
1953 of the keywords struct, union, or enum);
1954 <li> the members of structures or unions; each structure or union has a separate name
1955 space for its members (disambiguated by the type of the expression used to access the
1956 member via the . or -> operator);
1957 <li> all other identifiers, called ordinary identifiers (declared in ordinary declarators or as
1958 enumeration constants).
1960 <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>),
1961 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
1962 (<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>).
1970 <p><small><a name="note24" href="#note24">24)</a> There is only one name space for tags even though three are possible.
1973 <h4><a name="6.2.4" href="#6.2.4">6.2.4 Storage durations of objects</a></h4>
1975 An object has a storage duration that determines its lifetime. There are three storage
1976 durations: static, automatic, and allocated. Allocated storage is described in <a href="#7.20.3">7.20.3</a>.
1978 The lifetime of an object is the portion of program execution during which storage is
1979 guaranteed to be reserved for it. An object exists, has a constant address,<sup><a href="#note25"><b>25)</b></a></sup> and retains
1980 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
1981 lifetime, the behavior is undefined. The value of a pointer becomes indeterminate when
1982 the object it points to reaches the end of its lifetime.
1984 An object whose identifier is declared with external or internal linkage, or with the
1985 storage-class specifier static has static storage duration. Its lifetime is the entire
1986 execution of the program and its stored value is initialized only once, prior to program
1989 An object whose identifier is declared with no linkage and without the storage-class
1990 specifier static has automatic storage duration.
1992 For such an object that does not have a variable length array type, its lifetime extends
1993 from entry into the block with which it is associated until execution of that block ends in
1994 any way. (Entering an enclosed block or calling a function suspends, but does not end,
1995 execution of the current block.) If the block is entered recursively, a new instance of the
1996 object is created each time. The initial value of the object is indeterminate. If an
1997 initialization is specified for the object, it is performed each time the declaration is
1998 reached in the execution of the block; otherwise, the value becomes indeterminate each
1999 time the declaration is reached.
2001 For such an object that does have a variable length array type, its lifetime extends from
2002 the declaration of the object until execution of the program leaves the scope of the
2003 declaration.<sup><a href="#note27"><b>27)</b></a></sup> If the scope is entered recursively, a new instance of the object is created
2004 each time. The initial value of the object is indeterminate.
2005 <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
2006 declarators (<a href="#6.7.5.2">6.7.5.2</a>), initialization (<a href="#6.7.8">6.7.8</a>).
2014 <p><small><a name="note25" href="#note25">25)</a> The term ''constant address'' means that two pointers to the object constructed at possibly different
2015 times will compare equal. The address may be different during two different executions of the same
2018 <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.
2020 <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
2021 embedded block prior to the declaration, leaves the scope of the declaration.
2024 <h4><a name="6.2.5" href="#6.2.5">6.2.5 Types</a></h4>
2026 The meaning of a value stored in an object or returned by a function is determined by the
2027 type of the expression used to access it. (An identifier declared to be an object is the
2028 simplest such expression; the type is specified in the declaration of the identifier.) Types
2029 are partitioned into object types (types that fully describe objects), function types (types
2030 that describe functions), and incomplete types (types that describe objects but lack
2031 information needed to determine their sizes).
2033 An object declared as type _Bool is large enough to store the values 0 and 1.
2035 An object declared as type char is large enough to store any member of the basic
2036 execution character set. If a member of the basic execution character set is stored in a
2037 char object, its value is guaranteed to be nonnegative. If any other character is stored in
2038 a char object, the resulting value is implementation-defined but shall be within the range
2039 of values that can be represented in that type.
2041 There are five standard signed integer types, designated as signed char, short
2042 int, int, long int, and long long int. (These and other types may be
2043 designated in several additional ways, as described in <a href="#6.7.2">6.7.2</a>.) There may also be
2044 implementation-defined extended signed integer types.<sup><a href="#note28"><b>28)</b></a></sup> The standard and extended
2045 signed integer types are collectively called signed integer types.<sup><a href="#note29"><b>29)</b></a></sup>
2047 An object declared as type signed char occupies the same amount of storage as a
2048 ''plain'' char object. A ''plain'' int object has the natural size suggested by the
2049 architecture of the execution environment (large enough to contain any value in the range
2050 INT_MIN to INT_MAX as defined in the header <a href="#7.10"><limits.h></a>).
2052 For each of the signed integer types, there is a corresponding (but different) unsigned
2053 integer type (designated with the keyword unsigned) that uses the same amount of
2054 storage (including sign information) and has the same alignment requirements. The type
2055 _Bool and the unsigned integer types that correspond to the standard signed integer
2056 types are the standard unsigned integer types. The unsigned integer types that
2057 correspond to the extended signed integer types are the extended unsigned integer types.
2058 The standard and extended unsigned integer types are collectively called unsigned integer
2059 types.<sup><a href="#note30"><b>30)</b></a></sup>
2065 The standard signed integer types and standard unsigned integer types are collectively
2066 called the standard integer types, the extended signed integer types and extended
2067 unsigned integer types are collectively called the extended integer types.
2069 For any two integer types with the same signedness and different integer conversion rank
2070 (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
2071 subrange of the values of the other type.
2073 The range of nonnegative values of a signed integer type is a subrange of the
2074 corresponding unsigned integer type, and the representation of the same value in each
2075 type is the same.<sup><a href="#note31"><b>31)</b></a></sup> A computation involving unsigned operands can never overflow,
2076 because a result that cannot be represented by the resulting unsigned integer type is
2077 reduced modulo the number that is one greater than the largest value that can be
2078 represented by the resulting type.
2080 There are three real floating types, designated as float, double, and long
2081 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
2082 type double; the set of values of the type double is a subset of the set of values of the
2085 There are three complex types, designated as float _Complex, double
2086 _Complex, and long double _Complex.<sup><a href="#note33"><b>33)</b></a></sup> The real floating and complex types
2087 are collectively called the floating types.
2089 For each floating type there is a corresponding real type, which is always a real floating
2090 type. For real floating types, it is the same type. For complex types, it is the type given
2091 by deleting the keyword _Complex from the type name.
2093 Each complex type has the same representation and alignment requirements as an array
2094 type containing exactly two elements of the corresponding real type; the first element is
2095 equal to the real part, and the second element to the imaginary part, of the complex
2098 The type char, the signed and unsigned integer types, and the floating types are
2099 collectively called the basic types. Even if the implementation defines two or more basic
2100 types to have the same representation, they are nevertheless different types.<sup><a href="#note34"><b>34)</b></a></sup>
2104 The three types char, signed char, and unsigned char are collectively called
2105 the character types. The implementation shall define char to have the same range,
2106 representation, and behavior as either signed char or unsigned char.<sup><a href="#note35"><b>35)</b></a></sup>
2108 An enumeration comprises a set of named integer constant values. Each distinct
2109 enumeration constitutes a different enumerated type.
2111 The type char, the signed and unsigned integer types, and the enumerated types are
2112 collectively called integer types. The integer and real floating types are collectively called
2115 Integer and floating types are collectively called arithmetic types. Each arithmetic type
2116 belongs to one type domain: the real type domain comprises the real types, the complex
2117 type domain comprises the complex types.
2119 The void type comprises an empty set of values; it is an incomplete type that cannot be
2122 Any number of derived types can be constructed from the object, function, and
2123 incomplete types, as follows:
2125 <li> An array type describes a contiguously allocated nonempty set of objects with a
2126 particular member object type, called the element type.<sup><a href="#note36"><b>36)</b></a></sup> Array types are
2127 characterized by their element type and by the number of elements in the array. An
2128 array type is said to be derived from its element type, and if its element type is T , the
2129 array type is sometimes called ''array of T ''. The construction of an array type from
2130 an element type is called ''array type derivation''.
2131 <li> A structure type describes a sequentially allocated nonempty set of member objects
2132 (and, in certain circumstances, an incomplete array), each of which has an optionally
2133 specified name and possibly distinct type.
2134 <li> A union type describes an overlapping nonempty set of member objects, each of
2135 which has an optionally specified name and possibly distinct type.
2136 <li> A function type describes a function with specified return type. A function type is
2137 characterized by its return type and the number and types of its parameters. A
2138 function type is said to be derived from its return type, and if its return type is T , the
2139 function type is sometimes called ''function returning T ''. The construction of a
2140 function type from a return type is called ''function type derivation''.
2145 <li> A pointer type may be derived from a function type, an object type, or an incomplete
2146 type, called the referenced type. A pointer type describes an object whose value
2147 provides a reference to an entity of the referenced type. A pointer type derived from
2148 the referenced type T is sometimes called ''pointer to T ''. The construction of a
2149 pointer type from a referenced type is called ''pointer type derivation''.
2151 These methods of constructing derived types can be applied recursively.
2153 Arithmetic types and pointer types are collectively called scalar types. Array and
2154 structure types are collectively called aggregate types.<sup><a href="#note37"><b>37)</b></a></sup>
2156 An array type of unknown size is an incomplete type. It is completed, for an identifier of
2157 that type, by specifying the size in a later declaration (with internal or external linkage).
2158 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
2159 type. It is completed, for all declarations of that type, by declaring the same structure or
2160 union tag with its defining content later in the same scope.
2162 A type has known constant size if the type is not incomplete and is not a variable length
2165 Array, function, and pointer types are collectively called derived declarator types. A
2166 declarator type derivation from a type T is the construction of a derived declarator type
2167 from T by the application of an array-type, a function-type, or a pointer-type derivation to
2170 A type is characterized by its type category, which is either the outermost derivation of a
2171 derived type (as noted above in the construction of derived types), or the type itself if the
2172 type consists of no derived types.
2174 Any type so far mentioned is an unqualified type. Each unqualified type has several
2175 qualified versions of its type,<sup><a href="#note38"><b>38)</b></a></sup> corresponding to the combinations of one, two, or all
2176 three of the const, volatile, and restrict qualifiers. The qualified or unqualified
2177 versions of a type are distinct types that belong to the same type category and have the
2178 same representation and alignment requirements.<sup><a href="#note39"><b>39)</b></a></sup> A derived type is not qualified by the
2179 qualifiers (if any) of the type from which it is derived.
2181 A pointer to void shall have the same representation and alignment requirements as a
2182 pointer to a character type.39) Similarly, pointers to qualified or unqualified versions of
2183 compatible types shall have the same representation and alignment requirements. All
2187 pointers to structure types shall have the same representation and alignment requirements
2188 as each other. All pointers to union types shall have the same representation and
2189 alignment requirements as each other. Pointers to other types need not have the same
2190 representation or alignment requirements.
2192 EXAMPLE 1 The type designated as ''float *'' has type ''pointer to float''. Its type category is
2193 pointer, not a floating type. The const-qualified version of this type is designated as ''float * const''
2194 whereas the type designated as ''const float *'' is not a qualified type -- its type is ''pointer to const-
2195 qualified float'' and is a pointer to a qualified type.
2198 EXAMPLE 2 The type designated as ''struct tag (*[5])(float)'' has type ''array of pointer to
2199 function returning struct tag''. The array has length five and the function has a single parameter of type
2200 float. Its type category is array.
2202 <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>).
2205 <p><small><a name="note28" href="#note28">28)</a> Implementation-defined keywords shall have the form of an identifier reserved for any use as
2206 described in <a href="#7.1.3">7.1.3</a>.
2208 <p><small><a name="note29" href="#note29">29)</a> Therefore, any statement in this Standard about signed integer types also applies to the extended
2209 signed integer types.
2211 <p><small><a name="note30" href="#note30">30)</a> Therefore, any statement in this Standard about unsigned integer types also applies to the extended
2212 unsigned integer types.
2214 <p><small><a name="note31" href="#note31">31)</a> The same representation and alignment requirements are meant to imply interchangeability as
2215 arguments to functions, return values from functions, and members of unions.
2217 <p><small><a name="note32" href="#note32">32)</a> See ''future language directions'' (<a href="#6.11.1">6.11.1</a>).
2219 <p><small><a name="note33" href="#note33">33)</a> A specification for imaginary types is in informative <a href="#G">annex G</a>.
2221 <p><small><a name="note34" href="#note34">34)</a> An implementation may define new keywords that provide alternative ways to designate a basic (or
2222 any other) type; this does not violate the requirement that all basic types be different.
2223 Implementation-defined keywords shall have the form of an identifier reserved for any use as
2224 described in <a href="#7.1.3">7.1.3</a>.
2226 <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
2227 used to distinguish the two options. Irrespective of the choice made, char is a separate type from the
2228 other two and is not compatible with either.
2230 <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.
2232 <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
2233 contain one member at a time.
2235 <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.
2237 <p><small><a name="note39" href="#note39">39)</a> The same representation and alignment requirements are meant to imply interchangeability as
2238 arguments to functions, return values from functions, and members of unions.
2241 <h4><a name="6.2.6" href="#6.2.6">6.2.6 Representations of types</a></h4>
2243 <h5><a name="6.2.6.1" href="#6.2.6.1">6.2.6.1 General</a></h5>
2245 The representations of all types are unspecified except as stated in this subclause.
2247 Except for bit-fields, objects are composed of contiguous sequences of one or more bytes,
2248 the number, order, and encoding of which are either explicitly specified or
2249 implementation-defined.
2251 Values stored in unsigned bit-fields and objects of type unsigned char shall be
2252 represented using a pure binary notation.<sup><a href="#note40"><b>40)</b></a></sup>
2254 Values stored in non-bit-field objects of any other object type consist of n x CHAR_BIT
2255 bits, where n is the size of an object of that type, in bytes. The value may be copied into
2256 an object of type unsigned char [n] (e.g., by memcpy); the resulting set of bytes is
2257 called the object representation of the value. Values stored in bit-fields consist of m bits,
2258 where m is the size specified for the bit-field. The object representation is the set of m
2259 bits the bit-field comprises in the addressable storage unit holding it. Two values (other
2260 than NaNs) with the same object representation compare equal, but values that compare
2261 equal may have different object representations.
2263 Certain object representations need not represent a value of the object type. If the stored
2264 value of an object has such a representation and is read by an lvalue expression that does
2265 not have character type, the behavior is undefined. If such a representation is produced
2266 by a side effect that modifies all or any part of the object by an lvalue expression that
2267 does not have character type, the behavior is undefined.<sup><a href="#note41"><b>41)</b></a></sup> Such a representation is called
2270 a trap representation.
2272 When a value is stored in an object of structure or union type, including in a member
2273 object, the bytes of the object representation that correspond to any padding bytes take
2274 unspecified values.<sup><a href="#note42"><b>42)</b></a></sup> The value of a structure or union object is never a trap
2275 representation, even though the value of a member of the structure or union object may be
2276 a trap representation.
2278 When a value is stored in a member of an object of union type, the bytes of the object
2279 representation that do not correspond to that member but do correspond to other members
2280 take unspecified values.
2282 Where an operator is applied to a value that has more than one object representation,
2283 which object representation is used shall not affect the value of the result.<sup><a href="#note43"><b>43)</b></a></sup> Where a
2284 value is stored in an object using a type that has more than one object representation for
2285 that value, it is unspecified which representation is used, but a trap representation shall
2287 <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
2288 designators (<a href="#6.3.2.1">6.3.2.1</a>).
2291 <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
2292 represented by successive bits are additive, begin with 1, and are multiplied by successive integral
2293 powers of 2, except perhaps the bit with the highest position. (Adapted from the American National
2294 Dictionary for Information Processing Systems.) A byte contains CHAR_BIT bits, and the values of
2295 type unsigned char range from 0 to 2
2301 <p><small><a name="note41" href="#note41">41)</a> Thus, an automatic variable can be initialized to a trap representation without causing undefined
2302 behavior, but the value of the variable cannot be used until a proper value is stored in it.
2304 <p><small><a name="note42" href="#note42">42)</a> Thus, for example, structure assignment need not copy any padding bits.
2306 <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
2307 accessed as objects of type T, but to have different values in other contexts. In particular, if == is
2308 defined for type T, then x == y does not imply that memcmp(&x, &y, sizeof (T)) == 0.
2309 Furthermore, x == y does not necessarily imply that x and y have the same value; other operations
2310 on values of type T may distinguish between them.
2313 <h5><a name="6.2.6.2" href="#6.2.6.2">6.2.6.2 Integer types</a></h5>
2315 For unsigned integer types other than unsigned char, the bits of the object
2316 representation shall be divided into two groups: value bits and padding bits (there need
2317 not be any of the latter). If there are N value bits, each bit shall represent a different
2318 power of 2 between 1 and 2 N -1 , so that objects of that type shall be capable of
2319 representing values from 0 to 2 N - 1 using a pure binary representation; this shall be
2320 known as the value representation. The values of any padding bits are unspecified.<sup><a href="#note44"><b>44)</b></a></sup>
2322 For signed integer types, the bits of the object representation shall be divided into three
2323 groups: value bits, padding bits, and the sign bit. There need not be any padding bits;
2326 there shall be exactly one sign bit. Each bit that is a value bit shall have the same value as
2327 the same bit in the object representation of the corresponding unsigned type (if there are
2328 M value bits in the signed type and N in the unsigned type, then M <= N ). If the sign bit
2329 is zero, it shall not affect the resulting value. If the sign bit is one, the value shall be
2330 modified in one of the following ways:
2332 <li> the corresponding value with sign bit 0 is negated (sign and magnitude);
2333 <li> the sign bit has the value -(2 N ) (two's complement);
2334 <li> the sign bit has the value -(2 N - 1) (ones' complement ).
2336 Which of these applies is implementation-defined, as is whether the value with sign bit 1
2337 and all value bits zero (for the first two), or with sign bit and all value bits 1 (for ones'
2338 complement), is a trap representation or a normal value. In the case of sign and
2339 magnitude and ones' complement, if this representation is a normal value it is called a
2342 If the implementation supports negative zeros, they shall be generated only by:
2344 <li> the &, |, ^, ~, <<, and >> operators with arguments that produce such a value;
2345 <li> the +, -, *, /, and % operators where one argument is a negative zero and the result is
2347 <li> compound assignment operators based on the above cases.
2349 It is unspecified whether these cases actually generate a negative zero or a normal zero,
2350 and whether a negative zero becomes a normal zero when stored in an object.
2352 If the implementation does not support negative zeros, the behavior of the &, |, ^, ~, <<,
2353 and >> operators with arguments that would produce such a value is undefined.
2355 The values of any padding bits are unspecified.<sup><a href="#note45"><b>45)</b></a></sup> A valid (non-trap) object representation
2356 of a signed integer type where the sign bit is zero is a valid object representation of the
2357 corresponding unsigned type, and shall represent the same value. For any integer type,
2358 the object representation where all the bits are zero shall be a representation of the value
2361 The precision of an integer type is the number of bits it uses to represent values,
2362 excluding any sign and padding bits. The width of an integer type is the same but
2363 including any sign bit; thus for unsigned integer types the two values are the same, while
2367 for signed integer types the width is one greater than the precision.
2370 <p><small><a name="note44" href="#note44">44)</a> Some combinations of padding bits might generate trap representations, for example, if one padding
2371 bit is a parity bit. Regardless, no arithmetic operation on valid values can generate a trap
2372 representation other than as part of an exceptional condition such as an overflow, and this cannot occur
2373 with unsigned types. All other combinations of padding bits are alternative object representations of
2374 the value specified by the value bits.
2376 <p><small><a name="note45" href="#note45">45)</a> Some combinations of padding bits might generate trap representations, for example, if one padding
2377 bit is a parity bit. Regardless, no arithmetic operation on valid values can generate a trap
2378 representation other than as part of an exceptional condition such as an overflow. All other
2379 combinations of padding bits are alternative object representations of the value specified by the value
2383 <h4><a name="6.2.7" href="#6.2.7">6.2.7 Compatible type and composite type</a></h4>
2385 Two types have compatible type if their types are the same. Additional rules for
2386 determining whether two types are compatible are described in <a href="#6.7.2">6.7.2</a> for type specifiers,
2387 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,
2388 union, or enumerated types declared in separate translation units are compatible if their
2389 tags and members satisfy the following requirements: If one is declared with a tag, the
2390 other shall be declared with the same tag. If both are complete types, then the following
2391 additional requirements apply: there shall be a one-to-one correspondence between their
2392 members such that each pair of corresponding members are declared with compatible
2393 types, and such that if one member of a corresponding pair is declared with a name, the
2394 other member is declared with the same name. For two structures, corresponding
2395 members shall be declared in the same order. For two structures or unions, corresponding
2396 bit-fields shall have the same widths. For two enumerations, corresponding members
2397 shall have the same values.
2399 All declarations that refer to the same object or function shall have compatible type;
2400 otherwise, the behavior is undefined.
2402 A composite type can be constructed from two types that are compatible; it is a type that
2403 is compatible with both of the two types and satisfies the following conditions:
2405 <li> If one type is an array of known constant size, the composite type is an array of that
2406 size; otherwise, if one type is a variable length array, the composite type is that type.
2407 <li> If only one type is a function type with a parameter type list (a function prototype),
2408 the composite type is a function prototype with the parameter type list.
2409 <li> If both types are function types with parameter type lists, the type of each parameter
2410 in the composite parameter type list is the composite type of the corresponding
2413 These rules apply recursively to the types from which the two types are derived.
2415 For an identifier with internal or external linkage declared in a scope in which a prior
2416 declaration of that identifier is visible,<sup><a href="#note47"><b>47)</b></a></sup> if the prior declaration specifies internal or
2417 external linkage, the type of the identifier at the later declaration becomes the composite
2425 EXAMPLE Given the following two file scope declarations:
2427 int f(int (*)(), double (*)[3]);
2428 int f(int (*)(char *), double (*)[]);</pre>
2429 The resulting composite type for the function is:
2432 int f(int (*)(char *), double (*)[3]);</pre>
2435 <p><small><a name="note46" href="#note46">46)</a> Two types need not be identical to be compatible.
2437 <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.
2440 <h3><a name="6.3" href="#6.3">6.3 Conversions</a></h3>
2442 Several operators convert operand values from one type to another automatically. This
2443 subclause specifies the result required from such an implicit conversion, as well as those
2444 that result from a cast operation (an explicit conversion). The list in <a href="#6.3.1.8">6.3.1.8</a> summarizes
2445 the conversions performed by most ordinary operators; it is supplemented as required by
2446 the discussion of each operator in <a href="#6.5">6.5</a>.
2448 Conversion of an operand value to a compatible type causes no change to the value or the
2450 <p><b> Forward references</b>: cast operators (<a href="#6.5.4">6.5.4</a>).
2452 <h4><a name="6.3.1" href="#6.3.1">6.3.1 Arithmetic operands</a></h4>
2454 <h5><a name="6.3.1.1" href="#6.3.1.1">6.3.1.1 Boolean, characters, and integers</a></h5>
2456 Every integer type has an integer conversion rank defined as follows:
2458 <li> No two signed integer types shall have the same rank, even if they have the same
2460 <li> The rank of a signed integer type shall be greater than the rank of any signed integer
2461 type with less precision.
2462 <li> The rank of long long int shall be greater than the rank of long int, which
2463 shall be greater than the rank of int, which shall be greater than the rank of short
2464 int, which shall be greater than the rank of signed char.
2465 <li> The rank of any unsigned integer type shall equal the rank of the corresponding
2466 signed integer type, if any.
2467 <li> The rank of any standard integer type shall be greater than the rank of any extended
2468 integer type with the same width.
2469 <li> The rank of char shall equal the rank of signed char and unsigned char.
2470 <li> The rank of _Bool shall be less than the rank of all other standard integer types.
2471 <li> The rank of any enumerated type shall equal the rank of the compatible integer type
2472 (see <a href="#6.7.2.2">6.7.2.2</a>).
2473 <li> The rank of any extended signed integer type relative to another extended signed
2474 integer type with the same precision is implementation-defined, but still subject to the
2475 other rules for determining the integer conversion rank.
2476 <li> For all integer types T1, T2, and T3, if T1 has greater rank than T2 and T2 has
2477 greater rank than T3, then T1 has greater rank than T3.
2480 The following may be used in an expression wherever an int or unsigned int may
2484 <li> An object or expression with an integer type whose integer conversion rank is less
2485 than or equal to the rank of int and unsigned int.
2486 <li> A bit-field of type _Bool, int, signed int, or unsigned int.
2488 If an int can represent all values of the original type, the value is converted to an int;
2489 otherwise, it is converted to an unsigned int. These are called the integer
2490 promotions.<sup><a href="#note48"><b>48)</b></a></sup> All other types are unchanged by the integer promotions.
2492 The integer promotions preserve value including sign. As discussed earlier, whether a
2493 ''plain'' char is treated as signed is implementation-defined.
2494 <p><b> Forward references</b>: enumeration specifiers (<a href="#6.7.2.2">6.7.2.2</a>), structure and union specifiers
2495 (<a href="#6.7.2.1">6.7.2.1</a>).
2498 <p><small><a name="note48" href="#note48">48)</a> The integer promotions are applied only: as part of the usual arithmetic conversions, to certain
2499 argument expressions, to the operands of the unary +, -, and ~ operators, and to both operands of the
2500 shift operators, as specified by their respective subclauses.
2503 <h5><a name="6.3.1.2" href="#6.3.1.2">6.3.1.2 Boolean type</a></h5>
2505 When any scalar value is converted to _Bool, the result is 0 if the value compares equal
2506 to 0; otherwise, the result is 1.
2508 <h5><a name="6.3.1.3" href="#6.3.1.3">6.3.1.3 Signed and unsigned integers</a></h5>
2510 When a value with integer type is converted to another integer type other than _Bool, if
2511 the value can be represented by the new type, it is unchanged.
2513 Otherwise, if the new type is unsigned, the value is converted by repeatedly adding or
2514 subtracting one more than the maximum value that can be represented in the new type
2515 until the value is in the range of the new type.<sup><a href="#note49"><b>49)</b></a></sup>
2517 Otherwise, the new type is signed and the value cannot be represented in it; either the
2518 result is implementation-defined or an implementation-defined signal is raised.
2521 <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.
2524 <h5><a name="6.3.1.4" href="#6.3.1.4">6.3.1.4 Real floating and integer</a></h5>
2526 When a finite value of real floating type is converted to an integer type other than _Bool,
2527 the fractional part is discarded (i.e., the value is truncated toward zero). If the value of
2528 the integral part cannot be represented by the integer type, the behavior is undefined.<sup><a href="#note50"><b>50)</b></a></sup>
2530 When a value of integer type is converted to a real floating type, if the value being
2531 converted can be represented exactly in the new type, it is unchanged. If the value being
2532 converted is in the range of values that can be represented but cannot be represented
2535 exactly, the result is either the nearest higher or nearest lower representable value, chosen
2536 in an implementation-defined manner. If the value being converted is outside the range of
2537 values that can be represented, the behavior is undefined.
2540 <p><small><a name="note50" href="#note50">50)</a> The remaindering operation performed when a value of integer type is converted to unsigned type
2541 need not be performed when a value of real floating type is converted to unsigned type. Thus, the
2542 range of portable real floating values is (-1, Utype_MAX+1).
2545 <h5><a name="6.3.1.5" href="#6.3.1.5">6.3.1.5 Real floating types</a></h5>
2547 When a float is promoted to double or long double, or a double is promoted
2548 to long double, its value is unchanged (if the source value is represented in the
2549 precision and range of its type).
2551 When a double is demoted to float, a long double is demoted to double or
2552 float, or a value being represented in greater precision and range than required by its
2553 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
2554 being converted can be represented exactly in the new type, it is unchanged. If the value
2555 being converted is in the range of values that can be represented but cannot be
2556 represented exactly, the result is either the nearest higher or nearest lower representable
2557 value, chosen in an implementation-defined manner. If the value being converted is
2558 outside the range of values that can be represented, the behavior is undefined.
2560 <h5><a name="6.3.1.6" href="#6.3.1.6">6.3.1.6 Complex types</a></h5>
2562 When a value of complex type is converted to another complex type, both the real and
2563 imaginary parts follow the conversion rules for the corresponding real types.
2565 <h5><a name="6.3.1.7" href="#6.3.1.7">6.3.1.7 Real and complex</a></h5>
2567 When a value of real type is converted to a complex type, the real part of the complex
2568 result value is determined by the rules of conversion to the corresponding real type and
2569 the imaginary part of the complex result value is a positive zero or an unsigned zero.
2571 When a value of complex type is converted to a real type, the imaginary part of the
2572 complex value is discarded and the value of the real part is converted according to the
2573 conversion rules for the corresponding real type.
2575 <h5><a name="6.3.1.8" href="#6.3.1.8">6.3.1.8 Usual arithmetic conversions</a></h5>
2577 Many operators that expect operands of arithmetic type cause conversions and yield result
2578 types in a similar way. The purpose is to determine a common real type for the operands
2579 and result. For the specified operands, each operand is converted, without change of type
2580 domain, to a type whose corresponding real type is the common real type. Unless
2581 explicitly stated otherwise, the common real type is also the corresponding real type of
2582 the result, whose type domain is the type domain of the operands if they are the same,
2583 and complex otherwise. This pattern is called the usual arithmetic conversions:
2587 First, if the corresponding real type of either operand is long double, the other
2588 operand is converted, without change of type domain, to a type whose
2589 corresponding real type is long double.
2590 Otherwise, if the corresponding real type of either operand is double, the other
2591 operand is converted, without change of type domain, to a type whose
2592 corresponding real type is double.
2593 Otherwise, if the corresponding real type of either operand is float, the other
2594 operand is converted, without change of type domain, to a type whose
2595 corresponding real type is float.<sup><a href="#note51"><b>51)</b></a></sup>
2596 Otherwise, the integer promotions are performed on both operands. Then the
2597 following rules are applied to the promoted operands:
2598 If both operands have the same type, then no further conversion is needed.
2599 Otherwise, if both operands have signed integer types or both have unsigned
2600 integer types, the operand with the type of lesser integer conversion rank is
2601 converted to the type of the operand with greater rank.
2602 Otherwise, if the operand that has unsigned integer type has rank greater or
2603 equal to the rank of the type of the other operand, then the operand with
2604 signed integer type is converted to the type of the operand with unsigned
2606 Otherwise, if the type of the operand with signed integer type can represent
2607 all of the values of the type of the operand with unsigned integer type, then
2608 the operand with unsigned integer type is converted to the type of the
2609 operand with signed integer type.
2610 Otherwise, both operands are converted to the unsigned integer type
2611 corresponding to the type of the operand with signed integer type.</pre>
2612 The values of floating operands and of the results of floating expressions may be
2613 represented in greater precision and range than that required by the type; the types are not
2614 changed thereby.<sup><a href="#note52"><b>52)</b></a></sup>
2622 <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
2623 float operand to double (and yields a double _Complex result).
2625 <p><small><a name="note52" href="#note52">52)</a> The cast and assignment operators are still required to perform their specified conversions as
2626 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>.
2629 <h4><a name="6.3.2" href="#6.3.2">6.3.2 Other operands</a></h4>
2631 <h5><a name="6.3.2.1" href="#6.3.2.1">6.3.2.1 Lvalues, arrays, and function designators</a></h5>
2633 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>
2634 if an lvalue does not designate an object when it is evaluated, the behavior is undefined.
2635 When an object is said to have a particular type, the type is specified by the lvalue used to
2636 designate the object. A modifiable lvalue is an lvalue that does not have array type, does
2637 not have an incomplete type, does not have a const-qualified type, and if it is a structure
2638 or union, does not have any member (including, recursively, any member or element of
2639 all contained aggregates or unions) with a const-qualified type.
2641 Except when it is the operand of the sizeof operator, the unary & operator, the ++
2642 operator, the -- operator, or the left operand of the . operator or an assignment operator,
2643 an lvalue that does not have array type is converted to the value stored in the designated
2644 object (and is no longer an lvalue). If the lvalue has qualified type, the value has the
2645 unqualified version of the type of the lvalue; otherwise, the value has the type of the
2646 lvalue. If the lvalue has an incomplete type and does not have array type, the behavior is
2649 Except when it is the operand of the sizeof operator or the unary & operator, or is a
2650 string literal used to initialize an array, an expression that has type ''array of type'' is
2651 converted to an expression with type ''pointer to type'' that points to the initial element of
2652 the array object and is not an lvalue. If the array object has register storage class, the
2653 behavior is undefined.
2655 A function designator is an expression that has function type. Except when it is the
2656 operand of the sizeof operator<sup><a href="#note54"><b>54)</b></a></sup> or the unary & operator, a function designator with
2657 type ''function returning type'' is converted to an expression that has type ''pointer to
2658 function returning type''.
2659 <p><b> Forward references</b>: address and indirection operators (<a href="#6.5.3.2">6.5.3.2</a>), assignment operators
2660 (<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
2661 increment and decrement operators (<a href="#6.5.2.4">6.5.2.4</a>), prefix increment and decrement operators
2662 (<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>).
2668 <p><small><a name="note53" href="#note53">53)</a> The name ''lvalue'' comes originally from the assignment expression E1 = E2, in which the left
2669 operand E1 is required to be a (modifiable) lvalue. It is perhaps better considered as representing an
2670 object ''locator value''. What is sometimes called ''rvalue'' is in this International Standard described
2671 as the ''value of an expression''.
2672 An obvious example of an lvalue is an identifier of an object. As a further example, if E is a unary
2673 expression that is a pointer to an object, *E is an lvalue that designates the object to which E points.
2675 <p><small><a name="note54" href="#note54">54)</a> Because this conversion does not occur, the operand of the sizeof operator remains a function
2676 designator and violates the constraint in <a href="#6.5.3.4">6.5.3.4</a>.
2679 <h5><a name="6.3.2.2" href="#6.3.2.2">6.3.2.2 void</a></h5>
2681 The (nonexistent) value of a void expression (an expression that has type void) shall not
2682 be used in any way, and implicit or explicit conversions (except to void) shall not be
2683 applied to such an expression. If an expression of any other type is evaluated as a void
2684 expression, its value or designator is discarded. (A void expression is evaluated for its
2687 <h5><a name="6.3.2.3" href="#6.3.2.3">6.3.2.3 Pointers</a></h5>
2689 A pointer to void may be converted to or from a pointer to any incomplete or object
2690 type. A pointer to any incomplete or object type may be converted to a pointer to void
2691 and back again; the result shall compare equal to the original pointer.
2693 For any qualifier q, a pointer to a non-q-qualified type may be converted to a pointer to
2694 the q-qualified version of the type; the values stored in the original and converted pointers
2695 shall compare equal.
2697 An integer constant expression with the value 0, or such an expression cast to type
2698 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
2699 pointer type, the resulting pointer, called a null pointer, is guaranteed to compare unequal
2700 to a pointer to any object or function.
2702 Conversion of a null pointer to another pointer type yields a null pointer of that type.
2703 Any two null pointers shall compare equal.
2705 An integer may be converted to any pointer type. Except as previously specified, the
2706 result is implementation-defined, might not be correctly aligned, might not point to an
2707 entity of the referenced type, and might be a trap representation.<sup><a href="#note56"><b>56)</b></a></sup>
2709 Any pointer type may be converted to an integer type. Except as previously specified, the
2710 result is implementation-defined. If the result cannot be represented in the integer type,
2711 the behavior is undefined. The result need not be in the range of values of any integer
2714 A pointer to an object or incomplete type may be converted to a pointer to a different
2715 object or incomplete type. If the resulting pointer is not correctly aligned<sup><a href="#note57"><b>57)</b></a></sup> for the
2716 pointed-to type, the behavior is undefined. Otherwise, when converted back again, the
2717 result shall compare equal to the original pointer. When a pointer to an object is
2721 converted to a pointer to a character type, the result points to the lowest addressed byte of
2722 the object. Successive increments of the result, up to the size of the object, yield pointers
2723 to the remaining bytes of the object.
2725 A pointer to a function of one type may be converted to a pointer to a function of another
2726 type and back again; the result shall compare equal to the original pointer. If a converted
2727 pointer is used to call a function whose type is not compatible with the pointed-to type,
2728 the behavior is undefined.
2729 <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
2730 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>).
2734 <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>.
2736 <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
2737 be consistent with the addressing structure of the execution environment.
2739 <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
2740 pointer to type B, which in turn is correctly aligned for a pointer to type C, then a pointer to type A is
2741 correctly aligned for a pointer to type C.
2744 <h3><a name="6.4" href="#6.4">6.4 Lexical elements</a></h3>
2754 preprocessing-token:
2761 each non-white-space character that cannot be one of the above</pre>
2762 <h6>Constraints</h6>
2764 Each preprocessing token that is converted to a token shall have the lexical form of a
2765 keyword, an identifier, a constant, a string literal, or a punctuator.
2768 A token is the minimal lexical element of the language in translation phases 7 and 8. The
2769 categories of tokens are: keywords, identifiers, constants, string literals, and punctuators.
2770 A preprocessing token is the minimal lexical element of the language in translation
2771 phases 3 through 6. The categories of preprocessing tokens are: header names,
2772 identifiers, preprocessing numbers, character constants, string literals, punctuators, and
2773 single non-white-space characters that do not lexically match the other preprocessing
2774 token categories.<sup><a href="#note58"><b>58)</b></a></sup> If a ' or a " character matches the last category, the behavior is
2775 undefined. Preprocessing tokens can be separated by white space; this consists of
2776 comments (described later), or white-space characters (space, horizontal tab, new-line,
2777 vertical tab, and form-feed), or both. As described in <a href="#6.10">6.10</a>, in certain circumstances
2778 during translation phase 4, white space (or the absence thereof) serves as more than
2779 preprocessing token separation. White space may appear within a preprocessing token
2780 only as part of a header name or between the quotation characters in a character constant
2787 If the input stream has been parsed into preprocessing tokens up to a given character, the
2788 next preprocessing token is the longest sequence of characters that could constitute a
2789 preprocessing token. There is one exception to this rule: header name preprocessing
2790 tokens are recognized only within #include preprocessing directives and in
2791 implementation-defined locations within #pragma directives. In such contexts, a
2792 sequence of characters that could be either a header name or a string literal is recognized
2795 EXAMPLE 1 The program fragment 1Ex is parsed as a preprocessing number token (one that is not a
2796 valid floating or integer constant token), even though a parse as the pair of preprocessing tokens 1 and Ex
2797 might produce a valid expression (for example, if Ex were a macro defined as +1). Similarly, the program
2798 fragment 1E1 is parsed as a preprocessing number (one that is a valid floating constant token), whether or
2799 not E is a macro name.
2802 EXAMPLE 2 The program fragment x+++++y is parsed as x ++ ++ + y, which violates a constraint on
2803 increment operators, even though the parse x ++ + ++ y might yield a correct expression.
2805 <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>),
2806 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
2807 increment and decrement operators (<a href="#6.5.2.4">6.5.2.4</a>), prefix increment and decrement operators
2808 (<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
2809 (<a href="#6.4.5">6.4.5</a>).
2812 <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
2813 occur in source files.
2816 <h4><a name="6.4.1" href="#6.4.1">6.4.1 Keywords</a></h4>
2821 auto enum restrict unsigned
2822 break extern return void
2823 case float short volatile
2824 char for signed while
2825 const goto sizeof _Bool
2826 continue if static _Complex
2827 default inline struct _Imaginary
2830 else register union</pre>
2833 The above tokens (case sensitive) are reserved (in translation phases 7 and 8) for use as
2834 keywords, and shall not be used otherwise. The keyword _Imaginary is reserved for
2835 specifying imaginary types.<sup><a href="#note59"><b>59)</b></a></sup>
2842 <p><small><a name="note59" href="#note59">59)</a> One possible specification for imaginary types appears in <a href="#G">annex G</a>.
2845 <h4><a name="6.4.2" href="#6.4.2">6.4.2 Identifiers</a></h4>
2847 <h5><a name="6.4.2.1" href="#6.4.2.1">6.4.2.1 General</a></h5>
2853 identifier identifier-nondigit
2855 identifier-nondigit:
2857 universal-character-name
2858 other implementation-defined characters
2860 _ a b c d e f g h i j k l m
2861 n o p q r s t u v w x y z
2862 A B C D E F G H I J K L M
2863 N O P Q R S T U V W X Y Z
2865 0 1 2 3 4 5 6 7 8 9</pre>
2868 An identifier is a sequence of nondigit characters (including the underscore _, the
2869 lowercase and uppercase Latin letters, and other characters) and digits, which designates
2870 one or more entities as described in <a href="#6.2.1">6.2.1</a>. Lowercase and uppercase letters are distinct.
2871 There is no specific limit on the maximum length of an identifier.
2873 Each universal character name in an identifier shall designate a character whose encoding
2874 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
2875 character shall not be a universal character name designating a digit. An implementation
2876 may allow multibyte characters that are not part of the basic source character set to
2877 appear in identifiers; which characters and their correspondence to universal character
2878 names is implementation-defined.
2880 When preprocessing tokens are converted to tokens during translation phase 7, if a
2881 preprocessing token could be converted to either a keyword or an identifier, it is converted
2886 Implementation limits
2888 As discussed in <a href="#5.2.4.1">5.2.4.1</a>, an implementation may limit the number of significant initial
2889 characters in an identifier; the limit for an external name (an identifier that has external
2890 linkage) may be more restrictive than that for an internal name (a macro name or an
2891 identifier that does not have external linkage). The number of significant characters in an
2892 identifier is implementation-defined.
2894 Any identifiers that differ in a significant character are different identifiers. If two
2895 identifiers differ only in nonsignificant characters, the behavior is undefined.
2896 <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>).
2899 <p><small><a name="note60" href="#note60">60)</a> On systems in which linkers cannot accept extended characters, an encoding of the universal character
2900 name may be used in forming valid external identifiers. For example, some otherwise unused
2901 character or sequence of characters may be used to encode the \u in a universal character name.
2902 Extended characters may produce a long external identifier.
2905 <h5><a name="6.4.2.2" href="#6.4.2.2">6.4.2.2 Predefined identifiers</a></h5>
2908 The identifier __func__ shall be implicitly declared by the translator as if,
2909 immediately following the opening brace of each function definition, the declaration
2911 static const char __func__[] = "function-name";</pre>
2912 appeared, where function-name is the name of the lexically-enclosing function.<sup><a href="#note61"><b>61)</b></a></sup>
2914 This name is encoded as if the implicit declaration had been written in the source
2915 character set and then translated into the execution character set as indicated in translation
2918 EXAMPLE Consider the code fragment:
2920 #include <a href="#7.19"><stdio.h></a>
2923 printf("%s\n", __func__);
2926 Each time the function is called, it will print to the standard output stream:
2930 <p><b> Forward references</b>: function definitions (<a href="#6.9.1">6.9.1</a>).
2938 <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
2939 identifier is explicitly declared using the name __func__, the behavior is undefined.
2942 <h4><a name="6.4.3" href="#6.4.3">6.4.3 Universal character names</a></h4>
2946 universal-character-name:
2948 \U hex-quad hex-quad
2950 hexadecimal-digit hexadecimal-digit
2951 hexadecimal-digit hexadecimal-digit</pre>
2952 <h6>Constraints</h6>
2954 A universal character name shall not specify a character whose short identifier is less than
2955 00A0 other than 0024 ($), 0040 (@), or 0060 ('), nor one in the range D800 through
2956 DFFF inclusive.<sup><a href="#note62"><b>62)</b></a></sup>
2957 <h6>Description</h6>
2959 Universal character names may be used in identifiers, character constants, and string
2960 literals to designate characters that are not in the basic character set.
2963 The universal character name \Unnnnnnnn designates the character whose eight-digit
2964 short identifier (as specified by ISO/IEC 10646) is nnnnnnnn.<sup><a href="#note63"><b>63)</b></a></sup> Similarly, the universal
2965 character name \unnnn designates the character whose four-digit short identifier is nnnn
2966 (and whose eight-digit short identifier is 0000nnnn).
2974 <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
2975 by ISO/IEC 10646 for control characters, the character DELETE, and the S-zone (reserved for use by
2978 <p><small><a name="note63" href="#note63">63)</a> Short identifiers for characters were first specified in ISO/IEC 10646-1/AMD9:1997.
2981 <h4><a name="6.4.4" href="#6.4.4">6.4.4 Constants</a></h4>
2988 enumeration-constant
2989 character-constant</pre>
2990 <h6>Constraints</h6>
2992 Each constant shall have a type and the value of a constant shall be in the range of
2993 representable values for its type.
2996 Each constant has a type, determined by its form and value, as detailed later.
2998 <h5><a name="6.4.4.1" href="#6.4.4.1">6.4.4.1 Integer constants</a></h5>
3004 decimal-constant integer-suffixopt
3005 octal-constant integer-suffixopt
3006 hexadecimal-constant integer-suffixopt
3009 decimal-constant digit
3012 octal-constant octal-digit
3013 hexadecimal-constant:
3014 hexadecimal-prefix hexadecimal-digit
3015 hexadecimal-constant hexadecimal-digit
3016 hexadecimal-prefix: one of
3018 nonzero-digit: one of
3022 hexadecimal-digit: one of
3027 unsigned-suffix long-suffixopt
3028 unsigned-suffix long-long-suffix
3029 long-suffix unsigned-suffixopt
3030 long-long-suffix unsigned-suffixopt
3031 unsigned-suffix: one of
3035 long-long-suffix: one of
3037 <h6>Description</h6>
3039 An integer constant begins with a digit, but has no period or exponent part. It may have a
3040 prefix that specifies its base and a suffix that specifies its type.
3042 A decimal constant begins with a nonzero digit and consists of a sequence of decimal
3043 digits. An octal constant consists of the prefix 0 optionally followed by a sequence of the
3044 digits 0 through 7 only. A hexadecimal constant consists of the prefix 0x or 0X followed
3045 by a sequence of the decimal digits and the letters a (or A) through f (or F) with values
3046 10 through 15 respectively.
3049 The value of a decimal constant is computed base 10; that of an octal constant, base 8;
3050 that of a hexadecimal constant, base 16. The lexically first digit is the most significant.
3052 The type of an integer constant is the first of the corresponding list in which its value can
3056 Octal or Hexadecimal</pre>
3057 Suffix Decimal Constant Constant
3061 long int unsigned int
3062 long long int long int
3065 unsigned long long int</pre>
3067 u or U unsigned int unsigned int
3069 unsigned long int unsigned long int
3070 unsigned long long int unsigned long long int</pre>
3072 l or L long int long int
3074 long long int unsigned long int
3076 unsigned long long int</pre>
3078 Both u or U unsigned long int unsigned long int
3079 and l or L unsigned long long int unsigned long long int
3081 ll or LL long long int long long int
3083 unsigned long long int</pre>
3085 Both u or U unsigned long long int unsigned long long int
3088 If an integer constant cannot be represented by any type in its list, it may have an
3089 extended integer type, if the extended integer type can represent its value. If all of the
3090 types in the list for the constant are signed, the extended integer type shall be signed. If
3091 all of the types in the list for the constant are unsigned, the extended integer type shall be
3092 unsigned. If the list contains both signed and unsigned types, the extended integer type
3093 may be signed or unsigned. If an integer constant cannot be represented by any type in
3094 its list and has no extended integer type, then the integer constant has no type.
3097 <h5><a name="6.4.4.2" href="#6.4.4.2">6.4.4.2 Floating constants</a></h5>
3103 decimal-floating-constant
3104 hexadecimal-floating-constant
3105 decimal-floating-constant:
3106 fractional-constant exponent-partopt floating-suffixopt
3107 digit-sequence exponent-part floating-suffixopt
3108 hexadecimal-floating-constant:
3109 hexadecimal-prefix hexadecimal-fractional-constant
3110 binary-exponent-part floating-suffixopt
3111 hexadecimal-prefix hexadecimal-digit-sequence
3112 binary-exponent-part floating-suffixopt
3113 fractional-constant:
3114 digit-sequenceopt . digit-sequence
3117 e signopt digit-sequence
3118 E signopt digit-sequence
3123 digit-sequence digit
3124 hexadecimal-fractional-constant:
3125 hexadecimal-digit-sequenceopt .
3126 hexadecimal-digit-sequence
3127 hexadecimal-digit-sequence .
3128 binary-exponent-part:
3129 p signopt digit-sequence
3130 P signopt digit-sequence
3131 hexadecimal-digit-sequence:
3133 hexadecimal-digit-sequence hexadecimal-digit
3134 floating-suffix: one of
3136 <h6>Description</h6>
3138 A floating constant has a significand part that may be followed by an exponent part and a
3139 suffix that specifies its type. The components of the significand part may include a digit
3140 sequence representing the whole-number part, followed by a period (.), followed by a
3141 digit sequence representing the fraction part. The components of the exponent part are an
3142 e, E, p, or P followed by an exponent consisting of an optionally signed digit sequence.
3143 Either the whole-number part or the fraction part has to be present; for decimal floating
3144 constants, either the period or the exponent part has to be present.
3147 The significand part is interpreted as a (decimal or hexadecimal) rational number; the
3148 digit sequence in the exponent part is interpreted as a decimal integer. For decimal
3149 floating constants, the exponent indicates the power of 10 by which the significand part is
3150 to be scaled. For hexadecimal floating constants, the exponent indicates the power of 2
3151 by which the significand part is to be scaled. For decimal floating constants, and also for
3152 hexadecimal floating constants when FLT_RADIX is not a power of 2, the result is either
3153 the nearest representable value, or the larger or smaller representable value immediately
3154 adjacent to the nearest representable value, chosen in an implementation-defined manner.
3155 For hexadecimal floating constants when FLT_RADIX is a power of 2, the result is
3158 An unsuffixed floating constant has type double. If suffixed by the letter f or F, it has
3159 type float. If suffixed by the letter l or L, it has type long double.
3161 Floating constants are converted to internal format as if at translation-time. The
3162 conversion of a floating constant shall not raise an exceptional condition or a floating-
3163 point exception at execution time.
3164 Recommended practice
3166 The implementation should produce a diagnostic message if a hexadecimal constant
3167 cannot be represented exactly in its evaluation format; the implementation should then
3168 proceed with the translation of the program.
3170 The translation-time conversion of floating constants should match the execution-time
3171 conversion of character strings by library functions, such as strtod, given matching
3172 inputs suitable for both conversions, the same result format, and default execution-time
3173 rounding.<sup><a href="#note64"><b>64)</b></a></sup>
3181 <p><small><a name="note64" href="#note64">64)</a> The specification for the library functions recommends more accurate conversion than required for
3182 floating constants (see <a href="#7.20.1.3">7.20.1.3</a>).
3185 <h5><a name="6.4.4.3" href="#6.4.4.3">6.4.4.3 Enumeration constants</a></h5>
3189 enumeration-constant:
3193 An identifier declared as an enumeration constant has type int.
3194 <p><b> Forward references</b>: enumeration specifiers (<a href="#6.7.2.2">6.7.2.2</a>).
3196 <h5><a name="6.4.4.4" href="#6.4.4.4">6.4.4.4 Character constants</a></h5>
3203 L' c-char-sequence '
3206 c-char-sequence c-char
3208 any member of the source character set except
3209 the single-quote ', backslash \, or new-line character
3212 simple-escape-sequence
3213 octal-escape-sequence
3214 hexadecimal-escape-sequence
3215 universal-character-name
3216 simple-escape-sequence: one of
3218 \a \b \f \n \r \t \v
3219 octal-escape-sequence:
3221 \ octal-digit octal-digit
3222 \ octal-digit octal-digit octal-digit
3223 hexadecimal-escape-sequence:
3224 \x hexadecimal-digit
3225 hexadecimal-escape-sequence hexadecimal-digit</pre>
3226 <h6>Description</h6>
3228 An integer character constant is a sequence of one or more multibyte characters enclosed
3229 in single-quotes, as in 'x'. A wide character constant is the same, except prefixed by the
3230 letter L. With a few exceptions detailed later, the elements of the sequence are any
3231 members of the source character set; they are mapped in an implementation-defined
3232 manner to members of the execution character set.
3234 The single-quote ', the double-quote ", the question-mark ?, the backslash \, and
3235 arbitrary integer values are representable according to the following table of escape
3243 octal character \octal digits
3244 hexadecimal character \x hexadecimal digits</pre>
3245 The double-quote " and question-mark ? are representable either by themselves or by the
3246 escape sequences \" and \?, respectively, but the single-quote ' and the backslash \
3247 shall be represented, respectively, by the escape sequences \' and \\.
3249 The octal digits that follow the backslash in an octal escape sequence are taken to be part
3250 of the construction of a single character for an integer character constant or of a single
3251 wide character for a wide character constant. The numerical value of the octal integer so
3252 formed specifies the value of the desired character or wide character.
3254 The hexadecimal digits that follow the backslash and the letter x in a hexadecimal escape
3255 sequence are taken to be part of the construction of a single character for an integer
3256 character constant or of a single wide character for a wide character constant. The
3257 numerical value of the hexadecimal integer so formed specifies the value of the desired
3258 character or wide character.
3260 Each octal or hexadecimal escape sequence is the longest sequence of characters that can
3261 constitute the escape sequence.
3263 In addition, characters not in the basic character set are representable by universal
3264 character names and certain nongraphic characters are representable by escape sequences
3265 consisting of the backslash \ followed by a lowercase letter: \a, \b, \f, \n, \r, \t,
3266 and \v.<sup><a href="#note65"><b>65)</b></a></sup>
3272 <h6>Constraints</h6>
3274 The value of an octal or hexadecimal escape sequence shall be in the range of
3275 representable values for the type unsigned char for an integer character constant, or
3276 the unsigned type corresponding to wchar_t for a wide character constant.
3279 An integer character constant has type int. The value of an integer character constant
3280 containing a single character that maps to a single-byte execution character is the
3281 numerical value of the representation of the mapped character interpreted as an integer.
3282 The value of an integer character constant containing more than one character (e.g.,
3283 'ab'), or containing a character or escape sequence that does not map to a single-byte
3284 execution character, is implementation-defined. If an integer character constant contains
3285 a single character or escape sequence, its value is the one that results when an object with
3286 type char whose value is that of the single character or escape sequence is converted to
3289 A wide character constant has type wchar_t, an integer type defined in the
3290 <a href="#7.17"><stddef.h></a> header. The value of a wide character constant containing a single
3291 multibyte character that maps to a member of the extended execution character set is the
3292 wide character corresponding to that multibyte character, as defined by the mbtowc
3293 function, with an implementation-defined current locale. The value of a wide character
3294 constant containing more than one multibyte character, or containing a multibyte
3295 character or escape sequence not represented in the extended execution character set, is
3296 implementation-defined.
3298 EXAMPLE 1 The construction '\0' is commonly used to represent the null character.
3301 EXAMPLE 2 Consider implementations that use two's-complement representation for integers and eight
3302 bits for objects that have type char. In an implementation in which type char has the same range of
3303 values as signed char, the integer character constant '\xFF' has the value -1; if type char has the
3304 same range of values as unsigned char, the character constant '\xFF' has the value +255.
3307 EXAMPLE 3 Even if eight bits are used for objects that have type char, the construction '\x123'
3308 specifies an integer character constant containing only one character, since a hexadecimal escape sequence
3309 is terminated only by a non-hexadecimal character. To specify an integer character constant containing the
3310 two characters whose values are '\x12' and '3', the construction '\0223' may be used, since an octal
3311 escape sequence is terminated after three octal digits. (The value of this two-character integer character
3312 constant is implementation-defined.)
3315 EXAMPLE 4 Even if 12 or more bits are used for objects that have type wchar_t, the construction
3316 L'\1234' specifies the implementation-defined value that results from the combination of the values
3319 <p><b> Forward references</b>: common definitions <a href="#7.17"><stddef.h></a> (<a href="#7.17">7.17</a>), the mbtowc function
3320 (<a href="#7.20.7.2">7.20.7.2</a>).
3324 <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,
3325 the result is not a token and a diagnostic is required. See ''future language directions'' (<a href="#6.11.4">6.11.4</a>).
3328 <h4><a name="6.4.5" href="#6.4.5">6.4.5 String literals</a></h4>
3333 " s-char-sequenceopt "
3334 L" s-char-sequenceopt "
3337 s-char-sequence s-char
3339 any member of the source character set except
3340 the double-quote ", backslash \, or new-line character
3341 escape-sequence</pre>
3342 <h6>Description</h6>
3344 A character string literal is a sequence of zero or more multibyte characters enclosed in
3345 double-quotes, as in "xyz". A wide string literal is the same, except prefixed by the
3348 The same considerations apply to each element of the sequence in a character string
3349 literal or a wide string literal as if it were in an integer character constant or a wide
3350 character constant, except that the single-quote ' is representable either by itself or by the
3351 escape sequence \', but the double-quote " shall be represented by the escape sequence
3355 In translation phase 6, the multibyte character sequences specified by any sequence of
3356 adjacent character and wide string literal tokens are concatenated into a single multibyte
3357 character sequence. If any of the tokens are wide string literal tokens, the resulting
3358 multibyte character sequence is treated as a wide string literal; otherwise, it is treated as a
3359 character string literal.
3361 In translation phase 7, a byte or code of value zero is appended to each multibyte
3362 character sequence that results from a string literal or literals.<sup><a href="#note66"><b>66)</b></a></sup> The multibyte character
3363 sequence is then used to initialize an array of static storage duration and length just
3364 sufficient to contain the sequence. For character string literals, the array elements have
3365 type char, and are initialized with the individual bytes of the multibyte character
3366 sequence; for wide string literals, the array elements have type wchar_t, and are
3367 initialized with the sequence of wide characters corresponding to the multibyte character
3370 sequence, as defined by the mbstowcs function with an implementation-defined current
3371 locale. The value of a string literal containing a multibyte character or escape sequence
3372 not represented in the execution character set is implementation-defined.
3374 It is unspecified whether these arrays are distinct provided their elements have the
3375 appropriate values. If the program attempts to modify such an array, the behavior is
3378 EXAMPLE This pair of adjacent character string literals
3381 produces a single character string literal containing the two characters whose values are '\x12' and '3',
3382 because escape sequences are converted into single members of the execution character set just prior to
3383 adjacent string literal concatenation.
3385 <p><b> Forward references</b>: common definitions <a href="#7.17"><stddef.h></a> (<a href="#7.17">7.17</a>), the mbstowcs
3386 function (<a href="#7.20.8.1">7.20.8.1</a>).
3389 <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
3390 it by a \0 escape sequence.
3393 <h4><a name="6.4.6" href="#6.4.6">6.4.6 Punctuators</a></h4>
3399 ++ -- & * + - ~ !
3400 / % << >> < > <= >= == != ^ | && ||
3402 = *= /= %= += -= <<= >>= &= ^= |=
3404 <: :> <% %> %: %:%:</pre>
3407 A punctuator is a symbol that has independent syntactic and semantic significance.
3408 Depending on context, it may specify an operation to be performed (which in turn may
3409 yield a value or a function designator, produce a side effect, or some combination thereof)
3410 in which case it is known as an operator (other forms of operator also exist in some
3411 contexts). An operand is an entity on which an operator acts.
3414 In all aspects of the language, the six tokens<sup><a href="#note67"><b>67)</b></a></sup>
3416 <: :> <% %> %: %:%:</pre>
3417 behave, respectively, the same as the six tokens
3420 except for their spelling.<sup><a href="#note68"><b>68)</b></a></sup>
3421 <p><b> Forward references</b>: expressions (<a href="#6.5">6.5</a>), declarations (<a href="#6.7">6.7</a>), preprocessing directives
3422 (<a href="#6.10">6.10</a>), statements (<a href="#6.8">6.8</a>).
3425 <p><small><a name="note67" href="#note67">67)</a> These tokens are sometimes called ''digraphs''.
3427 <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
3431 <h4><a name="6.4.7" href="#6.4.7">6.4.7 Header names</a></h4>
3436 < h-char-sequence >
3440 h-char-sequence h-char
3442 any member of the source character set except
3443 the new-line character and >
3446 q-char-sequence q-char
3448 any member of the source character set except
3449 the new-line character and "</pre>
3452 The sequences in both forms of header names are mapped in an implementation-defined
3453 manner to headers or external source file names as specified in <a href="#6.10.2">6.10.2</a>.
3455 If the characters ', \, ", //, or /* occur in the sequence between the < and > delimiters,
3456 the behavior is undefined. Similarly, if the characters ', \, //, or /* occur in the
3462 sequence between the " delimiters, the behavior is undefined.<sup><a href="#note69"><b>69)</b></a></sup> Header name
3463 preprocessing tokens are recognized only within #include preprocessing directives and
3464 in implementation-defined locations within #pragma directives.<sup><a href="#note70"><b>70)</b></a></sup>
3466 EXAMPLE The following sequence of characters:
3469 #include <1/a.h>
3470 #define const.member@$</pre>
3471 forms the following sequence of preprocessing tokens (with each individual preprocessing token delimited
3472 by a { on the left and a } on the right).
3474 {0x3}{<}{1}{/}{a}{.}{h}{>}{1e2}
3475 {#}{include} {<1/a.h>}
3476 {#}{define} {const}{.}{member}{@}{$}</pre>
3478 <p><b> Forward references</b>: source file inclusion (<a href="#6.10.2">6.10.2</a>).
3481 <p><small><a name="note69" href="#note69">69)</a> Thus, sequences of characters that resemble escape sequences cause undefined behavior.
3483 <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>.
3486 <h4><a name="6.4.8" href="#6.4.8">6.4.8 Preprocessing numbers</a></h4>
3494 pp-number identifier-nondigit
3500 <h6>Description</h6>
3502 A preprocessing number begins with a digit optionally preceded by a period (.) and may
3503 be followed by valid identifier characters and the character sequences e+, e-, E+, E-,
3506 Preprocessing number tokens lexically include all floating and integer constant tokens.
3509 A preprocessing number does not have type or a value; it acquires both after a successful
3510 conversion (as part of translation phase 7) to a floating constant token or an integer
3516 <h4><a name="6.4.9" href="#6.4.9">6.4.9 Comments</a></h4>
3518 Except within a character constant, a string literal, or a comment, the characters /*
3519 introduce a comment. The contents of such a comment are examined only to identify
3520 multibyte characters and to find the characters */ that terminate it.<sup><a href="#note71"><b>71)</b></a></sup>
3522 Except within a character constant, a string literal, or a comment, the characters //
3523 introduce a comment that includes all multibyte characters up to, but not including, the
3524 next new-line character. The contents of such a comment are examined only to identify
3525 multibyte characters and to find the terminating new-line character.
3529 "a//b" // four-character string literal
3530 #include "//e" // undefined behavior
3531 // */ // comment, not syntax error
3532 f = g/**//h; // equivalent to f = g / h;
3534 i(); // part of a two-line comment
3536 / j(); // part of a two-line comment
3537 #define glue(x,y) x##y
3538 glue(/,/) k(); // syntax error, not comment
3539 /*//*/ l(); // equivalent to l();
3541 + p; // equivalent to m = n + p;</pre>
3549 <p><small><a name="note71" href="#note71">71)</a> Thus, /* ... */ comments do not nest.
3552 <h3><a name="6.5" href="#6.5">6.5 Expressions</a></h3>
3554 An expression is a sequence of operators and operands that specifies computation of a
3555 value, or that designates an object or a function, or that generates side effects, or that
3556 performs a combination thereof.
3558 Between the previous and next sequence point an object shall have its stored value
3559 modified at most once by the evaluation of an expression.<sup><a href="#note72"><b>72)</b></a></sup> Furthermore, the prior value
3560 shall be read only to determine the value to be stored.<sup><a href="#note73"><b>73)</b></a></sup>
3562 The grouping of operators and operands is indicated by the syntax.<sup><a href="#note74"><b>74)</b></a></sup> Except as specified
3563 later (for the function-call (), &&, ||, ?:, and comma operators), the order of evaluation
3564 of subexpressions and the order in which side effects take place are both unspecified.
3566 Some operators (the unary operator ~, and the binary operators <<, >>, &, ^, and |,
3567 collectively described as bitwise operators) are required to have operands that have
3568 integer type. These operators yield values that depend on the internal representations of
3569 integers, and have implementation-defined and undefined aspects for signed types.
3571 If an exceptional condition occurs during the evaluation of an expression (that is, if the
3572 result is not mathematically defined or not in the range of representable values for its
3573 type), the behavior is undefined.
3575 The effective type of an object for an access to its stored value is the declared type of the
3576 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
3577 lvalue having a type that is not a character type, then the type of the lvalue becomes the
3581 effective type of the object for that access and for subsequent accesses that do not modify
3582 the stored value. If a value is copied into an object having no declared type using
3583 memcpy or memmove, or is copied as an array of character type, then the effective type
3584 of the modified object for that access and for subsequent accesses that do not modify the
3585 value is the effective type of the object from which the value is copied, if it has one. For
3586 all other accesses to an object having no declared type, the effective type of the object is
3587 simply the type of the lvalue used for the access.
3589 An object shall have its stored value accessed only by an lvalue expression that has one of
3590 the following types:<sup><a href="#note76"><b>76)</b></a></sup>
3592 <li> a type compatible with the effective type of the object,
3593 <li> a qualified version of a type compatible with the effective type of the object,
3594 <li> a type that is the signed or unsigned type corresponding to the effective type of the
3596 <li> a type that is the signed or unsigned type corresponding to a qualified version of the
3597 effective type of the object,
3598 <li> an aggregate or union type that includes one of the aforementioned types among its
3599 members (including, recursively, a member of a subaggregate or contained union), or
3600 <li> a character type.
3603 A floating expression may be contracted, that is, evaluated as though it were an atomic
3604 operation, thereby omitting rounding errors implied by the source code and the
3605 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
3606 way to disallow contracted expressions. Otherwise, whether and how expressions are
3607 contracted is implementation-defined.<sup><a href="#note78"><b>78)</b></a></sup>
3608 <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>).
3616 <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.
3618 <p><small><a name="note73" href="#note73">73)</a> This paragraph renders undefined statement expressions such as
3628 <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
3629 as the order of the major subclauses of this subclause, highest precedence first. Thus, for example, the
3630 expressions allowed as the operands of the binary + operator (<a href="#6.5.6">6.5.6</a>) are those expressions defined in
3631 <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
3632 (<a href="#6.5.3">6.5.3</a>), and an operand contained between any of the following pairs of operators: grouping
3633 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
3634 the conditional operator ?: (<a href="#6.5.15">6.5.15</a>).
3637 Within each major subclause, the operators have the same precedence. Left- or right-associativity is
3638 indicated in each subclause by the syntax for the expressions discussed therein.</pre>
3640 <p><small><a name="note75" href="#note75">75)</a> Allocated objects have no declared type.
3642 <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.
3644 <p><small><a name="note77" href="#note77">77)</a> A contracted expression might also omit the raising of floating-point exceptions.
3646 <p><small><a name="note78" href="#note78">78)</a> This license is specifically intended to allow implementations to exploit fast machine instructions that
3647 combine multiple C operators. As contractions potentially undermine predictability, and can even
3648 decrease accuracy for containing expressions, their use needs to be well-defined and clearly
3652 <h4><a name="6.5.1" href="#6.5.1">6.5.1 Primary expressions</a></h4>
3660 ( expression )</pre>
3663 An identifier is a primary expression, provided it has been declared as designating an
3664 object (in which case it is an lvalue) or a function (in which case it is a function
3665 designator).<sup><a href="#note79"><b>79)</b></a></sup>
3667 A constant is a primary expression. Its type depends on its form and value, as detailed in
3668 <a href="#6.4.4">6.4.4</a>.
3670 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>.
3672 A parenthesized expression is a primary expression. Its type and value are identical to
3673 those of the unparenthesized expression. It is an lvalue, a function designator, or a void
3674 expression if the unparenthesized expression is, respectively, an lvalue, a function
3675 designator, or a void expression.
3676 <p><b> Forward references</b>: declarations (<a href="#6.7">6.7</a>).
3679 <p><small><a name="note79" href="#note79">79)</a> Thus, an undeclared identifier is a violation of the syntax.
3682 <h4><a name="6.5.2" href="#6.5.2">6.5.2 Postfix operators</a></h4>
3688 postfix-expression [ expression ]
3689 postfix-expression ( argument-expression-listopt )
3690 postfix-expression . identifier
3691 postfix-expression -> identifier
3692 postfix-expression ++
3693 postfix-expression --
3694 ( type-name ) { initializer-list }
3695 ( type-name ) { initializer-list , }</pre>
3702 argument-expression-list:
3703 assignment-expression
3704 argument-expression-list , assignment-expression</pre>
3706 <h5><a name="6.5.2.1" href="#6.5.2.1">6.5.2.1 Array subscripting</a></h5>
3707 <h6>Constraints</h6>
3709 One of the expressions shall have type ''pointer to object type'', the other expression shall
3710 have integer type, and the result has type ''type''.
3713 A postfix expression followed by an expression in square brackets [] is a subscripted
3714 designation of an element of an array object. The definition of the subscript operator []
3715 is that E1[E2] is identical to (*((E1)+(E2))). Because of the conversion rules that
3716 apply to the binary + operator, if E1 is an array object (equivalently, a pointer to the
3717 initial element of an array object) and E2 is an integer, E1[E2] designates the E2-th
3718 element of E1 (counting from zero).
3720 Successive subscript operators designate an element of a multidimensional array object.
3721 If E is an n-dimensional array (n >= 2) with dimensions i x j x . . . x k, then E (used as
3722 other than an lvalue) is converted to a pointer to an (n - 1)-dimensional array with
3723 dimensions j x . . . x k. If the unary * operator is applied to this pointer explicitly, or
3724 implicitly as a result of subscripting, the result is the pointed-to (n - 1)-dimensional array,
3725 which itself is converted into a pointer if used as other than an lvalue. It follows from this
3726 that arrays are stored in row-major order (last subscript varies fastest).
3728 EXAMPLE Consider the array object defined by the declaration
3731 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
3732 array of five ints. In the expression x[i], which is equivalent to (*((x)+(i))), x is first converted to
3733 a pointer to the initial array of five ints. Then i is adjusted according to the type of x, which conceptually
3734 entails multiplying i by the size of the object to which the pointer points, namely an array of five int
3735 objects. The results are added and indirection is applied to yield an array of five ints. When used in the
3736 expression x[i][j], that array is in turn converted to a pointer to the first of the ints, so x[i][j]
3739 <p><b> Forward references</b>: additive operators (<a href="#6.5.6">6.5.6</a>), address and indirection operators
3740 (<a href="#6.5.3.2">6.5.3.2</a>), array declarators (<a href="#6.7.5.2">6.7.5.2</a>).
3743 <h5><a name="6.5.2.2" href="#6.5.2.2">6.5.2.2 Function calls</a></h5>
3744 <h6>Constraints</h6>
3746 The expression that denotes the called function<sup><a href="#note80"><b>80)</b></a></sup> shall have type pointer to function
3747 returning void or returning an object type other than an array type.
3749 If the expression that denotes the called function has a type that includes a prototype, the
3750 number of arguments shall agree with the number of parameters. Each argument shall
3751 have a type such that its value may be assigned to an object with the unqualified version
3752 of the type of its corresponding parameter.
3755 A postfix expression followed by parentheses () containing a possibly empty, comma-
3756 separated list of expressions is a function call. The postfix expression denotes the called
3757 function. The list of expressions specifies the arguments to the function.
3759 An argument may be an expression of any object type. In preparing for the call to a
3760 function, the arguments are evaluated, and each parameter is assigned the value of the
3761 corresponding argument.<sup><a href="#note81"><b>81)</b></a></sup>
3763 If the expression that denotes the called function has type pointer to function returning an
3764 object type, the function call expression has the same type as that object type, and has the
3765 value determined as specified in <a href="#6.8.6.4">6.8.6.4</a>. Otherwise, the function call has type void. If
3766 an attempt is made to modify the result of a function call or to access it after the next
3767 sequence point, the behavior is undefined.
3769 If the expression that denotes the called function has a type that does not include a
3770 prototype, the integer promotions are performed on each argument, and arguments that
3771 have type float are promoted to double. These are called the default argument
3772 promotions. If the number of arguments does not equal the number of parameters, the
3773 behavior is undefined. If the function is defined with a type that includes a prototype, and
3774 either the prototype ends with an ellipsis (, ...) or the types of the arguments after
3775 promotion are not compatible with the types of the parameters, the behavior is undefined.
3776 If the function is defined with a type that does not include a prototype, and the types of
3777 the arguments after promotion are not compatible with those of the parameters after
3778 promotion, the behavior is undefined, except for the following cases:
3785 <li> one promoted type is a signed integer type, the other promoted type is the
3786 corresponding unsigned integer type, and the value is representable in both types;
3787 <li> both types are pointers to qualified or unqualified versions of a character type or
3791 If the expression that denotes the called function has a type that does include a prototype,
3792 the arguments are implicitly converted, as if by assignment, to the types of the
3793 corresponding parameters, taking the type of each parameter to be the unqualified version
3794 of its declared type. The ellipsis notation in a function prototype declarator causes
3795 argument type conversion to stop after the last declared parameter. The default argument
3796 promotions are performed on trailing arguments.
3798 No other conversions are performed implicitly; in particular, the number and types of
3799 arguments are not compared with those of the parameters in a function definition that
3800 does not include a function prototype declarator.
3802 If the function is defined with a type that is not compatible with the type (of the
3803 expression) pointed to by the expression that denotes the called function, the behavior is
3806 The order of evaluation of the function designator, the actual arguments, and
3807 subexpressions within the actual arguments is unspecified, but there is a sequence point
3808 before the actual call.
3810 Recursive function calls shall be permitted, both directly and indirectly through any chain
3813 EXAMPLE In the function call
3815 (*pf[f1()]) (f2(), f3() + f4())</pre>
3816 the functions f1, f2, f3, and f4 may be called in any order. All side effects have to be completed before
3817 the function pointed to by pf[f1()] is called.
3819 <p><b> Forward references</b>: function declarators (including prototypes) (<a href="#6.7.5.3">6.7.5.3</a>), function
3820 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>).
3823 <p><small><a name="note80" href="#note80">80)</a> Most often, this is the result of converting an identifier that is a function designator.
3825 <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
3826 arguments. On the other hand, it is possible to pass a pointer to an object, and the function may
3827 change the value of the object pointed to. A parameter declared to have array or function type is
3828 adjusted to have a pointer type as described in <a href="#6.9.1">6.9.1</a>.
3831 <h5><a name="6.5.2.3" href="#6.5.2.3">6.5.2.3 Structure and union members</a></h5>
3832 <h6>Constraints</h6>
3834 The first operand of the . operator shall have a qualified or unqualified structure or union
3835 type, and the second operand shall name a member of that type.
3837 The first operand of the -> operator shall have type ''pointer to qualified or unqualified
3838 structure'' or ''pointer to qualified or unqualified union'', and the second operand shall
3839 name a member of the type pointed to.
3843 A postfix expression followed by the . operator and an identifier designates a member of
3844 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
3845 the first expression is an lvalue. If the first expression has qualified type, the result has
3846 the so-qualified version of the type of the designated member.
3848 A postfix expression followed by the -> operator and an identifier designates a member
3849 of a structure or union object. The value is that of the named member of the object to
3850 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
3851 a qualified type, the result has the so-qualified version of the type of the designated
3854 One special guarantee is made in order to simplify the use of unions: if a union contains
3855 several structures that share a common initial sequence (see below), and if the union
3856 object currently contains one of these structures, it is permitted to inspect the common
3857 initial part of any of them anywhere that a declaration of the complete type of the union is
3858 visible. Two structures share a common initial sequence if corresponding members have
3859 compatible types (and, for bit-fields, the same widths) for a sequence of one or more
3862 EXAMPLE 1 If f is a function returning a structure or union, and x is a member of that structure or
3863 union, f().x is a valid postfix expression but is not an lvalue.
3868 struct s { int i; const int ci; };
3871 volatile struct s vs;</pre>
3872 the various members have the types:
3879 vs.ci volatile const int</pre>
3886 EXAMPLE 3 The following is a valid fragment:
3902 u.nf.doublenode = <a href="#3.14">3.14</a>;
3904 if (u.n.alltypes == 1)
3905 if (sin(u.nf.doublenode) == 0.0)
3907 The following is not a valid fragment (because the union type is not visible within function f):
3909 struct t1 { int m; };
3910 struct t2 { int m; };
3911 int f(struct t1 *p1, struct t2 *p2)
3913 if (p1->m < 0)
3914 p2->m = -p2->m;
3924 return f(&u.s1, &u.s2);
3927 <p><b> Forward references</b>: address and indirection operators (<a href="#6.5.3.2">6.5.3.2</a>), structure and union
3928 specifiers (<a href="#6.7.2.1">6.7.2.1</a>).
3932 <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
3933 store a value in the object, the appropriate part of the object representation of the value is reinterpreted
3934 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
3935 punning"). This might be a trap representation.
3937 <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
3938 its operand), the expression (&E)->MOS is the same as E.MOS.
3941 <h5><a name="6.5.2.4" href="#6.5.2.4">6.5.2.4 Postfix increment and decrement operators</a></h5>
3942 <h6>Constraints</h6>
3944 The operand of the postfix increment or decrement operator shall have qualified or
3945 unqualified real or pointer type and shall be a modifiable lvalue.
3948 The result of the postfix ++ operator is the value of the operand. After the result is
3949 obtained, the value of the operand is incremented. (That is, the value 1 of the appropriate
3950 type is added to it.) See the discussions of additive operators and compound assignment
3951 for information on constraints, types, and conversions and the effects of operations on
3952 pointers. The side effect of updating the stored value of the operand shall occur between
3953 the previous and the next sequence point.
3955 The postfix -- operator is analogous to the postfix ++ operator, except that the value of
3956 the operand is decremented (that is, the value 1 of the appropriate type is subtracted from
3958 <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>).
3960 <h5><a name="6.5.2.5" href="#6.5.2.5">6.5.2.5 Compound literals</a></h5>
3961 <h6>Constraints</h6>
3963 The type name shall specify an object type or an array of unknown size, but not a variable
3966 No initializer shall attempt to provide a value for an object not contained within the entire
3967 unnamed object specified by the compound literal.
3969 If the compound literal occurs outside the body of a function, the initializer list shall
3970 consist of constant expressions.
3973 A postfix expression that consists of a parenthesized type name followed by a brace-
3974 enclosed list of initializers is a compound literal. It provides an unnamed object whose
3975 value is given by the initializer list.<sup><a href="#note84"><b>84)</b></a></sup>
3977 If the type name specifies an array of unknown size, the size is determined by the
3978 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
3979 completed array type. Otherwise (when the type name specifies an object type), the type
3980 of the compound literal is that specified by the type name. In either case, the result is an
3986 The value of the compound literal is that of an unnamed object initialized by the
3987 initializer list. If the compound literal occurs outside the body of a function, the object
3988 has static storage duration; otherwise, it has automatic storage duration associated with
3989 the enclosing block.
3991 All the semantic rules and constraints for initializer lists in <a href="#6.7.8">6.7.8</a> are applicable to
3992 compound literals.<sup><a href="#note85"><b>85)</b></a></sup>
3994 String literals, and compound literals with const-qualified types, need not designate
3995 distinct objects.<sup><a href="#note86"><b>86)</b></a></sup>
3997 EXAMPLE 1 The file scope definition
3999 int *p = (int []){2, 4};</pre>
4000 initializes p to point to the first element of an array of two ints, the first having the value two and the
4001 second, four. The expressions in this compound literal are required to be constant. The unnamed object
4002 has static storage duration.
4005 EXAMPLE 2 In contrast, in
4014 p is assigned the address of the first element of an array of two ints, the first having the value previously
4015 pointed to by p and the second, zero. The expressions in this compound literal need not be constant. The
4016 unnamed object has automatic storage duration.
4019 EXAMPLE 3 Initializers with designations can be combined with compound literals. Structure objects
4020 created using compound literals can be passed to functions without depending on member order:
4022 drawline((struct point){.x=1, .y=1},
4023 (struct point){.x=3, .y=4});</pre>
4024 Or, if drawline instead expected pointers to struct point:
4026 drawline(&(struct point){.x=1, .y=1},
4027 &(struct point){.x=3, .y=4});</pre>
4030 EXAMPLE 4 A read-only compound literal can be specified through constructions like:
4032 (const float []){1e0, 1e1, 1e2, 1e3, 1e4, 1e5, 1e6}</pre>
4039 EXAMPLE 5 The following three expressions have different meanings:
4042 (char []){"/tmp/fileXXXXXX"}
4043 (const char []){"/tmp/fileXXXXXX"}</pre>
4044 The first always has static storage duration and has type array of char, but need not be modifiable; the last
4045 two have automatic storage duration when they occur within the body of a function, and the first of these
4049 EXAMPLE 6 Like string literals, const-qualified compound literals can be placed into read-only memory
4050 and can even be shared. For example,
4052 (const char []){"abc"} == "abc"</pre>
4053 might yield 1 if the literals' storage is shared.
4056 EXAMPLE 7 Since compound literals are unnamed, a single compound literal cannot specify a circularly
4057 linked object. For example, there is no way to write a self-referential compound literal that could be used
4058 as the function argument in place of the named object endless_zeros below:
4060 struct int_list { int car; struct int_list *cdr; };
4061 struct int_list endless_zeros = {0, &endless_zeros};
4062 eval(endless_zeros);</pre>
4065 EXAMPLE 8 Each compound literal creates only a single object in a given scope:
4067 struct s { int i; };
4070 struct s *p = 0, *q;
4073 q = p, p = &((struct s){ j++ });
4074 if (j < 2) goto again;
4075 return p == q && q->i == 1;
4077 The function f() always returns the value 1.
4079 Note that if an iteration statement were used instead of an explicit goto and a labeled statement, the
4080 lifetime of the unnamed object would be the body of the loop only, and on entry next time around p would
4081 have an indeterminate value, which would result in undefined behavior.
4083 <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>).
4087 <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
4088 or void only, and the result of a cast expression is not an lvalue.
4090 <p><small><a name="note85" href="#note85">85)</a> For example, subobjects without explicit initializers are initialized to zero.
4092 <p><small><a name="note86" href="#note86">86)</a> This allows implementations to share storage for string literals and constant compound literals with
4093 the same or overlapping representations.
4096 <h4><a name="6.5.3" href="#6.5.3">6.5.3 Unary operators</a></h4>
4104 unary-operator cast-expression
4105 sizeof unary-expression
4106 sizeof ( type-name )
4107 unary-operator: one of
4108 & * + - ~ !</pre>
4110 <h5><a name="6.5.3.1" href="#6.5.3.1">6.5.3.1 Prefix increment and decrement operators</a></h5>
4111 <h6>Constraints</h6>
4113 The operand of the prefix increment or decrement operator shall have qualified or
4114 unqualified real or pointer type and shall be a modifiable lvalue.
4117 The value of the operand of the prefix ++ operator is incremented. The result is the new
4118 value of the operand after incrementation. The expression ++E is equivalent to (E+=1).
4119 See the discussions of additive operators and compound assignment for information on
4120 constraints, types, side effects, and conversions and the effects of operations on pointers.
4122 The prefix -- operator is analogous to the prefix ++ operator, except that the value of the
4123 operand is decremented.
4124 <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>).
4126 <h5><a name="6.5.3.2" href="#6.5.3.2">6.5.3.2 Address and indirection operators</a></h5>
4127 <h6>Constraints</h6>
4129 The operand of the unary & operator shall be either a function designator, the result of a
4130 [] or unary * operator, or an lvalue that designates an object that is not a bit-field and is
4131 not declared with the register storage-class specifier.
4133 The operand of the unary * operator shall have pointer type.
4136 The unary & operator yields the address of its operand. If the operand has type ''type'',
4137 the result has type ''pointer to type''. If the operand is the result of a unary * operator,
4138 neither that operator nor the & operator is evaluated and the result is as if both were
4139 omitted, except that the constraints on the operators still apply and the result is not an
4140 lvalue. Similarly, if the operand is the result of a [] operator, neither the & operator nor
4142 the unary * that is implied by the [] is evaluated and the result is as if the & operator
4143 were removed and the [] operator were changed to a + operator. Otherwise, the result is
4144 a pointer to the object or function designated by its operand.
4146 The unary * operator denotes indirection. If the operand points to a function, the result is
4147 a function designator; if it points to an object, the result is an lvalue designating the
4148 object. If the operand has type ''pointer to type'', the result has type ''type''. If an
4149 invalid value has been assigned to the pointer, the behavior of the unary * operator is
4150 undefined.<sup><a href="#note87"><b>87)</b></a></sup>
4151 <p><b> Forward references</b>: storage-class specifiers (<a href="#6.7.1">6.7.1</a>), structure and union specifiers
4152 (<a href="#6.7.2.1">6.7.2.1</a>).
4155 <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
4156 always true that if E is a function designator or an lvalue that is a valid operand of the unary &
4157 operator, *&E is a function designator or an lvalue equal to E. If *P is an lvalue and T is the name of
4158 an object pointer type, *(T)P is an lvalue that has a type compatible with that to which T points.
4159 Among the invalid values for dereferencing a pointer by the unary * operator are a null pointer, an
4160 address inappropriately aligned for the type of object pointed to, and the address of an object after the
4161 end of its lifetime.
4164 <h5><a name="6.5.3.3" href="#6.5.3.3">6.5.3.3 Unary arithmetic operators</a></h5>
4165 <h6>Constraints</h6>
4167 The operand of the unary + or - operator shall have arithmetic type; of the ~ operator,
4168 integer type; of the ! operator, scalar type.
4171 The result of the unary + operator is the value of its (promoted) operand. The integer
4172 promotions are performed on the operand, and the result has the promoted type.
4174 The result of the unary - operator is the negative of its (promoted) operand. The integer
4175 promotions are performed on the operand, and the result has the promoted type.
4177 The result of the ~ operator is the bitwise complement of its (promoted) operand (that is,
4178 each bit in the result is set if and only if the corresponding bit in the converted operand is
4179 not set). The integer promotions are performed on the operand, and the result has the
4180 promoted type. If the promoted type is an unsigned type, the expression ~E is equivalent
4181 to the maximum value representable in that type minus E.
4183 The result of the logical negation operator ! is 0 if the value of its operand compares
4184 unequal to 0, 1 if the value of its operand compares equal to 0. The result has type int.
4185 The expression !E is equivalent to (0==E).
4192 <h5><a name="6.5.3.4" href="#6.5.3.4">6.5.3.4 The sizeof operator</a></h5>
4193 <h6>Constraints</h6>
4195 The sizeof operator shall not be applied to an expression that has function type or an
4196 incomplete type, to the parenthesized name of such a type, or to an expression that
4197 designates a bit-field member.
4200 The sizeof operator yields the size (in bytes) of its operand, which may be an
4201 expression or the parenthesized name of a type. The size is determined from the type of
4202 the operand. The result is an integer. If the type of the operand is a variable length array
4203 type, the operand is evaluated; otherwise, the operand is not evaluated and the result is an
4206 When applied to an operand that has type char, unsigned char, or signed char,
4207 (or a qualified version thereof) the result is 1. When applied to an operand that has array
4208 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
4209 that has structure or union type, the result is the total number of bytes in such an object,
4210 including internal and trailing padding.
4212 The value of the result is implementation-defined, and its type (an unsigned integer type)
4213 is size_t, defined in <a href="#7.17"><stddef.h></a> (and other headers).
4215 EXAMPLE 1 A principal use of the sizeof operator is in communication with routines such as storage
4216 allocators and I/O systems. A storage-allocation function might accept a size (in bytes) of an object to
4217 allocate and return a pointer to void. For example:
4219 extern void *alloc(size_t);
4220 double *dp = alloc(sizeof *dp);</pre>
4221 The implementation of the alloc function should ensure that its return value is aligned suitably for
4222 conversion to a pointer to double.
4225 EXAMPLE 2 Another use of the sizeof operator is to compute the number of elements in an array:
4227 sizeof array / sizeof array[0]</pre>
4230 EXAMPLE 3 In this example, the size of a variable length array is computed and returned from a
4233 #include <a href="#7.17"><stddef.h></a>
4234 size_t fsize3(int n)
4236 char b[n+3]; // variable length array
4237 return sizeof b; // execution time sizeof
4247 size = fsize3(10); // fsize3 returns 13
4251 <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>),
4252 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>).
4255 <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
4256 size of the adjusted (pointer) type (see <a href="#6.9.1">6.9.1</a>).
4259 <h4><a name="6.5.4" href="#6.5.4">6.5.4 Cast operators</a></h4>
4265 ( type-name ) cast-expression</pre>
4266 <h6>Constraints</h6>
4268 Unless the type name specifies a void type, the type name shall specify qualified or
4269 unqualified scalar type and the operand shall have scalar type.
4271 Conversions that involve pointers, other than where permitted by the constraints of
4272 <a href="#6.5.16.1">6.5.16.1</a>, shall be specified by means of an explicit cast.
4275 Preceding an expression by a parenthesized type name converts the value of the
4276 expression to the named type. This construction is called a cast.<sup><a href="#note89"><b>89)</b></a></sup> A cast that specifies
4277 no conversion has no effect on the type or value of an expression.
4279 If the value of the expression is represented with greater precision or range than required
4280 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
4281 type of the expression is the same as the named type.
4282 <p><b> Forward references</b>: equality operators (<a href="#6.5.9">6.5.9</a>), function declarators (including
4283 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>).
4291 <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
4292 unqualified version of the type.
4295 <h4><a name="6.5.5" href="#6.5.5">6.5.5 Multiplicative operators</a></h4>
4299 multiplicative-expression:
4301 multiplicative-expression * cast-expression
4302 multiplicative-expression / cast-expression
4303 multiplicative-expression % cast-expression</pre>
4304 <h6>Constraints</h6>
4306 Each of the operands shall have arithmetic type. The operands of the % operator shall
4310 The usual arithmetic conversions are performed on the operands.
4312 The result of the binary * operator is the product of the operands.
4314 The result of the / operator is the quotient from the division of the first operand by the
4315 second; the result of the % operator is the remainder. In both operations, if the value of
4316 the second operand is zero, the behavior is undefined.
4318 When integers are divided, the result of the / operator is the algebraic quotient with any
4319 fractional part discarded.<sup><a href="#note90"><b>90)</b></a></sup> If the quotient a/b is representable, the expression
4320 (a/b)*b + a%b shall equal a.
4323 <p><small><a name="note90" href="#note90">90)</a> This is often called ''truncation toward zero''.
4326 <h4><a name="6.5.6" href="#6.5.6">6.5.6 Additive operators</a></h4>
4330 additive-expression:
4331 multiplicative-expression
4332 additive-expression + multiplicative-expression
4333 additive-expression - multiplicative-expression</pre>
4334 <h6>Constraints</h6>
4336 For addition, either both operands shall have arithmetic type, or one operand shall be a
4337 pointer to an object type and the other shall have integer type. (Incrementing is
4338 equivalent to adding 1.)
4340 For subtraction, one of the following shall hold:
4342 <li> both operands have arithmetic type;
4347 <li> both operands are pointers to qualified or unqualified versions of compatible object
4349 <li> the left operand is a pointer to an object type and the right operand has integer type.
4351 (Decrementing is equivalent to subtracting 1.)
4354 If both operands have arithmetic type, the usual arithmetic conversions are performed on
4357 The result of the binary + operator is the sum of the operands.
4359 The result of the binary - operator is the difference resulting from the subtraction of the
4360 second operand from the first.
4362 For the purposes of these operators, a pointer to an object that is not an element of an
4363 array behaves the same as a pointer to the first element of an array of length one with the
4364 type of the object as its element type.
4366 When an expression that has integer type is added to or subtracted from a pointer, the
4367 result has the type of the pointer operand. If the pointer operand points to an element of
4368 an array object, and the array is large enough, the result points to an element offset from
4369 the original element such that the difference of the subscripts of the resulting and original
4370 array elements equals the integer expression. In other words, if the expression P points to
4371 the i-th element of an array object, the expressions (P)+N (equivalently, N+(P)) and
4372 (P)-N (where N has the value n) point to, respectively, the i+n-th and i-n-th elements of
4373 the array object, provided they exist. Moreover, if the expression P points to the last
4374 element of an array object, the expression (P)+1 points one past the last element of the
4375 array object, and if the expression Q points one past the last element of an array object,
4376 the expression (Q)-1 points to the last element of the array object. If both the pointer
4377 operand and the result point to elements of the same array object, or one past the last
4378 element of the array object, the evaluation shall not produce an overflow; otherwise, the
4379 behavior is undefined. If the result points one past the last element of the array object, it
4380 shall not be used as the operand of a unary * operator that is evaluated.
4382 When two pointers are subtracted, both shall point to elements of the same array object,
4383 or one past the last element of the array object; the result is the difference of the
4384 subscripts of the two array elements. The size of the result is implementation-defined,
4385 and its type (a signed integer type) is ptrdiff_t defined in the <a href="#7.17"><stddef.h></a> header.
4386 If the result is not representable in an object of that type, the behavior is undefined. In
4387 other words, if the expressions P and Q point to, respectively, the i-th and j-th elements of
4388 an array object, the expression (P)-(Q) has the value i-j provided the value fits in an
4389 object of type ptrdiff_t. Moreover, if the expression P points either to an element of
4390 an array object or one past the last element of an array object, and the expression Q points
4391 to the last element of the same array object, the expression ((Q)+1)-(P) has the same
4393 value as ((Q)-(P))+1 and as -((P)-((Q)+1)), and has the value zero if the
4394 expression P points one past the last element of the array object, even though the
4395 expression (Q)+1 does not point to an element of the array object.<sup><a href="#note91"><b>91)</b></a></sup>
4397 EXAMPLE Pointer arithmetic is well defined with pointers to variable length array types.
4403 int (*p)[m] = a; // p == &a[0]
4404 p += 1; // p == &a[1]
4405 (*p)[2] = 99; // a[1][2] == 99
4406 n = p - a; // n == 1
4408 If array a in the above example were declared to be an array of known constant size, and pointer p were
4409 declared to be a pointer to an array of the same known constant size (pointing to a), the results would be
4412 <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>
4413 (<a href="#7.17">7.17</a>).
4416 <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
4417 this scheme the integer expression added to or subtracted from the converted pointer is first multiplied
4418 by the size of the object originally pointed to, and the resulting pointer is converted back to the
4419 original type. For pointer subtraction, the result of the difference between the character pointers is
4420 similarly divided by the size of the object originally pointed to.
4421 When viewed in this way, an implementation need only provide one extra byte (which may overlap
4422 another object in the program) just after the end of the object in order to satisfy the ''one past the last
4423 element'' requirements.
4426 <h4><a name="6.5.7" href="#6.5.7">6.5.7 Bitwise shift operators</a></h4>
4432 shift-expression << additive-expression
4433 shift-expression >> additive-expression</pre>
4434 <h6>Constraints</h6>
4436 Each of the operands shall have integer type.
4439 The integer promotions are performed on each of the operands. The type of the result is
4440 that of the promoted left operand. If the value of the right operand is negative or is
4441 greater than or equal to the width of the promoted left operand, the behavior is undefined.
4448 The result of E1 << E2 is E1 left-shifted E2 bit positions; vacated bits are filled with
4449 zeros. If E1 has an unsigned type, the value of the result is E1 x 2E2 , reduced modulo
4450 one more than the maximum value representable in the result type. If E1 has a signed
4451 type and nonnegative value, and E1 x 2E2 is representable in the result type, then that is
4452 the resulting value; otherwise, the behavior is undefined.
4454 The result of E1 >> E2 is E1 right-shifted E2 bit positions. If E1 has an unsigned type
4455 or if E1 has a signed type and a nonnegative value, the value of the result is the integral
4456 part of the quotient of E1 / 2E2 . If E1 has a signed type and a negative value, the
4457 resulting value is implementation-defined.
4459 <h4><a name="6.5.8" href="#6.5.8">6.5.8 Relational operators</a></h4>
4463 relational-expression:
4465 relational-expression < shift-expression
4466 relational-expression > shift-expression
4467 relational-expression <= shift-expression
4468 relational-expression >= shift-expression</pre>
4469 <h6>Constraints</h6>
4471 One of the following shall hold:
4473 <li> both operands have real type;
4474 <li> both operands are pointers to qualified or unqualified versions of compatible object
4476 <li> both operands are pointers to qualified or unqualified versions of compatible
4481 If both of the operands have arithmetic type, the usual arithmetic conversions are
4484 For the purposes of these operators, a pointer to an object that is not an element of an
4485 array behaves the same as a pointer to the first element of an array of length one with the
4486 type of the object as its element type.
4488 When two pointers are compared, the result depends on the relative locations in the
4489 address space of the objects pointed to. If two pointers to object or incomplete types both
4490 point to the same object, or both point one past the last element of the same array object,
4491 they compare equal. If the objects pointed to are members of the same aggregate object,
4492 pointers to structure members declared later compare greater than pointers to members
4493 declared earlier in the structure, and pointers to array elements with larger subscript
4495 values compare greater than pointers to elements of the same array with lower subscript
4496 values. All pointers to members of the same union object compare equal. If the
4497 expression P points to an element of an array object and the expression Q points to the
4498 last element of the same array object, the pointer expression Q+1 compares greater than
4499 P. In all other cases, the behavior is undefined.
4501 Each of the operators < (less than), > (greater than), <= (less than or equal to), and >=
4502 (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>
4503 The result has type int.
4506 <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
4507 means (a<b)<c; in other words, ''if a is less than b, compare 1 to c; otherwise, compare 0 to c''.
4510 <h4><a name="6.5.9" href="#6.5.9">6.5.9 Equality operators</a></h4>
4514 equality-expression:
4515 relational-expression
4516 equality-expression == relational-expression
4517 equality-expression != relational-expression</pre>
4518 <h6>Constraints</h6>
4520 One of the following shall hold:
4522 <li> both operands have arithmetic type;
4523 <li> both operands are pointers to qualified or unqualified versions of compatible types;
4524 <li> one operand is a pointer to an object or incomplete type and the other is a pointer to a
4525 qualified or unqualified version of void; or
4526 <li> one operand is a pointer and the other is a null pointer constant.
4530 The == (equal to) and != (not equal to) operators are analogous to the relational
4531 operators except for their lower precedence.<sup><a href="#note93"><b>93)</b></a></sup> Each of the operators yields 1 if the
4532 specified relation is true and 0 if it is false. The result has type int. For any pair of
4533 operands, exactly one of the relations is true.
4535 If both of the operands have arithmetic type, the usual arithmetic conversions are
4536 performed. Values of complex types are equal if and only if both their real parts are equal
4537 and also their imaginary parts are equal. Any two values of arithmetic types from
4538 different type domains are equal if and only if the results of their conversions to the
4539 (complex) result type determined by the usual arithmetic conversions are equal.
4544 Otherwise, at least one operand is a pointer. If one operand is a pointer and the other is a
4545 null pointer constant, the null pointer constant is converted to the type of the pointer. If
4546 one operand is a pointer to an object or incomplete type and the other is a pointer to a
4547 qualified or unqualified version of void, the former is converted to the type of the latter.
4549 Two pointers compare equal if and only if both are null pointers, both are pointers to the
4550 same object (including a pointer to an object and a subobject at its beginning) or function,
4551 both are pointers to one past the last element of the same array object, or one is a pointer
4552 to one past the end of one array object and the other is a pointer to the start of a different
4553 array object that happens to immediately follow the first array object in the address
4554 space.<sup><a href="#note94"><b>94)</b></a></sup>
4556 For the purposes of these operators, a pointer to an object that is not an element of an
4557 array behaves the same as a pointer to the first element of an array of length one with the
4558 type of the object as its element type.
4561 <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.
4563 <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
4564 adjacent members of a structure with no padding between them, or because the implementation chose
4565 to place them so, even though they are unrelated. If prior invalid pointer operations (such as accesses
4566 outside array bounds) produced undefined behavior, subsequent comparisons also produce undefined
4570 <h4><a name="6.5.10" href="#6.5.10">6.5.10 Bitwise AND operator</a></h4>
4576 AND-expression & equality-expression</pre>
4577 <h6>Constraints</h6>
4579 Each of the operands shall have integer type.
4582 The usual arithmetic conversions are performed on the operands.
4584 The result of the binary & operator is the bitwise AND of the operands (that is, each bit in
4585 the result is set if and only if each of the corresponding bits in the converted operands is
4593 <h4><a name="6.5.11" href="#6.5.11">6.5.11 Bitwise exclusive OR operator</a></h4>
4597 exclusive-OR-expression:
4599 exclusive-OR-expression ^ AND-expression</pre>
4600 <h6>Constraints</h6>
4602 Each of the operands shall have integer type.
4605 The usual arithmetic conversions are performed on the operands.
4607 The result of the ^ operator is the bitwise exclusive OR of the operands (that is, each bit
4608 in the result is set if and only if exactly one of the corresponding bits in the converted
4611 <h4><a name="6.5.12" href="#6.5.12">6.5.12 Bitwise inclusive OR operator</a></h4>
4615 inclusive-OR-expression:
4616 exclusive-OR-expression
4617 inclusive-OR-expression | exclusive-OR-expression</pre>
4618 <h6>Constraints</h6>
4620 Each of the operands shall have integer type.
4623 The usual arithmetic conversions are performed on the operands.
4625 The result of the | operator is the bitwise inclusive OR of the operands (that is, each bit in
4626 the result is set if and only if at least one of the corresponding bits in the converted
4630 <h4><a name="6.5.13" href="#6.5.13">6.5.13 Logical AND operator</a></h4>
4634 logical-AND-expression:
4635 inclusive-OR-expression
4636 logical-AND-expression && inclusive-OR-expression</pre>
4637 <h6>Constraints</h6>
4639 Each of the operands shall have scalar type.
4642 The && operator shall yield 1 if both of its operands compare unequal to 0; otherwise, it
4643 yields 0. The result has type int.
4645 Unlike the bitwise binary & operator, the && operator guarantees left-to-right evaluation;
4646 there is a sequence point after the evaluation of the first operand. If the first operand
4647 compares equal to 0, the second operand is not evaluated.
4649 <h4><a name="6.5.14" href="#6.5.14">6.5.14 Logical OR operator</a></h4>
4653 logical-OR-expression:
4654 logical-AND-expression
4655 logical-OR-expression || logical-AND-expression</pre>
4656 <h6>Constraints</h6>
4658 Each of the operands shall have scalar type.
4661 The || operator shall yield 1 if either of its operands compare unequal to 0; otherwise, it
4662 yields 0. The result has type int.
4664 Unlike the bitwise | operator, the || operator guarantees left-to-right evaluation; there is
4665 a sequence point after the evaluation of the first operand. If the first operand compares
4666 unequal to 0, the second operand is not evaluated.
4669 <h4><a name="6.5.15" href="#6.5.15">6.5.15 Conditional operator</a></h4>
4673 conditional-expression:
4674 logical-OR-expression
4675 logical-OR-expression ? expression : conditional-expression</pre>
4676 <h6>Constraints</h6>
4678 The first operand shall have scalar type.
4680 One of the following shall hold for the second and third operands:
4682 <li> both operands have arithmetic type;
4683 <li> both operands have the same structure or union type;
4684 <li> both operands have void type;
4685 <li> both operands are pointers to qualified or unqualified versions of compatible types;
4686 <li> one operand is a pointer and the other is a null pointer constant; or
4687 <li> one operand is a pointer to an object or incomplete type and the other is a pointer to a
4688 qualified or unqualified version of void.
4692 The first operand is evaluated; there is a sequence point after its evaluation. The second
4693 operand is evaluated only if the first compares unequal to 0; the third operand is evaluated
4694 only if the first compares equal to 0; the result is the value of the second or third operand
4695 (whichever is evaluated), converted to the type described below.<sup><a href="#note95"><b>95)</b></a></sup> If an attempt is made
4696 to modify the result of a conditional operator or to access it after the next sequence point,
4697 the behavior is undefined.
4699 If both the second and third operands have arithmetic type, the result type that would be
4700 determined by the usual arithmetic conversions, were they applied to those two operands,
4701 is the type of the result. If both the operands have structure or union type, the result has
4702 that type. If both operands have void type, the result has void type.
4704 If both the second and third operands are pointers or one is a null pointer constant and the
4705 other is a pointer, the result type is a pointer to a type qualified with all the type qualifiers
4706 of the types pointed-to by both operands. Furthermore, if both operands are pointers to
4707 compatible types or to differently qualified versions of compatible types, the result type is
4708 a pointer to an appropriately qualified version of the composite type; if one operand is a
4709 null pointer constant, the result has the type of the other operand; otherwise, one operand
4710 is a pointer to void or a qualified version of void, in which case the result type is a
4713 pointer to an appropriately qualified version of void.
4715 EXAMPLE The common type that results when the second and third operands are pointers is determined
4716 in two independent stages. The appropriate qualifiers, for example, do not depend on whether the two
4717 pointers have compatible types.
4719 Given the declarations
4726 const char *c_cp;</pre>
4727 the third column in the following table is the common type that is the result of a conditional expression in
4728 which the first two columns are the second and third operands (in either order):
4730 c_vp c_ip const void *
4731 v_ip 0 volatile int *
4732 c_ip v_ip const volatile int *
4733 vp c_cp const void *
4739 <p><small><a name="note95" href="#note95">95)</a> A conditional expression does not yield an lvalue.
4742 <h4><a name="6.5.16" href="#6.5.16">6.5.16 Assignment operators</a></h4>
4746 assignment-expression:
4747 conditional-expression
4748 unary-expression assignment-operator assignment-expression
4749 assignment-operator: one of
4750 = *= /= %= += -= <<= >>= &= ^= |=</pre>
4751 <h6>Constraints</h6>
4753 An assignment operator shall have a modifiable lvalue as its left operand.
4756 An assignment operator stores a value in the object designated by the left operand. An
4757 assignment expression has the value of the left operand after the assignment, but is not an
4758 lvalue. The type of an assignment expression is the type of the left operand unless the
4759 left operand has qualified type, in which case it is the unqualified version of the type of
4760 the left operand. The side effect of updating the stored value of the left operand shall
4761 occur between the previous and the next sequence point.
4763 The order of evaluation of the operands is unspecified. If an attempt is made to modify
4764 the result of an assignment operator or to access it after the next sequence point, the
4765 behavior is undefined.
4768 <h5><a name="6.5.16.1" href="#6.5.16.1">6.5.16.1 Simple assignment</a></h5>
4769 <h6>Constraints</h6>
4771 One of the following shall hold:<sup><a href="#note96"><b>96)</b></a></sup>
4773 <li> the left operand has qualified or unqualified arithmetic type and the right has
4775 <li> the left operand has a qualified or unqualified version of a structure or union type
4776 compatible with the type of the right;
4777 <li> both operands are pointers to qualified or unqualified versions of compatible types,
4778 and the type pointed to by the left has all the qualifiers of the type pointed to by the
4780 <li> one operand is a pointer to an object or incomplete type and the other is a pointer to a
4781 qualified or unqualified version of void, and the type pointed to by the left has all
4782 the qualifiers of the type pointed to by the right;
4783 <li> the left operand is a pointer and the right is a null pointer constant; or
4784 <li> the left operand has type _Bool and the right is a pointer.
4788 In simple assignment (=), the value of the right operand is converted to the type of the
4789 assignment expression and replaces the value stored in the object designated by the left
4792 If the value being stored in an object is read from another object that overlaps in any way
4793 the storage of the first object, then the overlap shall be exact and the two objects shall
4794 have qualified or unqualified versions of a compatible type; otherwise, the behavior is
4797 EXAMPLE 1 In the program fragment
4802 if ((c = f()) == -1)
4804 the int value returned by the function may be truncated when stored in the char, and then converted back
4805 to int width prior to the comparison. In an implementation in which ''plain'' char has the same range of
4806 values as unsigned char (and char is narrower than int), the result of the conversion cannot be
4811 negative, so the operands of the comparison can never compare equal. Therefore, for full portability, the
4812 variable c should be declared as int.
4815 EXAMPLE 2 In the fragment:
4821 the value of i is converted to the type of the assignment expression c = i, that is, char type. The value
4822 of the expression enclosed in parentheses is then converted to the type of the outer assignment expression,
4823 that is, long int type.
4826 EXAMPLE 3 Consider the fragment:
4831 cpp = &p; // constraint violation
4832 *cpp = &c; // valid
4833 *p = 0; // valid</pre>
4834 The first assignment is unsafe because it would allow the following valid code to attempt to change the
4835 value of the const object c.
4839 <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
4840 (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
4841 qualifiers that were applied to the type category of the expression (for example, it removes const but
4842 not volatile from the type int volatile * const).
4845 <h5><a name="6.5.16.2" href="#6.5.16.2">6.5.16.2 Compound assignment</a></h5>
4846 <h6>Constraints</h6>
4848 For the operators += and -= only, either the left operand shall be a pointer to an object
4849 type and the right shall have integer type, or the left operand shall have qualified or
4850 unqualified arithmetic type and the right shall have arithmetic type.
4852 For the other operators, each operand shall have arithmetic type consistent with those
4853 allowed by the corresponding binary operator.
4856 A compound assignment of the form E1 op = E2 differs from the simple assignment
4857 expression E1 = E1 op (E2) only in that the lvalue E1 is evaluated only once.
4860 <h4><a name="6.5.17" href="#6.5.17">6.5.17 Comma operator</a></h4>
4865 assignment-expression
4866 expression , assignment-expression</pre>
4869 The left operand of a comma operator is evaluated as a void expression; there is a
4870 sequence point after its evaluation. Then the right operand is evaluated; the result has its
4871 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
4872 access it after the next sequence point, the behavior is undefined.
4874 EXAMPLE As indicated by the syntax, the comma operator (as described in this subclause) cannot
4875 appear in contexts where a comma is used to separate items in a list (such as arguments to functions or lists
4876 of initializers). On the other hand, it can be used within a parenthesized expression or within the second
4877 expression of a conditional operator in such contexts. In the function call
4879 f(a, (t=3, t+2), c)</pre>
4880 the function has three arguments, the second of which has the value 5.
4882 <p><b> Forward references</b>: initialization (<a href="#6.7.8">6.7.8</a>).
4890 <p><small><a name="note97" href="#note97">97)</a> A comma operator does not yield an lvalue.
4893 <h3><a name="6.6" href="#6.6">6.6 Constant expressions</a></h3>
4897 constant-expression:
4898 conditional-expression</pre>
4899 <h6>Description</h6>
4901 A constant expression can be evaluated during translation rather than runtime, and
4902 accordingly may be used in any place that a constant may be.
4903 <h6>Constraints</h6>
4905 Constant expressions shall not contain assignment, increment, decrement, function-call,
4906 or comma operators, except when they are contained within a subexpression that is not
4907 evaluated.<sup><a href="#note98"><b>98)</b></a></sup>
4909 Each constant expression shall evaluate to a constant that is in the range of representable
4910 values for its type.
4913 An expression that evaluates to a constant is required in several contexts. If a floating
4914 expression is evaluated in the translation environment, the arithmetic precision and range
4915 shall be at least as great as if the expression were being evaluated in the execution
4918 An integer constant expression<sup><a href="#note99"><b>99)</b></a></sup> shall have integer type and shall only have operands
4919 that are integer constants, enumeration constants, character constants, sizeof
4920 expressions whose results are integer constants, and floating constants that are the
4921 immediate operands of casts. Cast operators in an integer constant expression shall only
4922 convert arithmetic types to integer types, except as part of an operand to the sizeof
4925 More latitude is permitted for constant expressions in initializers. Such a constant
4926 expression shall be, or evaluate to, one of the following:
4928 <li> an arithmetic constant expression,
4929 <li> a null pointer constant,
4935 <li> an address constant, or
4936 <li> an address constant for an object type plus or minus an integer constant expression.
4939 An arithmetic constant expression shall have arithmetic type and shall only have
4940 operands that are integer constants, floating constants, enumeration constants, character
4941 constants, and sizeof expressions. Cast operators in an arithmetic constant expression
4942 shall only convert arithmetic types to arithmetic types, except as part of an operand to a
4943 sizeof operator whose result is an integer constant.
4945 An address constant is a null pointer, a pointer to an lvalue designating an object of static
4946 storage duration, or a pointer to a function designator; it shall be created explicitly using
4947 the unary & operator or an integer constant cast to pointer type, or implicitly by the use of
4948 an expression of array or function type. The array-subscript [] and member-access .
4949 and -> operators, the address & and indirection * unary operators, and pointer casts may
4950 be used in the creation of an address constant, but the value of an object shall not be
4951 accessed by use of these operators.
4953 An implementation may accept other forms of constant expressions.
4955 The semantic rules for the evaluation of a constant expression are the same as for
4956 nonconstant expressions.<sup><a href="#note100"><b>100)</b></a></sup>
4957 <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>).
4965 <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>).
4967 <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
4968 value of an enumeration constant, the size of an array, or the value of a case constant. Further
4969 constraints that apply to the integer constant expressions used in conditional-inclusion preprocessing
4970 directives are discussed in <a href="#6.10.1">6.10.1</a>.
4972 <p><small><a name="note100" href="#note100">100)</a> Thus, in the following initialization,
4975 static int i = 2 || 1 / 0;</pre>
4976 the expression is a valid integer constant expression with value one.
4979 <h3><a name="6.7" href="#6.7">6.7 Declarations</a></h3>
4984 declaration-specifiers init-declarator-listopt ;
4985 declaration-specifiers:
4986 storage-class-specifier declaration-specifiersopt
4987 type-specifier declaration-specifiersopt
4988 type-qualifier declaration-specifiersopt
4989 function-specifier declaration-specifiersopt
4990 init-declarator-list:
4992 init-declarator-list , init-declarator
4995 declarator = initializer</pre>
4996 <h6>Constraints</h6>
4998 A declaration shall declare at least a declarator (other than the parameters of a function or
4999 the members of a structure or union), a tag, or the members of an enumeration.
5001 If an identifier has no linkage, there shall be no more than one declaration of the identifier
5002 (in a declarator or type specifier) with the same scope and in the same name space, except
5003 for tags as specified in <a href="#6.7.2.3">6.7.2.3</a>.
5005 All declarations in the same scope that refer to the same object or function shall specify
5009 A declaration specifies the interpretation and attributes of a set of identifiers. A definition
5010 of an identifier is a declaration for that identifier that:
5012 <li> for an object, causes storage to be reserved for that object;
5013 <li> for a function, includes the function body;<sup><a href="#note101"><b>101)</b></a></sup>
5014 <li> for an enumeration constant or typedef name, is the (only) declaration of the
5018 The declaration specifiers consist of a sequence of specifiers that indicate the linkage,
5019 storage duration, and part of the type of the entities that the declarators denote. The init-
5020 declarator-list is a comma-separated sequence of declarators, each of which may have
5023 additional type information, or an initializer, or both. The declarators contain the
5024 identifiers (if any) being declared.
5026 If an identifier for an object is declared with no linkage, the type for the object shall be
5027 complete by the end of its declarator, or by the end of its init-declarator if it has an
5028 initializer; in the case of function parameters (including in prototypes), it is the adjusted
5029 type (see <a href="#6.7.5.3">6.7.5.3</a>) that is required to be complete.
5030 <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
5031 (<a href="#6.7.8">6.7.8</a>).
5034 <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>.
5037 <h4><a name="6.7.1" href="#6.7.1">6.7.1 Storage-class specifiers</a></h4>
5041 storage-class-specifier:
5047 <h6>Constraints</h6>
5049 At most, one storage-class specifier may be given in the declaration specifiers in a
5050 declaration.<sup><a href="#note102"><b>102)</b></a></sup>
5053 The typedef specifier is called a ''storage-class specifier'' for syntactic convenience
5054 only; it is discussed in <a href="#6.7.7">6.7.7</a>. The meanings of the various linkages and storage durations
5055 were discussed in <a href="#6.2.2">6.2.2</a> and <a href="#6.2.4">6.2.4</a>.
5057 A declaration of an identifier for an object with storage-class specifier register
5058 suggests that access to the object be as fast as possible. The extent to which such
5059 suggestions are effective is implementation-defined.<sup><a href="#note103"><b>103)</b></a></sup>
5061 The declaration of an identifier for a function that has block scope shall have no explicit
5062 storage-class specifier other than extern.
5068 If an aggregate or union object is declared with a storage-class specifier other than
5069 typedef, the properties resulting from the storage-class specifier, except with respect to
5070 linkage, also apply to the members of the object, and so on recursively for any aggregate
5071 or union member objects.
5072 <p><b> Forward references</b>: type definitions (<a href="#6.7.7">6.7.7</a>).
5075 <p><small><a name="note102" href="#note102">102)</a> See ''future language directions'' (<a href="#6.11.5">6.11.5</a>).
5077 <p><small><a name="note103" href="#note103">103)</a> The implementation may treat any register declaration simply as an auto declaration. However,
5078 whether or not addressable storage is actually used, the address of any part of an object declared with
5079 storage-class specifier register cannot be computed, either explicitly (by use of the unary &
5080 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
5081 <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
5085 <h4><a name="6.7.2" href="#6.7.2">6.7.2 Type specifiers</a></h4>
5101 struct-or-union-specifier *
5104 <h6>Constraints</h6>
5106 At least one type specifier shall be given in the declaration specifiers in each declaration,
5107 and in the specifier-qualifier list in each struct declaration and type name. Each list of
5108 type specifiers shall be one of the following sets (delimited by commas, when there is
5109 more than one set on a line); the type specifiers may occur in any order, possibly
5110 intermixed with the other declaration specifiers.
5116 <li> short, signed short, short int, or signed short int
5117 <li> unsigned short, or unsigned short int
5118 <li> int, signed, or signed int
5120 <li> unsigned, or unsigned int
5121 <li> long, signed long, long int, or signed long int
5122 <li> unsigned long, or unsigned long int
5123 <li> long long, signed long long, long long int, or
5124 signed long long int
5125 <li> unsigned long long, or unsigned long long int
5131 <li> double _Complex
5132 <li> long double _Complex
5133 <li> struct or union specifier *
5138 The type specifier _Complex shall not be used if the implementation does not provide
5139 complex types.<sup><a href="#note104"><b>104)</b></a></sup>
5142 Specifiers for structures, unions, and enumerations are discussed in <a href="#6.7.2.1">6.7.2.1</a> through
5143 <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
5144 other types are discussed in <a href="#6.2.5">6.2.5</a>.
5146 Each of the comma-separated sets designates the same type, except that for bit-fields, it is
5147 implementation-defined whether the specifier int designates the same type as signed
5148 int or the same type as unsigned int.
5149 <p><b> Forward references</b>: enumeration specifiers (<a href="#6.7.2.2">6.7.2.2</a>), structure and union specifiers
5150 (<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>).
5158 <p><small><a name="note104" href="#note104">104)</a> Freestanding implementations are not required to provide complex types. *
5161 <h5><a name="6.7.2.1" href="#6.7.2.1">6.7.2.1 Structure and union specifiers</a></h5>
5165 struct-or-union-specifier:
5166 struct-or-union identifieropt { struct-declaration-list }
5167 struct-or-union identifier
5171 struct-declaration-list:
5173 struct-declaration-list struct-declaration
5175 specifier-qualifier-list struct-declarator-list ;
5176 specifier-qualifier-list:
5177 type-specifier specifier-qualifier-listopt
5178 type-qualifier specifier-qualifier-listopt
5179 struct-declarator-list:
5181 struct-declarator-list , struct-declarator
5184 declaratoropt : constant-expression</pre>
5185 <h6>Constraints</h6>
5187 A structure or union shall not contain a member with incomplete or function type (hence,
5188 a structure shall not contain an instance of itself, but may contain a pointer to an instance
5189 of itself), except that the last member of a structure with more than one named member
5190 may have incomplete array type; such a structure (and any union containing, possibly
5191 recursively, a member that is such a structure) shall not be a member of a structure or an
5192 element of an array.
5194 The expression that specifies the width of a bit-field shall be an integer constant
5195 expression with a nonnegative value that does not exceed the width of an object of the
5196 type that would be specified were the colon and expression omitted. If the value is zero,
5197 the declaration shall have no declarator.
5199 A bit-field shall have a type that is a qualified or unqualified version of _Bool, signed
5200 int, unsigned int, or some other implementation-defined type.
5204 As discussed in <a href="#6.2.5">6.2.5</a>, a structure is a type consisting of a sequence of members, whose
5205 storage is allocated in an ordered sequence, and a union is a type consisting of a sequence
5206 of members whose storage overlap.
5208 Structure and union specifiers have the same form. The keywords struct and union
5209 indicate that the type being specified is, respectively, a structure type or a union type.
5211 The presence of a struct-declaration-list in a struct-or-union-specifier declares a new type,
5212 within a translation unit. The struct-declaration-list is a sequence of declarations for the
5213 members of the structure or union. If the struct-declaration-list contains no named
5214 members, the behavior is undefined. The type is incomplete until after the } that
5215 terminates the list.
5217 A member of a structure or union may have any object type other than a variably
5218 modified type.<sup><a href="#note105"><b>105)</b></a></sup> In addition, a member may be declared to consist of a specified
5219 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
5220 width is preceded by a colon.
5222 A bit-field is interpreted as a signed or unsigned integer type consisting of the specified
5223 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
5224 _Bool, the value of the bit-field shall compare equal to the value stored.
5226 An implementation may allocate any addressable storage unit large enough to hold a bit-
5227 field. If enough space remains, a bit-field that immediately follows another bit-field in a
5228 structure shall be packed into adjacent bits of the same unit. If insufficient space remains,
5229 whether a bit-field that does not fit is put into the next unit or overlaps adjacent units is
5230 implementation-defined. The order of allocation of bit-fields within a unit (high-order to
5231 low-order or low-order to high-order) is implementation-defined. The alignment of the
5232 addressable storage unit is unspecified.
5234 A bit-field declaration with no declarator, but only a colon and a width, indicates an
5235 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
5236 indicates that no further bit-field is to be packed into the unit in which the previous bit-
5237 field, if any, was placed.
5242 Each non-bit-field member of a structure or union object is aligned in an implementation-
5243 defined manner appropriate to its type.
5245 Within a structure object, the non-bit-field members and the units in which bit-fields
5246 reside have addresses that increase in the order in which they are declared. A pointer to a
5247 structure object, suitably converted, points to its initial member (or if that member is a
5248 bit-field, then to the unit in which it resides), and vice versa. There may be unnamed
5249 padding within a structure object, but not at its beginning.
5251 The size of a union is sufficient to contain the largest of its members. The value of at
5252 most one of the members can be stored in a union object at any time. A pointer to a
5253 union object, suitably converted, points to each of its members (or if a member is a bit-
5254 field, then to the unit in which it resides), and vice versa.
5256 There may be unnamed padding at the end of a structure or union.
5258 As a special case, the last element of a structure with more than one named member may
5259 have an incomplete array type; this is called a flexible array member. In most situations,
5260 the flexible array member is ignored. In particular, the size of the structure is as if the
5261 flexible array member were omitted except that it may have more trailing padding than
5262 the omission would imply. However, when a . (or ->) operator has a left operand that is
5263 (a pointer to) a structure with a flexible array member and the right operand names that
5264 member, it behaves as if that member were replaced with the longest array (with the same
5265 element type) that would not make the structure larger than the object being accessed; the
5266 offset of the array shall remain that of the flexible array member, even if this would differ
5267 from that of the replacement array. If this array would have no elements, it behaves as if
5268 it had one element but the behavior is undefined if any attempt is made to access that
5269 element or to generate a pointer one past it.
5271 EXAMPLE After the declaration:
5273 struct s { int n; double d[]; };</pre>
5274 the structure struct s has a flexible array member d. A typical way to use this is:
5276 int m = /* some value */;
5277 struct s *p = malloc(sizeof (struct s) + sizeof (double [m]));</pre>
5278 and assuming that the call to malloc succeeds, the object pointed to by p behaves, for most purposes, as if
5279 p had been declared as:
5281 struct { int n; double d[m]; } *p;</pre>
5282 (there are circumstances in which this equivalence is broken; in particular, the offsets of member d might
5285 Following the above declaration:
5288 struct s t1 = { 0 }; // valid
5289 struct s t2 = { 1, { <a href="#4.2">4.2</a> }}; // invalid
5291 t1.d[0] = <a href="#4.2">4.2</a>; // might be undefined behavior</pre>
5292 The initialization of t2 is invalid (and violates a constraint) because struct s is treated as if it did not
5293 contain member d. The assignment to t1.d[0] is probably undefined behavior, but it is possible that
5295 sizeof (struct s) >= offsetof(struct s, d) + sizeof (double)</pre>
5296 in which case the assignment would be legitimate. Nevertheless, it cannot appear in strictly conforming
5299 After the further declaration:
5301 struct ss { int n; };</pre>
5304 sizeof (struct s) >= sizeof (struct ss)
5305 sizeof (struct s) >= offsetof(struct s, d)</pre>
5306 are always equal to 1.
5308 If sizeof (double) is 8, then after the following code is executed:
5312 s1 = malloc(sizeof (struct s) + 64);
5313 s2 = malloc(sizeof (struct s) + 46);</pre>
5314 and assuming that the calls to malloc succeed, the objects pointed to by s1 and s2 behave, for most
5315 purposes, as if the identifiers had been declared as:
5318 struct { int n; double d[8]; } *s1;
5319 struct { int n; double d[5]; } *s2;</pre>
5320 Following the further successful assignments:
5322 s1 = malloc(sizeof (struct s) + 10);
5323 s2 = malloc(sizeof (struct s) + 6);</pre>
5324 they then behave as if the declarations were:
5326 struct { int n; double d[1]; } *s1, *s2;</pre>
5331 dp = &(s1->d[0]); // valid
5333 dp = &(s2->d[0]); // valid
5334 *dp = 42; // undefined behavior</pre>
5338 only copies the member n; if any of the array elements are within the first sizeof (struct s) bytes
5339 of the structure, they might be copied or simply overwritten with indeterminate values.
5341 <p><b> Forward references</b>: tags (<a href="#6.7.2.3">6.7.2.3</a>).
5345 <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
5346 are not ordinary identifiers as defined in <a href="#6.2.3">6.2.3</a>.
5348 <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
5349 or arrays of bit-field objects.
5351 <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,
5352 then it is implementation-defined whether the bit-field is signed or unsigned.
5354 <p><small><a name="note108" href="#note108">108)</a> An unnamed bit-field structure member is useful for padding to conform to externally imposed
5358 <h5><a name="6.7.2.2" href="#6.7.2.2">6.7.2.2 Enumeration specifiers</a></h5>
5363 enum identifieropt { enumerator-list }
5364 enum identifieropt { enumerator-list , }
5368 enumerator-list , enumerator
5370 enumeration-constant
5371 enumeration-constant = constant-expression</pre>
5372 <h6>Constraints</h6>
5374 The expression that defines the value of an enumeration constant shall be an integer
5375 constant expression that has a value representable as an int.
5378 The identifiers in an enumerator list are declared as constants that have type int and
5379 may appear wherever such are permitted.<sup><a href="#note109"><b>109)</b></a></sup> An enumerator with = defines its
5380 enumeration constant as the value of the constant expression. If the first enumerator has
5381 no =, the value of its enumeration constant is 0. Each subsequent enumerator with no =
5382 defines its enumeration constant as the value of the constant expression obtained by
5383 adding 1 to the value of the previous enumeration constant. (The use of enumerators with
5384 = may produce enumeration constants with values that duplicate other values in the same
5385 enumeration.) The enumerators of an enumeration are also known as its members.
5387 Each enumerated type shall be compatible with char, a signed integer type, or an
5388 unsigned integer type. The choice of type is implementation-defined,<sup><a href="#note110"><b>110)</b></a></sup> but shall be
5389 capable of representing the values of all the members of the enumeration. The
5390 enumerated type is incomplete until after the } that terminates the list of enumerator
5398 EXAMPLE The following fragment:
5400 enum hue { chartreuse, burgundy, claret=20, winedark };
5404 if (*cp != burgundy)
5406 makes hue the tag of an enumeration, and then declares col as an object that has that type and cp as a
5407 pointer to an object that has that type. The enumerated values are in the set { 0, 1, 20, 21 }.
5409 <p><b> Forward references</b>: tags (<a href="#6.7.2.3">6.7.2.3</a>).
5412 <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
5413 each other and from other identifiers declared in ordinary declarators.
5415 <p><small><a name="note110" href="#note110">110)</a> An implementation may delay the choice of which integer type until all enumeration constants have
5419 <h5><a name="6.7.2.3" href="#6.7.2.3">6.7.2.3 Tags</a></h5>
5420 <h6>Constraints</h6>
5422 A specific type shall have its content defined at most once.
5424 Where two declarations that use the same tag declare the same type, they shall both use
5425 the same choice of struct, union, or enum.
5427 A type specifier of the form
5429 enum identifier</pre>
5430 without an enumerator list shall only appear after the type it specifies is complete.
5433 All declarations of structure, union, or enumerated types that have the same scope and
5434 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
5435 of the list defining the content, and complete thereafter.
5437 Two declarations of structure, union, or enumerated types which are in different scopes or
5438 use different tags declare distinct types. Each declaration of a structure, union, or
5439 enumerated type which does not include a tag declares a distinct type.
5441 A type specifier of the form
5443 struct-or-union identifieropt { struct-declaration-list }</pre>
5446 enum identifier { enumerator-list }</pre>
5449 enum identifier { enumerator-list , }</pre>
5450 declares a structure, union, or enumerated type. The list defines the structure content,
5453 union content, or enumeration content. If an identifier is provided,<sup><a href="#note112"><b>112)</b></a></sup> the type specifier
5454 also declares the identifier to be the tag of that type.
5456 A declaration of the form
5458 struct-or-union identifier ;</pre>
5459 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>
5461 If a type specifier of the form
5463 struct-or-union identifier</pre>
5464 occurs other than as part of one of the above forms, and no other declaration of the
5465 identifier as a tag is visible, then it declares an incomplete structure or union type, and
5466 declares the identifier as the tag of that type.113)
5468 If a type specifier of the form
5470 struct-or-union identifier</pre>
5473 enum identifier</pre>
5474 occurs other than as part of one of the above forms, and a declaration of the identifier as a
5475 tag is visible, then it specifies the same type as that other declaration, and does not
5478 EXAMPLE 1 This mechanism allows declaration of a self-referential structure.
5482 struct tnode *left, *right;
5484 specifies a structure that contains an integer and two pointers to objects of the same type. Once this
5485 declaration has been given, the declaration
5487 struct tnode s, *sp;</pre>
5488 declares s to be an object of the given type and sp to be a pointer to an object of the given type. With
5489 these declarations, the expression sp->left refers to the left struct tnode pointer of the object to
5490 which sp points; the expression s.right->count designates the count member of the right struct
5491 tnode pointed to from s.
5493 The following alternative formulation uses the typedef mechanism:
5500 typedef struct tnode TNODE;
5503 TNODE *left, *right;
5508 EXAMPLE 2 To illustrate the use of prior declaration of a tag to specify a pair of mutually referential
5509 structures, the declarations
5511 struct s1 { struct s2 *s2p; /* ... */ }; // D1
5512 struct s2 { struct s1 *s1p; /* ... */ }; // D2</pre>
5513 specify a pair of structures that contain pointers to each other. Note, however, that if s2 were already
5514 declared as a tag in an enclosing scope, the declaration D1 would refer to it, not to the tag s2 declared in
5515 D2. To eliminate this context sensitivity, the declaration
5518 may be inserted ahead of D1. This declares a new tag s2 in the inner scope; the declaration D2 then
5519 completes the specification of the new type.
5521 <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
5522 (<a href="#6.7.7">6.7.7</a>).
5525 <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
5526 needed, for example, when a typedef name is declared to be a specifier for a structure or union, or
5527 when a pointer to or a function returning a structure or union is being declared. (See incomplete types
5528 in <a href="#6.2.5">6.2.5</a>.) The specification has to be complete before such a function is called or defined.
5530 <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
5531 of which it is a part. Of course, when the declaration is of a typedef name, subsequent declarations
5532 can make use of that typedef name to declare objects having the specified structure, union, or
5535 <p><small><a name="note113" href="#note113">113)</a> A similar construction with enum does not exist.
5538 <h4><a name="6.7.3" href="#6.7.3">6.7.3 Type qualifiers</a></h4>
5546 <h6>Constraints</h6>
5548 Types other than pointer types derived from object or incomplete types shall not be
5552 The properties associated with qualified types are meaningful only for expressions that
5553 are lvalues.<sup><a href="#note114"><b>114)</b></a></sup>
5555 If the same qualifier appears more than once in the same specifier-qualifier-list, either
5556 directly or via one or more typedefs, the behavior is the same as if it appeared only
5564 If an attempt is made to modify an object defined with a const-qualified type through use
5565 of an lvalue with non-const-qualified type, the behavior is undefined. If an attempt is
5566 made to refer to an object defined with a volatile-qualified type through use of an lvalue
5567 with non-volatile-qualified type, the behavior is undefined.<sup><a href="#note115"><b>115)</b></a></sup>
5569 An object that has volatile-qualified type may be modified in ways unknown to the
5570 implementation or have other unknown side effects. Therefore any expression referring
5571 to such an object shall be evaluated strictly according to the rules of the abstract machine,
5572 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
5573 object shall agree with that prescribed by the abstract machine, except as modified by the
5574 unknown factors mentioned previously.<sup><a href="#note116"><b>116)</b></a></sup> What constitutes an access to an object that
5575 has volatile-qualified type is implementation-defined.
5577 An object that is accessed through a restrict-qualified pointer has a special association
5578 with that pointer. This association, defined in <a href="#6.7.3.1">6.7.3.1</a> below, requires that all accesses to
5579 that object use, directly or indirectly, the value of that particular pointer.<sup><a href="#note117"><b>117)</b></a></sup> The intended
5580 use of the restrict qualifier (like the register storage class) is to promote
5581 optimization, and deleting all instances of the qualifier from all preprocessing translation
5582 units composing a conforming program does not change its meaning (i.e., observable
5585 If the specification of an array type includes any type qualifiers, the element type is so-
5586 qualified, not the array type. If the specification of a function type includes any type
5587 qualifiers, the behavior is undefined.<sup><a href="#note118"><b>118)</b></a></sup>
5589 For two qualified types to be compatible, both shall have the identically qualified version
5590 of a compatible type; the order of type qualifiers within a list of specifiers or qualifiers
5591 does not affect the specified type.
5593 EXAMPLE 1 An object declared
5595 extern const volatile int real_time_clock;</pre>
5596 may be modifiable by hardware, but cannot be assigned to, incremented, or decremented.
5603 EXAMPLE 2 The following declarations and expressions illustrate the behavior when type qualifiers
5604 modify an aggregate type:
5606 const struct s { int mem; } cs = { 1 };
5607 struct s ncs; // the object ncs is modifiable
5608 typedef int A[2][3];
5609 const A a = {{4, 5, 6}, {7, 8, 9}}; // array of array of const int
5613 cs = ncs; // violates modifiable lvalue constraint for =
5614 pi = &ncs.mem; // valid
5615 pi = &cs.mem; // violates type constraints for =
5616 pci = &cs.mem; // valid
5617 pi = a[0]; // invalid: a[0] has type ''const int *''</pre>
5621 <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
5622 storage. Moreover, the implementation need not allocate storage for such an object if its address is
5625 <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
5626 never actually defined as objects in the program (such as an object at a memory-mapped input/output
5629 <p><small><a name="note116" href="#note116">116)</a> A volatile declaration may be used to describe an object corresponding to a memory-mapped
5630 input/output port or an object accessed by an asynchronously interrupting function. Actions on
5631 objects so declared shall not be ''optimized out'' by an implementation or reordered except as
5632 permitted by the rules for evaluating expressions.
5634 <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
5635 association between the allocated object and the pointer.
5637 <p><small><a name="note118" href="#note118">118)</a> Both of these can occur through the use of typedefs.
5640 <h5><a name="6.7.3.1" href="#6.7.3.1">6.7.3.1 Formal definition of restrict</a></h5>
5642 Let D be a declaration of an ordinary identifier that provides a means of designating an
5643 object P as a restrict-qualified pointer to type T.
5645 If D appears inside a block and does not have storage class extern, let B denote the
5646 block. If D appears in the list of parameter declarations of a function definition, let B
5647 denote the associated block. Otherwise, let B denote the block of main (or the block of
5648 whatever function is called at program startup in a freestanding environment).
5650 In what follows, a pointer expression E is said to be based on object P if (at some
5651 sequence point in the execution of B prior to the evaluation of E) modifying P to point to
5652 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>
5653 Note that ''based'' is defined only for expressions with pointer types.
5655 During each execution of B, let L be any lvalue that has &L based on P. If L is used to
5656 access the value of the object X that it designates, and X is also modified (by any means),
5657 then the following requirements apply: T shall not be const-qualified. Every other lvalue
5658 used to access the value of X shall also have its address based on P. Every access that
5659 modifies X shall be considered also to modify P, for the purposes of this subclause. If P
5660 is assigned the value of a pointer expression E that is based on another restricted pointer
5661 object P2, associated with block B2, then either the execution of B2 shall begin before
5662 the execution of B, or the execution of B2 shall end prior to the assignment. If these
5663 requirements are not met, then the behavior is undefined.
5665 Here an execution of B means that portion of the execution of the program that would
5666 correspond to the lifetime of an object with scalar type and automatic storage duration
5671 A translator is free to ignore any or all aliasing implications of uses of restrict.
5673 EXAMPLE 1 The file scope declarations
5677 extern int c[];</pre>
5678 assert that if an object is accessed using one of a, b, or c, and that object is modified anywhere in the
5679 program, then it is never accessed using either of the other two.
5682 EXAMPLE 2 The function parameter declarations in the following example
5684 void f(int n, int * restrict p, int * restrict q)
5689 assert that, during each execution of the function, if an object is accessed through one of the pointer
5690 parameters, then it is not also accessed through the other.
5692 The benefit of the restrict qualifiers is that they enable a translator to make an effective dependence
5693 analysis of function f without examining any of the calls of f in the program. The cost is that the
5694 programmer has to examine all of those calls to ensure that none give undefined behavior. For example, the
5695 second call of f in g has undefined behavior because each of d[1] through d[49] is accessed through
5701 f(50, d + 50, d); // valid
5702 f(50, d + 1, d); // undefined behavior
5706 EXAMPLE 3 The function parameter declarations
5708 void h(int n, int * restrict p, int * restrict q, int * restrict r)
5711 for (i = 0; i < n; i++)
5714 illustrate how an unmodified object can be aliased through two restricted pointers. In particular, if a and b
5715 are disjoint arrays, a call of the form h(100, a, b, b) has defined behavior, because array b is not
5716 modified within function h.
5719 EXAMPLE 4 The rule limiting assignments between restricted pointers does not distinguish between a
5720 function call and an equivalent nested block. With one exception, only ''outer-to-inner'' assignments
5721 between restricted pointers declared in nested blocks have defined behavior.
5728 p1 = q1; // undefined behavior
5730 int * restrict p2 = p1; // valid
5731 int * restrict q2 = q1; // valid
5732 p1 = q2; // undefined behavior
5733 p2 = q2; // undefined behavior
5736 The one exception allows the value of a restricted pointer to be carried out of the block in which it (or, more
5737 precisely, the ordinary identifier used to designate it) is declared when that block finishes execution. For
5738 example, this permits new_vector to return a vector.
5740 typedef struct { int n; float * restrict v; } vector;
5741 vector new_vector(int n)
5745 t.v = malloc(n * sizeof (float));
5751 <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
5752 indirectly through P. For example, if identifier p has type (int **restrict), then the pointer
5753 expressions p and p+1 are based on the restricted pointer object designated by p, but the pointer
5754 expressions *p and p[1] are not.
5757 <h4><a name="6.7.4" href="#6.7.4">6.7.4 Function specifiers</a></h4>
5763 <h6>Constraints</h6>
5765 Function specifiers shall be used only in the declaration of an identifier for a function.
5767 An inline definition of a function with external linkage shall not contain a definition of a
5768 modifiable object with static storage duration, and shall not contain a reference to an
5769 identifier with internal linkage.
5771 In a hosted environment, the inline function specifier shall not appear in a declaration
5775 A function declared with an inline function specifier is an inline function. The
5776 function specifier may appear more than once; the behavior is the same as if it appeared
5777 only once. Making a function an inline function suggests that calls to the function be as
5778 fast as possible.<sup><a href="#note120"><b>120)</b></a></sup> The extent to which such suggestions are effective is
5779 implementation-defined.<sup><a href="#note121"><b>121)</b></a></sup>
5781 Any function with internal linkage can be an inline function. For a function with external
5782 linkage, the following restrictions apply: If a function is declared with an inline
5784 function specifier, then it shall also be defined in the same translation unit. If all of the
5785 file scope declarations for a function in a translation unit include the inline function
5786 specifier without extern, then the definition in that translation unit is an inline
5787 definition. An inline definition does not provide an external definition for the function,
5788 and does not forbid an external definition in another translation unit. An inline definition
5789 provides an alternative to an external definition, which a translator may use to implement
5790 any call to the function in the same translation unit. It is unspecified whether a call to the
5791 function uses the inline definition or the external definition.<sup><a href="#note122"><b>122)</b></a></sup>
5793 EXAMPLE The declaration of an inline function with external linkage can result in either an external
5794 definition, or a definition available for use only within the translation unit. A file scope declaration with
5795 extern creates an external definition. The following example shows an entire translation unit.
5798 inline double fahr(double t)
5800 return (9.0 * t) / 5.0 + 32.0;
5802 inline double cels(double t)
5804 return (5.0 * (t - 32.0)) / 9.0;
5806 extern double fahr(double); // creates an external definition
5807 double convert(int is_fahr, double temp)
5809 /* A translator may perform inline substitutions */
5810 return is_fahr ? cels(temp) : fahr(temp);
5812 Note that the definition of fahr is an external definition because fahr is also declared with extern, but
5813 the definition of cels is an inline definition. Because cels has external linkage and is referenced, an
5814 external definition has to appear in another translation unit (see <a href="#6.9">6.9</a>); the inline definition and the external
5815 definition are distinct and either may be used for the call.
5817 <p><b> Forward references</b>: function definitions (<a href="#6.9.1">6.9.1</a>).
5823 <p><small><a name="note120" href="#note120">120)</a> By using, for example, an alternative to the usual function call mechanism, such as ''inline
5824 substitution''. Inline substitution is not textual substitution, nor does it create a new function.
5825 Therefore, for example, the expansion of a macro used within the body of the function uses the
5826 definition it had at the point the function body appears, and not where the function is called; and
5827 identifiers refer to the declarations in scope where the body occurs. Likewise, the function has a
5828 single address, regardless of the number of inline definitions that occur in addition to the external
5831 <p><small><a name="note121" href="#note121">121)</a> For example, an implementation might never perform inline substitution, or might only perform inline
5832 substitutions to calls in the scope of an inline declaration.
5834 <p><small><a name="note122" href="#note122">122)</a> Since an inline definition is distinct from the corresponding external definition and from any other
5835 corresponding inline definitions in other translation units, all corresponding objects with static storage
5836 duration are also distinct in each of the definitions.
5839 <h4><a name="6.7.5" href="#6.7.5">6.7.5 Declarators</a></h4>
5844 pointeropt direct-declarator
5848 direct-declarator [ type-qualifier-listopt assignment-expressionopt ]
5849 direct-declarator [ static type-qualifier-listopt assignment-expression ]
5850 direct-declarator [ type-qualifier-list static assignment-expression ]
5851 direct-declarator [ type-qualifier-listopt * ]
5852 direct-declarator ( parameter-type-list )
5853 direct-declarator ( identifier-listopt )
5855 * type-qualifier-listopt
5856 * type-qualifier-listopt pointer
5857 type-qualifier-list:
5859 type-qualifier-list type-qualifier
5860 parameter-type-list:
5862 parameter-list , ...
5864 parameter-declaration
5865 parameter-list , parameter-declaration
5866 parameter-declaration:
5867 declaration-specifiers declarator
5868 declaration-specifiers abstract-declaratoropt
5871 identifier-list , identifier</pre>
5874 Each declarator declares one identifier, and asserts that when an operand of the same
5875 form as the declarator appears in an expression, it designates a function or object with the
5876 scope, storage duration, and type indicated by the declaration specifiers.
5878 A full declarator is a declarator that is not part of another declarator. The end of a full
5879 declarator is a sequence point. If, in the nested sequence of declarators in a full
5881 declarator, there is a declarator specifying a variable length array type, the type specified
5882 by the full declarator is said to be variably modified. Furthermore, any type derived by
5883 declarator type derivation from a variably modified type is itself variably modified.
5885 In the following subclauses, consider a declaration
5888 where T contains the declaration specifiers that specify a type T (such as int) and D1 is
5889 a declarator that contains an identifier ident. The type specified for the identifier ident in
5890 the various forms of declarator is described inductively using this notation.
5892 If, in the declaration ''T D1'', D1 has the form
5895 then the type specified for ident is T .
5897 If, in the declaration ''T D1'', D1 has the form
5900 then ident has the type specified by the declaration ''T D''. Thus, a declarator in
5901 parentheses is identical to the unparenthesized declarator, but the binding of complicated
5902 declarators may be altered by parentheses.
5903 Implementation limits
5905 As discussed in <a href="#5.2.4.1">5.2.4.1</a>, an implementation may limit the number of pointer, array, and
5906 function declarators that modify an arithmetic, structure, union, or incomplete type, either
5907 directly or via one or more typedefs.
5908 <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>).
5910 <h5><a name="6.7.5.1" href="#6.7.5.1">6.7.5.1 Pointer declarators</a></h5>
5913 If, in the declaration ''T D1'', D1 has the form
5915 * type-qualifier-listopt D</pre>
5916 and the type specified for ident in the declaration ''T D'' is ''derived-declarator-type-list
5917 T '', then the type specified for ident is ''derived-declarator-type-list type-qualifier-list
5918 pointer to T ''. For each type qualifier in the list, ident is a so-qualified pointer.
5920 For two pointer types to be compatible, both shall be identically qualified and both shall
5921 be pointers to compatible types.
5923 EXAMPLE The following pair of declarations demonstrates the difference between a ''variable pointer
5924 to a constant value'' and a ''constant pointer to a variable value''.
5927 const int *ptr_to_constant;
5928 int *const constant_ptr;</pre>
5929 The contents of any object pointed to by ptr_to_constant shall not be modified through that pointer,
5930 but ptr_to_constant itself may be changed to point to another object. Similarly, the contents of the
5931 int pointed to by constant_ptr may be modified, but constant_ptr itself shall always point to the
5934 The declaration of the constant pointer constant_ptr may be clarified by including a definition for the
5935 type ''pointer to int''.
5937 typedef int *int_ptr;
5938 const int_ptr constant_ptr;</pre>
5939 declares constant_ptr as an object that has type ''const-qualified pointer to int''.
5942 <h5><a name="6.7.5.2" href="#6.7.5.2">6.7.5.2 Array declarators</a></h5>
5943 <h6>Constraints</h6>
5945 In addition to optional type qualifiers and the keyword static, the [ and ] may delimit
5946 an expression or *. If they delimit an expression (which specifies the size of an array), the
5947 expression shall have an integer type. If the expression is a constant expression, it shall
5948 have a value greater than zero. The element type shall not be an incomplete or function
5949 type. The optional type qualifiers and the keyword static shall appear only in a
5950 declaration of a function parameter with an array type, and then only in the outermost
5951 array type derivation.
5953 An ordinary identifier (as defined in <a href="#6.2.3">6.2.3</a>) that has a variably modified type shall have
5954 either block scope and no linkage or function prototype scope. If an identifier is declared
5955 to be an object with static storage duration, it shall not have a variable length array type.
5958 If, in the declaration ''T D1'', D1 has one of the forms:
5960 D[ type-qualifier-listopt assignment-expressionopt ]
5961 D[ static type-qualifier-listopt assignment-expression ]
5962 D[ type-qualifier-list static assignment-expression ]
5963 D[ type-qualifier-listopt * ]</pre>
5964 and the type specified for ident in the declaration ''T D'' is ''derived-declarator-type-list
5965 T '', then the type specified for ident is ''derived-declarator-type-list array of T ''.<sup><a href="#note123"><b>123)</b></a></sup>
5966 (See <a href="#6.7.5.3">6.7.5.3</a> for the meaning of the optional type qualifiers and the keyword static.)
5968 If the size is not present, the array type is an incomplete type. If the size is * instead of
5969 being an expression, the array type is a variable length array type of unspecified size,
5970 which can only be used in declarations with function prototype scope;<sup><a href="#note124"><b>124)</b></a></sup> such arrays are
5971 nonetheless complete types. If the size is an integer constant expression and the element
5974 type has a known constant size, the array type is not a variable length array type;
5975 otherwise, the array type is a variable length array type.
5977 If the size is an expression that is not an integer constant expression: if it occurs in a
5978 declaration at function prototype scope, it is treated as if it were replaced by *; otherwise,
5979 each time it is evaluated it shall have a value greater than zero. The size of each instance
5980 of a variable length array type does not change during its lifetime. Where a size
5981 expression is part of the operand of a sizeof operator and changing the value of the
5982 size expression would not affect the result of the operator, it is unspecified whether or not
5983 the size expression is evaluated.
5985 For two array types to be compatible, both shall have compatible element types, and if
5986 both size specifiers are present, and are integer constant expressions, then both size
5987 specifiers shall have the same constant value. If the two array types are used in a context
5988 which requires them to be compatible, it is undefined behavior if the two size specifiers
5989 evaluate to unequal values.
5993 float fa[11], *afp[17];</pre>
5994 declares an array of float numbers and an array of pointers to float numbers.
5997 EXAMPLE 2 Note the distinction between the declarations
6000 extern int y[];</pre>
6001 The first declares x to be a pointer to int; the second declares y to be an array of int of unspecified size
6002 (an incomplete type), the storage for which is defined elsewhere.
6005 EXAMPLE 3 The following declarations demonstrate the compatibility rules for variably modified types.
6014 int (*r)[n][n][n+1];
6015 p = a; // invalid: not compatible because 4 != 6
6016 r = c; // compatible, but defined behavior only if
6017 // n == 6 and m == n+1
6025 EXAMPLE 4 All declarations of variably modified (VM) types have to be at either block scope or
6026 function prototype scope. Array objects declared with the static or extern storage-class specifier
6027 cannot have a variable length array (VLA) type. However, an object declared with the static storage-
6028 class specifier can have a VM type (that is, a pointer to a VLA type). Finally, all identifiers declared with a
6029 VM type have to be ordinary identifiers and cannot, therefore, be members of structures or unions.
6032 int A[n]; // invalid: file scope VLA
6033 extern int (*p2)[n]; // invalid: file scope VM
6034 int B[100]; // valid: file scope but not VM
6035 void fvla(int m, int C[m][m]); // valid: VLA with prototype scope
6036 void fvla(int m, int C[m][m]) // valid: adjusted to auto pointer to VLA
6038 typedef int VLA[m][m]; // valid: block scope typedef VLA
6040 int (*y)[n]; // invalid: y not ordinary identifier
6041 int z[n]; // invalid: z not ordinary identifier
6043 int D[m]; // valid: auto VLA
6044 static int E[m]; // invalid: static block scope VLA
6045 extern int F[m]; // invalid: F has linkage and is VLA
6046 int (*s)[m]; // valid: auto pointer to VLA
6047 extern int (*r)[m]; // invalid: r has linkage and points to VLA
6048 static int (*q)[m] = &B; // valid: q is a static block pointer to VLA
6051 <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>),
6052 initialization (<a href="#6.7.8">6.7.8</a>).
6055 <p><small><a name="note123" href="#note123">123)</a> When several ''array of'' specifications are adjacent, a multidimensional array is declared.
6057 <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>).
6060 <h5><a name="6.7.5.3" href="#6.7.5.3">6.7.5.3 Function declarators (including prototypes)</a></h5>
6061 <h6>Constraints</h6>
6063 A function declarator shall not specify a return type that is a function type or an array
6066 The only storage-class specifier that shall occur in a parameter declaration is register.
6068 An identifier list in a function declarator that is not part of a definition of that function
6071 After adjustment, the parameters in a parameter type list in a function declarator that is
6072 part of a definition of that function shall not have incomplete type.
6075 If, in the declaration ''T D1'', D1 has the form
6077 D( parameter-type-list )</pre>
6081 D( identifier-listopt )</pre>
6082 and the type specified for ident in the declaration ''T D'' is ''derived-declarator-type-list
6083 T '', then the type specified for ident is ''derived-declarator-type-list function returning
6086 A parameter type list specifies the types of, and may declare identifiers for, the
6087 parameters of the function.
6089 A declaration of a parameter as ''array of type'' shall be adjusted to ''qualified pointer to
6090 type'', where the type qualifiers (if any) are those specified within the [ and ] of the
6091 array type derivation. If the keyword static also appears within the [ and ] of the
6092 array type derivation, then for each call to the function, the value of the corresponding
6093 actual argument shall provide access to the first element of an array with at least as many
6094 elements as specified by the size expression.
6096 A declaration of a parameter as ''function returning type'' shall be adjusted to ''pointer to
6097 function returning type'', as in <a href="#6.3.2.1">6.3.2.1</a>.
6099 If the list terminates with an ellipsis (, ...), no information about the number or types
6100 of the parameters after the comma is supplied.<sup><a href="#note125"><b>125)</b></a></sup>
6102 The special case of an unnamed parameter of type void as the only item in the list
6103 specifies that the function has no parameters.
6105 If, in a parameter declaration, an identifier can be treated either as a typedef name or as a
6106 parameter name, it shall be taken as a typedef name.
6108 If the function declarator is not part of a definition of that function, parameters may have
6109 incomplete type and may use the [*] notation in their sequences of declarator specifiers
6110 to specify variable length array types.
6112 The storage-class specifier in the declaration specifiers for a parameter declaration, if
6113 present, is ignored unless the declared parameter is one of the members of the parameter
6114 type list for a function definition.
6116 An identifier list declares only the identifiers of the parameters of the function. An empty
6117 list in a function declarator that is part of a definition of that function specifies that the
6118 function has no parameters. The empty list in a function declarator that is not part of a
6119 definition of that function specifies that no information about the number or types of the
6120 parameters is supplied.<sup><a href="#note126"><b>126)</b></a></sup>
6122 For two function types to be compatible, both shall specify compatible return types.<sup><a href="#note127"><b>127)</b></a></sup>
6126 Moreover, the parameter type lists, if both are present, shall agree in the number of
6127 parameters and in use of the ellipsis terminator; corresponding parameters shall have
6128 compatible types. If one type has a parameter type list and the other type is specified by a
6129 function declarator that is not part of a function definition and that contains an empty
6130 identifier list, the parameter list shall not have an ellipsis terminator and the type of each
6131 parameter shall be compatible with the type that results from the application of the
6132 default argument promotions. If one type has a parameter type list and the other type is
6133 specified by a function definition that contains a (possibly empty) identifier list, both shall
6134 agree in the number of parameters, and the type of each prototype parameter shall be
6135 compatible with the type that results from the application of the default argument
6136 promotions to the type of the corresponding identifier. (In the determination of type
6137 compatibility and of a composite type, each parameter declared with function or array
6138 type is taken as having the adjusted type and each parameter declared with qualified type
6139 is taken as having the unqualified version of its declared type.)
6141 EXAMPLE 1 The declaration
6143 int f(void), *fip(), (*pfi)();</pre>
6144 declares a function f with no parameters returning an int, a function fip with no parameter specification
6145 returning a pointer to an int, and a pointer pfi to a function with no parameter specification returning an
6146 int. It is especially useful to compare the last two. The binding of *fip() is *(fip()), so that the
6147 declaration suggests, and the same construction in an expression requires, the calling of a function fip,
6148 and then using indirection through the pointer result to yield an int. In the declarator (*pfi)(), the
6149 extra parentheses are necessary to indicate that indirection through a pointer to a function yields a function
6150 designator, which is then used to call the function; it returns an int.
6152 If the declaration occurs outside of any function, the identifiers have file scope and external linkage. If the
6153 declaration occurs inside a function, the identifiers of the functions f and fip have block scope and either
6154 internal or external linkage (depending on what file scope declarations for these identifiers are visible), and
6155 the identifier of the pointer pfi has block scope and no linkage.
6158 EXAMPLE 2 The declaration
6160 int (*apfi[3])(int *x, int *y);</pre>
6161 declares an array apfi of three pointers to functions returning int. Each of these functions has two
6162 parameters that are pointers to int. The identifiers x and y are declared for descriptive purposes only and
6163 go out of scope at the end of the declaration of apfi.
6166 EXAMPLE 3 The declaration
6168 int (*fpfi(int (*)(long), int))(int, ...);</pre>
6169 declares a function fpfi that returns a pointer to a function returning an int. The function fpfi has two
6170 parameters: a pointer to a function returning an int (with one parameter of type long int), and an int.
6171 The pointer returned by fpfi points to a function that has one int parameter and accepts zero or more
6172 additional arguments of any type.
6175 EXAMPLE 4 The following prototype has a variably modified parameter.
6177 void addscalar(int n, int m,
6178 double a[n][n*m+300], double x);
6182 addscalar(4, 2, b, <a href="#2.17">2.17</a>);
6185 void addscalar(int n, int m,
6186 double a[n][n*m+300], double x)
6188 for (int i = 0; i < n; i++)
6189 for (int j = 0, k = n*m+300; j < k; j++)
6190 // a is a pointer to a VLA with n*m+300 elements
6195 EXAMPLE 5 The following are all compatible function prototype declarators.
6197 double maximum(int n, int m, double a[n][m]);
6198 double maximum(int n, int m, double a[*][*]);
6199 double maximum(int n, int m, double a[ ][*]);
6200 double maximum(int n, int m, double a[ ][m]);</pre>
6203 void f(double (* restrict a)[5]);
6204 void f(double a[restrict][5]);
6205 void f(double a[restrict 3][5]);
6206 void f(double a[restrict static 3][5]);</pre>
6207 (Note that the last declaration also specifies that the argument corresponding to a in any call to f must be a
6208 non-null pointer to the first of at least three arrays of 5 doubles, which the others do not.)
6210 <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>).
6214 <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
6215 correspond to the ellipsis.
6217 <p><small><a name="note126" href="#note126">126)</a> See ''future language directions'' (<a href="#6.11.6">6.11.6</a>).
6219 <p><small><a name="note127" href="#note127">127)</a> If both function types are ''old style'', parameter types are not compared.
6222 <h4><a name="6.7.6" href="#6.7.6">6.7.6 Type names</a></h4>
6227 specifier-qualifier-list abstract-declaratoropt
6228 abstract-declarator:
6230 pointeropt direct-abstract-declarator
6231 direct-abstract-declarator:
6232 ( abstract-declarator )
6233 direct-abstract-declaratoropt [ type-qualifier-listopt
6234 assignment-expressionopt ]
6235 direct-abstract-declaratoropt [ static type-qualifier-listopt
6236 assignment-expression ]
6237 direct-abstract-declaratoropt [ type-qualifier-list static
6238 assignment-expression ]
6239 direct-abstract-declaratoropt [ * ]
6240 direct-abstract-declaratoropt ( parameter-type-listopt )</pre>
6243 In several contexts, it is necessary to specify a type. This is accomplished using a type
6244 name, which is syntactically a declaration for a function or an object of that type that
6245 omits the identifier.<sup><a href="#note128"><b>128)</b></a></sup>
6247 EXAMPLE The constructions
6256 (h) int (*const [])(unsigned int, ...)</pre>
6257 name respectively the types (a) int, (b) pointer to int, (c) array of three pointers to int, (d) pointer to an
6258 array of three ints, (e) pointer to a variable length array of an unspecified number of ints, (f) function
6259 with no parameter specification returning a pointer to int, (g) pointer to function with no parameters
6260 returning an int, and (h) array of an unspecified number of constant pointers to functions, each with one
6261 parameter that has type unsigned int and an unspecified number of other parameters, returning an
6270 <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
6271 parameter specification'', rather than redundant parentheses around the omitted identifier.
6274 <h4><a name="6.7.7" href="#6.7.7">6.7.7 Type definitions</a></h4>
6280 <h6>Constraints</h6>
6282 If a typedef name specifies a variably modified type then it shall have block scope.
6285 In a declaration whose storage-class specifier is typedef, each declarator defines an
6286 identifier to be a typedef name that denotes the type specified for the identifier in the way
6287 described in <a href="#6.7.5">6.7.5</a>. Any array size expressions associated with variable length array
6288 declarators are evaluated each time the declaration of the typedef name is reached in the
6289 order of execution. A typedef declaration does not introduce a new type, only a
6290 synonym for the type so specified. That is, in the following declarations:
6292 typedef T type_ident;
6294 type_ident is defined as a typedef name with the type specified by the declaration
6295 specifiers in T (known as T ), and the identifier in D has the type ''derived-declarator-
6296 type-list T '' where the derived-declarator-type-list is specified by the declarators of D. A
6297 typedef name shares the same name space as other identifiers declared in ordinary
6302 typedef int MILES, KLICKSP();
6303 typedef struct { double hi, lo; } range;</pre>
6307 extern KLICKSP *metricp;
6310 are all valid declarations. The type of distance is int, that of metricp is ''pointer to function with no
6311 parameter specification returning int'', and that of x and z is the specified structure; zp is a pointer to
6312 such a structure. The object distance has a type compatible with any other int object.
6315 EXAMPLE 2 After the declarations
6317 typedef struct s1 { int x; } t1, *tp1;
6318 typedef struct s2 { int x; } t2, *tp2;</pre>
6319 type t1 and the type pointed to by tp1 are compatible. Type t1 is also compatible with type struct
6320 s1, but not compatible with the types struct s2, t2, the type pointed to by tp2, or int.
6323 EXAMPLE 3 The following obscure constructions
6325 typedef signed int t;
6332 declare a typedef name t with type signed int, a typedef name plain with type int, and a structure
6333 with three bit-field members, one named t that contains values in the range [0, 15], an unnamed const-
6334 qualified bit-field which (if it could be accessed) would contain values in either the range [-15, +15] or
6335 [-16, +15], and one named r that contains values in one of the ranges [0, 31], [-15, +15], or [-16, +15].
6336 (The choice of range is implementation-defined.) The first two bit-field declarations differ in that
6337 unsigned is a type specifier (which forces t to be the name of a structure member), while const is a
6338 type qualifier (which modifies t which is still visible as a typedef name). If these declarations are followed
6339 in an inner scope by
6343 then a function f is declared with type ''function returning signed int with one unnamed parameter
6344 with type pointer to function returning signed int with one unnamed parameter with type signed
6345 int'', and an identifier t with type long int.
6348 EXAMPLE 4 On the other hand, typedef names can be used to improve code readability. All three of the
6349 following declarations of the signal function specify exactly the same type, the first without making use
6350 of any typedef names.
6352 typedef void fv(int), (*pfv)(int);
6353 void (*signal(int, void (*)(int)))(int);
6354 fv *signal(int, fv *);
6355 pfv signal(int, pfv);</pre>
6358 EXAMPLE 5 If a typedef name denotes a variable length array type, the length of the array is fixed at the
6359 time the typedef name is defined, not each time it is used:
6364 typedef int B[n]; // B is n ints, n evaluated now
6366 B a; // a is n ints, n without += 1
6367 int b[n]; // a and b are different sizes
6368 for (int i = 1; i < n; i++)
6372 <h4><a name="6.7.8" href="#6.7.8">6.7.8 Initialization</a></h4>
6377 assignment-expression
6378 { initializer-list }
6379 { initializer-list , }
6381 designationopt initializer
6382 initializer-list , designationopt initializer
6387 designator-list designator
6389 [ constant-expression ]
6391 <h6>Constraints</h6>
6393 No initializer shall attempt to provide a value for an object not contained within the entity
6396 The type of the entity to be initialized shall be an array of unknown size or an object type
6397 that is not a variable length array type.
6399 All the expressions in an initializer for an object that has static storage duration shall be
6400 constant expressions or string literals.
6402 If the declaration of an identifier has block scope, and the identifier has external or
6403 internal linkage, the declaration shall have no initializer for the identifier.
6405 If a designator has the form
6407 [ constant-expression ]</pre>
6408 then the current object (defined below) shall have array type and the expression shall be
6409 an integer constant expression. If the array is of unknown size, any nonnegative value is
6412 If a designator has the form
6415 then the current object (defined below) shall have structure or union type and the
6416 identifier shall be the name of a member of that type.
6420 An initializer specifies the initial value stored in an object.
6422 Except where explicitly stated otherwise, for the purposes of this subclause unnamed
6423 members of objects of structure and union type do not participate in initialization.
6424 Unnamed members of structure objects have indeterminate value even after initialization.
6426 If an object that has automatic storage duration is not initialized explicitly, its value is
6427 indeterminate. If an object that has static storage duration is not initialized explicitly,
6430 <li> if it has pointer type, it is initialized to a null pointer;
6431 <li> if it has arithmetic type, it is initialized to (positive or unsigned) zero;
6432 <li> if it is an aggregate, every member is initialized (recursively) according to these rules;
6433 <li> if it is a union, the first named member is initialized (recursively) according to these
6437 The initializer for a scalar shall be a single expression, optionally enclosed in braces. The
6438 initial value of the object is that of the expression (after conversion); the same type
6439 constraints and conversions as for simple assignment apply, taking the type of the scalar
6440 to be the unqualified version of its declared type.
6442 The rest of this subclause deals with initializers for objects that have aggregate or union
6445 The initializer for a structure or union object that has automatic storage duration shall be
6446 either an initializer list as described below, or a single expression that has compatible
6447 structure or union type. In the latter case, the initial value of the object, including
6448 unnamed members, is that of the expression.
6450 An array of character type may be initialized by a character string literal, optionally
6451 enclosed in braces. Successive characters of the character string literal (including the
6452 terminating null character if there is room or if the array is of unknown size) initialize the
6453 elements of the array.
6455 An array with element type compatible with wchar_t may be initialized by a wide
6456 string literal, optionally enclosed in braces. Successive wide characters of the wide string
6457 literal (including the terminating null wide character if there is room or if the array is of
6458 unknown size) initialize the elements of the array.
6460 Otherwise, the initializer for an object that has aggregate or union type shall be a brace-
6461 enclosed list of initializers for the elements or named members.
6463 Each brace-enclosed initializer list has an associated current object. When no
6464 designations are present, subobjects of the current object are initialized in order according
6465 to the type of the current object: array elements in increasing subscript order, structure
6467 members in declaration order, and the first named member of a union.<sup><a href="#note129"><b>129)</b></a></sup> In contrast, a
6468 designation causes the following initializer to begin initialization of the subobject
6469 described by the designator. Initialization then continues forward in order, beginning
6470 with the next subobject after that described by the designator.<sup><a href="#note130"><b>130)</b></a></sup>
6472 Each designator list begins its description with the current object associated with the
6473 closest surrounding brace pair. Each item in the designator list (in order) specifies a
6474 particular member of its current object and changes the current object for the next
6475 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
6476 designator list is the subobject to be initialized by the following initializer.
6478 The initialization shall occur in initializer list order, each initializer provided for a
6479 particular subobject overriding any previously listed initializer for the same subobject;<sup><a href="#note132"><b>132)</b></a></sup>
6480 all subobjects that are not initialized explicitly shall be initialized implicitly the same as
6481 objects that have static storage duration.
6483 If the aggregate or union contains elements or members that are aggregates or unions,
6484 these rules apply recursively to the subaggregates or contained unions. If the initializer of
6485 a subaggregate or contained union begins with a left brace, the initializers enclosed by
6486 that brace and its matching right brace initialize the elements or members of the
6487 subaggregate or the contained union. Otherwise, only enough initializers from the list are
6488 taken to account for the elements or members of the subaggregate or the first member of
6489 the contained union; any remaining initializers are left to initialize the next element or
6490 member of the aggregate of which the current subaggregate or contained union is a part.
6492 If there are fewer initializers in a brace-enclosed list than there are elements or members
6493 of an aggregate, or fewer characters in a string literal used to initialize an array of known
6494 size than there are elements in the array, the remainder of the aggregate shall be
6495 initialized implicitly the same as objects that have static storage duration.
6497 If an array of unknown size is initialized, its size is determined by the largest indexed
6498 element with an explicit initializer. At the end of its initializer list, the array no longer
6499 has incomplete type.
6505 The order in which any side effects occur among the initialization list expressions is
6506 unspecified.<sup><a href="#note133"><b>133)</b></a></sup>
6508 EXAMPLE 1 Provided that <a href="#7.3"><complex.h></a> has been #included, the declarations
6510 int i = <a href="#3.5">3.5</a>;
6511 double complex c = 5 + 3 * I;</pre>
6512 define and initialize i with the value 3 and c with the value 5.0 + i3.0.
6515 EXAMPLE 2 The declaration
6517 int x[] = { 1, 3, 5 };</pre>
6518 defines and initializes x as a one-dimensional array object that has three elements, as no size was specified
6519 and there are three initializers.
6522 EXAMPLE 3 The declaration
6529 is a definition with a fully bracketed initialization: 1, 3, and 5 initialize the first row of y (the array object
6530 y[0]), namely y[0][0], y[0][1], and y[0][2]. Likewise the next two lines initialize y[1] and
6531 y[2]. The initializer ends early, so y[3] is initialized with zeros. Precisely the same effect could have
6535 1, 3, 5, 2, 4, 6, 3, 5, 7
6537 The initializer for y[0] does not begin with a left brace, so three items from the list are used. Likewise the
6538 next three are taken successively for y[1] and y[2].
6541 EXAMPLE 4 The declaration
6544 { 1 }, { 2 }, { 3 }, { 4 }
6546 initializes the first column of z as specified and initializes the rest with zeros.
6549 EXAMPLE 5 The declaration
6551 struct { int a[3], b; } w[] = { { 1 }, 2 };</pre>
6552 is a definition with an inconsistently bracketed initialization. It defines an array with two element
6553 structures: w[0].a[0] is 1 and w[1].a[0] is 2; all the other elements are zero.
6560 EXAMPLE 6 The declaration
6562 short q[4][3][2] = {
6567 contains an incompletely but consistently bracketed initialization. It defines a three-dimensional array
6568 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
6569 q[2][0][0], q[2][0][1], and q[2][1][0], respectively; all the rest are zero. The initializer for
6570 q[0][0] does not begin with a left brace, so up to six items from the current list may be used. There is
6571 only one, so the values for the remaining five elements are initialized with zero. Likewise, the initializers
6572 for q[1][0] and q[2][0] do not begin with a left brace, so each uses up to six items, initializing their
6573 respective two-dimensional subaggregates. If there had been more than six items in any of the lists, a
6574 diagnostic message would have been issued. The same initialization result could have been achieved by:
6576 short q[4][3][2] = {
6583 short q[4][3][2] = {
6595 in a fully bracketed form.
6597 Note that the fully bracketed and minimally bracketed forms of initialization are, in general, less likely to
6601 EXAMPLE 7 One form of initialization that completes array types involves typedef names. Given the
6604 typedef int A[]; // OK - declared with block scope</pre>
6607 A a = { 1, 2 }, b = { 3, 4, 5 };</pre>
6610 int a[] = { 1, 2 }, b[] = { 3, 4, 5 };</pre>
6611 due to the rules for incomplete types.
6614 EXAMPLE 8 The declaration
6616 char s[] = "abc", t[3] = "abc";</pre>
6617 defines ''plain'' char array objects s and t whose elements are initialized with character string literals.
6618 This declaration is identical to
6620 char s[] = { 'a', 'b', 'c', '\0' },
6621 t[] = { 'a', 'b', 'c' };</pre>
6622 The contents of the arrays are modifiable. On the other hand, the declaration
6624 char *p = "abc";</pre>
6625 defines p with type ''pointer to char'' and initializes it to point to an object with type ''array of char''
6626 with length 4 whose elements are initialized with a character string literal. If an attempt is made to use p to
6627 modify the contents of the array, the behavior is undefined.
6630 EXAMPLE 9 Arrays can be initialized to correspond to the elements of an enumeration by using
6633 enum { member_one, member_two };
6634 const char *nm[] = {
6635 [member_two] = "member two",
6636 [member_one] = "member one",
6640 EXAMPLE 10 Structure members can be initialized to nonzero values without depending on their order:
6642 div_t answer = { .quot = 2, .rem = -1 };</pre>
6645 EXAMPLE 11 Designators can be used to provide explicit initialization when unadorned initializer lists
6646 might be misunderstood:
6648 struct { int a[3], b; } w[] =
6649 { [0].a = {1}, [1].a[0] = 2 };</pre>
6652 EXAMPLE 12 Space can be ''allocated'' from both ends of an array by using a single designator:
6656 1, 3, 5, 7, 9, [MAX-5] = 8, 6, 4, 2, 0
6658 In the above, if MAX is greater than ten, there will be some zero-valued elements in the middle; if it is less
6659 than ten, some of the values provided by the first five initializers will be overridden by the second five.
6662 EXAMPLE 13 Any member of a union can be initialized:
6664 union { /* ... */ } u = { .any_member = 42 };</pre>
6666 <p><b> Forward references</b>: common definitions <a href="#7.17"><stddef.h></a> (<a href="#7.17">7.17</a>).
6670 <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
6671 subobjects are initialized as usual, but the subaggregate or contained union does not become the
6672 current object: current objects are associated only with brace-enclosed initializer lists.
6674 <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
6675 the next subobject of an object containing the union.
6677 <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
6678 the surrounding brace pair. Note, too, that each separate designator list is independent.
6680 <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
6681 not be evaluated at all.
6683 <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.
6686 <h3><a name="6.8" href="#6.8">6.8 Statements and blocks</a></h3>
6693 expression-statement
6696 jump-statement</pre>
6699 A statement specifies an action to be performed. Except as indicated, statements are
6700 executed in sequence.
6702 A block allows a set of declarations and statements to be grouped into one syntactic unit.
6703 The initializers of objects that have automatic storage duration, and the variable length
6704 array declarators of ordinary identifiers with block scope, are evaluated and the values are
6705 stored in the objects (including storing an indeterminate value in objects without an
6706 initializer) each time the declaration is reached in the order of execution, as if it were a
6707 statement, and within each declaration in the order that declarators appear.
6709 A full expression is an expression that is not part of another expression or of a declarator.
6710 Each of the following is a full expression: an initializer; the expression in an expression
6711 statement; the controlling expression of a selection statement (if or switch); the
6712 controlling expression of a while or do statement; each of the (optional) expressions of
6713 a for statement; the (optional) expression in a return statement. The end of a full
6714 expression is a sequence point.
6715 <p><b> Forward references</b>: expression and null statements (<a href="#6.8.3">6.8.3</a>), selection statements
6716 (<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>).
6718 <h4><a name="6.8.1" href="#6.8.1">6.8.1 Labeled statements</a></h4>
6723 identifier : statement
6724 case constant-expression : statement
6725 default : statement</pre>
6726 <h6>Constraints</h6>
6728 A case or default label shall appear only in a switch statement. Further
6729 constraints on such labels are discussed under the switch statement.
6732 Label names shall be unique within a function.
6735 Any statement may be preceded by a prefix that declares an identifier as a label name.
6736 Labels in themselves do not alter the flow of control, which continues unimpeded across
6738 <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>).
6740 <h4><a name="6.8.2" href="#6.8.2">6.8.2 Compound statement</a></h4>
6745 { block-item-listopt }
6748 block-item-list block-item
6754 A compound statement is a block.
6756 <h4><a name="6.8.3" href="#6.8.3">6.8.3 Expression and null statements</a></h4>
6760 expression-statement:
6761 expressionopt ;</pre>
6764 The expression in an expression statement is evaluated as a void expression for its side
6765 effects.<sup><a href="#note134"><b>134)</b></a></sup>
6767 A null statement (consisting of just a semicolon) performs no operations.
6769 EXAMPLE 1 If a function call is evaluated as an expression statement for its side effects only, the
6770 discarding of its value may be made explicit by converting the expression to a void expression by means of
6781 EXAMPLE 2 In the program fragment
6785 while (*s++ != '\0')
6787 a null statement is used to supply an empty loop body to the iteration statement.
6790 EXAMPLE 3 A null statement may also be used to carry a label just before the closing } of a compound
6805 <p><b> Forward references</b>: iteration statements (<a href="#6.8.5">6.8.5</a>).
6808 <p><small><a name="note134" href="#note134">134)</a> Such as assignments, and function calls which have side effects.
6811 <h4><a name="6.8.4" href="#6.8.4">6.8.4 Selection statements</a></h4>
6815 selection-statement:
6816 if ( expression ) statement
6817 if ( expression ) statement else statement
6818 switch ( expression ) statement</pre>
6821 A selection statement selects among a set of statements depending on the value of a
6822 controlling expression.
6824 A selection statement is a block whose scope is a strict subset of the scope of its
6825 enclosing block. Each associated substatement is also a block whose scope is a strict
6826 subset of the scope of the selection statement.
6828 <h5><a name="6.8.4.1" href="#6.8.4.1">6.8.4.1 The if statement</a></h5>
6829 <h6>Constraints</h6>
6831 The controlling expression of an if statement shall have scalar type.
6834 In both forms, the first substatement is executed if the expression compares unequal to 0.
6835 In the else form, the second substatement is executed if the expression compares equal
6837 to 0. If the first substatement is reached via a label, the second substatement is not
6840 An else is associated with the lexically nearest preceding if that is allowed by the
6843 <h5><a name="6.8.4.2" href="#6.8.4.2">6.8.4.2 The switch statement</a></h5>
6844 <h6>Constraints</h6>
6846 The controlling expression of a switch statement shall have integer type.
6848 If a switch statement has an associated case or default label within the scope of an
6849 identifier with a variably modified type, the entire switch statement shall be within the
6850 scope of that identifier.<sup><a href="#note135"><b>135)</b></a></sup>
6852 The expression of each case label shall be an integer constant expression and no two of
6853 the case constant expressions in the same switch statement shall have the same value
6854 after conversion. There may be at most one default label in a switch statement.
6855 (Any enclosed switch statement may have a default label or case constant
6856 expressions with values that duplicate case constant expressions in the enclosing
6860 A switch statement causes control to jump to, into, or past the statement that is the
6861 switch body, depending on the value of a controlling expression, and on the presence of a
6862 default label and the values of any case labels on or in the switch body. A case or
6863 default label is accessible only within the closest enclosing switch statement.
6865 The integer promotions are performed on the controlling expression. The constant
6866 expression in each case label is converted to the promoted type of the controlling
6867 expression. If a converted value matches that of the promoted controlling expression,
6868 control jumps to the statement following the matched case label. Otherwise, if there is
6869 a default label, control jumps to the labeled statement. If no converted case constant
6870 expression matches and there is no default label, no part of the switch body is
6872 Implementation limits
6874 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
6882 EXAMPLE In the artificial program fragment
6890 /* falls through into default code */
6894 the object whose identifier is i exists with automatic storage duration (within the block) but is never
6895 initialized, and thus if the controlling expression has a nonzero value, the call to the printf function will
6896 access an indeterminate value. Similarly, the call to the function f cannot be reached.
6900 <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
6901 default label associated with the switch that is in the block containing the declaration.
6904 <h4><a name="6.8.5" href="#6.8.5">6.8.5 Iteration statements</a></h4>
6908 iteration-statement:
6909 while ( expression ) statement
6910 do statement while ( expression ) ;
6911 for ( expressionopt ; expressionopt ; expressionopt ) statement
6912 for ( declaration expressionopt ; expressionopt ) statement</pre>
6913 <h6>Constraints</h6>
6915 The controlling expression of an iteration statement shall have scalar type.
6917 The declaration part of a for statement shall only declare identifiers for objects having
6918 storage class auto or register.
6921 An iteration statement causes a statement called the loop body to be executed repeatedly
6922 until the controlling expression compares equal to 0. The repetition occurs regardless of
6923 whether the loop body is entered from the iteration statement or by a jump.<sup><a href="#note136"><b>136)</b></a></sup>
6925 An iteration statement is a block whose scope is a strict subset of the scope of its
6926 enclosing block. The loop body is also a block whose scope is a strict subset of the scope
6927 of the iteration statement.
6935 <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
6936 statement is not evaluated before entering the loop body, nor is clause-1 of a for statement.
6939 <h5><a name="6.8.5.1" href="#6.8.5.1">6.8.5.1 The while statement</a></h5>
6941 The evaluation of the controlling expression takes place before each execution of the loop
6944 <h5><a name="6.8.5.2" href="#6.8.5.2">6.8.5.2 The do statement</a></h5>
6946 The evaluation of the controlling expression takes place after each execution of the loop
6949 <h5><a name="6.8.5.3" href="#6.8.5.3">6.8.5.3 The for statement</a></h5>
6953 for ( clause-1 ; expression-2 ; expression-3 ) statement</pre>
6954 behaves as follows: The expression expression-2 is the controlling expression that is
6955 evaluated before each execution of the loop body. The expression expression-3 is
6956 evaluated as a void expression after each execution of the loop body. If clause-1 is a
6957 declaration, the scope of any identifiers it declares is the remainder of the declaration and
6958 the entire loop, including the other two expressions; it is reached in the order of execution
6959 before the first evaluation of the controlling expression. If clause-1 is an expression, it is
6960 evaluated as a void expression before the first evaluation of the controlling expression.<sup><a href="#note137"><b>137)</b></a></sup>
6962 Both clause-1 and expression-3 can be omitted. An omitted expression-2 is replaced by a
6966 <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
6967 the loop; the controlling expression, expression-2, specifies an evaluation made before each iteration,
6968 such that execution of the loop continues until the expression compares equal to 0; and expression-3
6969 specifies an operation (such as incrementing) that is performed after each iteration.
6972 <h4><a name="6.8.6" href="#6.8.6">6.8.6 Jump statements</a></h4>
6980 return expressionopt ;</pre>
6983 A jump statement causes an unconditional jump to another place.
6990 <h5><a name="6.8.6.1" href="#6.8.6.1">6.8.6.1 The goto statement</a></h5>
6991 <h6>Constraints</h6>
6993 The identifier in a goto statement shall name a label located somewhere in the enclosing
6994 function. A goto statement shall not jump from outside the scope of an identifier having
6995 a variably modified type to inside the scope of that identifier.
6998 A goto statement causes an unconditional jump to the statement prefixed by the named
6999 label in the enclosing function.
7001 EXAMPLE 1 It is sometimes convenient to jump into the middle of a complicated set of statements. The
7002 following outline presents one possible approach to a problem based on these three assumptions:
7004 <li> The general initialization code accesses objects only visible to the current function.
7005 <li> The general initialization code is too large to warrant duplication.
7006 <li> The code to determine the next operation is at the head of the loop. (To allow it to be reached by
7007 continue statements, for example.)
7012 // determine next operation
7014 if (need to reinitialize) {
7015 // reinitialize-only code
7018 // general initialization code
7022 // handle other operations
7028 EXAMPLE 2 A goto statement is not allowed to jump past any declarations of objects with variably
7029 modified types. A jump within the scope, however, is permitted.
7031 goto lab3; // invalid: going INTO scope of VLA.
7034 a[j] = <a href="#4.4">4.4</a>;
7036 a[j] = <a href="#3.3">3.3</a>;
7037 goto lab4; // valid: going WITHIN scope of VLA.
7038 a[j] = <a href="#5.5">5.5</a>;
7040 a[j] = <a href="#6.6">6.6</a>;
7042 goto lab4; // invalid: going INTO scope of VLA.</pre>
7045 <h5><a name="6.8.6.2" href="#6.8.6.2">6.8.6.2 The continue statement</a></h5>
7046 <h6>Constraints</h6>
7048 A continue statement shall appear only in or as a loop body.
7051 A continue statement causes a jump to the loop-continuation portion of the smallest
7052 enclosing iteration statement; that is, to the end of the loop body. More precisely, in each
7054 while (/* ... */) { do { for (/* ... */) {
7056 /* ... */ /* ... */ /* ... */
7057 continue; continue; continue;
7058 /* ... */ /* ... */ /* ... */</pre>
7059 contin: ; contin: ; contin: ;
7060 } } while (/* ... */); }
7061 unless the continue statement shown is in an enclosed iteration statement (in which
7062 case it is interpreted within that statement), it is equivalent to goto contin;.<sup><a href="#note138"><b>138)</b></a></sup>
7065 <p><small><a name="note138" href="#note138">138)</a> Following the contin: label is a null statement.
7068 <h5><a name="6.8.6.3" href="#6.8.6.3">6.8.6.3 The break statement</a></h5>
7069 <h6>Constraints</h6>
7071 A break statement shall appear only in or as a switch body or loop body.
7074 A break statement terminates execution of the smallest enclosing switch or iteration
7081 <h5><a name="6.8.6.4" href="#6.8.6.4">6.8.6.4 The return statement</a></h5>
7082 <h6>Constraints</h6>
7084 A return statement with an expression shall not appear in a function whose return type
7085 is void. A return statement without an expression shall only appear in a function
7086 whose return type is void.
7089 A return statement terminates execution of the current function and returns control to
7090 its caller. A function may have any number of return statements.
7092 If a return statement with an expression is executed, the value of the expression is
7093 returned to the caller as the value of the function call expression. If the expression has a
7094 type different from the return type of the function in which it appears, the value is
7095 converted as if by assignment to an object having the return type of the function.<sup><a href="#note139"><b>139)</b></a></sup>
7099 struct s { double i; } f(void);
7115 g.u2.f3 = f();</pre>
7116 there is no undefined behavior, although there would be if the assignment were done directly (without using
7117 a function call to fetch the value).
7125 <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
7126 apply to the case of function return. The representation of floating-point values may have wider range
7127 or precision and is determined by FLT_EVAL_METHOD. A cast may be used to remove this extra
7128 range and precision.
7131 <h3><a name="6.9" href="#6.9">6.9 External definitions</a></h3>
7136 external-declaration
7137 translation-unit external-declaration
7138 external-declaration:
7141 <h6>Constraints</h6>
7143 The storage-class specifiers auto and register shall not appear in the declaration
7144 specifiers in an external declaration.
7146 There shall be no more than one external definition for each identifier declared with
7147 internal linkage in a translation unit. Moreover, if an identifier declared with internal
7148 linkage is used in an expression (other than as a part of the operand of a sizeof
7149 operator whose result is an integer constant), there shall be exactly one external definition
7150 for the identifier in the translation unit.
7153 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,
7154 which consists of a sequence of external declarations. These are described as ''external''
7155 because they appear outside any function (and hence have file scope). As discussed in
7156 <a href="#6.7">6.7</a>, a declaration that also causes storage to be reserved for an object or a function named
7157 by the identifier is a definition.
7159 An external definition is an external declaration that is also a definition of a function
7160 (other than an inline definition) or an object. If an identifier declared with external
7161 linkage is used in an expression (other than as part of the operand of a sizeof operator
7162 whose result is an integer constant), somewhere in the entire program there shall be
7163 exactly one external definition for the identifier; otherwise, there shall be no more than
7164 one.<sup><a href="#note140"><b>140)</b></a></sup>
7172 <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
7173 external definition for it.
7176 <h4><a name="6.9.1" href="#6.9.1">6.9.1 Function definitions</a></h4>
7180 function-definition:
7181 declaration-specifiers declarator declaration-listopt compound-statement
7184 declaration-list declaration</pre>
7185 <h6>Constraints</h6>
7187 The identifier declared in a function definition (which is the name of the function) shall
7188 have a function type, as specified by the declarator portion of the function definition.<sup><a href="#note141"><b>141)</b></a></sup>
7190 The return type of a function shall be void or an object type other than array type.
7192 The storage-class specifier, if any, in the declaration specifiers shall be either extern or
7195 If the declarator includes a parameter type list, the declaration of each parameter shall
7196 include an identifier, except for the special case of a parameter list consisting of a single
7197 parameter of type void, in which case there shall not be an identifier. No declaration list
7200 If the declarator includes an identifier list, each declaration in the declaration list shall
7201 have at least one declarator, those declarators shall declare only identifiers from the
7202 identifier list, and every identifier in the identifier list shall be declared. An identifier
7203 declared as a typedef name shall not be redeclared as a parameter. The declarations in the
7204 declaration list shall contain no storage-class specifier other than register and no
7213 The declarator in a function definition specifies the name of the function being defined
7214 and the identifiers of its parameters. If the declarator includes a parameter type list, the
7215 list also specifies the types of all the parameters; such a declarator also serves as a
7216 function prototype for later calls to the same function in the same translation unit. If the
7217 declarator includes an identifier list,<sup><a href="#note142"><b>142)</b></a></sup> the types of the parameters shall be declared in a
7218 following declaration list. In either case, the type of each parameter is adjusted as
7219 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.
7221 If a function that accepts a variable number of arguments is defined without a parameter
7222 type list that ends with the ellipsis notation, the behavior is undefined.
7224 Each parameter has automatic storage duration. Its identifier is an lvalue, which is in
7225 effect declared at the head of the compound statement that constitutes the function body
7226 (and therefore cannot be redeclared in the function body except in an enclosed block).
7227 The layout of the storage for parameters is unspecified.
7229 On entry to the function, the size expressions of each variably modified parameter are
7230 evaluated and the value of each argument expression is converted to the type of the
7231 corresponding parameter as if by assignment. (Array expressions and function
7232 designators as arguments were converted to pointers before the call.)
7234 After all parameters have been assigned, the compound statement that constitutes the
7235 body of the function definition is executed.
7237 If the } that terminates a function is reached, and the value of the function call is used by
7238 the caller, the behavior is undefined.
7240 EXAMPLE 1 In the following:
7242 extern int max(int a, int b)
7244 return a > b ? a : b;
7246 extern is the storage-class specifier and int is the type specifier; max(int a, int b) is the
7247 function declarator; and
7249 { return a > b ? a : b; }</pre>
7250 is the function body. The following similar definition uses the identifier-list form for the parameter
7258 extern int max(a, b)
7261 return a > b ? a : b;
7263 Here int a, b; is the declaration list for the parameters. The difference between these two definitions is
7264 that the first form acts as a prototype declaration that forces conversion of the arguments of subsequent calls
7265 to the function, whereas the second form does not.
7268 EXAMPLE 2 To pass one function to another, one might say
7273 Then the definition of g might read
7275 void g(int (*funcp)(void))
7278 (*funcp)(); /* or funcp(); ... */
7282 void g(int func(void))
7285 func(); /* or (*func)(); ... */
7290 <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:
7293 typedef int F(void); // type F is ''function with no parameters
7295 F f, g; // f and g both have type compatible with F
7296 F f { /* ... */ } // WRONG: syntax/constraint error
7297 F g() { /* ... */ } // WRONG: declares that g returns a function
7298 int f(void) { /* ... */ } // RIGHT: f has type compatible with F
7299 int g() { /* ... */ } // RIGHT: g has type compatible with F
7300 F *e(void) { /* ... */ } // e returns a pointer to a function
7301 F *((e))(void) { /* ... */ } // same: parentheses irrelevant
7302 int (*fp)(void); // fp points to a function that has type F
7303 F *Fp; // Fp points to a function that has type F</pre>
7305 <p><small><a name="note142" href="#note142">142)</a> See ''future language directions'' (<a href="#6.11.7">6.11.7</a>).
7308 <h4><a name="6.9.2" href="#6.9.2">6.9.2 External object definitions</a></h4>
7311 If the declaration of an identifier for an object has file scope and an initializer, the
7312 declaration is an external definition for the identifier.
7314 A declaration of an identifier for an object that has file scope without an initializer, and
7315 without a storage-class specifier or with the storage-class specifier static, constitutes a
7316 tentative definition. If a translation unit contains one or more tentative definitions for an
7317 identifier, and the translation unit contains no external definition for that identifier, then
7318 the behavior is exactly as if the translation unit contains a file scope declaration of that
7319 identifier, with the composite type as of the end of the translation unit, with an initializer
7322 If the declaration of an identifier for an object is a tentative definition and has internal
7323 linkage, the declared type shall not be an incomplete type.
7328 int i1 = 1; // definition, external linkage
7329 static int i2 = 2; // definition, internal linkage
7330 extern int i3 = 3; // definition, external linkage
7331 int i4; // tentative definition, external linkage
7332 static int i5; // tentative definition, internal linkage
7333 int i1; // valid tentative definition, refers to previous
7334 int i2; // <a href="#6.2.2">6.2.2</a> renders undefined, linkage disagreement
7335 int i3; // valid tentative definition, refers to previous
7336 int i4; // valid tentative definition, refers to previous
7337 int i5; // <a href="#6.2.2">6.2.2</a> renders undefined, linkage disagreement
7338 extern int i1; // refers to previous, whose linkage is external
7339 extern int i2; // refers to previous, whose linkage is internal
7340 extern int i3; // refers to previous, whose linkage is external
7341 extern int i4; // refers to previous, whose linkage is external
7342 extern int i5; // refers to previous, whose linkage is internal</pre>
7345 EXAMPLE 2 If at the end of the translation unit containing
7348 the array i still has incomplete type, the implicit initializer causes it to have one element, which is set to
7349 zero on program startup.
7352 <h3><a name="6.10" href="#6.10">6.10 Preprocessing directives</a></h3>
7368 if-group elif-groupsopt else-groupopt endif-line
7370 # if constant-expression new-line groupopt
7371 # ifdef identifier new-line groupopt
7372 # ifndef identifier new-line groupopt
7375 elif-groups elif-group
7377 # elif constant-expression new-line groupopt
7379 # else new-line groupopt
7383 # include pp-tokens new-line
7384 # define identifier replacement-list new-line
7385 # define identifier lparen identifier-listopt )
7386 replacement-list new-line
7387 # define identifier lparen ... ) replacement-list new-line
7388 # define identifier lparen identifier-list , ... )
7389 replacement-list new-line
7390 # undef identifier new-line
7391 # line pp-tokens new-line
7392 # error pp-tokensopt new-line
7393 # pragma pp-tokensopt new-line
7396 pp-tokensopt new-line
7400 a ( character not immediately preceded by white-space
7405 pp-tokens preprocessing-token
7407 the new-line character</pre>
7408 <h6>Description</h6>
7410 A preprocessing directive consists of a sequence of preprocessing tokens that satisfies the
7411 following constraints: The first token in the sequence is a # preprocessing token that (at
7412 the start of translation phase 4) is either the first character in the source file (optionally
7413 after white space containing no new-line characters) or that follows white space
7414 containing at least one new-line character. The last token in the sequence is the first new-
7415 line character that follows the first token in the sequence.<sup><a href="#note143"><b>143)</b></a></sup> A new-line character ends
7416 the preprocessing directive even if it occurs within what would otherwise be an
7419 invocation of a function-like macro.
7421 A text line shall not begin with a # preprocessing token. A non-directive shall not begin
7422 with any of the directive names appearing in the syntax.
7424 When in a group that is skipped (<a href="#6.10.1">6.10.1</a>), the directive syntax is relaxed to allow any
7425 sequence of preprocessing tokens to occur between the directive name and the following
7427 <h6>Constraints</h6>
7429 The only white-space characters that shall appear between preprocessing tokens within a
7430 preprocessing directive (from just after the introducing # preprocessing token through
7431 just before the terminating new-line character) are space and horizontal-tab (including
7432 spaces that have replaced comments or possibly other white-space characters in
7433 translation phase 3).
7436 The implementation can process and skip sections of source files conditionally, include
7437 other source files, and replace macros. These capabilities are called preprocessing,
7438 because conceptually they occur before translation of the resulting translation unit.
7440 The preprocessing tokens within a preprocessing directive are not subject to macro
7441 expansion unless otherwise stated.
7446 EMPTY # include <file.h></pre>
7447 the sequence of preprocessing tokens on the second line is not a preprocessing directive, because it does not
7448 begin with a # at the start of translation phase 4, even though it will do so after the macro EMPTY has been
7453 <p><small><a name="note143" href="#note143">143)</a> Thus, preprocessing directives are commonly called ''lines''. These ''lines'' have no other syntactic
7454 significance, as all white space is equivalent except in certain situations during preprocessing (see the
7455 # character string literal creation operator in <a href="#6.10.3.2">6.10.3.2</a>, for example).
7458 <h4><a name="6.10.1" href="#6.10.1">6.10.1 Conditional inclusion</a></h4>
7459 <h6>Constraints</h6>
7461 The expression that controls conditional inclusion shall be an integer constant expression
7462 except that: it shall not contain a cast; identifiers (including those lexically identical to
7463 keywords) are interpreted as described below;<sup><a href="#note144"><b>144)</b></a></sup> and it may contain unary operator
7464 expressions of the form
7471 defined identifier</pre>
7474 defined ( identifier )</pre>
7475 which evaluate to 1 if the identifier is currently defined as a macro name (that is, if it is
7476 predefined or if it has been the subject of a #define preprocessing directive without an
7477 intervening #undef directive with the same subject identifier), 0 if it is not.
7479 Each preprocessing token that remains (in the list of preprocessing tokens that will
7480 become the controlling expression) after all macro replacements have occurred shall be in
7481 the lexical form of a token (<a href="#6.4">6.4</a>).
7484 Preprocessing directives of the forms
7486 # if constant-expression new-line groupopt
7487 # elif constant-expression new-line groupopt</pre>
7488 check whether the controlling constant expression evaluates to nonzero.
7490 Prior to evaluation, macro invocations in the list of preprocessing tokens that will become
7491 the controlling constant expression are replaced (except for those macro names modified
7492 by the defined unary operator), just as in normal text. If the token defined is
7493 generated as a result of this replacement process or use of the defined unary operator
7494 does not match one of the two specified forms prior to macro replacement, the behavior is
7495 undefined. After all replacements due to macro expansion and the defined unary
7496 operator have been performed, all remaining identifiers (including those lexically
7497 identical to keywords) are replaced with the pp-number 0, and then each preprocessing
7498 token is converted into a token. The resulting tokens compose the controlling constant
7499 expression which is evaluated according to the rules of <a href="#6.6">6.6</a>. For the purposes of this
7500 token conversion and evaluation, all signed integer types and all unsigned integer types
7501 act as if they have the same representation as, respectively, the types intmax_t and
7502 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
7503 character constants, which may involve converting escape sequences into execution
7504 character set members. Whether the numeric value for these character constants matches
7505 the value obtained when an identical character constant occurs in an expression (other
7506 than within a #if or #elif directive) is implementation-defined.<sup><a href="#note146"><b>146)</b></a></sup> Also, whether a
7507 single-character character constant may have a negative value is implementation-defined.
7509 Preprocessing directives of the forms
7515 # ifdef identifier new-line groupopt
7516 # ifndef identifier new-line groupopt</pre>
7517 check whether the identifier is or is not currently defined as a macro name. Their
7518 conditions are equivalent to #if defined identifier and #if !defined identifier
7521 Each directive's condition is checked in order. If it evaluates to false (zero), the group
7522 that it controls is skipped: directives are processed only through the name that determines
7523 the directive in order to keep track of the level of nested conditionals; the rest of the
7524 directives' preprocessing tokens are ignored, as are the other preprocessing tokens in the
7525 group. Only the first group whose control condition evaluates to true (nonzero) is
7526 processed. If none of the conditions evaluates to true, and there is a #else directive, the
7527 group controlled by the #else is processed; lacking a #else directive, all the groups
7528 until the #endif are skipped.<sup><a href="#note147"><b>147)</b></a></sup>
7529 <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
7530 integer types (<a href="#7.18.1.5">7.18.1.5</a>).
7533 <p><small><a name="note144" href="#note144">144)</a> Because the controlling constant expression is evaluated during translation phase 4, all identifiers
7534 either are or are not macro names -- there simply are no keywords, enumeration constants, etc.
7536 <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
7537 0x8000 is signed and positive within a #if expression even though it would be unsigned in
7538 translation phase 7.
7540 <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
7541 evaluate to the same value in these two contexts.
7543 if ('z' - 'a' == 25)
7546 <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
7547 before the terminating new-line character. However, comments may appear anywhere in a source file,
7548 including within a preprocessing directive.
7551 <h4><a name="6.10.2" href="#6.10.2">6.10.2 Source file inclusion</a></h4>
7552 <h6>Constraints</h6>
7554 A #include directive shall identify a header or source file that can be processed by the
7558 A preprocessing directive of the form
7560 # include <h-char-sequence> new-line</pre>
7561 searches a sequence of implementation-defined places for a header identified uniquely by
7562 the specified sequence between the < and > delimiters, and causes the replacement of that
7563 directive by the entire contents of the header. How the places are specified or the header
7564 identified is implementation-defined.
7566 A preprocessing directive of the form
7572 # include "q-char-sequence" new-line</pre>
7573 causes the replacement of that directive by the entire contents of the source file identified
7574 by the specified sequence between the " delimiters. The named source file is searched
7575 for in an implementation-defined manner. If this search is not supported, or if the search
7576 fails, the directive is reprocessed as if it read
7578 # include <h-char-sequence> new-line</pre>
7579 with the identical contained sequence (including > characters, if any) from the original
7582 A preprocessing directive of the form
7584 # include pp-tokens new-line</pre>
7585 (that does not match one of the two previous forms) is permitted. The preprocessing
7586 tokens after include in the directive are processed just as in normal text. (Each
7587 identifier currently defined as a macro name is replaced by its replacement list of
7588 preprocessing tokens.) The directive resulting after all replacements shall match one of
7589 the two previous forms.<sup><a href="#note148"><b>148)</b></a></sup> The method by which a sequence of preprocessing tokens
7590 between a < and a > preprocessing token pair or a pair of " characters is combined into a
7591 single header name preprocessing token is implementation-defined.
7593 The implementation shall provide unique mappings for sequences consisting of one or
7594 more nondigits or digits (<a href="#6.4.2.1">6.4.2.1</a>) followed by a period (.) and a single nondigit. The
7595 first character shall not be a digit. The implementation may ignore distinctions of
7596 alphabetical case and restrict the mapping to eight significant characters before the
7599 A #include preprocessing directive may appear in a source file that has been read
7600 because of a #include directive in another file, up to an implementation-defined
7601 nesting limit (see <a href="#5.2.4.1">5.2.4.1</a>).
7603 EXAMPLE 1 The most common uses of #include preprocessing directives are as in the following:
7605 #include <a href="#7.19"><stdio.h></a>
7606 #include "myprog.h"</pre>
7609 EXAMPLE 2 This illustrates macro-replaced #include directives:
7617 #define INCFILE "vers1.h"
7619 #define INCFILE "vers2.h" // and so on
7621 #define INCFILE "versN.h"
7623 #include INCFILE</pre>
7625 <p><b> Forward references</b>: macro replacement (<a href="#6.10.3">6.10.3</a>).
7628 <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
7629 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.
7632 <h4><a name="6.10.3" href="#6.10.3">6.10.3 Macro replacement</a></h4>
7633 <h6>Constraints</h6>
7635 Two replacement lists are identical if and only if the preprocessing tokens in both have
7636 the same number, ordering, spelling, and white-space separation, where all white-space
7637 separations are considered identical.
7639 An identifier currently defined as an object-like macro shall not be redefined by another
7640 #define preprocessing directive unless the second definition is an object-like macro
7641 definition and the two replacement lists are identical. Likewise, an identifier currently
7642 defined as a function-like macro shall not be redefined by another #define
7643 preprocessing directive unless the second definition is a function-like macro definition
7644 that has the same number and spelling of parameters, and the two replacement lists are
7647 There shall be white-space between the identifier and the replacement list in the definition
7648 of an object-like macro.
7650 If the identifier-list in the macro definition does not end with an ellipsis, the number of
7651 arguments (including those arguments consisting of no preprocessing tokens) in an
7652 invocation of a function-like macro shall equal the number of parameters in the macro
7653 definition. Otherwise, there shall be more arguments in the invocation than there are
7654 parameters in the macro definition (excluding the ...). There shall exist a )
7655 preprocessing token that terminates the invocation.
7657 The identifier __VA_ARGS__ shall occur only in the replacement-list of a function-like
7658 macro that uses the ellipsis notation in the parameters.
7660 A parameter identifier in a function-like macro shall be uniquely declared within its
7664 The identifier immediately following the define is called the macro name. There is one
7665 name space for macro names. Any white-space characters preceding or following the
7666 replacement list of preprocessing tokens are not considered part of the replacement list
7667 for either form of macro.
7670 If a # preprocessing token, followed by an identifier, occurs lexically at the point at which
7671 a preprocessing directive could begin, the identifier is not subject to macro replacement.
7673 A preprocessing directive of the form
7675 # define identifier replacement-list new-line</pre>
7676 defines an object-like macro that causes each subsequent instance of the macro name<sup><a href="#note149"><b>149)</b></a></sup>
7677 to be replaced by the replacement list of preprocessing tokens that constitute the
7678 remainder of the directive. The replacement list is then rescanned for more macro names
7681 A preprocessing directive of the form
7683 # define identifier lparen identifier-listopt ) replacement-list new-line
7684 # define identifier lparen ... ) replacement-list new-line
7685 # define identifier lparen identifier-list , ... ) replacement-list new-line</pre>
7686 defines a function-like macro with parameters, whose use is similar syntactically to a
7687 function call. The parameters are specified by the optional list of identifiers, whose scope
7688 extends from their declaration in the identifier list until the new-line character that
7689 terminates the #define preprocessing directive. Each subsequent instance of the
7690 function-like macro name followed by a ( as the next preprocessing token introduces the
7691 sequence of preprocessing tokens that is replaced by the replacement list in the definition
7692 (an invocation of the macro). The replaced sequence of preprocessing tokens is
7693 terminated by the matching ) preprocessing token, skipping intervening matched pairs of
7694 left and right parenthesis preprocessing tokens. Within the sequence of preprocessing
7695 tokens making up an invocation of a function-like macro, new-line is considered a normal
7696 white-space character.
7698 The sequence of preprocessing tokens bounded by the outside-most matching parentheses
7699 forms the list of arguments for the function-like macro. The individual arguments within
7700 the list are separated by comma preprocessing tokens, but comma preprocessing tokens
7701 between matching inner parentheses do not separate arguments. If there are sequences of
7702 preprocessing tokens within the list of arguments that would otherwise act as
7703 preprocessing directives,<sup><a href="#note150"><b>150)</b></a></sup> the behavior is undefined.
7705 If there is a ... in the identifier-list in the macro definition, then the trailing arguments,
7706 including any separating comma preprocessing tokens, are merged to form a single item:
7707 the variable arguments. The number of arguments so combined is such that, following
7711 merger, the number of arguments is one more than the number of parameters in the macro
7712 definition (excluding the ...).
7715 <p><small><a name="note149" href="#note149">149)</a> Since, by macro-replacement time, all character constants and string literals are preprocessing tokens,
7716 not sequences possibly containing identifier-like subsequences (see <a href="#5.1.1.2">5.1.1.2</a>, translation phases), they
7717 are never scanned for macro names or parameters.
7719 <p><small><a name="note150" href="#note150">150)</a> Despite the name, a non-directive is a preprocessing directive.
7722 <h5><a name="6.10.3.1" href="#6.10.3.1">6.10.3.1 Argument substitution</a></h5>
7724 After the arguments for the invocation of a function-like macro have been identified,
7725 argument substitution takes place. A parameter in the replacement list, unless preceded
7726 by a # or ## preprocessing token or followed by a ## preprocessing token (see below), is
7727 replaced by the corresponding argument after all macros contained therein have been
7728 expanded. Before being substituted, each argument's preprocessing tokens are
7729 completely macro replaced as if they formed the rest of the preprocessing file; no other
7730 preprocessing tokens are available.
7732 An identifier __VA_ARGS__ that occurs in the replacement list shall be treated as if it
7733 were a parameter, and the variable arguments shall form the preprocessing tokens used to
7736 <h5><a name="6.10.3.2" href="#6.10.3.2">6.10.3.2 The # operator</a></h5>
7737 <h6>Constraints</h6>
7739 Each # preprocessing token in the replacement list for a function-like macro shall be
7740 followed by a parameter as the next preprocessing token in the replacement list.
7743 If, in the replacement list, a parameter is immediately preceded by a # preprocessing
7744 token, both are replaced by a single character string literal preprocessing token that
7745 contains the spelling of the preprocessing token sequence for the corresponding
7746 argument. Each occurrence of white space between the argument's preprocessing tokens
7747 becomes a single space character in the character string literal. White space before the
7748 first preprocessing token and after the last preprocessing token composing the argument
7749 is deleted. Otherwise, the original spelling of each preprocessing token in the argument
7750 is retained in the character string literal, except for special handling for producing the
7751 spelling of string literals and character constants: a \ character is inserted before each "
7752 and \ character of a character constant or string literal (including the delimiting "
7753 characters), except that it is implementation-defined whether a \ character is inserted
7754 before the \ character beginning a universal character name. If the replacement that
7755 results is not a valid character string literal, the behavior is undefined. The character
7756 string literal corresponding to an empty argument is "". The order of evaluation of # and
7757 ## operators is unspecified.
7760 <h5><a name="6.10.3.3" href="#6.10.3.3">6.10.3.3 The ## operator</a></h5>
7761 <h6>Constraints</h6>
7763 A ## preprocessing token shall not occur at the beginning or at the end of a replacement
7764 list for either form of macro definition.
7767 If, in the replacement list of a function-like macro, a parameter is immediately preceded
7768 or followed by a ## preprocessing token, the parameter is replaced by the corresponding
7769 argument's preprocessing token sequence; however, if an argument consists of no
7770 preprocessing tokens, the parameter is replaced by a placemarker preprocessing token
7771 instead.<sup><a href="#note151"><b>151)</b></a></sup>
7773 For both object-like and function-like macro invocations, before the replacement list is
7774 reexamined for more macro names to replace, each instance of a ## preprocessing token
7775 in the replacement list (not from an argument) is deleted and the preceding preprocessing
7776 token is concatenated with the following preprocessing token. Placemarker
7777 preprocessing tokens are handled specially: concatenation of two placemarkers results in
7778 a single placemarker preprocessing token, and concatenation of a placemarker with a
7779 non-placemarker preprocessing token results in the non-placemarker preprocessing token.
7780 If the result is not a valid preprocessing token, the behavior is undefined. The resulting
7781 token is available for further macro replacement. The order of evaluation of ## operators
7784 EXAMPLE In the following fragment:
7786 #define hash_hash # ## #
7787 #define mkstr(a) # a
7788 #define in_between(a) mkstr(a)
7789 #define join(c, d) in_between(c hash_hash d)
7790 char p[] = join(x, y); // equivalent to
7791 // char p[] = "x ## y";</pre>
7792 The expansion produces, at various stages:
7795 in_between(x hash_hash y)
7799 In other words, expanding hash_hash produces a new token, consisting of two adjacent sharp signs, but
7800 this new token is not the ## operator.
7806 <p><small><a name="note151" href="#note151">151)</a> Placemarker preprocessing tokens do not appear in the syntax because they are temporary entities that
7807 exist only within translation phase 4.
7810 <h5><a name="6.10.3.4" href="#6.10.3.4">6.10.3.4 Rescanning and further replacement</a></h5>
7812 After all parameters in the replacement list have been substituted and # and ##
7813 processing has taken place, all placemarker preprocessing tokens are removed. Then, the
7814 resulting preprocessing token sequence is rescanned, along with all subsequent
7815 preprocessing tokens of the source file, for more macro names to replace.
7817 If the name of the macro being replaced is found during this scan of the replacement list
7818 (not including the rest of the source file's preprocessing tokens), it is not replaced.
7819 Furthermore, if any nested replacements encounter the name of the macro being replaced,
7820 it is not replaced. These nonreplaced macro name preprocessing tokens are no longer
7821 available for further replacement even if they are later (re)examined in contexts in which
7822 that macro name preprocessing token would otherwise have been replaced.
7824 The resulting completely macro-replaced preprocessing token sequence is not processed
7825 as a preprocessing directive even if it resembles one, but all pragma unary operator
7826 expressions within it are then processed as specified in <a href="#6.10.9">6.10.9</a> below.
7828 <h5><a name="6.10.3.5" href="#6.10.3.5">6.10.3.5 Scope of macro definitions</a></h5>
7830 A macro definition lasts (independent of block structure) until a corresponding #undef
7831 directive is encountered or (if none is encountered) until the end of the preprocessing
7832 translation unit. Macro definitions have no significance after translation phase 4.
7834 A preprocessing directive of the form
7836 # undef identifier new-line</pre>
7837 causes the specified identifier no longer to be defined as a macro name. It is ignored if
7838 the specified identifier is not currently defined as a macro name.
7840 EXAMPLE 1 The simplest use of this facility is to define a ''manifest constant'', as in
7843 int table[TABSIZE];</pre>
7846 EXAMPLE 2 The following defines a function-like macro whose value is the maximum of its arguments.
7847 It has the advantages of working for any compatible types of the arguments and of generating in-line code
7848 without the overhead of function calling. It has the disadvantages of evaluating one or the other of its
7849 arguments a second time (including side effects) and generating more code than a function if invoked
7850 several times. It also cannot have its address taken, as it has none.
7852 #define max(a, b) ((a) > (b) ? (a) : (b))</pre>
7853 The parentheses ensure that the arguments and the resulting expression are bound properly.
7856 EXAMPLE 3 To illustrate the rules for redefinition and reexamination, the sequence
7859 #define f(a) f(x * (a))
7870 #define r(x,y) x ## y
7872 f(y+1) + f(f(z)) % t(t(g)(0) + t)(1);
7873 g(x+(3,4)-w) | h 5) & m
7875 p() i[q()] = { q(1), r(2,3), r(4,), r(,5), r(,) };
7876 char c[2][6] = { str(hello), str() };</pre>
7879 f(2 * (y+1)) + f(2 * (f(2 * (z[0])))) % f(2 * (0)) + t(1);
7880 f(2 * (2+(3,4)-0,1)) | f(2 * (~ 5)) & f(2 * (0,1))^m(0,1);
7881 int i[] = { 1, 23, 4, 5, };
7882 char c[2][6] = { "hello", "" };</pre>
7885 EXAMPLE 4 To illustrate the rules for creating character string literals and concatenating tokens, the
7889 #define xstr(s) str(s)
7890 #define debug(s, t) printf("x" # s "= %d, x" # t "= %s", \
7892 #define INCFILE(n) vers ## n
7893 #define glue(a, b) a ## b
7894 #define xglue(a, b) glue(a, b)
7895 #define HIGHLOW "hello"
7896 #define LOW LOW ", world"
7898 fputs(str(strncmp("abc\0d", "abc", '\4') // this goes away
7899 == 0) str(: @\n), s);
7900 #include xstr(INCFILE(2).h)
7902 xglue(HIGH, LOW)</pre>
7906 printf("x" "1" "= %d, x" "2" "= %s", x1, x2);
7908 "strncmp(\"abc\\0d\", \"abc\", '\\4') == 0" ": @\n",
7910 #include "vers2.h" (after macro replacement, before file access)
7912 "hello" ", world"</pre>
7913 or, after concatenation of the character string literals,
7915 printf("x1= %d, x2= %s", x1, x2);
7917 "strncmp(\"abc\\0d\", \"abc\", '\\4') == 0: @\n",
7919 #include "vers2.h" (after macro replacement, before file access)
7921 "hello, world"</pre>
7922 Space around the # and ## tokens in the macro definition is optional.
7925 EXAMPLE 5 To illustrate the rules for placemarker preprocessing tokens, the sequence
7927 #define t(x,y,z) x ## y ## z
7928 int j[] = { t(1,2,3), t(,4,5), t(6,,7), t(8,9,),
7929 t(10,,), t(,11,), t(,,12), t(,,) };</pre>
7932 int j[] = { 123, 45, 67, 89,
7933 10, 11, 12, };</pre>
7936 EXAMPLE 6 To demonstrate the redefinition rules, the following sequence is valid.
7938 #define OBJ_LIKE (1-1)
7939 #define OBJ_LIKE /* white space */ (1-1) /* other */
7940 #define FUNC_LIKE(a) ( a )
7941 #define FUNC_LIKE( a )( /* note the white space */ \
7942 a /* other stuff on this line
7944 But the following redefinitions are invalid:
7946 #define OBJ_LIKE (0) // different token sequence
7947 #define OBJ_LIKE (1 - 1) // different white space
7948 #define FUNC_LIKE(b) ( a ) // different parameter usage
7949 #define FUNC_LIKE(b) ( b ) // different parameter spelling</pre>
7952 EXAMPLE 7 Finally, to show the variable argument list macro facilities:
7955 #define debug(...) fprintf(stderr, __VA_ARGS__)
7956 #define showlist(...) puts(#__VA_ARGS__)
7957 #define report(test, ...) ((test)?puts(#test):\
7958 printf(__VA_ARGS__))
7960 debug("X = %d\n", x);
7961 showlist(The first, second, and third items.);
7962 report(x>y, "x is %d but y is %d", x, y);</pre>
7965 fprintf(stderr, "Flag" );
7966 fprintf(stderr, "X = %d\n", x );
7967 puts( "The first, second, and third items." );
7968 ((x>y)?puts("x>y"):
7969 printf("x is %d but y is %d", x, y));</pre>
7972 <h4><a name="6.10.4" href="#6.10.4">6.10.4 Line control</a></h4>
7973 <h6>Constraints</h6>
7975 The string literal of a #line directive, if present, shall be a character string literal.
7978 The line number of the current source line is one greater than the number of new-line
7979 characters read or introduced in translation phase 1 (<a href="#5.1.1.2">5.1.1.2</a>) while processing the source
7980 file to the current token.
7982 A preprocessing directive of the form
7984 # line digit-sequence new-line</pre>
7985 causes the implementation to behave as if the following sequence of source lines begins
7986 with a source line that has a line number as specified by the digit sequence (interpreted as
7987 a decimal integer). The digit sequence shall not specify zero, nor a number greater than
7990 A preprocessing directive of the form
7992 # line digit-sequence "s-char-sequenceopt" new-line</pre>
7993 sets the presumed line number similarly and changes the presumed name of the source
7994 file to be the contents of the character string literal.
7996 A preprocessing directive of the form
7998 # line pp-tokens new-line</pre>
7999 (that does not match one of the two previous forms) is permitted. The preprocessing
8000 tokens after line on the directive are processed just as in normal text (each identifier
8001 currently defined as a macro name is replaced by its replacement list of preprocessing
8002 tokens). The directive resulting after all replacements shall match one of the two
8003 previous forms and is then processed as appropriate.
8006 <h4><a name="6.10.5" href="#6.10.5">6.10.5 Error directive</a></h4>
8009 A preprocessing directive of the form
8011 # error pp-tokensopt new-line</pre>
8012 causes the implementation to produce a diagnostic message that includes the specified
8013 sequence of preprocessing tokens.
8015 <h4><a name="6.10.6" href="#6.10.6">6.10.6 Pragma directive</a></h4>
8018 A preprocessing directive of the form
8020 # pragma pp-tokensopt new-line</pre>
8021 where the preprocessing token STDC does not immediately follow pragma in the
8022 directive (prior to any macro replacement)<sup><a href="#note152"><b>152)</b></a></sup> causes the implementation to behave in an
8023 implementation-defined manner. The behavior might cause translation to fail or cause the
8024 translator or the resulting program to behave in a non-conforming manner. Any such
8025 pragma that is not recognized by the implementation is ignored.
8027 If the preprocessing token STDC does immediately follow pragma in the directive (prior
8028 to any macro replacement), then no macro replacement is performed on the directive, and
8029 the directive shall have one of the following forms<sup><a href="#note153"><b>153)</b></a></sup> whose meanings are described
8032 #pragma STDC FP_CONTRACT on-off-switch
8033 #pragma STDC FENV_ACCESS on-off-switch
8034 #pragma STDC CX_LIMITED_RANGE on-off-switch
8035 on-off-switch: one of
8036 ON OFF DEFAULT</pre>
8037 <p><b> Forward references</b>: the FP_CONTRACT pragma (<a href="#7.12.2">7.12.2</a>), the FENV_ACCESS pragma
8038 (<a href="#7.6.1">7.6.1</a>), the CX_LIMITED_RANGE pragma (<a href="#7.3.4">7.3.4</a>).
8046 <p><small><a name="note152" href="#note152">152)</a> An implementation is not required to perform macro replacement in pragmas, but it is permitted
8047 except for in standard pragmas (where STDC immediately follows pragma). If the result of macro
8048 replacement in a non-standard pragma has the same form as a standard pragma, the behavior is still
8049 implementation-defined; an implementation is permitted to behave as if it were the standard pragma,
8050 but is not required to.
8052 <p><small><a name="note153" href="#note153">153)</a> See ''future language directions'' (<a href="#6.11.8">6.11.8</a>).
8055 <h4><a name="6.10.7" href="#6.10.7">6.10.7 Null directive</a></h4>
8058 A preprocessing directive of the form
8063 <h4><a name="6.10.8" href="#6.10.8">6.10.8 Predefined macro names</a></h4>
8065 The following macro names<sup><a href="#note154"><b>154)</b></a></sup> shall be defined by the implementation:
8066 __DATE__ The date of translation of the preprocessing translation unit: a character
8068 string literal of the form "Mmm dd yyyy", where the names of the
8069 months are the same as those generated by the asctime function, and the
8070 first character of dd is a space character if the value is less than 10. If the
8071 date of translation is not available, an implementation-defined valid date
8072 shall be supplied.</pre>
8073 __FILE__ The presumed name of the current source file (a character string literal).<sup><a href="#note155"><b>155)</b></a></sup>
8074 __LINE__ The presumed line number (within the current source file) of the current
8076 source line (an integer constant).155)</pre>
8077 __STDC__ The integer constant 1, intended to indicate a conforming implementation.
8078 __STDC_HOSTED__ The integer constant 1 if the implementation is a hosted
8080 implementation or the integer constant 0 if it is not.</pre>
8081 __STDC_MB_MIGHT_NEQ_WC__ The integer constant 1, intended to indicate that, in
8083 the encoding for wchar_t, a member of the basic character set need not
8084 have a code value equal to its value when used as the lone character in an
8085 integer character constant.</pre>
8086 __STDC_VERSION__ The integer constant 199901L.<sup><a href="#note156"><b>156)</b></a></sup>
8087 __TIME__ The time of translation of the preprocessing translation unit: a character
8089 string literal of the form "hh:mm:ss" as in the time generated by the
8090 asctime function. If the time of translation is not available, an
8091 implementation-defined valid time shall be supplied.</pre>
8097 The following macro names are conditionally defined by the implementation:
8098 __STDC_IEC_559__ The integer constant 1, intended to indicate conformance to the
8100 specifications in <a href="#F">annex F</a> (IEC 60559 floating-point arithmetic).</pre>
8101 __STDC_IEC_559_COMPLEX__ The integer constant 1, intended to indicate
8103 adherence to the specifications in informative <a href="#G">annex G</a> (IEC 60559
8104 compatible complex arithmetic).</pre>
8105 __STDC_ISO_10646__ An integer constant of the form yyyymmL (for example,
8108 199712L). If this symbol is defined, then every character in the Unicode
8109 required set, when stored in an object of type wchar_t, has the same
8110 value as the short identifier of that character. The Unicode required set
8111 consists of all the characters that are defined by ISO/IEC 10646, along with
8112 all amendments and technical corrigenda, as of the specified year and
8114 The values of the predefined macros (except for __FILE__ and __LINE__) remain
8115 constant throughout the translation unit.
8117 None of these macro names, nor the identifier defined, shall be the subject of a
8118 #define or a #undef preprocessing directive. Any other predefined macro names
8119 shall begin with a leading underscore followed by an uppercase letter or a second
8122 The implementation shall not predefine the macro __cplusplus, nor shall it define it
8123 in any standard header.
8124 <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>).
8127 <p><small><a name="note154" href="#note154">154)</a> See ''future language directions'' (<a href="#6.11.9">6.11.9</a>).
8129 <p><small><a name="note155" href="#note155">155)</a> The presumed source file name and line number can be changed by the #line directive.
8131 <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
8132 ISO/IEC 9899/AMD1:1995. The intention is that this will remain an integer constant of type long
8133 int that is increased with each revision of this International Standard.
8136 <h4><a name="6.10.9" href="#6.10.9">6.10.9 Pragma operator</a></h4>
8139 A unary operator expression of the form:
8141 _Pragma ( string-literal )</pre>
8142 is processed as follows: The string literal is destringized by deleting the L prefix, if
8143 present, deleting the leading and trailing double-quotes, replacing each escape sequence
8144 \" by a double-quote, and replacing each escape sequence \\ by a single backslash. The
8145 resulting sequence of characters is processed through translation phase 3 to produce
8146 preprocessing tokens that are executed as if they were the pp-tokens in a pragma
8147 directive. The original four preprocessing tokens in the unary operator expression are
8150 EXAMPLE A directive of the form:
8152 #pragma listing on "..\listing.dir"</pre>
8153 can also be expressed as:
8156 _Pragma ( "listing on \"..\\listing.dir\"" )</pre>
8157 The latter form is processed in the same way whether it appears literally as shown, or results from macro
8161 #define LISTING(x) PRAGMA(listing on #x)
8162 #define PRAGMA(x) _Pragma(#x)
8163 LISTING ( ..\listing.dir )</pre>
8165 <h3><a name="6.11" href="#6.11">6.11 Future language directions</a></h3>
8167 <h4><a name="6.11.1" href="#6.11.1">6.11.1 Floating types</a></h4>
8169 Future standardization may include additional floating-point types, including those with
8170 greater range, precision, or both than long double.
8172 <h4><a name="6.11.2" href="#6.11.2">6.11.2 Linkages of identifiers</a></h4>
8174 Declaring an identifier with internal linkage at file scope without the static storage-
8175 class specifier is an obsolescent feature.
8177 <h4><a name="6.11.3" href="#6.11.3">6.11.3 External names</a></h4>
8179 Restriction of the significance of an external name to fewer than 255 characters
8180 (considering each universal character name or extended source character as a single
8181 character) is an obsolescent feature that is a concession to existing implementations.
8183 <h4><a name="6.11.4" href="#6.11.4">6.11.4 Character escape sequences</a></h4>
8185 Lowercase letters as escape sequences are reserved for future standardization. Other
8186 characters may be used in extensions.
8188 <h4><a name="6.11.5" href="#6.11.5">6.11.5 Storage-class specifiers</a></h4>
8190 The placement of a storage-class specifier other than at the beginning of the declaration
8191 specifiers in a declaration is an obsolescent feature.
8193 <h4><a name="6.11.6" href="#6.11.6">6.11.6 Function declarators</a></h4>
8195 The use of function declarators with empty parentheses (not prototype-format parameter
8196 type declarators) is an obsolescent feature.
8198 <h4><a name="6.11.7" href="#6.11.7">6.11.7 Function definitions</a></h4>
8200 The use of function definitions with separate parameter identifier and declaration lists
8201 (not prototype-format parameter type and identifier declarators) is an obsolescent feature.
8203 <h4><a name="6.11.8" href="#6.11.8">6.11.8 Pragma directives</a></h4>
8205 Pragmas whose first preprocessing token is STDC are reserved for future standardization.
8207 <h4><a name="6.11.9" href="#6.11.9">6.11.9 Predefined macro names</a></h4>
8209 Macro names beginning with __STDC_ are reserved for future standardization.
8212 <h2><a name="7" href="#7">7. Library</a></h2>
8215 <h3><a name="7.1" href="#7.1">7.1 Introduction</a></h3>
8217 <h4><a name="7.1.1" href="#7.1.1">7.1.1 Definitions of terms</a></h4>
8219 A string is a contiguous sequence of characters terminated by and including the first null
8220 character. The term multibyte string is sometimes used instead to emphasize special
8221 processing given to multibyte characters contained in the string or to avoid confusion
8222 with a wide string. A pointer to a string is a pointer to its initial (lowest addressed)
8223 character. The length of a string is the number of bytes preceding the null character and
8224 the value of a string is the sequence of the values of the contained characters, in order.
8226 The decimal-point character is the character used by functions that convert floating-point
8227 numbers to or from character sequences to denote the beginning of the fractional part of
8228 such character sequences.<sup><a href="#note157"><b>157)</b></a></sup> It is represented in the text and examples by a period, but
8229 may be changed by the setlocale function.
8231 A null wide character is a wide character with code value zero.
8233 A wide string is a contiguous sequence of wide characters terminated by and including
8234 the first null wide character. A pointer to a wide string is a pointer to its initial (lowest
8235 addressed) wide character. The length of a wide string is the number of wide characters
8236 preceding the null wide character and the value of a wide string is the sequence of code
8237 values of the contained wide characters, in order.
8239 A shift sequence is a contiguous sequence of bytes within a multibyte string that
8240 (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
8241 corresponding wide character; it is instead taken to be an adjunct to an adjacent multibyte
8242 character.<sup><a href="#note158"><b>158)</b></a></sup>
8243 <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>).
8251 <p><small><a name="note157" href="#note157">157)</a> The functions that make use of the decimal-point character are the numeric conversion functions
8252 (<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>).
8254 <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
8255 enough to count all the bytes in any complete multibyte character plus at least one adjacent shift
8256 sequence of maximum length. Whether these counts provide for more than one shift sequence is the
8257 implementation's choice.
8260 <h4><a name="7.1.2" href="#7.1.2">7.1.2 Standard headers</a></h4>
8262 Each library function is declared, with a type that includes a prototype, in a header,<sup><a href="#note159"><b>159)</b></a></sup>
8263 whose contents are made available by the #include preprocessing directive. The
8264 header declares a set of related functions, plus any necessary types and additional macros
8265 needed to facilitate their use. Declarations of types described in this clause shall not
8266 include type qualifiers, unless explicitly stated otherwise.
8268 The standard headers are
8271 <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>
8272 <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>
8273 <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>
8274 <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>
8275 <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>
8276 <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>
8277 If a file with the same name as one of the above < and > delimited sequences, not
8278 provided as part of the implementation, is placed in any of the standard places that are
8279 searched for included source files, the behavior is undefined.
8281 Standard headers may be included in any order; each may be included more than once in
8282 a given scope, with no effect different from being included only once, except that the
8283 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
8284 used, a header shall be included outside of any external declaration or definition, and it
8285 shall first be included before the first reference to any of the functions or objects it
8286 declares, or to any of the types or macros it defines. However, if an identifier is declared
8287 or defined in more than one header, the second and subsequent associated headers may be
8288 included after the initial reference to the identifier. The program shall not have any
8289 macros with names lexically identical to keywords currently defined prior to the
8292 Any definition of an object-like macro described in this clause shall expand to code that is
8293 fully protected by parentheses where necessary, so that it groups in an arbitrary
8294 expression as if it were a single identifier.
8296 Any declaration of a library function shall have external linkage.
8298 A summary of the contents of the standard headers is given in <a href="#B">annex B</a>.
8299 <p><b> Forward references</b>: diagnostics (<a href="#7.2">7.2</a>).
8307 <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
8308 necessarily valid source file names.
8311 <h4><a name="7.1.3" href="#7.1.3">7.1.3 Reserved identifiers</a></h4>
8313 Each header declares or defines all identifiers listed in its associated subclause, and
8314 optionally declares or defines identifiers listed in its associated future library directions
8315 subclause and identifiers which are always reserved either for any use or for use as file
8318 <li> All identifiers that begin with an underscore and either an uppercase letter or another
8319 underscore are always reserved for any use.
8320 <li> All identifiers that begin with an underscore are always reserved for use as identifiers
8321 with file scope in both the ordinary and tag name spaces.
8322 <li> Each macro name in any of the following subclauses (including the future library
8323 directions) is reserved for use as specified if any of its associated headers is included;
8324 unless explicitly stated otherwise (see <a href="#7.1.4">7.1.4</a>).
8325 <li> All identifiers with external linkage in any of the following subclauses (including the
8326 future library directions) are always reserved for use as identifiers with external
8327 linkage.<sup><a href="#note160"><b>160)</b></a></sup>
8328 <li> Each identifier with file scope listed in any of the following subclauses (including the
8329 future library directions) is reserved for use as a macro name and as an identifier with
8330 file scope in the same name space if any of its associated headers is included.
8333 No other identifiers are reserved. If the program declares or defines an identifier in a
8334 context in which it is reserved (other than as allowed by <a href="#7.1.4">7.1.4</a>), or defines a reserved
8335 identifier as a macro name, the behavior is undefined.
8337 If the program removes (with #undef) any macro definition of an identifier in the first
8338 group listed above, the behavior is undefined.
8341 <p><small><a name="note160" href="#note160">160)</a> The list of reserved identifiers with external linkage includes errno, math_errhandling,
8345 <h4><a name="7.1.4" href="#7.1.4">7.1.4 Use of library functions</a></h4>
8347 Each of the following statements applies unless explicitly stated otherwise in the detailed
8348 descriptions that follow: If an argument to a function has an invalid value (such as a value
8349 outside the domain of the function, or a pointer outside the address space of the program,
8350 or a null pointer, or a pointer to non-modifiable storage when the corresponding
8351 parameter is not const-qualified) or a type (after promotion) not expected by a function
8352 with variable number of arguments, the behavior is undefined. If a function argument is
8353 described as being an array, the pointer actually passed to the function shall have a value
8354 such that all address computations and accesses to objects (that would be valid if the
8355 pointer did point to the first element of such an array) are in fact valid. Any function
8356 declared in a header may be additionally implemented as a function-like macro defined in
8359 the header, so if a library function is declared explicitly when its header is included, one
8360 of the techniques shown below can be used to ensure the declaration is not affected by
8361 such a macro. Any macro definition of a function can be suppressed locally by enclosing
8362 the name of the function in parentheses, because the name is then not followed by the left
8363 parenthesis that indicates expansion of a macro function name. For the same syntactic
8364 reason, it is permitted to take the address of a library function even if it is also defined as
8365 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
8366 actual function is referred to. Any invocation of a library function that is implemented as
8367 a macro shall expand to code that evaluates each of its arguments exactly once, fully
8368 protected by parentheses where necessary, so it is generally safe to use arbitrary
8369 expressions as arguments.<sup><a href="#note162"><b>162)</b></a></sup> Likewise, those function-like macros described in the
8370 following subclauses may be invoked in an expression anywhere a function with a
8371 compatible return type could be called.<sup><a href="#note163"><b>163)</b></a></sup> All object-like macros listed as expanding to
8372 integer constant expressions shall additionally be suitable for use in #if preprocessing
8375 Provided that a library function can be declared without reference to any type defined in a
8376 header, it is also permissible to declare the function and use it without including its
8379 There is a sequence point immediately before a library function returns.
8381 The functions in the standard library are not guaranteed to be reentrant and may modify
8382 objects with static storage duration.<sup><a href="#note164"><b>164)</b></a></sup>
8388 EXAMPLE The function atoi may be used in any of several ways:
8390 <li> by use of its associated header (possibly generating a macro expansion)
8392 #include <a href="#7.20"><stdlib.h></a>
8395 i = atoi(str);</pre>
8396 <li> by use of its associated header (assuredly generating a true function reference)
8398 #include <a href="#7.20"><stdlib.h></a>
8402 i = atoi(str);</pre>
8405 #include <a href="#7.20"><stdlib.h></a>
8408 i = (atoi)(str);</pre>
8409 <li> by explicit declaration
8412 extern int atoi(const char *);
8415 i = atoi(str);</pre>
8419 <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
8420 also provides a macro for that function.
8422 <p><small><a name="note162" href="#note162">162)</a> Such macros might not contain the sequence points that the corresponding function calls do.
8424 <p><small><a name="note163" href="#note163">163)</a> Because external identifiers and some macro names beginning with an underscore are reserved,
8425 implementations may provide special semantics for such names. For example, the identifier
8426 _BUILTIN_abs could be used to indicate generation of in-line code for the abs function. Thus, the
8427 appropriate header could specify
8430 #define abs(x) _BUILTIN_abs(x)</pre>
8431 for a compiler whose code generator will accept it.
8432 In this manner, a user desiring to guarantee that a given library function such as abs will be a genuine
8437 whether the implementation's header provides a macro implementation of abs or a built-in
8438 implementation. The prototype for the function, which precedes and is hidden by any macro
8439 definition, is thereby revealed also.
8441 <p><small><a name="note164" href="#note164">164)</a> Thus, a signal handler cannot, in general, call standard library functions.
8444 <h3><a name="7.2" href="#7.2">7.2 Diagnostics <assert.h></a></h3>
8446 The header <a href="#7.2"><assert.h></a> defines the assert macro and refers to another macro,
8449 which is not defined by <a href="#7.2"><assert.h></a>. If NDEBUG is defined as a macro name at the
8450 point in the source file where <a href="#7.2"><assert.h></a> is included, the assert macro is defined
8453 #define assert(ignore) ((void)0)</pre>
8454 The assert macro is redefined according to the current state of NDEBUG each time that
8455 <a href="#7.2"><assert.h></a> is included.
8457 The assert macro shall be implemented as a macro, not as an actual function. If the
8458 macro definition is suppressed in order to access an actual function, the behavior is
8461 <h4><a name="7.2.1" href="#7.2.1">7.2.1 Program diagnostics</a></h4>
8463 <h5><a name="7.2.1.1" href="#7.2.1.1">7.2.1.1 The assert macro</a></h5>
8467 #include <a href="#7.2"><assert.h></a>
8468 void assert(scalar expression);</pre>
8469 <h6>Description</h6>
8471 The assert macro puts diagnostic tests into programs; it expands to a void expression.
8472 When it is executed, if expression (which shall have a scalar type) is false (that is,
8473 compares equal to 0), the assert macro writes information about the particular call that
8474 failed (including the text of the argument, the name of the source file, the source line
8475 number, and the name of the enclosing function -- the latter are respectively the values of
8476 the preprocessing macros __FILE__ and __LINE__ and of the identifier
8477 __func__) on the standard error stream in an implementation-defined format.<sup><a href="#note165"><b>165)</b></a></sup> It
8478 then calls the abort function.
8481 The assert macro returns no value.
8482 <p><b> Forward references</b>: the abort function (<a href="#7.20.4.1">7.20.4.1</a>).
8490 <p><small><a name="note165" href="#note165">165)</a> The message written might be of the form:
8491 Assertion failed: expression, function abc, file xyz, line nnn.
8494 <h3><a name="7.3" href="#7.3">7.3 Complex arithmetic <complex.h></a></h3>
8496 <h4><a name="7.3.1" href="#7.3.1">7.3.1 Introduction</a></h4>
8498 The header <a href="#7.3"><complex.h></a> defines macros and declares functions that support complex
8499 arithmetic.<sup><a href="#note166"><b>166)</b></a></sup> Each synopsis specifies a family of functions consisting of a principal
8500 function with one or more double complex parameters and a double complex or
8501 double return value; and other functions with the same name but with f and l suffixes
8502 which are corresponding functions with float and long double parameters and
8508 expands to _Complex; the macro
8511 expands to a constant expression of type const float _Complex, with the value of
8512 the imaginary unit.<sup><a href="#note167"><b>167)</b></a></sup>
8520 are defined if and only if the implementation supports imaginary types;<sup><a href="#note168"><b>168)</b></a></sup> if defined,
8521 they expand to _Imaginary and a constant expression of type const float
8522 _Imaginary with the value of the imaginary unit.
8527 expands to either _Imaginary_I or _Complex_I. If _Imaginary_I is not
8528 defined, I shall expand to _Complex_I.
8530 Notwithstanding the provisions of <a href="#7.1.3">7.1.3</a>, a program may undefine and perhaps then
8531 redefine the macros complex, imaginary, and I.
8532 <p><b> Forward references</b>: IEC 60559-compatible complex arithmetic (<a href="#G">annex G</a>).
8539 <p><small><a name="note166" href="#note166">166)</a> See ''future library directions'' (<a href="#7.26.1">7.26.1</a>).
8541 <p><small><a name="note167" href="#note167">167)</a> The imaginary unit is a number i such that i 2 = -1.
8543 <p><small><a name="note168" href="#note168">168)</a> A specification for imaginary types is in informative <a href="#G">annex G</a>.
8546 <h4><a name="7.3.2" href="#7.3.2">7.3.2 Conventions</a></h4>
8548 Values are interpreted as radians, not degrees. An implementation may set errno but is
8551 <h4><a name="7.3.3" href="#7.3.3">7.3.3 Branch cuts</a></h4>
8553 Some of the functions below have branch cuts, across which the function is
8554 discontinuous. For implementations with a signed zero (including all IEC 60559
8555 implementations) that follow the specifications of <a href="#G">annex G</a>, the sign of zero distinguishes
8556 one side of a cut from another so the function is continuous (except for format
8557 limitations) as the cut is approached from either side. For example, for the square root
8558 function, which has a branch cut along the negative real axis, the top of the cut, with
8559 imaginary part +0, maps to the positive imaginary axis, and the bottom of the cut, with
8560 imaginary part -0, maps to the negative imaginary axis.
8562 Implementations that do not support a signed zero (see <a href="#F">annex F</a>) cannot distinguish the
8563 sides of branch cuts. These implementations shall map a cut so the function is continuous
8564 as the cut is approached coming around the finite endpoint of the cut in a counter
8565 clockwise direction. (Branch cuts for the functions specified here have just one finite
8566 endpoint.) For example, for the square root function, coming counter clockwise around
8567 the finite endpoint of the cut along the negative real axis approaches the cut from above,
8568 so the cut maps to the positive imaginary axis.
8570 <h4><a name="7.3.4" href="#7.3.4">7.3.4 The CX_LIMITED_RANGE pragma</a></h4>
8574 #include <a href="#7.3"><complex.h></a>
8575 #pragma STDC CX_LIMITED_RANGE on-off-switch</pre>
8576 <h6>Description</h6>
8578 The usual mathematical formulas for complex multiply, divide, and absolute value are
8579 problematic because of their treatment of infinities and because of undue overflow and
8580 underflow. The CX_LIMITED_RANGE pragma can be used to inform the
8581 implementation that (where the state is ''on'') the usual mathematical formulas are
8582 acceptable.<sup><a href="#note169"><b>169)</b></a></sup> The pragma can occur either outside external declarations or preceding all
8583 explicit declarations and statements inside a compound statement. When outside external
8586 declarations, the pragma takes effect from its occurrence until another
8587 CX_LIMITED_RANGE pragma is encountered, or until the end of the translation unit.
8588 When inside a compound statement, the pragma takes effect from its occurrence until
8589 another CX_LIMITED_RANGE pragma is encountered (including within a nested
8590 compound statement), or until the end of the compound statement; at the end of a
8591 compound statement the state for the pragma is restored to its condition just before the
8592 compound statement. If this pragma is used in any other context, the behavior is
8593 undefined. The default state for the pragma is ''off''.
8596 <p><small><a name="note169" href="#note169">169)</a> The purpose of the pragma is to allow the implementation to use the formulas:
8599 (x + iy) x (u + iv) = (xu - yv) + i(yu + xv)
8600 (x + iy) / (u + iv) = [(xu + yv) + i(yu - xv)]/(u2 + v 2 )
8601 | x + iy | = (sqrt) x 2 + y 2
8602 ???????????????</pre>
8603 where the programmer can determine they are safe.
8606 <h4><a name="7.3.5" href="#7.3.5">7.3.5 Trigonometric functions</a></h4>
8608 <h5><a name="7.3.5.1" href="#7.3.5.1">7.3.5.1 The cacos functions</a></h5>
8612 #include <a href="#7.3"><complex.h></a>
8613 double complex cacos(double complex z);
8614 float complex cacosf(float complex z);
8615 long double complex cacosl(long double complex z);</pre>
8616 <h6>Description</h6>
8618 The cacos functions compute the complex arc cosine of z, with branch cuts outside the
8619 interval [-1, +1] along the real axis.
8622 The cacos functions return the complex arc cosine value, in the range of a strip
8623 mathematically unbounded along the imaginary axis and in the interval [0, pi ] along the
8626 <h5><a name="7.3.5.2" href="#7.3.5.2">7.3.5.2 The casin functions</a></h5>
8630 #include <a href="#7.3"><complex.h></a>
8631 double complex casin(double complex z);
8632 float complex casinf(float complex z);
8633 long double complex casinl(long double complex z);</pre>
8634 <h6>Description</h6>
8636 The casin functions compute the complex arc sine of z, with branch cuts outside the
8637 interval [-1, +1] along the real axis.
8640 The casin functions return the complex arc sine value, in the range of a strip
8641 mathematically unbounded along the imaginary axis and in the interval [-pi /2, +pi /2]
8642 along the real axis.
8645 <h5><a name="7.3.5.3" href="#7.3.5.3">7.3.5.3 The catan functions</a></h5>
8649 #include <a href="#7.3"><complex.h></a>
8650 double complex catan(double complex z);
8651 float complex catanf(float complex z);
8652 long double complex catanl(long double complex z);</pre>
8653 <h6>Description</h6>
8655 The catan functions compute the complex arc tangent of z, with branch cuts outside the
8656 interval [-i, +i] along the imaginary axis.
8659 The catan functions return the complex arc tangent value, in the range of a strip
8660 mathematically unbounded along the imaginary axis and in the interval [-pi /2, +pi /2]
8661 along the real axis.
8663 <h5><a name="7.3.5.4" href="#7.3.5.4">7.3.5.4 The ccos functions</a></h5>
8667 #include <a href="#7.3"><complex.h></a>
8668 double complex ccos(double complex z);
8669 float complex ccosf(float complex z);
8670 long double complex ccosl(long double complex z);</pre>
8671 <h6>Description</h6>
8673 The ccos functions compute the complex cosine of z.
8676 The ccos functions return the complex cosine value.
8678 <h5><a name="7.3.5.5" href="#7.3.5.5">7.3.5.5 The csin functions</a></h5>
8682 #include <a href="#7.3"><complex.h></a>
8683 double complex csin(double complex z);
8684 float complex csinf(float complex z);
8685 long double complex csinl(long double complex z);</pre>
8686 <h6>Description</h6>
8688 The csin functions compute the complex sine of z.
8691 The csin functions return the complex sine value.
8694 <h5><a name="7.3.5.6" href="#7.3.5.6">7.3.5.6 The ctan functions</a></h5>
8698 #include <a href="#7.3"><complex.h></a>
8699 double complex ctan(double complex z);
8700 float complex ctanf(float complex z);
8701 long double complex ctanl(long double complex z);</pre>
8702 <h6>Description</h6>
8704 The ctan functions compute the complex tangent of z.
8707 The ctan functions return the complex tangent value.
8709 <h4><a name="7.3.6" href="#7.3.6">7.3.6 Hyperbolic functions</a></h4>
8711 <h5><a name="7.3.6.1" href="#7.3.6.1">7.3.6.1 The cacosh functions</a></h5>
8715 #include <a href="#7.3"><complex.h></a>
8716 double complex cacosh(double complex z);
8717 float complex cacoshf(float complex z);
8718 long double complex cacoshl(long double complex z);</pre>
8719 <h6>Description</h6>
8721 The cacosh functions compute the complex arc hyperbolic cosine of z, with a branch
8722 cut at values less than 1 along the real axis.
8725 The cacosh functions return the complex arc hyperbolic cosine value, in the range of a
8726 half-strip of non-negative values along the real axis and in the interval [-ipi , +ipi ] along
8729 <h5><a name="7.3.6.2" href="#7.3.6.2">7.3.6.2 The casinh functions</a></h5>
8733 #include <a href="#7.3"><complex.h></a>
8734 double complex casinh(double complex z);
8735 float complex casinhf(float complex z);
8736 long double complex casinhl(long double complex z);</pre>
8737 <h6>Description</h6>
8739 The casinh functions compute the complex arc hyperbolic sine of z, with branch cuts
8740 outside the interval [-i, +i] along the imaginary axis.
8744 The casinh functions return the complex arc hyperbolic sine value, in the range of a
8745 strip mathematically unbounded along the real axis and in the interval [-ipi /2, +ipi /2]
8746 along the imaginary axis.
8748 <h5><a name="7.3.6.3" href="#7.3.6.3">7.3.6.3 The catanh functions</a></h5>
8752 #include <a href="#7.3"><complex.h></a>
8753 double complex catanh(double complex z);
8754 float complex catanhf(float complex z);
8755 long double complex catanhl(long double complex z);</pre>
8756 <h6>Description</h6>
8758 The catanh functions compute the complex arc hyperbolic tangent of z, with branch
8759 cuts outside the interval [-1, +1] along the real axis.
8762 The catanh functions return the complex arc hyperbolic tangent value, in the range of a
8763 strip mathematically unbounded along the real axis and in the interval [-ipi /2, +ipi /2]
8764 along the imaginary axis.
8766 <h5><a name="7.3.6.4" href="#7.3.6.4">7.3.6.4 The ccosh functions</a></h5>
8770 #include <a href="#7.3"><complex.h></a>
8771 double complex ccosh(double complex z);
8772 float complex ccoshf(float complex z);
8773 long double complex ccoshl(long double complex z);</pre>
8774 <h6>Description</h6>
8776 The ccosh functions compute the complex hyperbolic cosine of z.
8779 The ccosh functions return the complex hyperbolic cosine value.
8781 <h5><a name="7.3.6.5" href="#7.3.6.5">7.3.6.5 The csinh functions</a></h5>
8786 #include <a href="#7.3"><complex.h></a>
8787 double complex csinh(double complex z);
8788 float complex csinhf(float complex z);
8789 long double complex csinhl(long double complex z);</pre>
8790 <h6>Description</h6>
8792 The csinh functions compute the complex hyperbolic sine of z.
8795 The csinh functions return the complex hyperbolic sine value.
8797 <h5><a name="7.3.6.6" href="#7.3.6.6">7.3.6.6 The ctanh functions</a></h5>
8801 #include <a href="#7.3"><complex.h></a>
8802 double complex ctanh(double complex z);
8803 float complex ctanhf(float complex z);
8804 long double complex ctanhl(long double complex z);</pre>
8805 <h6>Description</h6>
8807 The ctanh functions compute the complex hyperbolic tangent of z.
8810 The ctanh functions return the complex hyperbolic tangent value.
8812 <h4><a name="7.3.7" href="#7.3.7">7.3.7 Exponential and logarithmic functions</a></h4>
8814 <h5><a name="7.3.7.1" href="#7.3.7.1">7.3.7.1 The cexp functions</a></h5>
8818 #include <a href="#7.3"><complex.h></a>
8819 double complex cexp(double complex z);
8820 float complex cexpf(float complex z);
8821 long double complex cexpl(long double complex z);</pre>
8822 <h6>Description</h6>
8824 The cexp functions compute the complex base-e exponential of z.
8827 The cexp functions return the complex base-e exponential value.
8829 <h5><a name="7.3.7.2" href="#7.3.7.2">7.3.7.2 The clog functions</a></h5>
8834 #include <a href="#7.3"><complex.h></a>
8835 double complex clog(double complex z);
8836 float complex clogf(float complex z);
8837 long double complex clogl(long double complex z);</pre>
8838 <h6>Description</h6>
8840 The clog functions compute the complex natural (base-e) logarithm of z, with a branch
8841 cut along the negative real axis.
8844 The clog functions return the complex natural logarithm value, in the range of a strip
8845 mathematically unbounded along the real axis and in the interval [-ipi , +ipi ] along the
8848 <h4><a name="7.3.8" href="#7.3.8">7.3.8 Power and absolute-value functions</a></h4>
8850 <h5><a name="7.3.8.1" href="#7.3.8.1">7.3.8.1 The cabs functions</a></h5>
8854 #include <a href="#7.3"><complex.h></a>
8855 double cabs(double complex z);
8856 float cabsf(float complex z);
8857 long double cabsl(long double complex z);</pre>
8858 <h6>Description</h6>
8860 The cabs functions compute the complex absolute value (also called norm, modulus, or
8864 The cabs functions return the complex absolute value.
8866 <h5><a name="7.3.8.2" href="#7.3.8.2">7.3.8.2 The cpow functions</a></h5>
8870 #include <a href="#7.3"><complex.h></a>
8871 double complex cpow(double complex x, double complex y);
8872 float complex cpowf(float complex x, float complex y);
8873 long double complex cpowl(long double complex x,
8874 long double complex y);</pre>
8875 <h6>Description</h6>
8877 The cpow functions compute the complex power function xy , with a branch cut for the
8878 first parameter along the negative real axis.
8881 The cpow functions return the complex power function value.
8884 <h5><a name="7.3.8.3" href="#7.3.8.3">7.3.8.3 The csqrt functions</a></h5>
8888 #include <a href="#7.3"><complex.h></a>
8889 double complex csqrt(double complex z);
8890 float complex csqrtf(float complex z);
8891 long double complex csqrtl(long double complex z);</pre>
8892 <h6>Description</h6>
8894 The csqrt functions compute the complex square root of z, with a branch cut along the
8898 The csqrt functions return the complex square root value, in the range of the right half-
8899 plane (including the imaginary axis).
8901 <h4><a name="7.3.9" href="#7.3.9">7.3.9 Manipulation functions</a></h4>
8903 <h5><a name="7.3.9.1" href="#7.3.9.1">7.3.9.1 The carg functions</a></h5>
8907 #include <a href="#7.3"><complex.h></a>
8908 double carg(double complex z);
8909 float cargf(float complex z);
8910 long double cargl(long double complex z);</pre>
8911 <h6>Description</h6>
8913 The carg functions compute the argument (also called phase angle) of z, with a branch
8914 cut along the negative real axis.
8917 The carg functions return the value of the argument in the interval [-pi , +pi ].
8919 <h5><a name="7.3.9.2" href="#7.3.9.2">7.3.9.2 The cimag functions</a></h5>
8924 #include <a href="#7.3"><complex.h></a>
8925 double cimag(double complex z);
8926 float cimagf(float complex z);
8927 long double cimagl(long double complex z);</pre>
8928 <h6>Description</h6>
8930 The cimag functions compute the imaginary part of z.<sup><a href="#note170"><b>170)</b></a></sup>
8933 The cimag functions return the imaginary part value (as a real).
8936 <p><small><a name="note170" href="#note170">170)</a> For a variable z of complex type, z == creal(z) + cimag(z)*I.
8939 <h5><a name="7.3.9.3" href="#7.3.9.3">7.3.9.3 The conj functions</a></h5>
8943 #include <a href="#7.3"><complex.h></a>
8944 double complex conj(double complex z);
8945 float complex conjf(float complex z);
8946 long double complex conjl(long double complex z);</pre>
8947 <h6>Description</h6>
8949 The conj functions compute the complex conjugate of z, by reversing the sign of its
8953 The conj functions return the complex conjugate value.
8955 <h5><a name="7.3.9.4" href="#7.3.9.4">7.3.9.4 The cproj functions</a></h5>
8959 #include <a href="#7.3"><complex.h></a>
8960 double complex cproj(double complex z);
8961 float complex cprojf(float complex z);
8962 long double complex cprojl(long double complex z);</pre>
8963 <h6>Description</h6>
8965 The cproj functions compute a projection of z onto the Riemann sphere: z projects to
8966 z except that all complex infinities (even those with one infinite part and one NaN part)
8967 project to positive infinity on the real axis. If z has an infinite part, then cproj(z) is
8970 INFINITY + I * copysign(0.0, cimag(z))</pre>
8973 The cproj functions return the value of the projection onto the Riemann sphere.
8980 <h5><a name="7.3.9.5" href="#7.3.9.5">7.3.9.5 The creal functions</a></h5>
8984 #include <a href="#7.3"><complex.h></a>
8985 double creal(double complex z);
8986 float crealf(float complex z);
8987 long double creall(long double complex z);</pre>
8988 <h6>Description</h6>
8990 The creal functions compute the real part of z.<sup><a href="#note171"><b>171)</b></a></sup>
8993 The creal functions return the real part value.
9001 <p><small><a name="note171" href="#note171">171)</a> For a variable z of complex type, z == creal(z) + cimag(z)*I.
9004 <h3><a name="7.4" href="#7.4">7.4 Character handling <ctype.h></a></h3>
9006 The header <a href="#7.4"><ctype.h></a> declares several functions useful for classifying and mapping
9007 characters.<sup><a href="#note172"><b>172)</b></a></sup> In all cases the argument is an int, the value of which shall be
9008 representable as an unsigned char or shall equal the value of the macro EOF. If the
9009 argument has any other value, the behavior is undefined.
9011 The behavior of these functions is affected by the current locale. Those functions that
9012 have locale-specific aspects only when not in the "C" locale are noted below.
9014 The term printing character refers to a member of a locale-specific set of characters, each
9015 of which occupies one printing position on a display device; the term control character
9016 refers to a member of a locale-specific set of characters that are not printing
9017 characters.<sup><a href="#note173"><b>173)</b></a></sup> All letters and digits are printing characters.
9018 <p><b> Forward references</b>: EOF (<a href="#7.19.1">7.19.1</a>), localization (<a href="#7.11">7.11</a>).
9021 <p><small><a name="note172" href="#note172">172)</a> See ''future library directions'' (<a href="#7.26.2">7.26.2</a>).
9023 <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
9024 whose values lie from 0x20 (space) through 0x7E (tilde); the control characters are those whose
9025 values lie from 0 (NUL) through 0x1F (US), and the character 0x7F (DEL).
9028 <h4><a name="7.4.1" href="#7.4.1">7.4.1 Character classification functions</a></h4>
9030 The functions in this subclause return nonzero (true) if and only if the value of the
9031 argument c conforms to that in the description of the function.
9033 <h5><a name="7.4.1.1" href="#7.4.1.1">7.4.1.1 The isalnum function</a></h5>
9037 #include <a href="#7.4"><ctype.h></a>
9038 int isalnum(int c);</pre>
9039 <h6>Description</h6>
9041 The isalnum function tests for any character for which isalpha or isdigit is true.
9043 <h5><a name="7.4.1.2" href="#7.4.1.2">7.4.1.2 The isalpha function</a></h5>
9047 #include <a href="#7.4"><ctype.h></a>
9048 int isalpha(int c);</pre>
9049 <h6>Description</h6>
9051 The isalpha function tests for any character for which isupper or islower is true,
9052 or any character that is one of a locale-specific set of alphabetic characters for which
9057 none of iscntrl, isdigit, ispunct, or isspace is true.<sup><a href="#note174"><b>174)</b></a></sup> In the "C" locale,
9058 isalpha returns true only for the characters for which isupper or islower is true.
9061 <p><small><a name="note174" href="#note174">174)</a> The functions islower and isupper test true or false separately for each of these additional
9062 characters; all four combinations are possible.
9065 <h5><a name="7.4.1.3" href="#7.4.1.3">7.4.1.3 The isblank function</a></h5>
9069 #include <a href="#7.4"><ctype.h></a>
9070 int isblank(int c);</pre>
9071 <h6>Description</h6>
9073 The isblank function tests for any character that is a standard blank character or is one
9074 of a locale-specific set of characters for which isspace is true and that is used to
9075 separate words within a line of text. The standard blank characters are the following:
9076 space (' '), and horizontal tab ('\t'). In the "C" locale, isblank returns true only
9077 for the standard blank characters.
9079 <h5><a name="7.4.1.4" href="#7.4.1.4">7.4.1.4 The iscntrl function</a></h5>
9083 #include <a href="#7.4"><ctype.h></a>
9084 int iscntrl(int c);</pre>
9085 <h6>Description</h6>
9087 The iscntrl function tests for any control character.
9089 <h5><a name="7.4.1.5" href="#7.4.1.5">7.4.1.5 The isdigit function</a></h5>
9093 #include <a href="#7.4"><ctype.h></a>
9094 int isdigit(int c);</pre>
9095 <h6>Description</h6>
9097 The isdigit function tests for any decimal-digit character (as defined in <a href="#5.2.1">5.2.1</a>).
9099 <h5><a name="7.4.1.6" href="#7.4.1.6">7.4.1.6 The isgraph function</a></h5>
9103 #include <a href="#7.4"><ctype.h></a>
9104 int isgraph(int c);</pre>
9110 <h6>Description</h6>
9112 The isgraph function tests for any printing character except space (' ').
9114 <h5><a name="7.4.1.7" href="#7.4.1.7">7.4.1.7 The islower function</a></h5>
9118 #include <a href="#7.4"><ctype.h></a>
9119 int islower(int c);</pre>
9120 <h6>Description</h6>
9122 The islower function tests for any character that is a lowercase letter or is one of a
9123 locale-specific set of characters for which none of iscntrl, isdigit, ispunct, or
9124 isspace is true. In the "C" locale, islower returns true only for the lowercase
9125 letters (as defined in <a href="#5.2.1">5.2.1</a>).
9127 <h5><a name="7.4.1.8" href="#7.4.1.8">7.4.1.8 The isprint function</a></h5>
9131 #include <a href="#7.4"><ctype.h></a>
9132 int isprint(int c);</pre>
9133 <h6>Description</h6>
9135 The isprint function tests for any printing character including space (' ').
9137 <h5><a name="7.4.1.9" href="#7.4.1.9">7.4.1.9 The ispunct function</a></h5>
9141 #include <a href="#7.4"><ctype.h></a>
9142 int ispunct(int c);</pre>
9143 <h6>Description</h6>
9145 The ispunct function tests for any printing character that is one of a locale-specific set
9146 of punctuation characters for which neither isspace nor isalnum is true. In the "C"
9147 locale, ispunct returns true for every printing character for which neither isspace
9148 nor isalnum is true.
9150 <h5><a name="7.4.1.10" href="#7.4.1.10">7.4.1.10 The isspace function</a></h5>
9154 #include <a href="#7.4"><ctype.h></a>
9155 int isspace(int c);</pre>
9156 <h6>Description</h6>
9158 The isspace function tests for any character that is a standard white-space character or
9159 is one of a locale-specific set of characters for which isalnum is false. The standard
9161 white-space characters are the following: space (' '), form feed ('\f'), new-line
9162 ('\n'), carriage return ('\r'), horizontal tab ('\t'), and vertical tab ('\v'). In the
9163 "C" locale, isspace returns true only for the standard white-space characters.
9165 <h5><a name="7.4.1.11" href="#7.4.1.11">7.4.1.11 The isupper function</a></h5>
9169 #include <a href="#7.4"><ctype.h></a>
9170 int isupper(int c);</pre>
9171 <h6>Description</h6>
9173 The isupper function tests for any character that is an uppercase letter or is one of a
9174 locale-specific set of characters for which none of iscntrl, isdigit, ispunct, or
9175 isspace is true. In the "C" locale, isupper returns true only for the uppercase
9176 letters (as defined in <a href="#5.2.1">5.2.1</a>).
9178 <h5><a name="7.4.1.12" href="#7.4.1.12">7.4.1.12 The isxdigit function</a></h5>
9182 #include <a href="#7.4"><ctype.h></a>
9183 int isxdigit(int c);</pre>
9184 <h6>Description</h6>
9186 The isxdigit function tests for any hexadecimal-digit character (as defined in <a href="#6.4.4.1">6.4.4.1</a>).
9188 <h4><a name="7.4.2" href="#7.4.2">7.4.2 Character case mapping functions</a></h4>
9190 <h5><a name="7.4.2.1" href="#7.4.2.1">7.4.2.1 The tolower function</a></h5>
9194 #include <a href="#7.4"><ctype.h></a>
9195 int tolower(int c);</pre>
9196 <h6>Description</h6>
9198 The tolower function converts an uppercase letter to a corresponding lowercase letter.
9201 If the argument is a character for which isupper is true and there are one or more
9202 corresponding characters, as specified by the current locale, for which islower is true,
9203 the tolower function returns one of the corresponding characters (always the same one
9204 for any given locale); otherwise, the argument is returned unchanged.
9207 <h5><a name="7.4.2.2" href="#7.4.2.2">7.4.2.2 The toupper function</a></h5>
9211 #include <a href="#7.4"><ctype.h></a>
9212 int toupper(int c);</pre>
9213 <h6>Description</h6>
9215 The toupper function converts a lowercase letter to a corresponding uppercase letter.
9218 If the argument is a character for which islower is true and there are one or more
9219 corresponding characters, as specified by the current locale, for which isupper is true,
9220 the toupper function returns one of the corresponding characters (always the same one
9221 for any given locale); otherwise, the argument is returned unchanged.
9224 <h3><a name="7.5" href="#7.5">7.5 Errors <errno.h></a></h3>
9226 The header <a href="#7.5"><errno.h></a> defines several macros, all relating to the reporting of error
9234 which expand to integer constant expressions with type int, distinct positive values, and
9235 which are suitable for use in #if preprocessing directives; and
9238 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
9239 positive error number by several library functions. It is unspecified whether errno is a
9240 macro or an identifier declared with external linkage. If a macro definition is suppressed
9241 in order to access an actual object, or a program defines an identifier with the name
9242 errno, the behavior is undefined.
9244 The value of errno is zero at program startup, but is never set to zero by any library
9245 function.<sup><a href="#note176"><b>176)</b></a></sup> The value of errno may be set to nonzero by a library function call
9246 whether or not there is an error, provided the use of errno is not documented in the
9247 description of the function in this International Standard.
9249 Additional macro definitions, beginning with E and a digit or E and an uppercase
9250 letter,<sup><a href="#note177"><b>177)</b></a></sup> may also be specified by the implementation.
9258 <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
9259 resulting from a function call (for example, *errno()).
9261 <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,
9262 then inspect it before a subsequent library function call. Of course, a library function can save the
9263 value of errno on entry and then set it to zero, as long as the original value is restored if errno's
9264 value is still zero just before the return.
9266 <p><small><a name="note177" href="#note177">177)</a> See ''future library directions'' (<a href="#7.26.3">7.26.3</a>).
9269 <h3><a name="7.6" href="#7.6">7.6 Floating-point environment <fenv.h></a></h3>
9271 The header <a href="#7.6"><fenv.h></a> declares two types and several macros and functions to provide
9272 access to the floating-point environment. The floating-point environment refers
9273 collectively to any floating-point status flags and control modes supported by the
9274 implementation.<sup><a href="#note178"><b>178)</b></a></sup> A floating-point status flag is a system variable whose value is set
9275 (but never cleared) when a floating-point exception is raised, which occurs as a side effect
9276 of exceptional floating-point arithmetic to provide auxiliary information.<sup><a href="#note179"><b>179)</b></a></sup> A floating-
9277 point control mode is a system variable whose value may be set by the user to affect the
9278 subsequent behavior of floating-point arithmetic.
9280 Certain programming conventions support the intended model of use for the floating-
9281 point environment:<sup><a href="#note180"><b>180)</b></a></sup>
9283 <li> a function call does not alter its caller's floating-point control modes, clear its caller's
9284 floating-point status flags, nor depend on the state of its caller's floating-point status
9285 flags unless the function is so documented;
9286 <li> a function call is assumed to require default floating-point control modes, unless its
9287 documentation promises otherwise;
9288 <li> a function call is assumed to have the potential for raising floating-point exceptions,
9289 unless its documentation promises otherwise.
9295 represents the entire floating-point environment.
9300 represents the floating-point status flags collectively, including any status the
9301 implementation associates with the flags.
9315 is defined if and only if the implementation supports the floating-point exception by
9316 means of the functions in 7.6.2.<sup><a href="#note181"><b>181)</b></a></sup> Additional implementation-defined floating-point
9317 exceptions, with macro definitions beginning with FE_ and an uppercase letter, may also
9318 be specified by the implementation. The defined macros expand to integer constant
9319 expressions with values such that bitwise ORs of all combinations of the macros result in
9320 distinct values, and furthermore, bitwise ANDs of all combinations of the macros result in
9321 zero.<sup><a href="#note182"><b>182)</b></a></sup>
9326 is simply the bitwise OR of all floating-point exception macros defined by the
9327 implementation. If no such macros are defined, FE_ALL_EXCEPT shall be defined as 0.
9335 is defined if and only if the implementation supports getting and setting the represented
9336 rounding direction by means of the fegetround and fesetround functions.
9337 Additional implementation-defined rounding directions, with macro definitions beginning
9338 with FE_ and an uppercase letter, may also be specified by the implementation. The
9339 defined macros expand to integer constant expressions whose values are distinct
9340 nonnegative values.<sup><a href="#note183"><b>183)</b></a></sup>
9349 represents the default floating-point environment -- the one installed at program startup
9351 <li> and has type ''pointer to const-qualified fenv_t''. It can be used as an argument to
9353 <a href="#7.6"><fenv.h></a> functions that manage the floating-point environment.
9355 Additional implementation-defined environments, with macro definitions beginning with
9356 FE_ and an uppercase letter, and having type ''pointer to const-qualified fenv_t'', may
9357 also be specified by the implementation.
9360 <p><small><a name="note178" href="#note178">178)</a> This header is designed to support the floating-point exception status flags and directed-rounding
9361 control modes required by IEC 60559, and other similar floating-point state information. Also it is
9362 designed to facilitate code portability among all systems.
9364 <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.
9366 <p><small><a name="note180" href="#note180">180)</a> With these conventions, a programmer can safely assume default floating-point control modes (or be
9367 unaware of them). The responsibilities associated with accessing the floating-point environment fall
9368 on the programmer or program that does so explicitly.
9370 <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
9371 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
9372 all the functions to succeed all the time.
9374 <p><small><a name="note182" href="#note182">182)</a> The macros should be distinct powers of two.
9376 <p><small><a name="note183" href="#note183">183)</a> Even though the rounding direction macros may expand to constants corresponding to the values of
9377 FLT_ROUNDS, they are not required to do so.
9380 <h4><a name="7.6.1" href="#7.6.1">7.6.1 The FENV_ACCESS pragma</a></h4>
9384 #include <a href="#7.6"><fenv.h></a>
9385 #pragma STDC FENV_ACCESS on-off-switch</pre>
9386 <h6>Description</h6>
9388 The FENV_ACCESS pragma provides a means to inform the implementation when a
9389 program might access the floating-point environment to test floating-point status flags or
9390 run under non-default floating-point control modes.<sup><a href="#note184"><b>184)</b></a></sup> The pragma shall occur either
9391 outside external declarations or preceding all explicit declarations and statements inside a
9392 compound statement. When outside external declarations, the pragma takes effect from
9393 its occurrence until another FENV_ACCESS pragma is encountered, or until the end of
9394 the translation unit. When inside a compound statement, the pragma takes effect from its
9395 occurrence until another FENV_ACCESS pragma is encountered (including within a
9396 nested compound statement), or until the end of the compound statement; at the end of a
9397 compound statement the state for the pragma is restored to its condition just before the
9398 compound statement. If this pragma is used in any other context, the behavior is
9399 undefined. If part of a program tests floating-point status flags, sets floating-point control
9400 modes, or runs under non-default mode settings, but was translated with the state for the
9401 FENV_ACCESS pragma ''off'', the behavior is undefined. The default state (''on'' or
9402 ''off'') for the pragma is implementation-defined. (When execution passes from a part of
9403 the program translated with FENV_ACCESS ''off'' to a part translated with
9404 FENV_ACCESS ''on'', the state of the floating-point status flags is unspecified and the
9405 floating-point control modes have their default settings.)
9415 #include <a href="#7.6"><fenv.h></a>
9418 #pragma STDC FENV_ACCESS ON
9426 If the function g might depend on status flags set as a side effect of the first x + 1, or if the second
9427 x + 1 might depend on control modes set as a side effect of the call to function g, then the program shall
9428 contain an appropriately placed invocation of #pragma STDC FENV_ACCESS ON.<sup><a href="#note185"><b>185)</b></a></sup>
9432 <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
9433 tests and mode changes (e.g., global common subexpression elimination, code motion, and constant
9434 folding). In general, if the state of FENV_ACCESS is ''off'', the translator can assume that default
9435 modes are in effect and the flags are not tested.
9437 <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
9438 hand, without the #pragma STDC FENV_ACCESS ON pragma, and assuming the default state is
9439 ''off'', just one evaluation of x + 1 would suffice.
9442 <h4><a name="7.6.2" href="#7.6.2">7.6.2 Floating-point exceptions</a></h4>
9444 The following functions provide access to the floating-point status flags.<sup><a href="#note186"><b>186)</b></a></sup> The int
9445 input argument for the functions represents a subset of floating-point exceptions, and can
9446 be zero or the bitwise OR of one or more floating-point exception macros, for example
9447 FE_OVERFLOW | FE_INEXACT. For other argument values the behavior of these
9448 functions is undefined.
9451 <p><small><a name="note186" href="#note186">186)</a> The functions fetestexcept, feraiseexcept, and feclearexcept support the basic
9452 abstraction of flags that are either set or clear. An implementation may endow floating-point status
9453 flags with more information -- for example, the address of the code which first raised the floating-
9454 point exception; the functions fegetexceptflag and fesetexceptflag deal with the full
9458 <h5><a name="7.6.2.1" href="#7.6.2.1">7.6.2.1 The feclearexcept function</a></h5>
9462 #include <a href="#7.6"><fenv.h></a>
9463 int feclearexcept(int excepts);</pre>
9464 <h6>Description</h6>
9466 The feclearexcept function attempts to clear the supported floating-point exceptions
9467 represented by its argument.
9470 The feclearexcept function returns zero if the excepts argument is zero or if all
9471 the specified exceptions were successfully cleared. Otherwise, it returns a nonzero value.
9476 <h5><a name="7.6.2.2" href="#7.6.2.2">7.6.2.2 The fegetexceptflag function</a></h5>
9480 #include <a href="#7.6"><fenv.h></a>
9481 int fegetexceptflag(fexcept_t *flagp,
9483 <h6>Description</h6>
9485 The fegetexceptflag function attempts to store an implementation-defined
9486 representation of the states of the floating-point status flags indicated by the argument
9487 excepts in the object pointed to by the argument flagp.
9490 The fegetexceptflag function returns zero if the representation was successfully
9491 stored. Otherwise, it returns a nonzero value.
9493 <h5><a name="7.6.2.3" href="#7.6.2.3">7.6.2.3 The feraiseexcept function</a></h5>
9497 #include <a href="#7.6"><fenv.h></a>
9498 int feraiseexcept(int excepts);</pre>
9499 <h6>Description</h6>
9501 The feraiseexcept function attempts to raise the supported floating-point exceptions
9502 represented by its argument.<sup><a href="#note187"><b>187)</b></a></sup> The order in which these floating-point exceptions are
9503 raised is unspecified, except as stated in <a href="#F.7.6">F.7.6</a>. Whether the feraiseexcept function
9504 additionally raises the ''inexact'' floating-point exception whenever it raises the
9505 ''overflow'' or ''underflow'' floating-point exception is implementation-defined.
9508 The feraiseexcept function returns zero if the excepts argument is zero or if all
9509 the specified exceptions were successfully raised. Otherwise, it returns a nonzero value.
9517 <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.
9518 Hence, enabled traps for floating-point exceptions raised by this function are taken. The specification
9519 in <a href="#F.7.6">F.7.6</a> is in the same spirit.
9522 <h5><a name="7.6.2.4" href="#7.6.2.4">7.6.2.4 The fesetexceptflag function</a></h5>
9526 #include <a href="#7.6"><fenv.h></a>
9527 int fesetexceptflag(const fexcept_t *flagp,
9529 <h6>Description</h6>
9531 The fesetexceptflag function attempts to set the floating-point status flags
9532 indicated by the argument excepts to the states stored in the object pointed to by
9533 flagp. The value of *flagp shall have been set by a previous call to
9534 fegetexceptflag whose second argument represented at least those floating-point
9535 exceptions represented by the argument excepts. This function does not raise floating-
9536 point exceptions, but only sets the state of the flags.
9539 The fesetexceptflag function returns zero if the excepts argument is zero or if
9540 all the specified flags were successfully set to the appropriate state. Otherwise, it returns
9543 <h5><a name="7.6.2.5" href="#7.6.2.5">7.6.2.5 The fetestexcept function</a></h5>
9547 #include <a href="#7.6"><fenv.h></a>
9548 int fetestexcept(int excepts);</pre>
9549 <h6>Description</h6>
9551 The fetestexcept function determines which of a specified subset of the floating-
9552 point exception flags are currently set. The excepts argument specifies the floating-
9553 point status flags to be queried.<sup><a href="#note188"><b>188)</b></a></sup>
9556 The fetestexcept function returns the value of the bitwise OR of the floating-point
9557 exception macros corresponding to the currently set floating-point exceptions included in
9560 EXAMPLE Call f if ''invalid'' is set, then g if ''overflow'' is set:
9567 #include <a href="#7.6"><fenv.h></a>
9570 #pragma STDC FENV_ACCESS ON
9572 feclearexcept(FE_INVALID | FE_OVERFLOW);
9573 // maybe raise exceptions
9574 set_excepts = fetestexcept(FE_INVALID | FE_OVERFLOW);
9575 if (set_excepts & FE_INVALID) f();
9576 if (set_excepts & FE_OVERFLOW) g();
9582 <p><small><a name="note188" href="#note188">188)</a> This mechanism allows testing several floating-point exceptions with just one function call.
9585 <h4><a name="7.6.3" href="#7.6.3">7.6.3 Rounding</a></h4>
9587 The fegetround and fesetround functions provide control of rounding direction
9590 <h5><a name="7.6.3.1" href="#7.6.3.1">7.6.3.1 The fegetround function</a></h5>
9594 #include <a href="#7.6"><fenv.h></a>
9595 int fegetround(void);</pre>
9596 <h6>Description</h6>
9598 The fegetround function gets the current rounding direction.
9601 The fegetround function returns the value of the rounding direction macro
9602 representing the current rounding direction or a negative value if there is no such
9603 rounding direction macro or the current rounding direction is not determinable.
9605 <h5><a name="7.6.3.2" href="#7.6.3.2">7.6.3.2 The fesetround function</a></h5>
9609 #include <a href="#7.6"><fenv.h></a>
9610 int fesetround(int round);</pre>
9611 <h6>Description</h6>
9613 The fesetround function establishes the rounding direction represented by its
9614 argument round. If the argument is not equal to the value of a rounding direction macro,
9615 the rounding direction is not changed.
9618 The fesetround function returns zero if and only if the requested rounding direction
9622 EXAMPLE Save, set, and restore the rounding direction. Report an error and abort if setting the
9623 rounding direction fails.
9625 #include <a href="#7.6"><fenv.h></a>
9626 #include <a href="#7.2"><assert.h></a>
9627 void f(int round_dir)
9629 #pragma STDC FENV_ACCESS ON
9632 save_round = fegetround();
9633 setround_ok = fesetround(round_dir);
9634 assert(setround_ok == 0);
9636 fesetround(save_round);
9641 <h4><a name="7.6.4" href="#7.6.4">7.6.4 Environment</a></h4>
9643 The functions in this section manage the floating-point environment -- status flags and
9644 control modes -- as one entity.
9646 <h5><a name="7.6.4.1" href="#7.6.4.1">7.6.4.1 The fegetenv function</a></h5>
9650 #include <a href="#7.6"><fenv.h></a>
9651 int fegetenv(fenv_t *envp);</pre>
9652 <h6>Description</h6>
9654 The fegetenv function attempts to store the current floating-point environment in the
9655 object pointed to by envp.
9658 The fegetenv function returns zero if the environment was successfully stored.
9659 Otherwise, it returns a nonzero value.
9661 <h5><a name="7.6.4.2" href="#7.6.4.2">7.6.4.2 The feholdexcept function</a></h5>
9665 #include <a href="#7.6"><fenv.h></a>
9666 int feholdexcept(fenv_t *envp);</pre>
9667 <h6>Description</h6>
9669 The feholdexcept function saves the current floating-point environment in the object
9670 pointed to by envp, clears the floating-point status flags, and then installs a non-stop
9671 (continue on floating-point exceptions) mode, if available, for all floating-point
9672 exceptions.<sup><a href="#note189"><b>189)</b></a></sup>
9676 The feholdexcept function returns zero if and only if non-stop floating-point
9677 exception handling was successfully installed.
9680 <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
9681 handling or aborting; if the system provides only the non-stop mode then installing it is trivial. For
9682 such systems, the feholdexcept function can be used in conjunction with the feupdateenv
9683 function to write routines that hide spurious floating-point exceptions from their callers.
9686 <h5><a name="7.6.4.3" href="#7.6.4.3">7.6.4.3 The fesetenv function</a></h5>
9690 #include <a href="#7.6"><fenv.h></a>
9691 int fesetenv(const fenv_t *envp);</pre>
9692 <h6>Description</h6>
9694 The fesetenv function attempts to establish the floating-point environment represented
9695 by the object pointed to by envp. The argument envp shall point to an object set by a
9696 call to fegetenv or feholdexcept, or equal a floating-point environment macro.
9697 Note that fesetenv merely installs the state of the floating-point status flags
9698 represented through its argument, and does not raise these floating-point exceptions.
9701 The fesetenv function returns zero if the environment was successfully established.
9702 Otherwise, it returns a nonzero value.
9704 <h5><a name="7.6.4.4" href="#7.6.4.4">7.6.4.4 The feupdateenv function</a></h5>
9708 #include <a href="#7.6"><fenv.h></a>
9709 int feupdateenv(const fenv_t *envp);</pre>
9710 <h6>Description</h6>
9712 The feupdateenv function attempts to save the currently raised floating-point
9713 exceptions in its automatic storage, install the floating-point environment represented by
9714 the object pointed to by envp, and then raise the saved floating-point exceptions. The
9715 argument envp shall point to an object set by a call to feholdexcept or fegetenv,
9716 or equal a floating-point environment macro.
9719 The feupdateenv function returns zero if all the actions were successfully carried out.
9720 Otherwise, it returns a nonzero value.
9727 EXAMPLE Hide spurious underflow floating-point exceptions:
9730 #include <a href="#7.6"><fenv.h></a>
9733 #pragma STDC FENV_ACCESS ON
9736 if (feholdexcept(&save_env))
9737 return /* indication of an environmental problem */;
9739 if (/* test spurious underflow */)
9740 if (feclearexcept(FE_UNDERFLOW))
9741 return /* indication of an environmental problem */;
9742 if (feupdateenv(&save_env))
9743 return /* indication of an environmental problem */;
9747 <h3><a name="7.7" href="#7.7">7.7 Characteristics of floating types <float.h></a></h3>
9749 The header <a href="#7.7"><float.h></a> defines several macros that expand to various limits and
9750 parameters of the standard floating-point types.
9752 The macros, their meanings, and the constraints (or restrictions) on their values are listed
9753 in <a href="#5.2.4.2.2">5.2.4.2.2</a>.
9756 <h3><a name="7.8" href="#7.8">7.8 Format conversion of integer types <inttypes.h></a></h3>
9758 The header <a href="#7.8"><inttypes.h></a> includes the header <a href="#7.18"><stdint.h></a> and extends it with
9759 additional facilities provided by hosted implementations.
9761 It declares functions for manipulating greatest-width integers and converting numeric
9762 character strings to greatest-width integers, and it declares the type
9765 which is a structure type that is the type of the value returned by the imaxdiv function.
9766 For each type declared in <a href="#7.18"><stdint.h></a>, it defines corresponding macros for conversion
9767 specifiers for use with the formatted input/output functions.<sup><a href="#note190"><b>190)</b></a></sup>
9768 <p><b> Forward references</b>: integer types <a href="#7.18"><stdint.h></a> (<a href="#7.18">7.18</a>), formatted input/output
9769 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>).
9772 <p><small><a name="note190" href="#note190">190)</a> See ''future library directions'' (<a href="#7.26.4">7.26.4</a>).
9775 <h4><a name="7.8.1" href="#7.8.1">7.8.1 Macros for format specifiers</a></h4>
9777 Each of the following object-like macros<sup><a href="#note191"><b>191)</b></a></sup> expands to a character string literal
9778 containing a conversion specifier, possibly modified by a length modifier, suitable for use
9779 within the format argument of a formatted input/output function when converting the
9780 corresponding integer type. These macro names have the general form of PRI (character
9781 string literals for the fprintf and fwprintf family) or SCN (character string literals
9782 for the fscanf and fwscanf family),<sup><a href="#note192"><b>192)</b></a></sup> followed by the conversion specifier,
9783 followed by a name corresponding to a similar type name in <a href="#7.18.1">7.18.1</a>. In these names, N
9784 represents the width of the type as described in <a href="#7.18.1">7.18.1</a>. For example, PRIdFAST32 can
9785 be used in a format string to print the value of an integer of type int_fast32_t.
9787 The fprintf macros for signed integers are:
9789 PRIdN PRIdLEASTN PRIdFASTN PRIdMAX PRIdPTR
9790 PRIiN PRIiLEASTN PRIiFASTN PRIiMAX PRIiPTR</pre>
9797 The fprintf macros for unsigned integers are:
9800 PRIoN PRIoLEASTN PRIoFASTN PRIoMAX PRIoPTR
9801 PRIuN PRIuLEASTN PRIuFASTN PRIuMAX PRIuPTR
9802 PRIxN PRIxLEASTN PRIxFASTN PRIxMAX PRIxPTR
9803 PRIXN PRIXLEASTN PRIXFASTN PRIXMAX PRIXPTR</pre>
9804 The fscanf macros for signed integers are:
9807 SCNdN SCNdLEASTN SCNdFASTN SCNdMAX SCNdPTR
9808 SCNiN SCNiLEASTN SCNiFASTN SCNiMAX SCNiPTR</pre>
9809 The fscanf macros for unsigned integers are:
9812 SCNoN SCNoLEASTN SCNoFASTN SCNoMAX SCNoPTR
9813 SCNuN SCNuLEASTN SCNuFASTN SCNuMAX SCNuPTR
9814 SCNxN SCNxLEASTN SCNxFASTN SCNxMAX SCNxPTR</pre>
9815 For each type that the implementation provides in <a href="#7.18"><stdint.h></a>, the corresponding
9816 fprintf macros shall be defined and the corresponding fscanf macros shall be
9817 defined unless the implementation does not have a suitable fscanf length modifier for
9822 #include <a href="#7.8"><inttypes.h></a>
9823 #include <a href="#7.24"><wchar.h></a>
9826 uintmax_t i = UINTMAX_MAX; // this type always exists
9827 wprintf(L"The largest integer value is %020"
9834 <p><small><a name="note191" href="#note191">191)</a> C++ implementations should define these macros only when __STDC_FORMAT_MACROS is defined
9835 before <a href="#7.8"><inttypes.h></a> is included.
9837 <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,
9838 different format specifiers may be required for fprintf and fscanf, even when the type is the
9842 <h4><a name="7.8.2" href="#7.8.2">7.8.2 Functions for greatest-width integer types</a></h4>
9844 <h5><a name="7.8.2.1" href="#7.8.2.1">7.8.2.1 The imaxabs function</a></h5>
9848 #include <a href="#7.8"><inttypes.h></a>
9849 intmax_t imaxabs(intmax_t j);</pre>
9850 <h6>Description</h6>
9852 The imaxabs function computes the absolute value of an integer j. If the result cannot
9853 be represented, the behavior is undefined.<sup><a href="#note193"><b>193)</b></a></sup>
9860 The imaxabs function returns the absolute value.
9863 <p><small><a name="note193" href="#note193">193)</a> The absolute value of the most negative number cannot be represented in two's complement.
9866 <h5><a name="7.8.2.2" href="#7.8.2.2">7.8.2.2 The imaxdiv function</a></h5>
9870 #include <a href="#7.8"><inttypes.h></a>
9871 imaxdiv_t imaxdiv(intmax_t numer, intmax_t denom);</pre>
9872 <h6>Description</h6>
9874 The imaxdiv function computes numer / denom and numer % denom in a single
9878 The imaxdiv function returns a structure of type imaxdiv_t comprising both the
9879 quotient and the remainder. The structure shall contain (in either order) the members
9880 quot (the quotient) and rem (the remainder), each of which has type intmax_t. If
9881 either part of the result cannot be represented, the behavior is undefined.
9883 <h5><a name="7.8.2.3" href="#7.8.2.3">7.8.2.3 The strtoimax and strtoumax functions</a></h5>
9887 #include <a href="#7.8"><inttypes.h></a>
9888 intmax_t strtoimax(const char * restrict nptr,
9889 char ** restrict endptr, int base);
9890 uintmax_t strtoumax(const char * restrict nptr,
9891 char ** restrict endptr, int base);</pre>
9892 <h6>Description</h6>
9894 The strtoimax and strtoumax functions are equivalent to the strtol, strtoll,
9895 strtoul, and strtoull functions, except that the initial portion of the string is
9896 converted to intmax_t and uintmax_t representation, respectively.
9899 The strtoimax and strtoumax functions return the converted value, if any. If no
9900 conversion could be performed, zero is returned. If the correct value is outside the range
9901 of representable values, INTMAX_MAX, INTMAX_MIN, or UINTMAX_MAX is returned
9902 (according to the return type and sign of the value, if any), and the value of the macro
9903 ERANGE is stored in errno.
9904 <p><b> Forward references</b>: the strtol, strtoll, strtoul, and strtoull functions
9905 (<a href="#7.20.1.4">7.20.1.4</a>).
9908 <h5><a name="7.8.2.4" href="#7.8.2.4">7.8.2.4 The wcstoimax and wcstoumax functions</a></h5>
9912 #include <a href="#7.17"><stddef.h></a> // for wchar_t
9913 #include <a href="#7.8"><inttypes.h></a>
9914 intmax_t wcstoimax(const wchar_t * restrict nptr,
9915 wchar_t ** restrict endptr, int base);
9916 uintmax_t wcstoumax(const wchar_t * restrict nptr,
9917 wchar_t ** restrict endptr, int base);</pre>
9918 <h6>Description</h6>
9920 The wcstoimax and wcstoumax functions are equivalent to the wcstol, wcstoll,
9921 wcstoul, and wcstoull functions except that the initial portion of the wide string is
9922 converted to intmax_t and uintmax_t representation, respectively.
9925 The wcstoimax function returns the converted value, if any. If no conversion could be
9926 performed, zero is returned. If the correct value is outside the range of representable
9927 values, INTMAX_MAX, INTMAX_MIN, or UINTMAX_MAX is returned (according to the
9928 return type and sign of the value, if any), and the value of the macro ERANGE is stored in
9930 <p><b> Forward references</b>: the wcstol, wcstoll, wcstoul, and wcstoull functions
9931 (<a href="#7.24.4.1.2">7.24.4.1.2</a>).
9934 <h3><a name="7.9" href="#7.9">7.9 Alternative spellings <iso646.h></a></h3>
9936 The header <a href="#7.9"><iso646.h></a> defines the following eleven macros (on the left) that expand
9937 to the corresponding tokens (on the right):
9952 <h3><a name="7.10" href="#7.10">7.10 Sizes of integer types <limits.h></a></h3>
9954 The header <a href="#7.10"><limits.h></a> defines several macros that expand to various limits and
9955 parameters of the standard integer types.
9957 The macros, their meanings, and the constraints (or restrictions) on their values are listed
9958 in <a href="#5.2.4.2.1">5.2.4.2.1</a>.
9961 <h3><a name="7.11" href="#7.11">7.11 Localization <locale.h></a></h3>
9963 The header <a href="#7.11"><locale.h></a> declares two functions, one type, and defines several macros.
9968 which contains members related to the formatting of numeric values. The structure shall
9969 contain at least the following members, in any order. The semantics of the members and
9970 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
9971 the values specified in the comments.
9975 char *decimal_point; // "."
9976 char *thousands_sep; // ""
9977 char *grouping; // ""
9978 char *mon_decimal_point; // ""
9979 char *mon_thousands_sep; // ""
9980 char *mon_grouping; // ""
9981 char *positive_sign; // ""
9982 char *negative_sign; // ""
9983 char *currency_symbol; // ""
9984 char frac_digits; // CHAR_MAX
9985 char p_cs_precedes; // CHAR_MAX
9986 char n_cs_precedes; // CHAR_MAX
9987 char p_sep_by_space; // CHAR_MAX
9988 char n_sep_by_space; // CHAR_MAX
9989 char p_sign_posn; // CHAR_MAX
9990 char n_sign_posn; // CHAR_MAX
9991 char *int_curr_symbol; // ""
9992 char int_frac_digits; // CHAR_MAX
9993 char int_p_cs_precedes; // CHAR_MAX
9994 char int_n_cs_precedes; // CHAR_MAX
9995 char int_p_sep_by_space; // CHAR_MAX
9996 char int_n_sep_by_space; // CHAR_MAX
9997 char int_p_sign_posn; // CHAR_MAX
9998 char int_n_sign_posn; // CHAR_MAX</pre>
9999 The macros defined are NULL (described in <a href="#7.17">7.17</a>); and
10007 which expand to integer constant expressions with distinct values, suitable for use as the
10008 first argument to the setlocale function.<sup><a href="#note194"><b>194)</b></a></sup> Additional macro definitions, beginning
10009 with the characters LC_ and an uppercase letter,<sup><a href="#note195"><b>195)</b></a></sup> may also be specified by the
10013 <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.
10015 <p><small><a name="note195" href="#note195">195)</a> See ''future library directions'' (<a href="#7.26.5">7.26.5</a>).
10018 <h4><a name="7.11.1" href="#7.11.1">7.11.1 Locale control</a></h4>
10020 <h5><a name="7.11.1.1" href="#7.11.1.1">7.11.1.1 The setlocale function</a></h5>
10024 #include <a href="#7.11"><locale.h></a>
10025 char *setlocale(int category, const char *locale);</pre>
10026 <h6>Description</h6>
10028 The setlocale function selects the appropriate portion of the program's locale as
10029 specified by the category and locale arguments. The setlocale function may be
10030 used to change or query the program's entire current locale or portions thereof. The value
10031 LC_ALL for category names the program's entire locale; the other values for
10032 category name only a portion of the program's locale. LC_COLLATE affects the
10033 behavior of the strcoll and strxfrm functions. LC_CTYPE affects the behavior of
10034 the character handling functions<sup><a href="#note196"><b>196)</b></a></sup> and the multibyte and wide character functions.
10035 LC_MONETARY affects the monetary formatting information returned by the
10036 localeconv function. LC_NUMERIC affects the decimal-point character for the
10037 formatted input/output functions and the string conversion functions, as well as the
10038 nonmonetary formatting information returned by the localeconv function. LC_TIME
10039 affects the behavior of the strftime and wcsftime functions.
10041 A value of "C" for locale specifies the minimal environment for C translation; a value
10042 of "" for locale specifies the locale-specific native environment. Other
10043 implementation-defined strings may be passed as the second argument to setlocale.
10047 At program startup, the equivalent of
10049 setlocale(LC_ALL, "C");</pre>
10052 The implementation shall behave as if no library function calls the setlocale function.
10055 If a pointer to a string is given for locale and the selection can be honored, the
10056 setlocale function returns a pointer to the string associated with the specified
10057 category for the new locale. If the selection cannot be honored, the setlocale
10058 function returns a null pointer and the program's locale is not changed.
10060 A null pointer for locale causes the setlocale function to return a pointer to the
10061 string associated with the category for the program's current locale; the program's
10062 locale is not changed.<sup><a href="#note197"><b>197)</b></a></sup>
10064 The pointer to string returned by the setlocale function is such that a subsequent call
10065 with that string value and its associated category will restore that part of the program's
10066 locale. The string pointed to shall not be modified by the program, but may be
10067 overwritten by a subsequent call to the setlocale function.
10068 <p><b> Forward references</b>: formatted input/output functions (<a href="#7.19.6">7.19.6</a>), multibyte/wide
10069 character conversion functions (<a href="#7.20.7">7.20.7</a>), multibyte/wide string conversion functions
10070 (<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
10071 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>).
10074 <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
10077 <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
10078 locale when category has the value LC_ALL.
10081 <h4><a name="7.11.2" href="#7.11.2">7.11.2 Numeric formatting convention inquiry</a></h4>
10083 <h5><a name="7.11.2.1" href="#7.11.2.1">7.11.2.1 The localeconv function</a></h5>
10087 #include <a href="#7.11"><locale.h></a>
10088 struct lconv *localeconv(void);</pre>
10089 <h6>Description</h6>
10091 The localeconv function sets the components of an object with type struct lconv
10092 with values appropriate for the formatting of numeric quantities (monetary and otherwise)
10093 according to the rules of the current locale.
10095 The members of the structure with type char * are pointers to strings, any of which
10096 (except decimal_point) can point to "", to indicate that the value is not available in
10097 the current locale or is of zero length. Apart from grouping and mon_grouping, the
10100 strings shall start and end in the initial shift state. The members with type char are
10101 nonnegative numbers, any of which can be CHAR_MAX to indicate that the value is not
10102 available in the current locale. The members include the following:
10103 char *decimal_point
10105 The decimal-point character used to format nonmonetary quantities.</pre>
10106 char *thousands_sep
10108 The character used to separate groups of digits before the decimal-point
10109 character in formatted nonmonetary quantities.</pre>
10112 A string whose elements indicate the size of each group of digits in
10113 formatted nonmonetary quantities.</pre>
10114 char *mon_decimal_point
10116 The decimal-point used to format monetary quantities.</pre>
10117 char *mon_thousands_sep
10119 The separator for groups of digits before the decimal-point in formatted
10120 monetary quantities.</pre>
10123 A string whose elements indicate the size of each group of digits in
10124 formatted monetary quantities.</pre>
10125 char *positive_sign
10127 The string used to indicate a nonnegative-valued formatted monetary
10129 char *negative_sign
10131 The string used to indicate a negative-valued formatted monetary quantity.</pre>
10132 char *currency_symbol
10134 The local currency symbol applicable to the current locale.</pre>
10137 The number of fractional digits (those after the decimal-point) to be
10138 displayed in a locally formatted monetary quantity.</pre>
10141 Set to 1 or 0 if the currency_symbol respectively precedes or
10142 succeeds the value for a nonnegative locally formatted monetary quantity.</pre>
10146 Set to 1 or 0 if the currency_symbol respectively precedes or
10147 succeeds the value for a negative locally formatted monetary quantity.</pre>
10148 char p_sep_by_space
10150 Set to a value indicating the separation of the currency_symbol, the
10151 sign string, and the value for a nonnegative locally formatted monetary
10153 char n_sep_by_space
10155 Set to a value indicating the separation of the currency_symbol, the
10156 sign string, and the value for a negative locally formatted monetary
10160 Set to a value indicating the positioning of the positive_sign for a
10161 nonnegative locally formatted monetary quantity.</pre>
10164 Set to a value indicating the positioning of the negative_sign for a
10165 negative locally formatted monetary quantity.</pre>
10166 char *int_curr_symbol
10168 The international currency symbol applicable to the current locale. The
10169 first three characters contain the alphabetic international currency symbol
10170 in accordance with those specified in ISO 4217. The fourth character
10171 (immediately preceding the null character) is the character used to separate
10172 the international currency symbol from the monetary quantity.</pre>
10173 char int_frac_digits
10175 The number of fractional digits (those after the decimal-point) to be
10176 displayed in an internationally formatted monetary quantity.</pre>
10177 char int_p_cs_precedes
10179 Set to 1 or 0 if the int_curr_symbol respectively precedes or
10180 succeeds the value for a nonnegative internationally formatted monetary
10182 char int_n_cs_precedes
10184 Set to 1 or 0 if the int_curr_symbol respectively precedes or
10185 succeeds the value for a negative internationally formatted monetary
10187 char int_p_sep_by_space
10190 Set to a value indicating the separation of the int_curr_symbol, the
10191 sign string, and the value for a nonnegative internationally formatted
10192 monetary quantity.</pre>
10193 char int_n_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 negative internationally formatted monetary
10198 char int_p_sign_posn
10200 Set to a value indicating the positioning of the positive_sign for a
10201 nonnegative internationally formatted monetary quantity.</pre>
10202 char int_n_sign_posn
10205 Set to a value indicating the positioning of the negative_sign for a
10206 negative internationally formatted monetary quantity.</pre>
10207 The elements of grouping and mon_grouping are interpreted according to the
10209 CHAR_MAX No further grouping is to be performed.
10210 0 The previous element is to be repeatedly used for the remainder of the
10213 other The integer value is the number of digits that compose the current group.
10216 The next element is examined to determine the size of the next group of
10217 digits before the current group.</pre>
10218 The values of p_sep_by_space, n_sep_by_space, int_p_sep_by_space,
10219 and int_n_sep_by_space are interpreted according to the following:
10220 0 No space separates the currency symbol and value.
10221 1 If the currency symbol and sign string are adjacent, a space separates them from the
10223 value; otherwise, a space separates the currency symbol from the value.</pre>
10224 2 If the currency symbol and sign string are adjacent, a space separates them;
10226 otherwise, a space separates the sign string from the value.</pre>
10227 For int_p_sep_by_space and int_n_sep_by_space, the fourth character of
10228 int_curr_symbol is used instead of a space.
10230 The values of p_sign_posn, n_sign_posn, int_p_sign_posn, and
10231 int_n_sign_posn are interpreted according to the following:
10232 0 Parentheses surround the quantity and currency symbol.
10233 1 The sign string precedes the quantity and currency symbol.
10234 2 The sign string succeeds the quantity and currency symbol.
10235 3 The sign string immediately precedes the currency symbol.
10236 4 The sign string immediately succeeds the currency symbol.
10239 The implementation shall behave as if no library function calls the localeconv
10243 The localeconv function returns a pointer to the filled-in object. The structure
10244 pointed to by the return value shall not be modified by the program, but may be
10245 overwritten by a subsequent call to the localeconv function. In addition, calls to the
10246 setlocale function with categories LC_ALL, LC_MONETARY, or LC_NUMERIC may
10247 overwrite the contents of the structure.
10249 EXAMPLE 1 The following table illustrates rules which may well be used by four countries to format
10250 monetary quantities.
10252 Local format International format</pre>
10254 Country Positive Negative Positive Negative
10256 Country1 1.234,56 mk -1.234,56 mk FIM 1.234,56 FIM -1.234,56
10257 Country2 L.1.234 -L.1.234 ITL 1.234 -ITL 1.234
10258 Country3 fl. 1.234,56 fl. -1.234,56 NLG 1.234,56 NLG -1.234,56
10259 Country4 SFrs.1,234.56 SFrs.1,234.56C CHF 1,234.56 CHF 1,234.56C
10261 For these four countries, the respective values for the monetary members of the structure returned by
10262 localeconv could be:
10264 Country1 Country2 Country3 Country4</pre>
10266 mon_decimal_point "," "" "," "."
10267 mon_thousands_sep "." "." "." ","
10268 mon_grouping "\3" "\3" "\3" "\3"
10269 positive_sign "" "" "" ""
10270 negative_sign "-" "-" "-" "C"
10271 currency_symbol "mk" "L." "\u0192" "SFrs."
10272 frac_digits 2 0 2 2
10273 p_cs_precedes 0 1 1 1
10274 n_cs_precedes 0 1 1 1
10275 p_sep_by_space 1 0 1 0
10276 n_sep_by_space 1 0 2 0
10277 p_sign_posn 1 1 1 1
10278 n_sign_posn 1 1 4 2
10279 int_curr_symbol "FIM " "ITL " "NLG " "CHF "
10280 int_frac_digits 2 0 2 2
10281 int_p_cs_precedes 1 1 1 1
10282 int_n_cs_precedes 1 1 1 1
10283 int_p_sep_by_space 1 1 1 1
10284 int_n_sep_by_space 2 1 2 1
10285 int_p_sign_posn 1 1 1 1
10286 int_n_sign_posn 4 1 4 2
10289 EXAMPLE 2 The following table illustrates how the cs_precedes, sep_by_space, and sign_posn members
10290 affect the formatted value.
10292 p_sep_by_space</pre>
10294 p_cs_precedes p_sign_posn 0 1 2
10297 0 0 (<a href="#1.25">1.25</a>$) (<a href="#1.25">1.25</a> $) (<a href="#1.25">1.25</a>$)
10298 1 +1.25$ +1.25 $ + <a href="#1.25">1.25</a>$
10299 2 <a href="#1.25">1.25</a>$+ <a href="#1.25">1.25</a> $+ <a href="#1.25">1.25</a>$ +
10300 3 <a href="#1.25">1.25</a>+$ <a href="#1.25">1.25</a> +$ <a href="#1.25">1.25</a>+ $
10301 4 <a href="#1.25">1.25</a>$+ <a href="#1.25">1.25</a> $+ <a href="#1.25">1.25</a>$ +</pre>
10305 1 0 ($1.25) ($ <a href="#1.25">1.25</a>) ($1.25)
10306 1 +$1.25 +$ <a href="#1.25">1.25</a> + $1.25
10307 2 $1.25+ $ <a href="#1.25">1.25</a>+ $1.25 +
10308 3 +$1.25 +$ <a href="#1.25">1.25</a> + $1.25
10309 4 $+1.25 $+ <a href="#1.25">1.25</a> $ +1.25</pre>
10311 <h3><a name="7.12" href="#7.12">7.12 Mathematics <math.h></a></h3>
10313 The header <a href="#7.12"><math.h></a> declares two types and many mathematical functions and defines
10314 several macros. Most synopses specify a family of functions consisting of a principal
10315 function with one or more double parameters, a double return value, or both; and
10316 other functions with the same name but with f and l suffixes, which are corresponding
10317 functions with float and long double parameters, return values, or both.<sup><a href="#note198"><b>198)</b></a></sup>
10318 Integer arithmetic functions and conversion functions are discussed later.
10324 are floating types at least as wide as float and double, respectively, and such that
10325 double_t is at least as wide as float_t. If FLT_EVAL_METHOD equals 0,
10326 float_t and double_t are float and double, respectively; if
10327 FLT_EVAL_METHOD equals 1, they are both double; if FLT_EVAL_METHOD equals
10328 2, they are both long double; and for other values of FLT_EVAL_METHOD, they are
10329 otherwise implementation-defined.<sup><a href="#note199"><b>199)</b></a></sup>
10334 expands to a positive double constant expression, not necessarily representable as a
10339 are respectively float and long double analogs of HUGE_VAL.<sup><a href="#note200"><b>200)</b></a></sup>
10344 expands to a constant expression of type float representing positive or unsigned
10345 infinity, if available; else to a positive constant of type float that overflows at
10350 translation time.<sup><a href="#note201"><b>201)</b></a></sup>
10355 is defined if and only if the implementation supports quiet NaNs for the float type. It
10356 expands to a constant expression of type float representing a quiet NaN.
10358 The number classification macros
10365 represent the mutually exclusive kinds of floating-point values. They expand to integer
10366 constant expressions with distinct values. Additional implementation-defined floating-
10367 point classifications, with macro definitions beginning with FP_ and an uppercase letter,
10368 may also be specified by the implementation.
10373 is optionally defined. If defined, it indicates that the fma function generally executes
10374 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
10379 are, respectively, float and long double analogs of FP_FAST_FMA. If defined,
10380 these macros expand to the integer constant 1.
10386 expand to integer constant expressions whose values are returned by ilogb(x) if x is
10387 zero or NaN, respectively. The value of FP_ILOGB0 shall be either INT_MIN or
10388 -INT_MAX. The value of FP_ILOGBNAN shall be either INT_MAX or INT_MIN.
10396 MATH_ERREXCEPT</pre>
10397 expand to the integer constants 1 and 2, respectively; the macro
10399 math_errhandling</pre>
10400 expands to an expression that has type int and the value MATH_ERRNO,
10401 MATH_ERREXCEPT, or the bitwise OR of both. The value of math_errhandling is
10402 constant for the duration of the program. It is unspecified whether
10403 math_errhandling is a macro or an identifier with external linkage. If a macro
10404 definition is suppressed or a program defines an identifier with the name
10405 math_errhandling, the behavior is undefined. If the expression
10406 math_errhandling & MATH_ERREXCEPT can be nonzero, the implementation
10407 shall define the macros FE_DIVBYZERO, FE_INVALID, and FE_OVERFLOW in
10408 <a href="#7.6"><fenv.h></a>.
10411 <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
10412 and return values in wider format than the synopsis prototype indicates.
10414 <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
10415 least as wide as float and double, respectively. For FLT_EVAL_METHOD equal 0, 1, or 2, the
10416 type float_t is the narrowest type used by the implementation to evaluate floating expressions.
10418 <p><small><a name="note200" href="#note200">200)</a> HUGE_VAL, HUGE_VALF, and HUGE_VALL can be positive infinities in an implementation that
10419 supports infinities.
10421 <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.
10423 <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
10424 directly with a hardware multiply-add instruction. Software implementations are expected to be
10425 substantially slower.
10428 <h4><a name="7.12.1" href="#7.12.1">7.12.1 Treatment of error conditions</a></h4>
10430 The behavior of each of the functions in <a href="#7.12"><math.h></a> is specified for all representable
10431 values of its input arguments, except where stated otherwise. Each function shall execute
10432 as if it were a single operation without generating any externally visible exceptional
10435 For all functions, a domain error occurs if an input argument is outside the domain over
10436 which the mathematical function is defined. The description of each function lists any
10437 required domain errors; an implementation may define additional domain errors, provided
10438 that such errors are consistent with the mathematical definition of the function.<sup><a href="#note203"><b>203)</b></a></sup> On a
10439 domain error, the function returns an implementation-defined value; if the integer
10440 expression math_errhandling & MATH_ERRNO is nonzero, the integer expression
10441 errno acquires the value EDOM; if the integer expression math_errhandling &
10442 MATH_ERREXCEPT is nonzero, the ''invalid'' floating-point exception is raised.
10444 Similarly, a range error occurs if the mathematical result of the function cannot be
10445 represented in an object of the specified type, due to extreme magnitude.
10447 A floating result overflows if the magnitude of the mathematical result is finite but so
10448 large that the mathematical result cannot be represented without extraordinary roundoff
10449 error in an object of the specified type. If a floating result overflows and default rounding
10450 is in effect, or if the mathematical result is an exact infinity from finite arguments (for
10451 example log(0.0)), then the function returns the value of the macro HUGE_VAL,
10455 HUGE_VALF, or HUGE_VALL according to the return type, with the same sign as the
10456 correct value of the function; if the integer expression math_errhandling &
10457 MATH_ERRNO is nonzero, the integer expression errno acquires the value ERANGE; if
10458 the integer expression math_errhandling & MATH_ERREXCEPT is nonzero, the
10459 ''divide-by-zero'' floating-point exception is raised if the mathematical result is an exact
10460 infinity and the ''overflow'' floating-point exception is raised otherwise.
10462 The result underflows if the magnitude of the mathematical result is so small that the
10463 mathematical result cannot be represented, without extraordinary roundoff error, in an
10464 object of the specified type.<sup><a href="#note204"><b>204)</b></a></sup> If the result underflows, the function returns an
10465 implementation-defined value whose magnitude is no greater than the smallest
10466 normalized positive number in the specified type; if the integer expression
10467 math_errhandling & MATH_ERRNO is nonzero, whether errno acquires the
10468 value ERANGE is implementation-defined; if the integer expression
10469 math_errhandling & MATH_ERREXCEPT is nonzero, whether the ''underflow''
10470 floating-point exception is raised is implementation-defined.
10473 <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
10474 error if the mathematical domain of the function does not include the infinity.
10476 <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
10477 also ''flush-to-zero'' underflow.
10480 <h4><a name="7.12.2" href="#7.12.2">7.12.2 The FP_CONTRACT pragma</a></h4>
10484 #include <a href="#7.12"><math.h></a>
10485 #pragma STDC FP_CONTRACT on-off-switch</pre>
10486 <h6>Description</h6>
10488 The FP_CONTRACT pragma can be used to allow (if the state is ''on'') or disallow (if the
10489 state is ''off'') the implementation to contract expressions (<a href="#6.5">6.5</a>). Each pragma can occur
10490 either outside external declarations or preceding all explicit declarations and statements
10491 inside a compound statement. When outside external declarations, the pragma takes
10492 effect from its occurrence until another FP_CONTRACT pragma is encountered, or until
10493 the end of the translation unit. When inside a compound statement, the pragma takes
10494 effect from its occurrence until another FP_CONTRACT pragma is encountered
10495 (including within a nested compound statement), or until the end of the compound
10496 statement; at the end of a compound statement the state for the pragma is restored to its
10497 condition just before the compound statement. If this pragma is used in any other
10498 context, the behavior is undefined. The default state (''on'' or ''off'') for the pragma is
10499 implementation-defined.
10506 <h4><a name="7.12.3" href="#7.12.3">7.12.3 Classification macros</a></h4>
10508 In the synopses in this subclause, real-floating indicates that the argument shall be an
10509 expression of real floating type.
10511 <h5><a name="7.12.3.1" href="#7.12.3.1">7.12.3.1 The fpclassify macro</a></h5>
10515 #include <a href="#7.12"><math.h></a>
10516 int fpclassify(real-floating x);</pre>
10517 <h6>Description</h6>
10519 The fpclassify macro classifies its argument value as NaN, infinite, normal,
10520 subnormal, zero, or into another implementation-defined category. First, an argument
10521 represented in a format wider than its semantic type is converted to its semantic type.
10522 Then classification is based on the type of the argument.<sup><a href="#note205"><b>205)</b></a></sup>
10525 The fpclassify macro returns the value of the number classification macro
10526 appropriate to the value of its argument.
10528 EXAMPLE The fpclassify macro might be implemented in terms of ordinary functions as
10530 #define fpclassify(x) \
10531 ((sizeof (x) == sizeof (float)) ? __fpclassifyf(x) : \
10532 (sizeof (x) == sizeof (double)) ? __fpclassifyd(x) : \
10533 __fpclassifyl(x))</pre>
10537 <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
10538 know the type that classification is based on. For example, a normal long double value might
10539 become subnormal when converted to double, and zero when converted to float.
10542 <h5><a name="7.12.3.2" href="#7.12.3.2">7.12.3.2 The isfinite macro</a></h5>
10546 #include <a href="#7.12"><math.h></a>
10547 int isfinite(real-floating x);</pre>
10548 <h6>Description</h6>
10550 The isfinite macro determines whether its argument has a finite value (zero,
10551 subnormal, or normal, and not infinite or NaN). First, an argument represented in a
10552 format wider than its semantic type is converted to its semantic type. Then determination
10553 is based on the type of the argument.
10561 The isfinite macro returns a nonzero value if and only if its argument has a finite
10564 <h5><a name="7.12.3.3" href="#7.12.3.3">7.12.3.3 The isinf macro</a></h5>
10568 #include <a href="#7.12"><math.h></a>
10569 int isinf(real-floating x);</pre>
10570 <h6>Description</h6>
10572 The isinf macro determines whether its argument value is an infinity (positive or
10573 negative). First, an argument represented in a format wider than its semantic type is
10574 converted to its semantic type. Then determination is based on the type of the argument.
10577 The isinf macro returns a nonzero value if and only if its argument has an infinite
10580 <h5><a name="7.12.3.4" href="#7.12.3.4">7.12.3.4 The isnan macro</a></h5>
10584 #include <a href="#7.12"><math.h></a>
10585 int isnan(real-floating x);</pre>
10586 <h6>Description</h6>
10588 The isnan macro determines whether its argument value is a NaN. First, an argument
10589 represented in a format wider than its semantic type is converted to its semantic type.
10590 Then determination is based on the type of the argument.<sup><a href="#note206"><b>206)</b></a></sup>
10593 The isnan macro returns a nonzero value if and only if its argument has a NaN value.
10596 <p><small><a name="note206" href="#note206">206)</a> For the isnan macro, the type for determination does not matter unless the implementation supports
10597 NaNs in the evaluation type but not in the semantic type.
10600 <h5><a name="7.12.3.5" href="#7.12.3.5">7.12.3.5 The isnormal macro</a></h5>
10604 #include <a href="#7.12"><math.h></a>
10605 int isnormal(real-floating x);</pre>
10611 <h6>Description</h6>
10613 The isnormal macro determines whether its argument value is normal (neither zero,
10614 subnormal, infinite, nor NaN). First, an argument represented in a format wider than its
10615 semantic type is converted to its semantic type. Then determination is based on the type
10619 The isnormal macro returns a nonzero value if and only if its argument has a normal
10622 <h5><a name="7.12.3.6" href="#7.12.3.6">7.12.3.6 The signbit macro</a></h5>
10626 #include <a href="#7.12"><math.h></a>
10627 int signbit(real-floating x);</pre>
10628 <h6>Description</h6>
10630 The signbit macro determines whether the sign of its argument value is negative.<sup><a href="#note207"><b>207)</b></a></sup>
10633 The signbit macro returns a nonzero value if and only if the sign of its argument value
10637 <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
10638 unsigned, it is treated as positive.
10641 <h4><a name="7.12.4" href="#7.12.4">7.12.4 Trigonometric functions</a></h4>
10643 <h5><a name="7.12.4.1" href="#7.12.4.1">7.12.4.1 The acos functions</a></h5>
10647 #include <a href="#7.12"><math.h></a>
10648 double acos(double x);
10649 float acosf(float x);
10650 long double acosl(long double x);</pre>
10651 <h6>Description</h6>
10653 The acos functions compute the principal value of the arc cosine of x. A domain error
10654 occurs for arguments not in the interval [-1, +1].
10657 The acos functions return arccos x in the interval [0, pi ] radians.
10664 <h5><a name="7.12.4.2" href="#7.12.4.2">7.12.4.2 The asin functions</a></h5>
10668 #include <a href="#7.12"><math.h></a>
10669 double asin(double x);
10670 float asinf(float x);
10671 long double asinl(long double x);</pre>
10672 <h6>Description</h6>
10674 The asin functions compute the principal value of the arc sine of x. A domain error
10675 occurs for arguments not in the interval [-1, +1].
10678 The asin functions return arcsin x in the interval [-pi /2, +pi /2] radians.
10680 <h5><a name="7.12.4.3" href="#7.12.4.3">7.12.4.3 The atan functions</a></h5>
10684 #include <a href="#7.12"><math.h></a>
10685 double atan(double x);
10686 float atanf(float x);
10687 long double atanl(long double x);</pre>
10688 <h6>Description</h6>
10690 The atan functions compute the principal value of the arc tangent of x.
10693 The atan functions return arctan x in the interval [-pi /2, +pi /2] radians.
10695 <h5><a name="7.12.4.4" href="#7.12.4.4">7.12.4.4 The atan2 functions</a></h5>
10699 #include <a href="#7.12"><math.h></a>
10700 double atan2(double y, double x);
10701 float atan2f(float y, float x);
10702 long double atan2l(long double y, long double x);</pre>
10703 <h6>Description</h6>
10705 The atan2 functions compute the value of the arc tangent of y/x, using the signs of both
10706 arguments to determine the quadrant of the return value. A domain error may occur if
10707 both arguments are zero.
10710 The atan2 functions return arctan y/x in the interval [-pi , +pi ] radians.
10713 <h5><a name="7.12.4.5" href="#7.12.4.5">7.12.4.5 The cos functions</a></h5>
10717 #include <a href="#7.12"><math.h></a>
10718 double cos(double x);
10719 float cosf(float x);
10720 long double cosl(long double x);</pre>
10721 <h6>Description</h6>
10723 The cos functions compute the cosine of x (measured in radians).
10726 The cos functions return cos x.
10728 <h5><a name="7.12.4.6" href="#7.12.4.6">7.12.4.6 The sin functions</a></h5>
10732 #include <a href="#7.12"><math.h></a>
10733 double sin(double x);
10734 float sinf(float x);
10735 long double sinl(long double x);</pre>
10736 <h6>Description</h6>
10738 The sin functions compute the sine of x (measured in radians).
10741 The sin functions return sin x.
10743 <h5><a name="7.12.4.7" href="#7.12.4.7">7.12.4.7 The tan functions</a></h5>
10747 #include <a href="#7.12"><math.h></a>
10748 double tan(double x);
10749 float tanf(float x);
10750 long double tanl(long double x);</pre>
10751 <h6>Description</h6>
10753 The tan functions return the tangent of x (measured in radians).
10756 The tan functions return tan x.
10759 <h4><a name="7.12.5" href="#7.12.5">7.12.5 Hyperbolic functions</a></h4>
10761 <h5><a name="7.12.5.1" href="#7.12.5.1">7.12.5.1 The acosh functions</a></h5>
10765 #include <a href="#7.12"><math.h></a>
10766 double acosh(double x);
10767 float acoshf(float x);
10768 long double acoshl(long double x);</pre>
10769 <h6>Description</h6>
10771 The acosh functions compute the (nonnegative) arc hyperbolic cosine of x. A domain
10772 error occurs for arguments less than 1.
10775 The acosh functions return arcosh x in the interval [0, +(inf)].
10777 <h5><a name="7.12.5.2" href="#7.12.5.2">7.12.5.2 The asinh functions</a></h5>
10781 #include <a href="#7.12"><math.h></a>
10782 double asinh(double x);
10783 float asinhf(float x);
10784 long double asinhl(long double x);</pre>
10785 <h6>Description</h6>
10787 The asinh functions compute the arc hyperbolic sine of x.
10790 The asinh functions return arsinh x.
10792 <h5><a name="7.12.5.3" href="#7.12.5.3">7.12.5.3 The atanh functions</a></h5>
10796 #include <a href="#7.12"><math.h></a>
10797 double atanh(double x);
10798 float atanhf(float x);
10799 long double atanhl(long double x);</pre>
10800 <h6>Description</h6>
10802 The atanh functions compute the arc hyperbolic tangent of x. A domain error occurs
10803 for arguments not in the interval [-1, +1]. A range error may occur if the argument
10808 The atanh functions return artanh x.
10810 <h5><a name="7.12.5.4" href="#7.12.5.4">7.12.5.4 The cosh functions</a></h5>
10814 #include <a href="#7.12"><math.h></a>
10815 double cosh(double x);
10816 float coshf(float x);
10817 long double coshl(long double x);</pre>
10818 <h6>Description</h6>
10820 The cosh functions compute the hyperbolic cosine of x. A range error occurs if the
10821 magnitude of x is too large.
10824 The cosh functions return cosh x.
10826 <h5><a name="7.12.5.5" href="#7.12.5.5">7.12.5.5 The sinh functions</a></h5>
10830 #include <a href="#7.12"><math.h></a>
10831 double sinh(double x);
10832 float sinhf(float x);
10833 long double sinhl(long double x);</pre>
10834 <h6>Description</h6>
10836 The sinh functions compute the hyperbolic sine of x. A range error occurs if the
10837 magnitude of x is too large.
10840 The sinh functions return sinh x.
10842 <h5><a name="7.12.5.6" href="#7.12.5.6">7.12.5.6 The tanh functions</a></h5>
10846 #include <a href="#7.12"><math.h></a>
10847 double tanh(double x);
10848 float tanhf(float x);
10849 long double tanhl(long double x);</pre>
10850 <h6>Description</h6>
10852 The tanh functions compute the hyperbolic tangent of x.
10856 The tanh functions return tanh x.
10858 <h4><a name="7.12.6" href="#7.12.6">7.12.6 Exponential and logarithmic functions</a></h4>
10860 <h5><a name="7.12.6.1" href="#7.12.6.1">7.12.6.1 The exp functions</a></h5>
10864 #include <a href="#7.12"><math.h></a>
10865 double exp(double x);
10866 float expf(float x);
10867 long double expl(long double x);</pre>
10868 <h6>Description</h6>
10870 The exp functions compute the base-e exponential of x. A range error occurs if the
10871 magnitude of x is too large.
10874 The exp functions return ex .
10876 <h5><a name="7.12.6.2" href="#7.12.6.2">7.12.6.2 The exp2 functions</a></h5>
10880 #include <a href="#7.12"><math.h></a>
10881 double exp2(double x);
10882 float exp2f(float x);
10883 long double exp2l(long double x);</pre>
10884 <h6>Description</h6>
10886 The exp2 functions compute the base-2 exponential of x. A range error occurs if the
10887 magnitude of x is too large.
10890 The exp2 functions return 2x .
10892 <h5><a name="7.12.6.3" href="#7.12.6.3">7.12.6.3 The expm1 functions</a></h5>
10897 #include <a href="#7.12"><math.h></a>
10898 double expm1(double x);
10899 float expm1f(float x);
10900 long double expm1l(long double x);</pre>
10901 <h6>Description</h6>
10903 The expm1 functions compute the base-e exponential of the argument, minus 1. A range
10904 error occurs if x is too large.<sup><a href="#note208"><b>208)</b></a></sup>
10907 The expm1 functions return ex - 1.
10910 <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.
10913 <h5><a name="7.12.6.4" href="#7.12.6.4">7.12.6.4 The frexp functions</a></h5>
10917 #include <a href="#7.12"><math.h></a>
10918 double frexp(double value, int *exp);
10919 float frexpf(float value, int *exp);
10920 long double frexpl(long double value, int *exp);</pre>
10921 <h6>Description</h6>
10923 The frexp functions break a floating-point number into a normalized fraction and an
10924 integral power of 2. They store the integer in the int object pointed to by exp.
10927 If value is not a floating-point number, the results are unspecified. Otherwise, the
10928 frexp functions return the value x, such that x has a magnitude in the interval [1/2, 1) or
10929 zero, and value equals x x 2*exp . If value is zero, both parts of the result are zero.
10931 <h5><a name="7.12.6.5" href="#7.12.6.5">7.12.6.5 The ilogb functions</a></h5>
10935 #include <a href="#7.12"><math.h></a>
10936 int ilogb(double x);
10937 int ilogbf(float x);
10938 int ilogbl(long double x);</pre>
10939 <h6>Description</h6>
10941 The ilogb functions extract the exponent of x as a signed int value. If x is zero they
10942 compute the value FP_ILOGB0; if x is infinite they compute the value INT_MAX; if x is
10943 a NaN they compute the value FP_ILOGBNAN; otherwise, they are equivalent to calling
10944 the corresponding logb function and casting the returned value to type int. A domain
10945 error or range error may occur if x is zero, infinite, or NaN. If the correct value is outside
10946 the range of the return type, the numeric result is unspecified.
10954 The ilogb functions return the exponent of x as a signed int value.
10955 <p><b> Forward references</b>: the logb functions (<a href="#7.12.6.11">7.12.6.11</a>).
10957 <h5><a name="7.12.6.6" href="#7.12.6.6">7.12.6.6 The ldexp functions</a></h5>
10961 #include <a href="#7.12"><math.h></a>
10962 double ldexp(double x, int exp);
10963 float ldexpf(float x, int exp);
10964 long double ldexpl(long double x, int exp);</pre>
10965 <h6>Description</h6>
10967 The ldexp functions multiply a floating-point number by an integral power of 2. A
10968 range error may occur.
10971 The ldexp functions return x x 2exp .
10973 <h5><a name="7.12.6.7" href="#7.12.6.7">7.12.6.7 The log functions</a></h5>
10977 #include <a href="#7.12"><math.h></a>
10978 double log(double x);
10979 float logf(float x);
10980 long double logl(long double x);</pre>
10981 <h6>Description</h6>
10983 The log functions compute the base-e (natural) logarithm of x. A domain error occurs if
10984 the argument is negative. A range error may occur if the argument is zero.
10987 The log functions return loge x.
10989 <h5><a name="7.12.6.8" href="#7.12.6.8">7.12.6.8 The log10 functions</a></h5>
10994 #include <a href="#7.12"><math.h></a>
10995 double log10(double x);
10996 float log10f(float x);
10997 long double log10l(long double x);</pre>
10998 <h6>Description</h6>
11000 The log10 functions compute the base-10 (common) logarithm of x. A domain error
11001 occurs if the argument is negative. A range error may occur if the argument is zero.
11004 The log10 functions return log10 x.
11006 <h5><a name="7.12.6.9" href="#7.12.6.9">7.12.6.9 The log1p functions</a></h5>
11010 #include <a href="#7.12"><math.h></a>
11011 double log1p(double x);
11012 float log1pf(float x);
11013 long double log1pl(long double x);</pre>
11014 <h6>Description</h6>
11016 The log1p functions compute the base-e (natural) logarithm of 1 plus the argument.<sup><a href="#note209"><b>209)</b></a></sup>
11017 A domain error occurs if the argument is less than -1. A range error may occur if the
11018 argument equals -1.
11021 The log1p functions return loge (1 + x).
11024 <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).
11027 <h5><a name="7.12.6.10" href="#7.12.6.10">7.12.6.10 The log2 functions</a></h5>
11031 #include <a href="#7.12"><math.h></a>
11032 double log2(double x);
11033 float log2f(float x);
11034 long double log2l(long double x);</pre>
11035 <h6>Description</h6>
11037 The log2 functions compute the base-2 logarithm of x. A domain error occurs if the
11038 argument is less than zero. A range error may occur if the argument is zero.
11041 The log2 functions return log2 x.
11048 <h5><a name="7.12.6.11" href="#7.12.6.11">7.12.6.11 The logb functions</a></h5>
11052 #include <a href="#7.12"><math.h></a>
11053 double logb(double x);
11054 float logbf(float x);
11055 long double logbl(long double x);</pre>
11056 <h6>Description</h6>
11058 The logb functions extract the exponent of x, as a signed integer value in floating-point
11059 format. If x is subnormal it is treated as though it were normalized; thus, for positive
11062 1 <= x x FLT_RADIX-logb(x) < FLT_RADIX</pre>
11063 A domain error or range error may occur if the argument is zero.
11066 The logb functions return the signed exponent of x.
11068 <h5><a name="7.12.6.12" href="#7.12.6.12">7.12.6.12 The modf functions</a></h5>
11072 #include <a href="#7.12"><math.h></a>
11073 double modf(double value, double *iptr);
11074 float modff(float value, float *iptr);
11075 long double modfl(long double value, long double *iptr);</pre>
11076 <h6>Description</h6>
11078 The modf functions break the argument value into integral and fractional parts, each of
11079 which has the same type and sign as the argument. They store the integral part (in
11080 floating-point format) in the object pointed to by iptr.
11083 The modf functions return the signed fractional part of value.
11086 <h5><a name="7.12.6.13" href="#7.12.6.13">7.12.6.13 The scalbn and scalbln functions</a></h5>
11090 #include <a href="#7.12"><math.h></a>
11091 double scalbn(double x, int n);
11092 float scalbnf(float x, int n);
11093 long double scalbnl(long double x, int n);
11094 double scalbln(double x, long int n);
11095 float scalblnf(float x, long int n);
11096 long double scalblnl(long double x, long int n);</pre>
11097 <h6>Description</h6>
11099 The scalbn and scalbln functions compute x x FLT_RADIXn efficiently, not
11100 normally by computing FLT_RADIXn explicitly. A range error may occur.
11103 The scalbn and scalbln functions return x x FLT_RADIXn .
11105 <h4><a name="7.12.7" href="#7.12.7">7.12.7 Power and absolute-value functions</a></h4>
11107 <h5><a name="7.12.7.1" href="#7.12.7.1">7.12.7.1 The cbrt functions</a></h5>
11111 #include <a href="#7.12"><math.h></a>
11112 double cbrt(double x);
11113 float cbrtf(float x);
11114 long double cbrtl(long double x);</pre>
11115 <h6>Description</h6>
11117 The cbrt functions compute the real cube root of x.
11120 The cbrt functions return x1/3 .
11122 <h5><a name="7.12.7.2" href="#7.12.7.2">7.12.7.2 The fabs functions</a></h5>
11126 #include <a href="#7.12"><math.h></a>
11127 double fabs(double x);
11128 float fabsf(float x);
11129 long double fabsl(long double x);</pre>
11130 <h6>Description</h6>
11132 The fabs functions compute the absolute value of a floating-point number x.
11136 The fabs functions return | x |.
11138 <h5><a name="7.12.7.3" href="#7.12.7.3">7.12.7.3 The hypot functions</a></h5>
11142 #include <a href="#7.12"><math.h></a>
11143 double hypot(double x, double y);
11144 float hypotf(float x, float y);
11145 long double hypotl(long double x, long double y);</pre>
11146 <h6>Description</h6>
11148 The hypot functions compute the square root of the sum of the squares of x and y,
11149 without undue overflow or underflow. A range error may occur.
11153 The hypot functions return (sqrt)x2 + y2 .
11156 ???????????????</pre>
11158 <h5><a name="7.12.7.4" href="#7.12.7.4">7.12.7.4 The pow functions</a></h5>
11162 #include <a href="#7.12"><math.h></a>
11163 double pow(double x, double y);
11164 float powf(float x, float y);
11165 long double powl(long double x, long double y);</pre>
11166 <h6>Description</h6>
11168 The pow functions compute x raised to the power y. A domain error occurs if x is finite
11169 and negative and y is finite and not an integer value. A range error may occur. A domain
11170 error may occur if x is zero and y is zero. A domain error or range error may occur if x
11171 is zero and y is less than zero.
11174 The pow functions return xy .
11176 <h5><a name="7.12.7.5" href="#7.12.7.5">7.12.7.5 The sqrt functions</a></h5>
11181 #include <a href="#7.12"><math.h></a>
11182 double sqrt(double x);
11183 float sqrtf(float x);
11184 long double sqrtl(long double x);</pre>
11185 <h6>Description</h6>
11187 The sqrt functions compute the nonnegative square root of x. A domain error occurs if
11188 the argument is less than zero.
11191 The sqrt functions return (sqrt)x.
11196 <h4><a name="7.12.8" href="#7.12.8">7.12.8 Error and gamma functions</a></h4>
11198 <h5><a name="7.12.8.1" href="#7.12.8.1">7.12.8.1 The erf functions</a></h5>
11202 #include <a href="#7.12"><math.h></a>
11203 double erf(double x);
11204 float erff(float x);
11205 long double erfl(long double x);</pre>
11206 <h6>Description</h6>
11208 The erf functions compute the error function of x.
11214 The erf functions return erf x = e-t dt.
11225 <h5><a name="7.12.8.2" href="#7.12.8.2">7.12.8.2 The erfc functions</a></h5>
11229 #include <a href="#7.12"><math.h></a>
11230 double erfc(double x);
11231 float erfcf(float x);
11232 long double erfcl(long double x);</pre>
11233 <h6>Description</h6>
11235 The erfc functions compute the complementary error function of x. A range error
11236 occurs if x is too large.
11242 The erfc functions return erfc x = 1 - erf x = e-t dt.
11253 <h5><a name="7.12.8.3" href="#7.12.8.3">7.12.8.3 The lgamma functions</a></h5>
11257 #include <a href="#7.12"><math.h></a>
11258 double lgamma(double x);
11259 float lgammaf(float x);
11260 long double lgammal(long double x);</pre>
11261 <h6>Description</h6>
11263 The lgamma functions compute the natural logarithm of the absolute value of gamma of
11264 x. A range error occurs if x is too large. A range error may occur if x is a negative
11268 The lgamma functions return loge | (Gamma)(x) |.
11270 <h5><a name="7.12.8.4" href="#7.12.8.4">7.12.8.4 The tgamma functions</a></h5>
11274 #include <a href="#7.12"><math.h></a>
11275 double tgamma(double x);
11276 float tgammaf(float x);
11277 long double tgammal(long double x);</pre>
11278 <h6>Description</h6>
11280 The tgamma functions compute the gamma function of x. A domain error or range error
11281 may occur if x is a negative integer or zero. A range error may occur if the magnitude of
11282 x is too large or too small.
11285 The tgamma functions return (Gamma)(x).
11287 <h4><a name="7.12.9" href="#7.12.9">7.12.9 Nearest integer functions</a></h4>
11289 <h5><a name="7.12.9.1" href="#7.12.9.1">7.12.9.1 The ceil functions</a></h5>
11293 #include <a href="#7.12"><math.h></a>
11294 double ceil(double x);
11295 float ceilf(float x);
11296 long double ceill(long double x);</pre>
11297 <h6>Description</h6>
11299 The ceil functions compute the smallest integer value not less than x.
11303 The ceil functions return ???x???, expressed as a floating-point number.
11305 <h5><a name="7.12.9.2" href="#7.12.9.2">7.12.9.2 The floor functions</a></h5>
11309 #include <a href="#7.12"><math.h></a>
11310 double floor(double x);
11311 float floorf(float x);
11312 long double floorl(long double x);</pre>
11313 <h6>Description</h6>
11315 The floor functions compute the largest integer value not greater than x.
11318 The floor functions return ???x???, expressed as a floating-point number.
11320 <h5><a name="7.12.9.3" href="#7.12.9.3">7.12.9.3 The nearbyint functions</a></h5>
11324 #include <a href="#7.12"><math.h></a>
11325 double nearbyint(double x);
11326 float nearbyintf(float x);
11327 long double nearbyintl(long double x);</pre>
11328 <h6>Description</h6>
11330 The nearbyint functions round their argument to an integer value in floating-point
11331 format, using the current rounding direction and without raising the ''inexact'' floating-
11335 The nearbyint functions return the rounded integer value.
11337 <h5><a name="7.12.9.4" href="#7.12.9.4">7.12.9.4 The rint functions</a></h5>
11341 #include <a href="#7.12"><math.h></a>
11342 double rint(double x);
11343 float rintf(float x);
11344 long double rintl(long double x);</pre>
11345 <h6>Description</h6>
11347 The rint functions differ from the nearbyint functions (<a href="#7.12.9.3">7.12.9.3</a>) only in that the
11348 rint functions may raise the ''inexact'' floating-point exception if the result differs in
11349 value from the argument.
11353 The rint functions return the rounded integer value.
11355 <h5><a name="7.12.9.5" href="#7.12.9.5">7.12.9.5 The lrint and llrint functions</a></h5>
11359 #include <a href="#7.12"><math.h></a>
11360 long int lrint(double x);
11361 long int lrintf(float x);
11362 long int lrintl(long double x);
11363 long long int llrint(double x);
11364 long long int llrintf(float x);
11365 long long int llrintl(long double x);</pre>
11366 <h6>Description</h6>
11368 The lrint and llrint functions round their argument to the nearest integer value,
11369 rounding according to the current rounding direction. If the rounded value is outside the
11370 range of the return type, the numeric result is unspecified and a domain error or range
11374 The lrint and llrint functions return the rounded integer value.
11376 <h5><a name="7.12.9.6" href="#7.12.9.6">7.12.9.6 The round functions</a></h5>
11380 #include <a href="#7.12"><math.h></a>
11381 double round(double x);
11382 float roundf(float x);
11383 long double roundl(long double x);</pre>
11384 <h6>Description</h6>
11386 The round functions round their argument to the nearest integer value in floating-point
11387 format, rounding halfway cases away from zero, regardless of the current rounding
11391 The round functions return the rounded integer value.
11394 <h5><a name="7.12.9.7" href="#7.12.9.7">7.12.9.7 The lround and llround functions</a></h5>
11398 #include <a href="#7.12"><math.h></a>
11399 long int lround(double x);
11400 long int lroundf(float x);
11401 long int lroundl(long double x);
11402 long long int llround(double x);
11403 long long int llroundf(float x);
11404 long long int llroundl(long double x);</pre>
11405 <h6>Description</h6>
11407 The lround and llround functions round their argument to the nearest integer value,
11408 rounding halfway cases away from zero, regardless of the current rounding direction. If
11409 the rounded value is outside the range of the return type, the numeric result is unspecified
11410 and a domain error or range error may occur.
11413 The lround and llround functions return the rounded integer value.
11415 <h5><a name="7.12.9.8" href="#7.12.9.8">7.12.9.8 The trunc functions</a></h5>
11419 #include <a href="#7.12"><math.h></a>
11420 double trunc(double x);
11421 float truncf(float x);
11422 long double truncl(long double x);</pre>
11423 <h6>Description</h6>
11425 The trunc functions round their argument to the integer value, in floating format,
11426 nearest to but no larger in magnitude than the argument.
11429 The trunc functions return the truncated integer value.
11432 <h4><a name="7.12.10" href="#7.12.10">7.12.10 Remainder functions</a></h4>
11434 <h5><a name="7.12.10.1" href="#7.12.10.1">7.12.10.1 The fmod functions</a></h5>
11438 #include <a href="#7.12"><math.h></a>
11439 double fmod(double x, double y);
11440 float fmodf(float x, float y);
11441 long double fmodl(long double x, long double y);</pre>
11442 <h6>Description</h6>
11444 The fmod functions compute the floating-point remainder of x/y.
11447 The fmod functions return the value x - ny, for some integer n such that, if y is nonzero,
11448 the result has the same sign as x and magnitude less than the magnitude of y. If y is zero,
11449 whether a domain error occurs or the fmod functions return zero is implementation-
11452 <h5><a name="7.12.10.2" href="#7.12.10.2">7.12.10.2 The remainder functions</a></h5>
11456 #include <a href="#7.12"><math.h></a>
11457 double remainder(double x, double y);
11458 float remainderf(float x, float y);
11459 long double remainderl(long double x, long double y);</pre>
11460 <h6>Description</h6>
11462 The remainder functions compute the remainder x REM y required by IEC 60559.<sup><a href="#note210"><b>210)</b></a></sup>
11465 The remainder functions return x REM y. If y is zero, whether a domain error occurs
11466 or the functions return zero is implementation defined.
11474 <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
11475 mathematical relation r = x - ny, where n is the integer nearest the exact value of x/y; whenever
11476 | n - x/y | = 1/2, then n is even. Thus, the remainder is always exact. If r = 0, its sign shall be that of
11477 x.'' This definition is applicable for all implementations.
11480 <h5><a name="7.12.10.3" href="#7.12.10.3">7.12.10.3 The remquo functions</a></h5>
11484 #include <a href="#7.12"><math.h></a>
11485 double remquo(double x, double y, int *quo);
11486 float remquof(float x, float y, int *quo);
11487 long double remquol(long double x, long double y,
11489 <h6>Description</h6>
11491 The remquo functions compute the same remainder as the remainder functions. In
11492 the object pointed to by quo they store a value whose sign is the sign of x/y and whose
11493 magnitude is congruent modulo 2n to the magnitude of the integral quotient of x/y, where
11494 n is an implementation-defined integer greater than or equal to 3.
11497 The remquo functions return x REM y. If y is zero, the value stored in the object
11498 pointed to by quo is unspecified and whether a domain error occurs or the functions
11499 return zero is implementation defined.
11501 <h4><a name="7.12.11" href="#7.12.11">7.12.11 Manipulation functions</a></h4>
11503 <h5><a name="7.12.11.1" href="#7.12.11.1">7.12.11.1 The copysign functions</a></h5>
11507 #include <a href="#7.12"><math.h></a>
11508 double copysign(double x, double y);
11509 float copysignf(float x, float y);
11510 long double copysignl(long double x, long double y);</pre>
11511 <h6>Description</h6>
11513 The copysign functions produce a value with the magnitude of x and the sign of y.
11514 They produce a NaN (with the sign of y) if x is a NaN. On implementations that
11515 represent a signed zero but do not treat negative zero consistently in arithmetic
11516 operations, the copysign functions regard the sign of zero as positive.
11519 The copysign functions return a value with the magnitude of x and the sign of y.
11522 <h5><a name="7.12.11.2" href="#7.12.11.2">7.12.11.2 The nan functions</a></h5>
11526 #include <a href="#7.12"><math.h></a>
11527 double nan(const char *tagp);
11528 float nanf(const char *tagp);
11529 long double nanl(const char *tagp);</pre>
11530 <h6>Description</h6>
11532 The call nan("n-char-sequence") is equivalent to strtod("NAN(n-char-
11533 sequence)", (char**) NULL); the call nan("") is equivalent to
11534 strtod("NAN()", (char**) NULL). If tagp does not point to an n-char
11535 sequence or an empty string, the call is equivalent to strtod("NAN", (char**)
11536 NULL). Calls to nanf and nanl are equivalent to the corresponding calls to strtof
11540 The nan functions return a quiet NaN, if available, with content indicated through tagp.
11541 If the implementation does not support quiet NaNs, the functions return zero.
11542 <p><b> Forward references</b>: the strtod, strtof, and strtold functions (<a href="#7.20.1.3">7.20.1.3</a>).
11544 <h5><a name="7.12.11.3" href="#7.12.11.3">7.12.11.3 The nextafter functions</a></h5>
11548 #include <a href="#7.12"><math.h></a>
11549 double nextafter(double x, double y);
11550 float nextafterf(float x, float y);
11551 long double nextafterl(long double x, long double y);</pre>
11552 <h6>Description</h6>
11554 The nextafter functions determine the next representable value, in the type of the
11555 function, after x in the direction of y, where x and y are first converted to the type of the
11556 function.<sup><a href="#note211"><b>211)</b></a></sup> The nextafter functions return y if x equals y. A range error may occur
11557 if the magnitude of x is the largest finite value representable in the type and the result is
11558 infinite or not representable in the type.
11561 The nextafter functions return the next representable value in the specified format
11562 after x in the direction of y.
11568 <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
11572 <h5><a name="7.12.11.4" href="#7.12.11.4">7.12.11.4 The nexttoward functions</a></h5>
11576 #include <a href="#7.12"><math.h></a>
11577 double nexttoward(double x, long double y);
11578 float nexttowardf(float x, long double y);
11579 long double nexttowardl(long double x, long double y);</pre>
11580 <h6>Description</h6>
11582 The nexttoward functions are equivalent to the nextafter functions except that the
11583 second parameter has type long double and the functions return y converted to the
11584 type of the function if x equals y.<sup><a href="#note212"><b>212)</b></a></sup>
11587 <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
11588 range or precision in a floating second argument.
11591 <h4><a name="7.12.12" href="#7.12.12">7.12.12 Maximum, minimum, and positive difference functions</a></h4>
11593 <h5><a name="7.12.12.1" href="#7.12.12.1">7.12.12.1 The fdim functions</a></h5>
11597 #include <a href="#7.12"><math.h></a>
11598 double fdim(double x, double y);
11599 float fdimf(float x, float y);
11600 long double fdiml(long double x, long double y);</pre>
11601 <h6>Description</h6>
11603 The fdim functions determine the positive difference between their arguments:
11605 ???x - y if x > y
11607 ???+0 if x <= y</pre>
11608 A range error may occur.
11611 The fdim functions return the positive difference value.
11613 <h5><a name="7.12.12.2" href="#7.12.12.2">7.12.12.2 The fmax functions</a></h5>
11617 #include <a href="#7.12"><math.h></a>
11618 double fmax(double x, double y);
11619 float fmaxf(float x, float y);
11620 long double fmaxl(long double x, long double y);</pre>
11625 <h6>Description</h6>
11627 The fmax functions determine the maximum numeric value of their arguments.<sup><a href="#note213"><b>213)</b></a></sup>
11630 The fmax functions return the maximum numeric value of their arguments.
11633 <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
11634 fmax functions choose the numeric value. See <a href="#F.9.9.2">F.9.9.2</a>.
11637 <h5><a name="7.12.12.3" href="#7.12.12.3">7.12.12.3 The fmin functions</a></h5>
11641 #include <a href="#7.12"><math.h></a>
11642 double fmin(double x, double y);
11643 float fminf(float x, float y);
11644 long double fminl(long double x, long double y);</pre>
11645 <h6>Description</h6>
11647 The fmin functions determine the minimum numeric value of their arguments.<sup><a href="#note214"><b>214)</b></a></sup>
11650 The fmin functions return the minimum numeric value of their arguments.
11653 <p><small><a name="note214" href="#note214">214)</a> The fmin functions are analogous to the fmax functions in their treatment of NaNs.
11656 <h4><a name="7.12.13" href="#7.12.13">7.12.13 Floating multiply-add</a></h4>
11658 <h5><a name="7.12.13.1" href="#7.12.13.1">7.12.13.1 The fma functions</a></h5>
11662 #include <a href="#7.12"><math.h></a>
11663 double fma(double x, double y, double z);
11664 float fmaf(float x, float y, float z);
11665 long double fmal(long double x, long double y,
11666 long double z);</pre>
11667 <h6>Description</h6>
11669 The fma functions compute (x x y) + z, rounded as one ternary operation: they compute
11670 the value (as if) to infinite precision and round once to the result format, according to the
11671 current rounding mode. A range error may occur.
11674 The fma functions return (x x y) + z, rounded as one ternary operation.
11681 <h4><a name="7.12.14" href="#7.12.14">7.12.14 Comparison macros</a></h4>
11683 The relational and equality operators support the usual mathematical relationships
11684 between numeric values. For any ordered pair of numeric values exactly one of the
11685 relationships -- less, greater, and equal -- is true. Relational operators may raise the
11686 ''invalid'' floating-point exception when argument values are NaNs. For a NaN and a
11687 numeric value, or for two NaNs, just the unordered relationship is true.<sup><a href="#note215"><b>215)</b></a></sup> The following
11688 subclauses provide macros that are quiet (non floating-point exception raising) versions
11689 of the relational operators, and other comparison macros that facilitate writing efficient
11690 code that accounts for NaNs without suffering the ''invalid'' floating-point exception. In
11691 the synopses in this subclause, real-floating indicates that the argument shall be an
11692 expression of real floating type.
11695 <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
11696 the operands compare unordered, as an error indicator for programs written without consideration of
11697 NaNs; the result in these cases is false.
11700 <h5><a name="7.12.14.1" href="#7.12.14.1">7.12.14.1 The isgreater macro</a></h5>
11704 #include <a href="#7.12"><math.h></a>
11705 int isgreater(real-floating x, real-floating y);</pre>
11706 <h6>Description</h6>
11708 The isgreater macro determines whether its first argument is greater than its second
11709 argument. The value of isgreater(x, y) is always equal to (x) > (y); however,
11710 unlike (x) > (y), isgreater(x, y) does not raise the ''invalid'' floating-point
11711 exception when x and y are unordered.
11714 The isgreater macro returns the value of (x) > (y).
11716 <h5><a name="7.12.14.2" href="#7.12.14.2">7.12.14.2 The isgreaterequal macro</a></h5>
11720 #include <a href="#7.12"><math.h></a>
11721 int isgreaterequal(real-floating x, real-floating y);</pre>
11722 <h6>Description</h6>
11724 The isgreaterequal macro determines whether its first argument is greater than or
11725 equal to its second argument. The value of isgreaterequal(x, y) is always equal
11726 to (x) >= (y); however, unlike (x) >= (y), isgreaterequal(x, y) does
11727 not raise the ''invalid'' floating-point exception when x and y are unordered.
11734 The isgreaterequal macro returns the value of (x) >= (y).
11736 <h5><a name="7.12.14.3" href="#7.12.14.3">7.12.14.3 The isless macro</a></h5>
11740 #include <a href="#7.12"><math.h></a>
11741 int isless(real-floating x, real-floating y);</pre>
11742 <h6>Description</h6>
11744 The isless macro determines whether its first argument is less than its second
11745 argument. The value of isless(x, y) is always equal to (x) < (y); however,
11746 unlike (x) < (y), isless(x, y) does not raise the ''invalid'' floating-point
11747 exception when x and y are unordered.
11750 The isless macro returns the value of (x) < (y).
11752 <h5><a name="7.12.14.4" href="#7.12.14.4">7.12.14.4 The islessequal macro</a></h5>
11756 #include <a href="#7.12"><math.h></a>
11757 int islessequal(real-floating x, real-floating y);</pre>
11758 <h6>Description</h6>
11760 The islessequal macro determines whether its first argument is less than or equal to
11761 its second argument. The value of islessequal(x, y) is always equal to
11762 (x) <= (y); however, unlike (x) <= (y), islessequal(x, y) does not raise
11763 the ''invalid'' floating-point exception when x and y are unordered.
11766 The islessequal macro returns the value of (x) <= (y).
11768 <h5><a name="7.12.14.5" href="#7.12.14.5">7.12.14.5 The islessgreater macro</a></h5>
11772 #include <a href="#7.12"><math.h></a>
11773 int islessgreater(real-floating x, real-floating y);</pre>
11774 <h6>Description</h6>
11776 The islessgreater macro determines whether its first argument is less than or
11777 greater than its second argument. The islessgreater(x, y) macro is similar to
11778 (x) < (y) || (x) > (y); however, islessgreater(x, y) does not raise
11779 the ''invalid'' floating-point exception when x and y are unordered (nor does it evaluate x
11784 The islessgreater macro returns the value of (x) < (y) || (x) > (y).
11786 <h5><a name="7.12.14.6" href="#7.12.14.6">7.12.14.6 The isunordered macro</a></h5>
11790 #include <a href="#7.12"><math.h></a>
11791 int isunordered(real-floating x, real-floating y);</pre>
11792 <h6>Description</h6>
11794 The isunordered macro determines whether its arguments are unordered.
11797 The isunordered macro returns 1 if its arguments are unordered and 0 otherwise.
11800 <h3><a name="7.13" href="#7.13">7.13 Nonlocal jumps <setjmp.h></a></h3>
11802 The header <a href="#7.13"><setjmp.h></a> defines the macro setjmp, and declares one function and
11803 one type, for bypassing the normal function call and return discipline.<sup><a href="#note216"><b>216)</b></a></sup>
11805 The type declared is
11808 which is an array type suitable for holding the information needed to restore a calling
11809 environment. The environment of a call to the setjmp macro consists of information
11810 sufficient for a call to the longjmp function to return execution to the correct block and
11811 invocation of that block, were it called recursively. It does not include the state of the
11812 floating-point status flags, of open files, or of any other component of the abstract
11815 It is unspecified whether setjmp is a macro or an identifier declared with external
11816 linkage. If a macro definition is suppressed in order to access an actual function, or a
11817 program defines an external identifier with the name setjmp, the behavior is undefined.
11820 <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
11824 <h4><a name="7.13.1" href="#7.13.1">7.13.1 Save calling environment</a></h4>
11826 <h5><a name="7.13.1.1" href="#7.13.1.1">7.13.1.1 The setjmp macro</a></h5>
11830 #include <a href="#7.13"><setjmp.h></a>
11831 int setjmp(jmp_buf env);</pre>
11832 <h6>Description</h6>
11834 The setjmp macro saves its calling environment in its jmp_buf argument for later use
11835 by the longjmp function.
11838 If the return is from a direct invocation, the setjmp macro returns the value zero. If the
11839 return is from a call to the longjmp function, the setjmp macro returns a nonzero
11841 Environmental limits
11843 An invocation of the setjmp macro shall appear only in one of the following contexts:
11845 <li> the entire controlling expression of a selection or iteration statement;
11846 <li> one operand of a relational or equality operator with the other operand an integer
11847 constant expression, with the resulting expression being the entire controlling
11851 expression of a selection or iteration statement;
11852 <li> the operand of a unary ! operator with the resulting expression being the entire
11853 controlling expression of a selection or iteration statement; or
11854 <li> the entire expression of an expression statement (possibly cast to void).
11857 If the invocation appears in any other context, the behavior is undefined.
11859 <h4><a name="7.13.2" href="#7.13.2">7.13.2 Restore calling environment</a></h4>
11861 <h5><a name="7.13.2.1" href="#7.13.2.1">7.13.2.1 The longjmp function</a></h5>
11865 #include <a href="#7.13"><setjmp.h></a>
11866 void longjmp(jmp_buf env, int val);</pre>
11867 <h6>Description</h6>
11869 The longjmp function restores the environment saved by the most recent invocation of
11870 the setjmp macro in the same invocation of the program with the corresponding
11871 jmp_buf argument. If there has been no such invocation, or if the function containing
11872 the invocation of the setjmp macro has terminated execution<sup><a href="#note217"><b>217)</b></a></sup> in the interim, or if the
11873 invocation of the setjmp macro was within the scope of an identifier with variably
11874 modified type and execution has left that scope in the interim, the behavior is undefined.
11876 All accessible objects have values, and all other components of the abstract machine<sup><a href="#note218"><b>218)</b></a></sup>
11877 have state, as of the time the longjmp function was called, except that the values of
11878 objects of automatic storage duration that are local to the function containing the
11879 invocation of the corresponding setjmp macro that do not have volatile-qualified type
11880 and have been changed between the setjmp invocation and longjmp call are
11884 After longjmp is completed, program execution continues as if the corresponding
11885 invocation of the setjmp macro had just returned the value specified by val. The
11886 longjmp function cannot cause the setjmp macro to return the value 0; if val is 0,
11887 the setjmp macro returns the value 1.
11889 EXAMPLE The longjmp function that returns control back to the point of the setjmp invocation
11890 might cause memory associated with a variable length array object to be squandered.
11898 #include <a href="#7.13"><setjmp.h></a>
11905 int x[n]; // valid: f is not terminated
11911 int a[n]; // a may remain allocated
11916 int b[n]; // b may remain allocated
11917 longjmp(buf, 2); // might cause memory loss
11921 <p><small><a name="note217" href="#note217">217)</a> For example, by executing a return statement or because another longjmp call has caused a
11922 transfer to a setjmp invocation in a function earlier in the set of nested calls.
11924 <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.
11927 <h3><a name="7.14" href="#7.14">7.14 Signal handling <signal.h></a></h3>
11929 The header <a href="#7.14"><signal.h></a> declares a type and two functions and defines several macros,
11930 for handling various signals (conditions that may be reported during program execution).
11932 The type defined is
11935 which is the (possibly volatile-qualified) integer type of an object that can be accessed as
11936 an atomic entity, even in the presence of asynchronous interrupts.
11938 The macros defined are
11943 which expand to constant expressions with distinct values that have type compatible with
11944 the second argument to, and the return value of, the signal function, and whose values
11945 compare unequal to the address of any declarable function; and the following, which
11946 expand to positive integer constant expressions with type int and distinct values that are
11947 the signal numbers, each corresponding to the specified condition:
11950 SIGABRT abnormal termination, such as is initiated by the abort function
11951 SIGFPE an erroneous arithmetic operation, such as zero divide or an operation
11952 resulting in overflow
11953 SIGILL detection of an invalid function image, such as an invalid instruction
11954 SIGINT receipt of an interactive attention signal
11955 SIGSEGV an invalid access to storage
11956 SIGTERM a termination request sent to the program</pre>
11957 An implementation need not generate any of these signals, except as a result of explicit
11958 calls to the raise function. Additional signals and pointers to undeclarable functions,
11959 with macro definitions beginning, respectively, with the letters SIG and an uppercase
11960 letter or with SIG_ and an uppercase letter,<sup><a href="#note219"><b>219)</b></a></sup> may also be specified by the
11961 implementation. The complete set of signals, their semantics, and their default handling
11962 is implementation-defined; all signal numbers shall be positive.
11970 <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
11971 (respectively): abort, floating-point exception, illegal instruction, interrupt, segmentation violation,
11975 <h4><a name="7.14.1" href="#7.14.1">7.14.1 Specify signal handling</a></h4>
11977 <h5><a name="7.14.1.1" href="#7.14.1.1">7.14.1.1 The signal function</a></h5>
11981 #include <a href="#7.14"><signal.h></a>
11982 void (*signal(int sig, void (*func)(int)))(int);</pre>
11983 <h6>Description</h6>
11985 The signal function chooses one of three ways in which receipt of the signal number
11986 sig is to be subsequently handled. If the value of func is SIG_DFL, default handling
11987 for that signal will occur. If the value of func is SIG_IGN, the signal will be ignored.
11988 Otherwise, func shall point to a function to be called when that signal occurs. An
11989 invocation of such a function because of a signal, or (recursively) of any further functions
11990 called by that invocation (other than functions in the standard library), is called a signal
11993 When a signal occurs and func points to a function, it is implementation-defined
11994 whether the equivalent of signal(sig, SIG_DFL); is executed or the
11995 implementation prevents some implementation-defined set of signals (at least including
11996 sig) from occurring until the current signal handling has completed; in the case of
11997 SIGILL, the implementation may alternatively define that no action is taken. Then the
11998 equivalent of (*func)(sig); is executed. If and when the function returns, if the
11999 value of sig is SIGFPE, SIGILL, SIGSEGV, or any other implementation-defined
12000 value corresponding to a computational exception, the behavior is undefined; otherwise
12001 the program will resume execution at the point it was interrupted.
12003 If the signal occurs as the result of calling the abort or raise function, the signal
12004 handler shall not call the raise function.
12006 If the signal occurs other than as the result of calling the abort or raise function, the
12007 behavior is undefined if the signal handler refers to any object with static storage duration
12008 other than by assigning a value to an object declared as volatile sig_atomic_t, or
12009 the signal handler calls any function in the standard library other than the abort
12010 function, the _Exit function, or the signal function with the first argument equal to
12011 the signal number corresponding to the signal that caused the invocation of the handler.
12012 Furthermore, if such a call to the signal function results in a SIG_ERR return, the
12013 value of errno is indeterminate.<sup><a href="#note220"><b>220)</b></a></sup>
12015 At program startup, the equivalent of
12017 signal(sig, SIG_IGN);</pre>
12021 may be executed for some signals selected in an implementation-defined manner; the
12024 signal(sig, SIG_DFL);</pre>
12025 is executed for all other signals defined by the implementation.
12027 The implementation shall behave as if no library function calls the signal function.
12030 If the request can be honored, the signal function returns the value of func for the
12031 most recent successful call to signal for the specified signal sig. Otherwise, a value of
12032 SIG_ERR is returned and a positive value is stored in errno.
12033 <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
12034 _Exit function (<a href="#7.20.4.4">7.20.4.4</a>).
12037 <p><small><a name="note220" href="#note220">220)</a> If any signal is generated by an asynchronous signal handler, the behavior is undefined.
12040 <h4><a name="7.14.2" href="#7.14.2">7.14.2 Send signal</a></h4>
12042 <h5><a name="7.14.2.1" href="#7.14.2.1">7.14.2.1 The raise function</a></h5>
12046 #include <a href="#7.14"><signal.h></a>
12047 int raise(int sig);</pre>
12048 <h6>Description</h6>
12050 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
12051 signal handler is called, the raise function shall not return until after the signal handler
12055 The raise function returns zero if successful, nonzero if unsuccessful.
12058 <h3><a name="7.15" href="#7.15">7.15 Variable arguments <stdarg.h></a></h3>
12060 The header <a href="#7.15"><stdarg.h></a> declares a type and defines four macros, for advancing
12061 through a list of arguments whose number and types are not known to the called function
12062 when it is translated.
12064 A function may be called with a variable number of arguments of varying types. As
12065 described in <a href="#6.9.1">6.9.1</a>, its parameter list contains one or more parameters. The rightmost
12066 parameter plays a special role in the access mechanism, and will be designated parmN in
12069 The type declared is
12072 which is an object type suitable for holding information needed by the macros
12073 va_start, va_arg, va_end, and va_copy. If access to the varying arguments is
12074 desired, the called function shall declare an object (generally referred to as ap in this
12075 subclause) having type va_list. The object ap may be passed as an argument to
12076 another function; if that function invokes the va_arg macro with parameter ap, the
12077 value of ap in the calling function is indeterminate and shall be passed to the va_end
12078 macro prior to any further reference to ap.<sup><a href="#note221"><b>221)</b></a></sup>
12081 <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
12082 case the original function may make further use of the original list after the other function returns.
12085 <h4><a name="7.15.1" href="#7.15.1">7.15.1 Variable argument list access macros</a></h4>
12087 The va_start and va_arg macros described in this subclause shall be implemented
12088 as macros, not functions. It is unspecified whether va_copy and va_end are macros or
12089 identifiers declared with external linkage. If a macro definition is suppressed in order to
12090 access an actual function, or a program defines an external identifier with the same name,
12091 the behavior is undefined. Each invocation of the va_start and va_copy macros
12092 shall be matched by a corresponding invocation of the va_end macro in the same
12095 <h5><a name="7.15.1.1" href="#7.15.1.1">7.15.1.1 The va_arg macro</a></h5>
12099 #include <a href="#7.15"><stdarg.h></a>
12100 type va_arg(va_list ap, type);</pre>
12101 <h6>Description</h6>
12103 The va_arg macro expands to an expression that has the specified type and the value of
12104 the next argument in the call. The parameter ap shall have been initialized by the
12105 va_start or va_copy macro (without an intervening invocation of the va_end
12108 macro for the same ap). Each invocation of the va_arg macro modifies ap so that the
12109 values of successive arguments are returned in turn. The parameter type shall be a type
12110 name specified such that the type of a pointer to an object that has the specified type can
12111 be obtained simply by postfixing a * to type. If there is no actual next argument, or if
12112 type is not compatible with the type of the actual next argument (as promoted according
12113 to the default argument promotions), the behavior is undefined, except for the following
12116 <li> one type is a signed integer type, the other type is the corresponding unsigned integer
12117 type, and the value is representable in both types;
12118 <li> one type is pointer to void and the other is a pointer to a character type.
12122 The first invocation of the va_arg macro after that of the va_start macro returns the
12123 value of the argument after that specified by parmN . Successive invocations return the
12124 values of the remaining arguments in succession.
12126 <h5><a name="7.15.1.2" href="#7.15.1.2">7.15.1.2 The va_copy macro</a></h5>
12130 #include <a href="#7.15"><stdarg.h></a>
12131 void va_copy(va_list dest, va_list src);</pre>
12132 <h6>Description</h6>
12134 The va_copy macro initializes dest as a copy of src, as if the va_start macro had
12135 been applied to dest followed by the same sequence of uses of the va_arg macro as
12136 had previously been used to reach the present state of src. Neither the va_copy nor
12137 va_start macro shall be invoked to reinitialize dest without an intervening
12138 invocation of the va_end macro for the same dest.
12141 The va_copy macro returns no value.
12143 <h5><a name="7.15.1.3" href="#7.15.1.3">7.15.1.3 The va_end macro</a></h5>
12147 #include <a href="#7.15"><stdarg.h></a>
12148 void va_end(va_list ap);</pre>
12149 <h6>Description</h6>
12151 The va_end macro facilitates a normal return from the function whose variable
12152 argument list was referred to by the expansion of the va_start macro, or the function
12153 containing the expansion of the va_copy macro, that initialized the va_list ap. The
12154 va_end macro may modify ap so that it is no longer usable (without being reinitialized
12156 by the va_start or va_copy macro). If there is no corresponding invocation of the
12157 va_start or va_copy macro, or if the va_end macro is not invoked before the
12158 return, the behavior is undefined.
12161 The va_end macro returns no value.
12163 <h5><a name="7.15.1.4" href="#7.15.1.4">7.15.1.4 The va_start macro</a></h5>
12167 #include <a href="#7.15"><stdarg.h></a>
12168 void va_start(va_list ap, parmN);</pre>
12169 <h6>Description</h6>
12171 The va_start macro shall be invoked before any access to the unnamed arguments.
12173 The va_start macro initializes ap for subsequent use by the va_arg and va_end
12174 macros. Neither the va_start nor va_copy macro shall be invoked to reinitialize ap
12175 without an intervening invocation of the va_end macro for the same ap.
12177 The parameter parmN is the identifier of the rightmost parameter in the variable
12178 parameter list in the function definition (the one just before the , ...). If the parameter
12179 parmN is declared with the register storage class, with a function or array type, or
12180 with a type that is not compatible with the type that results after application of the default
12181 argument promotions, the behavior is undefined.
12184 The va_start macro returns no value.
12186 EXAMPLE 1 The function f1 gathers into an array a list of arguments that are pointers to strings (but not
12187 more than MAXARGS arguments), then passes the array as a single argument to function f2. The number of
12188 pointers is specified by the first argument to f1.
12191 #include <a href="#7.15"><stdarg.h></a>
12193 void f1(int n_ptrs, ...)
12196 char *array[MAXARGS];
12198 if (n_ptrs > MAXARGS)
12200 va_start(ap, n_ptrs);
12201 while (ptr_no < n_ptrs)
12202 array[ptr_no++] = va_arg(ap, char *);
12206 Each call to f1 is required to have visible the definition of the function or a declaration such as
12208 void f1(int, ...);</pre>
12211 EXAMPLE 2 The function f3 is similar, but saves the status of the variable argument list after the
12212 indicated number of arguments; after f2 has been called once with the whole list, the trailing part of the list
12213 is gathered again and passed to function f4.
12216 #include <a href="#7.15"><stdarg.h></a>
12218 void f3(int n_ptrs, int f4_after, ...)
12220 va_list ap, ap_save;
12221 char *array[MAXARGS];
12223 if (n_ptrs > MAXARGS)
12225 va_start(ap, f4_after);
12226 while (ptr_no < n_ptrs) {
12227 array[ptr_no++] = va_arg(ap, char *);
12228 if (ptr_no == f4_after)
12229 va_copy(ap_save, ap);
12233 // Now process the saved copy.
12234 n_ptrs -= f4_after;
12236 while (ptr_no < n_ptrs)
12237 array[ptr_no++] = va_arg(ap_save, char *);
12242 <h3><a name="7.16" href="#7.16">7.16 Boolean type and values <stdbool.h></a></h3>
12244 The header <a href="#7.16"><stdbool.h></a> defines four macros.
12251 The remaining three macros are suitable for use in #if preprocessing directives. They
12255 which expands to the integer constant 1,
12258 which expands to the integer constant 0, and
12260 __bool_true_false_are_defined</pre>
12261 which expands to the integer constant 1.
12263 Notwithstanding the provisions of <a href="#7.1.3">7.1.3</a>, a program may undefine and perhaps then
12264 redefine the macros bool, true, and false.<sup><a href="#note222"><b>222)</b></a></sup>
12272 <p><small><a name="note222" href="#note222">222)</a> See ''future library directions'' (<a href="#7.26.7">7.26.7</a>).
12275 <h3><a name="7.17" href="#7.17">7.17 Common definitions <stddef.h></a></h3>
12277 The following types and macros are defined in the standard header <a href="#7.17"><stddef.h></a>. Some
12278 are also defined in other headers, as noted in their respective subclauses.
12283 which is the signed integer type of the result of subtracting two pointers;
12286 which is the unsigned integer type of the result of the sizeof operator; and
12289 which is an integer type whose range of values can represent distinct codes for all
12290 members of the largest extended character set specified among the supported locales; the
12291 null character shall have the code value zero. Each member of the basic character set
12292 shall have a code value equal to its value when used as the lone character in an integer
12293 character constant if an implementation does not define
12294 __STDC_MB_MIGHT_NEQ_WC__.
12299 which expands to an implementation-defined null pointer constant; and
12301 offsetof(type, member-designator)</pre>
12302 which expands to an integer constant expression that has type size_t, the value of
12303 which is the offset in bytes, to the structure member (designated by member-designator),
12304 from the beginning of its structure (designated by type). The type and member designator
12305 shall be such that given
12307 static type t;</pre>
12308 then the expression &(t.member-designator) evaluates to an address constant. (If the
12309 specified member is a bit-field, the behavior is undefined.)
12310 Recommended practice
12312 The types used for size_t and ptrdiff_t should not have an integer conversion rank
12313 greater than that of signed long int unless the implementation supports objects
12314 large enough to make this necessary.
12315 <p><b> Forward references</b>: localization (<a href="#7.11">7.11</a>).
12318 <h3><a name="7.18" href="#7.18">7.18 Integer types <stdint.h></a></h3>
12320 The header <a href="#7.18"><stdint.h></a> declares sets of integer types having specified widths, and
12321 defines corresponding sets of macros.<sup><a href="#note223"><b>223)</b></a></sup> It also defines macros that specify limits of
12322 integer types corresponding to types defined in other standard headers.
12324 Types are defined in the following categories:
12326 <li> integer types having certain exact widths;
12327 <li> integer types having at least certain specified widths;
12328 <li> fastest integer types having at least certain specified widths;
12329 <li> integer types wide enough to hold pointers to objects;
12330 <li> integer types having greatest width.
12332 (Some of these types may denote the same type.)
12334 Corresponding macros specify limits of the declared types and construct suitable
12337 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
12338 declare that typedef name and define the associated macros. Conversely, for each type
12339 described herein that the implementation does not provide, <a href="#7.18"><stdint.h></a> shall not
12340 declare that typedef name nor shall it define the associated macros. An implementation
12341 shall provide those types described as ''required'', but need not provide any of the others
12342 (described as ''optional'').
12345 <p><small><a name="note223" href="#note223">223)</a> See ''future library directions'' (<a href="#7.26.8">7.26.8</a>).
12347 <p><small><a name="note224" href="#note224">224)</a> Some of these types may denote implementation-defined extended integer types.
12350 <h4><a name="7.18.1" href="#7.18.1">7.18.1 Integer types</a></h4>
12352 When typedef names differing only in the absence or presence of the initial u are defined,
12353 they shall denote corresponding signed and unsigned types as described in <a href="#6.2.5">6.2.5</a>; an
12354 implementation providing one of these corresponding types shall also provide the other.
12356 In the following descriptions, the symbol N represents an unsigned decimal integer with
12357 no leading zeros (e.g., 8 or 24, but not 04 or 048).
12364 <h5><a name="7.18.1.1" href="#7.18.1.1">7.18.1.1 Exact-width integer types</a></h5>
12366 The typedef name intN_t designates a signed integer type with width N , no padding
12367 bits, and a two's complement representation. Thus, int8_t denotes a signed integer
12368 type with a width of exactly 8 bits.
12370 The typedef name uintN_t designates an unsigned integer type with width N . Thus,
12371 uint24_t denotes an unsigned integer type with a width of exactly 24 bits.
12373 These types are optional. However, if an implementation provides integer types with
12374 widths of 8, 16, 32, or 64 bits, no padding bits, and (for the signed types) that have a
12375 two's complement representation, it shall define the corresponding typedef names.
12377 <h5><a name="7.18.1.2" href="#7.18.1.2">7.18.1.2 Minimum-width integer types</a></h5>
12379 The typedef name int_leastN_t designates a signed integer type with a width of at
12380 least N , such that no signed integer type with lesser size has at least the specified width.
12381 Thus, int_least32_t denotes a signed integer type with a width of at least 32 bits.
12383 The typedef name uint_leastN_t designates an unsigned integer type with a width
12384 of at least N , such that no unsigned integer type with lesser size has at least the specified
12385 width. Thus, uint_least16_t denotes an unsigned integer type with a width of at
12388 The following types are required:
12390 int_least8_t uint_least8_t
12391 int_least16_t uint_least16_t
12392 int_least32_t uint_least32_t
12393 int_least64_t uint_least64_t</pre>
12394 All other types of this form are optional.
12396 <h5><a name="7.18.1.3" href="#7.18.1.3">7.18.1.3 Fastest minimum-width integer types</a></h5>
12398 Each of the following types designates an integer type that is usually fastest<sup><a href="#note225"><b>225)</b></a></sup> to operate
12399 with among all integer types that have at least the specified width.
12401 The typedef name int_fastN_t designates the fastest signed integer type with a width
12402 of at least N . The typedef name uint_fastN_t designates the fastest unsigned integer
12403 type with a width of at least N .
12410 The following types are required:
12412 int_fast8_t uint_fast8_t
12413 int_fast16_t uint_fast16_t
12414 int_fast32_t uint_fast32_t
12415 int_fast64_t uint_fast64_t</pre>
12416 All other types of this form are optional.
12419 <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
12420 grounds for choosing one type over another, it will simply pick some integer type satisfying the
12421 signedness and width requirements.
12424 <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>
12426 The following type designates a signed integer type with the property that any valid
12427 pointer to void can be converted to this type, then converted back to pointer to void,
12428 and the result will compare equal to the original pointer:
12431 The following type designates an unsigned 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 These types are optional.
12438 <h5><a name="7.18.1.5" href="#7.18.1.5">7.18.1.5 Greatest-width integer types</a></h5>
12440 The following type designates a signed integer type capable of representing any value of
12441 any signed integer type:
12444 The following type designates an unsigned integer type capable of representing any value
12445 of any unsigned integer type:
12448 These types are required.
12450 <h4><a name="7.18.2" href="#7.18.2">7.18.2 Limits of specified-width integer types</a></h4>
12452 The following object-like macros<sup><a href="#note226"><b>226)</b></a></sup> specify the minimum and maximum limits of the
12453 types declared in <a href="#7.18"><stdint.h></a>. Each macro name corresponds to a similar type name in
12454 <a href="#7.18.1">7.18.1</a>.
12456 Each instance of any defined macro shall be replaced by a constant expression suitable
12457 for use in #if preprocessing directives, and this expression shall have the same type as
12458 would an expression that is an object of the corresponding type converted according to
12461 the integer promotions. Its implementation-defined value shall be equal to or greater in
12462 magnitude (absolute value) than the corresponding value given below, with the same sign,
12463 except where stated to be exactly the given value.
12466 <p><small><a name="note226" href="#note226">226)</a> C++ implementations should define these macros only when __STDC_LIMIT_MACROS is defined
12467 before <a href="#7.18"><stdint.h></a> is included.
12470 <h5><a name="7.18.2.1" href="#7.18.2.1">7.18.2.1 Limits of exact-width integer types</a></h5>
12473 <li> minimum values of exact-width signed integer types
12474 INTN_MIN exactly -(2 N -1 )
12475 <li> maximum values of exact-width signed integer types
12476 INTN_MAX exactly 2 N -1 - 1
12477 <li> maximum values of exact-width unsigned integer types
12478 UINTN_MAX exactly 2 N - 1
12481 <h5><a name="7.18.2.2" href="#7.18.2.2">7.18.2.2 Limits of minimum-width integer types</a></h5>
12484 <li> minimum values of minimum-width signed integer types
12485 INT_LEASTN_MIN -(2 N -1 - 1)
12486 <li> maximum values of minimum-width signed integer types
12487 INT_LEASTN_MAX 2 N -1 - 1
12488 <li> maximum values of minimum-width unsigned integer types
12489 UINT_LEASTN_MAX 2N - 1
12492 <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>
12495 <li> minimum values of fastest minimum-width signed integer types
12496 INT_FASTN_MIN -(2 N -1 - 1)
12497 <li> maximum values of fastest minimum-width signed integer types
12498 INT_FASTN_MAX 2 N -1 - 1
12499 <li> maximum values of fastest minimum-width unsigned integer types
12500 UINT_FASTN_MAX 2N - 1
12503 <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>
12506 <li> minimum value of pointer-holding signed integer type
12508 INTPTR_MIN -(215 - 1)</pre>
12509 <li> maximum value of pointer-holding signed integer type
12512 INTPTR_MAX 215 - 1</pre>
12513 <li> maximum value of pointer-holding unsigned integer type
12514 UINTPTR_MAX 216 - 1
12517 <h5><a name="7.18.2.5" href="#7.18.2.5">7.18.2.5 Limits of greatest-width integer types</a></h5>
12520 <li> minimum value of greatest-width signed integer type
12521 INTMAX_MIN -(263 - 1)
12522 <li> maximum value of greatest-width signed integer type
12524 <li> maximum value of greatest-width unsigned integer type
12525 UINTMAX_MAX 264 - 1
12528 <h4><a name="7.18.3" href="#7.18.3">7.18.3 Limits of other integer types</a></h4>
12530 The following object-like macros<sup><a href="#note227"><b>227)</b></a></sup> specify the minimum and maximum limits of
12531 integer types corresponding to types defined in other standard headers.
12533 Each instance of these macros shall be replaced by a constant expression suitable for use
12534 in #if preprocessing directives, and this expression shall have the same type as would an
12535 expression that is an object of the corresponding type converted according to the integer
12536 promotions. Its implementation-defined value shall be equal to or greater in magnitude
12537 (absolute value) than the corresponding value given below, with the same sign. An
12538 implementation shall define only the macros corresponding to those typedef names it
12539 actually provides.<sup><a href="#note228"><b>228)</b></a></sup>
12541 <li> limits of ptrdiff_t
12544 <li> limits of sig_atomic_t
12545 SIG_ATOMIC_MIN see below
12546 SIG_ATOMIC_MAX see below
12547 <li> limit of size_t
12549 <li> limits of wchar_t
12554 WCHAR_MIN see below
12555 WCHAR_MAX see below
12556 <li> limits of wint_t
12561 If sig_atomic_t (see <a href="#7.14">7.14</a>) is defined as a signed integer type, the value of
12562 SIG_ATOMIC_MIN shall be no greater than -127 and the value of SIG_ATOMIC_MAX
12563 shall be no less than 127; otherwise, sig_atomic_t is defined as an unsigned integer
12564 type, and the value of SIG_ATOMIC_MIN shall be 0 and the value of
12565 SIG_ATOMIC_MAX shall be no less than 255.
12567 If wchar_t (see <a href="#7.17">7.17</a>) is defined as a signed integer type, the value of WCHAR_MIN
12568 shall be no greater than -127 and the value of WCHAR_MAX shall be no less than 127;
12569 otherwise, wchar_t is defined as an unsigned integer type, and the value of
12570 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>
12572 If wint_t (see <a href="#7.24">7.24</a>) is defined as a signed integer type, the value of WINT_MIN shall
12573 be no greater than -32767 and the value of WINT_MAX shall be no less than 32767;
12574 otherwise, wint_t is defined as an unsigned integer type, and the value of WINT_MIN
12575 shall be 0 and the value of WINT_MAX shall be no less than 65535.
12578 <p><small><a name="note227" href="#note227">227)</a> C++ implementations should define these macros only when __STDC_LIMIT_MACROS is defined
12579 before <a href="#7.18"><stdint.h></a> is included.
12581 <p><small><a name="note228" href="#note228">228)</a> A freestanding implementation need not provide all of these types.
12583 <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
12587 <h4><a name="7.18.4" href="#7.18.4">7.18.4 Macros for integer constants</a></h4>
12589 The following function-like macros<sup><a href="#note230"><b>230)</b></a></sup> expand to integer constants suitable for
12590 initializing objects that have integer types corresponding to types defined in
12591 <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
12592 <a href="#7.18.1.5">7.18.1.5</a>.
12594 The argument in any instance of these macros shall be an unsuffixed integer constant (as
12595 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.
12597 Each invocation of one of these macros shall expand to an integer constant expression
12598 suitable for use in #if preprocessing directives. The type of the expression shall have
12599 the same type as would an expression of the corresponding type converted according to
12600 the integer promotions. The value of the expression shall be that of the argument.
12608 <p><small><a name="note230" href="#note230">230)</a> C++ implementations should define these macros only when __STDC_CONSTANT_MACROS is
12609 defined before <a href="#7.18"><stdint.h></a> is included.
12612 <h5><a name="7.18.4.1" href="#7.18.4.1">7.18.4.1 Macros for minimum-width integer constants</a></h5>
12614 The macro INTN_C(value) shall expand to an integer constant expression
12615 corresponding to the type int_leastN_t. The macro UINTN_C(value) shall expand
12616 to an integer constant expression corresponding to the type uint_leastN_t. For
12617 example, if uint_least64_t is a name for the type unsigned long long int,
12618 then UINT64_C(0x123) might expand to the integer constant 0x123ULL.
12620 <h5><a name="7.18.4.2" href="#7.18.4.2">7.18.4.2 Macros for greatest-width integer constants</a></h5>
12622 The following macro expands to an integer constant expression having the value specified
12623 by its argument and the type intmax_t:
12625 INTMAX_C(value)</pre>
12626 The following macro expands to an integer constant expression having the value specified
12627 by its argument and the type uintmax_t:
12630 UINTMAX_C(value)</pre>
12632 <h3><a name="7.19" href="#7.19">7.19 Input/output <stdio.h></a></h3>
12634 <h4><a name="7.19.1" href="#7.19.1">7.19.1 Introduction</a></h4>
12636 The header <a href="#7.19"><stdio.h></a> declares three types, several macros, and many functions for
12637 performing input and output.
12639 The types declared are size_t (described in <a href="#7.17">7.17</a>);
12642 which is an object type capable of recording all the information needed to control a
12643 stream, including its file position indicator, a pointer to its associated buffer (if any), an
12644 error indicator that records whether a read/write error has occurred, and an end-of-file
12645 indicator that records whether the end of the file has been reached; and
12648 which is an object type other than an array type capable of recording all the information
12649 needed to specify uniquely every position within a file.
12651 The macros are NULL (described in <a href="#7.17">7.17</a>);
12656 which expand to integer constant expressions with distinct values, suitable for use as the
12657 third argument to the setvbuf function;
12660 which expands to an integer constant expression that is the size of the buffer used by the
12664 which expands to an integer constant expression, with type int and a negative value, that
12665 is returned by several functions to indicate end-of-file, that is, no more input from a
12669 which expands to an integer constant expression that is the minimum number of files that
12670 the implementation guarantees can be open simultaneously;
12673 which expands to an integer constant expression that is the size needed for an array of
12674 char large enough to hold the longest file name string that the implementation
12676 guarantees can be opened;<sup><a href="#note231"><b>231)</b></a></sup>
12679 which expands to an integer constant expression that is the size needed for an array of
12680 char large enough to hold a temporary file name string generated by the tmpnam
12686 which expand to integer constant expressions with distinct values, suitable for use as the
12687 third argument to the fseek function;
12690 which expands to an integer constant expression that is the maximum number of unique
12691 file names that can be generated by the tmpnam function;
12696 which are expressions of type ''pointer to FILE'' that point to the FILE objects
12697 associated, respectively, with the standard error, input, and output streams.
12699 The header <a href="#7.24"><wchar.h></a> declares a number of functions useful for wide character input
12700 and output. The wide character input/output functions described in that subclause
12701 provide operations analogous to most of those described here, except that the
12702 fundamental units internal to the program are wide characters. The external
12703 representation (in the file) is a sequence of ''generalized'' multibyte characters, as
12704 described further in <a href="#7.19.3">7.19.3</a>.
12706 The input/output functions are given the following collective terms:
12708 <li> The wide character input functions -- those functions described in <a href="#7.24">7.24</a> that perform
12709 input into wide characters and wide strings: fgetwc, fgetws, getwc, getwchar,
12710 fwscanf, wscanf, vfwscanf, and vwscanf.
12711 <li> The wide character output functions -- those functions described in <a href="#7.24">7.24</a> that perform
12712 output from wide characters and wide strings: fputwc, fputws, putwc,
12713 putwchar, fwprintf, wprintf, vfwprintf, and vwprintf.
12717 <li> The wide character input/output functions -- the union of the ungetwc function, the
12718 wide character input functions, and the wide character output functions.
12719 <li> The byte input/output functions -- those functions described in this subclause that
12720 perform input/output: fgetc, fgets, fprintf, fputc, fputs, fread,
12721 fscanf, fwrite, getc, getchar, gets, printf, putc, putchar, puts,
12722 scanf, ungetc, vfprintf, vfscanf, vprintf, and vscanf.
12724 <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
12725 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>).
12728 <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
12729 FILENAME_MAX should instead be the recommended size of an array intended to hold a file name
12730 string. Of course, file name string contents are subject to other system-specific constraints; therefore
12731 all possible strings of length FILENAME_MAX cannot be expected to be opened successfully.
12734 <h4><a name="7.19.2" href="#7.19.2">7.19.2 Streams</a></h4>
12736 Input and output, whether to or from physical devices such as terminals and tape drives,
12737 or whether to or from files supported on structured storage devices, are mapped into
12738 logical data streams, whose properties are more uniform than their various inputs and
12739 outputs. Two forms of mapping are supported, for text streams and for binary
12740 streams.<sup><a href="#note232"><b>232)</b></a></sup>
12742 A text stream is an ordered sequence of characters composed into lines, each line
12743 consisting of zero or more characters plus a terminating new-line character. Whether the
12744 last line requires a terminating new-line character is implementation-defined. Characters
12745 may have to be added, altered, or deleted on input and output to conform to differing
12746 conventions for representing text in the host environment. Thus, there need not be a one-
12747 to-one correspondence between the characters in a stream and those in the external
12748 representation. Data read in from a text stream will necessarily compare equal to the data
12749 that were earlier written out to that stream only if: the data consist only of printing
12750 characters and the control characters horizontal tab and new-line; no new-line character is
12751 immediately preceded by space characters; and the last character is a new-line character.
12752 Whether space characters that are written out immediately before a new-line character
12753 appear when read in is implementation-defined.
12755 A binary stream is an ordered sequence of characters that can transparently record
12756 internal data. Data read in from a binary stream shall compare equal to the data that were
12757 earlier written out to that stream, under the same implementation. Such a stream may,
12758 however, have an implementation-defined number of null characters appended to the end
12761 Each stream has an orientation. After a stream is associated with an external file, but
12762 before any operations are performed on it, the stream is without orientation. Once a wide
12763 character input/output function has been applied to a stream without orientation, the
12767 stream becomes a wide-oriented stream. Similarly, once a byte input/output function has
12768 been applied to a stream without orientation, the stream becomes a byte-oriented stream.
12769 Only a call to the freopen function or the fwide function can otherwise alter the
12770 orientation of a stream. (A successful call to freopen removes any orientation.)<sup><a href="#note233"><b>233)</b></a></sup>
12772 Byte input/output functions shall not be applied to a wide-oriented stream and wide
12773 character input/output functions shall not be applied to a byte-oriented stream. The
12774 remaining stream operations do not affect, and are not affected by, a stream's orientation,
12775 except for the following additional restrictions:
12777 <li> Binary wide-oriented streams have the file-positioning restrictions ascribed to both
12778 text and binary streams.
12779 <li> For wide-oriented streams, after a successful call to a file-positioning function that
12780 leaves the file position indicator prior to the end-of-file, a wide character output
12781 function can overwrite a partial multibyte character; any file contents beyond the
12782 byte(s) written are henceforth indeterminate.
12785 Each wide-oriented stream has an associated mbstate_t object that stores the current
12786 parse state of the stream. A successful call to fgetpos stores a representation of the
12787 value of this mbstate_t object as part of the value of the fpos_t object. A later
12788 successful call to fsetpos using the same stored fpos_t value restores the value of
12789 the associated mbstate_t object as well as the position within the controlled stream.
12790 Environmental limits
12792 An implementation shall support text files with lines containing at least 254 characters,
12793 including the terminating new-line character. The value of the macro BUFSIZ shall be at
12795 <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>),
12796 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
12797 (<a href="#7.19.9.3">7.19.9.3</a>).
12805 <p><small><a name="note232" href="#note232">232)</a> An implementation need not distinguish between text streams and binary streams. In such an
12806 implementation, there need be no new-line characters in a text stream nor any limit to the length of a
12809 <p><small><a name="note233" href="#note233">233)</a> The three predefined streams stdin, stdout, and stderr are unoriented at program startup.
12812 <h4><a name="7.19.3" href="#7.19.3">7.19.3 Files</a></h4>
12814 A stream is associated with an external file (which may be a physical device) by opening
12815 a file, which may involve creating a new file. Creating an existing file causes its former
12816 contents to be discarded, if necessary. If a file can support positioning requests (such as a
12817 disk file, as opposed to a terminal), then a file position indicator associated with the
12818 stream is positioned at the start (character number zero) of the file, unless the file is
12819 opened with append mode in which case it is implementation-defined whether the file
12820 position indicator is initially positioned at the beginning or the end of the file. The file
12821 position indicator is maintained by subsequent reads, writes, and positioning requests, to
12822 facilitate an orderly progression through the file.
12824 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
12825 stream causes the associated file to be truncated beyond that point is implementation-
12828 When a stream is unbuffered, characters are intended to appear from the source or at the
12829 destination as soon as possible. Otherwise characters may be accumulated and
12830 transmitted to or from the host environment as a block. When a stream is fully buffered,
12831 characters are intended to be transmitted to or from the host environment as a block when
12832 a buffer is filled. When a stream is line buffered, characters are intended to be
12833 transmitted to or from the host environment as a block when a new-line character is
12834 encountered. Furthermore, characters are intended to be transmitted as a block to the host
12835 environment when a buffer is filled, when input is requested on an unbuffered stream, or
12836 when input is requested on a line buffered stream that requires the transmission of
12837 characters from the host environment. Support for these characteristics is
12838 implementation-defined, and may be affected via the setbuf and setvbuf functions.
12840 A file may be disassociated from a controlling stream by closing the file. Output streams
12841 are flushed (any unwritten buffer contents are transmitted to the host environment) before
12842 the stream is disassociated from the file. The value of a pointer to a FILE object is
12843 indeterminate after the associated file is closed (including the standard text streams).
12844 Whether a file of zero length (on which no characters have been written by an output
12845 stream) actually exists is implementation-defined.
12847 The file may be subsequently reopened, by the same or another program execution, and
12848 its contents reclaimed or modified (if it can be repositioned at its start). If the main
12849 function returns to its original caller, or if the exit function is called, all open files are
12850 closed (hence all output streams are flushed) before program termination. Other paths to
12851 program termination, such as calling the abort function, need not close all files
12854 The address of the FILE object used to control a stream may be significant; a copy of a
12855 FILE object need not serve in place of the original.
12858 At program startup, three text streams are predefined and need not be opened explicitly
12860 <li> standard input (for reading conventional input), standard output (for writing
12862 conventional output), and standard error (for writing diagnostic output). As initially
12863 opened, the standard error stream is not fully buffered; the standard input and standard
12864 output streams are fully buffered if and only if the stream can be determined not to refer
12865 to an interactive device.
12867 Functions that open additional (nontemporary) files require a file name, which is a string.
12868 The rules for composing valid file names are implementation-defined. Whether the same
12869 file can be simultaneously open multiple times is also implementation-defined.
12871 Although both text and binary wide-oriented streams are conceptually sequences of wide
12872 characters, the external file associated with a wide-oriented stream is a sequence of
12873 multibyte characters, generalized as follows:
12875 <li> Multibyte encodings within files may contain embedded null bytes (unlike multibyte
12876 encodings valid for use internal to the program).
12877 <li> A file need not begin nor end in the initial shift state.<sup><a href="#note234"><b>234)</b></a></sup>
12880 Moreover, the encodings used for multibyte characters may differ among files. Both the
12881 nature and choice of such encodings are implementation-defined.
12883 The wide character input functions read multibyte characters from the stream and convert
12884 them to wide characters as if they were read by successive calls to the fgetwc function.
12885 Each conversion occurs as if by a call to the mbrtowc function, with the conversion state
12886 described by the stream's own mbstate_t object. The byte input functions read
12887 characters from the stream as if by successive calls to the fgetc function.
12889 The wide character output functions convert wide characters to multibyte characters and
12890 write them to the stream as if they were written by successive calls to the fputwc
12891 function. Each conversion occurs as if by a call to the wcrtomb function, with the
12892 conversion state described by the stream's own mbstate_t object. The byte output
12893 functions write characters to the stream as if by successive calls to the fputc function.
12895 In some cases, some of the byte input/output functions also perform conversions between
12896 multibyte characters and wide characters. These conversions also occur as if by calls to
12897 the mbrtowc and wcrtomb functions.
12899 An encoding error occurs if the character sequence presented to the underlying
12900 mbrtowc function does not form a valid (generalized) multibyte character, or if the code
12901 value passed to the underlying wcrtomb does not correspond to a valid (generalized)
12905 multibyte character. The wide character input/output functions and the byte input/output
12906 functions store the value of the macro EILSEQ in errno if and only if an encoding error
12908 Environmental limits
12910 The value of FOPEN_MAX shall be at least eight, including the three standard text
12912 <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
12913 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
12914 (<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
12915 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
12916 (<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>).
12919 <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
12920 undefined behavior for a binary stream (because of possible trailing null characters) or for any stream
12921 with state-dependent encoding that does not assuredly end in the initial shift state.
12924 <h4><a name="7.19.4" href="#7.19.4">7.19.4 Operations on files</a></h4>
12926 <h5><a name="7.19.4.1" href="#7.19.4.1">7.19.4.1 The remove function</a></h5>
12930 #include <a href="#7.19"><stdio.h></a>
12931 int remove(const char *filename);</pre>
12932 <h6>Description</h6>
12934 The remove function causes the file whose name is the string pointed to by filename
12935 to be no longer accessible by that name. A subsequent attempt to open that file using that
12936 name will fail, unless it is created anew. If the file is open, the behavior of the remove
12937 function is implementation-defined.
12940 The remove function returns zero if the operation succeeds, nonzero if it fails.
12942 <h5><a name="7.19.4.2" href="#7.19.4.2">7.19.4.2 The rename function</a></h5>
12946 #include <a href="#7.19"><stdio.h></a>
12947 int rename(const char *old, const char *new);</pre>
12948 <h6>Description</h6>
12950 The rename function causes the file whose name is the string pointed to by old to be
12951 henceforth known by the name given by the string pointed to by new. The file named
12952 old is no longer accessible by that name. If a file named by the string pointed to by new
12953 exists prior to the call to the rename function, the behavior is implementation-defined.
12957 The rename function returns zero if the operation succeeds, nonzero if it fails,<sup><a href="#note235"><b>235)</b></a></sup> in
12958 which case if the file existed previously it is still known by its original name.
12961 <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
12962 or that it is necessary to copy its contents to effectuate its renaming.
12965 <h5><a name="7.19.4.3" href="#7.19.4.3">7.19.4.3 The tmpfile function</a></h5>
12969 #include <a href="#7.19"><stdio.h></a>
12970 FILE *tmpfile(void);</pre>
12971 <h6>Description</h6>
12973 The tmpfile function creates a temporary binary file that is different from any other
12974 existing file and that will automatically be removed when it is closed or at program
12975 termination. If the program terminates abnormally, whether an open temporary file is
12976 removed is implementation-defined. The file is opened for update with "wb+" mode.
12977 Recommended practice
12979 It should be possible to open at least TMP_MAX temporary files during the lifetime of the
12980 program (this limit may be shared with tmpnam) and there should be no limit on the
12981 number simultaneously open other than this limit and any limit on the number of open
12985 The tmpfile function returns a pointer to the stream of the file that it created. If the file
12986 cannot be created, the tmpfile function returns a null pointer.
12987 <p><b> Forward references</b>: the fopen function (<a href="#7.19.5.3">7.19.5.3</a>).
12989 <h5><a name="7.19.4.4" href="#7.19.4.4">7.19.4.4 The tmpnam function</a></h5>
12993 #include <a href="#7.19"><stdio.h></a>
12994 char *tmpnam(char *s);</pre>
12995 <h6>Description</h6>
12997 The tmpnam function generates a string that is a valid file name and that is not the same
12998 as the name of an existing file.<sup><a href="#note236"><b>236)</b></a></sup> The function is potentially capable of generating
13002 TMP_MAX different strings, but any or all of them may already be in use by existing files
13003 and thus not be suitable return values.
13005 The tmpnam function generates a different string each time it is called.
13007 The implementation shall behave as if no library function calls the tmpnam function.
13010 If no suitable string can be generated, the tmpnam function returns a null pointer.
13011 Otherwise, if the argument is a null pointer, the tmpnam function leaves its result in an
13012 internal static object and returns a pointer to that object (subsequent calls to the tmpnam
13013 function may modify the same object). If the argument is not a null pointer, it is assumed
13014 to point to an array of at least L_tmpnam chars; the tmpnam function writes its result
13015 in that array and returns the argument as its value.
13016 Environmental limits
13018 The value of the macro TMP_MAX shall be at least 25.
13021 <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
13022 their names should not collide with those generated by conventional naming rules for the
13023 implementation. It is still necessary to use the remove function to remove such files when their use
13024 is ended, and before program termination.
13027 <h4><a name="7.19.5" href="#7.19.5">7.19.5 File access functions</a></h4>
13029 <h5><a name="7.19.5.1" href="#7.19.5.1">7.19.5.1 The fclose function</a></h5>
13033 #include <a href="#7.19"><stdio.h></a>
13034 int fclose(FILE *stream);</pre>
13035 <h6>Description</h6>
13037 A successful call to the fclose function causes the stream pointed to by stream to be
13038 flushed and the associated file to be closed. Any unwritten buffered data for the stream
13039 are delivered to the host environment to be written to the file; any unread buffered data
13040 are discarded. Whether or not the call succeeds, the stream is disassociated from the file
13041 and any buffer set by the setbuf or setvbuf function is disassociated from the stream
13042 (and deallocated if it was automatically allocated).
13045 The fclose function returns zero if the stream was successfully closed, or EOF if any
13046 errors were detected.
13048 <h5><a name="7.19.5.2" href="#7.19.5.2">7.19.5.2 The fflush function</a></h5>
13053 #include <a href="#7.19"><stdio.h></a>
13054 int fflush(FILE *stream);</pre>
13055 <h6>Description</h6>
13057 If stream points to an output stream or an update stream in which the most recent
13058 operation was not input, the fflush function causes any unwritten data for that stream
13059 to be delivered to the host environment to be written to the file; otherwise, the behavior is
13062 If stream is a null pointer, the fflush function performs this flushing action on all
13063 streams for which the behavior is defined above.
13066 The fflush function sets the error indicator for the stream and returns EOF if a write
13067 error occurs, otherwise it returns zero.
13068 <p><b> Forward references</b>: the fopen function (<a href="#7.19.5.3">7.19.5.3</a>).
13070 <h5><a name="7.19.5.3" href="#7.19.5.3">7.19.5.3 The fopen function</a></h5>
13074 #include <a href="#7.19"><stdio.h></a>
13075 FILE *fopen(const char * restrict filename,
13076 const char * restrict mode);</pre>
13077 <h6>Description</h6>
13079 The fopen function opens the file whose name is the string pointed to by filename,
13080 and associates a stream with it.
13082 The argument mode points to a string. If the string is one of the following, the file is
13083 open in the indicated mode. Otherwise, the behavior is undefined.<sup><a href="#note237"><b>237)</b></a></sup>
13084 r open text file for reading
13085 w truncate to zero length or create text file for writing
13086 a append; open or create text file for writing at end-of-file
13087 rb open binary file for reading
13088 wb truncate to zero length or create binary file for writing
13089 ab append; open or create binary file for writing at end-of-file
13090 r+ open text file for update (reading and writing)
13091 w+ truncate to zero length or create text file for update
13092 a+ append; open or create text file for update, writing at end-of-file
13098 r+b or rb+ open binary file for update (reading and writing)
13099 w+b or wb+ truncate to zero length or create binary file for update
13100 a+b or ab+ append; open or create binary file for update, writing at end-of-file
13102 Opening a file with read mode ('r' as the first character in the mode argument) fails if
13103 the file does not exist or cannot be read.
13105 Opening a file with append mode ('a' as the first character in the mode argument)
13106 causes all subsequent writes to the file to be forced to the then current end-of-file,
13107 regardless of intervening calls to the fseek function. In some implementations, opening
13108 a binary file with append mode ('b' as the second or third character in the above list of
13109 mode argument values) may initially position the file position indicator for the stream
13110 beyond the last data written, because of null character padding.
13112 When a file is opened with update mode ('+' as the second or third character in the
13113 above list of mode argument values), both input and output may be performed on the
13114 associated stream. However, output shall not be directly followed by input without an
13115 intervening call to the fflush function or to a file positioning function (fseek,
13116 fsetpos, or rewind), and input shall not be directly followed by output without an
13117 intervening call to a file positioning function, unless the input operation encounters end-
13118 of-file. Opening (or creating) a text file with update mode may instead open (or create) a
13119 binary stream in some implementations.
13121 When opened, a stream is fully buffered if and only if it can be determined not to refer to
13122 an interactive device. The error and end-of-file indicators for the stream are cleared.
13125 The fopen function returns a pointer to the object controlling the stream. If the open
13126 operation fails, fopen returns a null pointer.
13127 <p><b> Forward references</b>: file positioning functions (<a href="#7.19.9">7.19.9</a>).
13130 <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
13131 remaining characters, or it might use them to select different kinds of a file (some of which might not
13132 conform to the properties in <a href="#7.19.2">7.19.2</a>).
13135 <h5><a name="7.19.5.4" href="#7.19.5.4">7.19.5.4 The freopen function</a></h5>
13139 #include <a href="#7.19"><stdio.h></a>
13140 FILE *freopen(const char * restrict filename,
13141 const char * restrict mode,
13142 FILE * restrict stream);</pre>
13143 <h6>Description</h6>
13145 The freopen function opens the file whose name is the string pointed to by filename
13146 and associates the stream pointed to by stream with it. The mode argument is used just
13148 as in the fopen function.<sup><a href="#note238"><b>238)</b></a></sup>
13150 If filename is a null pointer, the freopen function attempts to change the mode of
13151 the stream to that specified by mode, as if the name of the file currently associated with
13152 the stream had been used. It is implementation-defined which changes of mode are
13153 permitted (if any), and under what circumstances.
13155 The freopen function first attempts to close any file that is associated with the specified
13156 stream. Failure to close the file is ignored. The error and end-of-file indicators for the
13157 stream are cleared.
13160 The freopen function returns a null pointer if the open operation fails. Otherwise,
13161 freopen returns the value of stream.
13164 <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
13165 (stderr, stdin, or stdout), as those identifiers need not be modifiable lvalues to which the value
13166 returned by the fopen function may be assigned.
13169 <h5><a name="7.19.5.5" href="#7.19.5.5">7.19.5.5 The setbuf function</a></h5>
13173 #include <a href="#7.19"><stdio.h></a>
13174 void setbuf(FILE * restrict stream,
13175 char * restrict buf);</pre>
13176 <h6>Description</h6>
13178 Except that it returns no value, the setbuf function is equivalent to the setvbuf
13179 function invoked with the values _IOFBF for mode and BUFSIZ for size, or (if buf
13180 is a null pointer), with the value _IONBF for mode.
13183 The setbuf function returns no value.
13184 <p><b> Forward references</b>: the setvbuf function (<a href="#7.19.5.6">7.19.5.6</a>).
13186 <h5><a name="7.19.5.6" href="#7.19.5.6">7.19.5.6 The setvbuf function</a></h5>
13190 #include <a href="#7.19"><stdio.h></a>
13191 int setvbuf(FILE * restrict stream,
13192 char * restrict buf,
13193 int mode, size_t size);</pre>
13199 <h6>Description</h6>
13201 The setvbuf function may be used only after the stream pointed to by stream has
13202 been associated with an open file and before any other operation (other than an
13203 unsuccessful call to setvbuf) is performed on the stream. The argument mode
13204 determines how stream will be buffered, as follows: _IOFBF causes input/output to be
13205 fully buffered; _IOLBF causes input/output to be line buffered; _IONBF causes
13206 input/output to be unbuffered. If buf is not a null pointer, the array it points to may be
13207 used instead of a buffer allocated by the setvbuf function<sup><a href="#note239"><b>239)</b></a></sup> and the argument size
13208 specifies the size of the array; otherwise, size may determine the size of a buffer
13209 allocated by the setvbuf function. The contents of the array at any time are
13213 The setvbuf function returns zero on success, or nonzero if an invalid value is given
13214 for mode or if the request cannot be honored.
13217 <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
13218 before a buffer that has automatic storage duration is deallocated upon block exit.
13221 <h4><a name="7.19.6" href="#7.19.6">7.19.6 Formatted input/output functions</a></h4>
13223 The formatted input/output functions shall behave as if there is a sequence point after the
13224 actions associated with each specifier.<sup><a href="#note240"><b>240)</b></a></sup>
13227 <p><small><a name="note240" href="#note240">240)</a> The fprintf functions perform writes to memory for the %n specifier.
13230 <h5><a name="7.19.6.1" href="#7.19.6.1">7.19.6.1 The fprintf function</a></h5>
13234 #include <a href="#7.19"><stdio.h></a>
13235 int fprintf(FILE * restrict stream,
13236 const char * restrict format, ...);</pre>
13237 <h6>Description</h6>
13239 The fprintf function writes output to the stream pointed to by stream, under control
13240 of the string pointed to by format that specifies how subsequent arguments are
13241 converted for output. If there are insufficient arguments for the format, the behavior is
13242 undefined. If the format is exhausted while arguments remain, the excess arguments are
13243 evaluated (as always) but are otherwise ignored. The fprintf function returns when
13244 the end of the format string is encountered.
13246 The format shall be a multibyte character sequence, beginning and ending in its initial
13247 shift state. The format is composed of zero or more directives: ordinary multibyte
13248 characters (not %), which are copied unchanged to the output stream; and conversion
13252 specifications, each of which results in fetching zero or more subsequent arguments,
13253 converting them, if applicable, according to the corresponding conversion specifier, and
13254 then writing the result to the output stream.
13256 Each conversion specification is introduced by the character %. After the %, the following
13257 appear in sequence:
13259 <li> Zero or more flags (in any order) that modify the meaning of the conversion
13261 <li> An optional minimum field width. If the converted value has fewer characters than the
13262 field width, it is padded with spaces (by default) on the left (or right, if the left
13263 adjustment flag, described later, has been given) to the field width. The field width
13264 takes the form of an asterisk * (described later) or a nonnegative decimal integer.<sup><a href="#note241"><b>241)</b></a></sup>
13265 <li> An optional precision that gives the minimum number of digits to appear for the d, i,
13266 o, u, x, and X conversions, the number of digits to appear after the decimal-point
13267 character for a, A, e, E, f, and F conversions, the maximum number of significant
13268 digits for the g and G conversions, or the maximum number of bytes to be written for
13269 s conversions. The precision takes the form of a period (.) followed either by an
13270 asterisk * (described later) or by an optional decimal integer; if only the period is
13271 specified, the precision is taken as zero. If a precision appears with any other
13272 conversion specifier, the behavior is undefined.
13273 <li> An optional length modifier that specifies the size of the argument.
13274 <li> A conversion specifier character that specifies the type of conversion to be applied.
13277 As noted above, a field width, or precision, or both, may be indicated by an asterisk. In
13278 this case, an int argument supplies the field width or precision. The arguments
13279 specifying field width, or precision, or both, shall appear (in that order) before the
13280 argument (if any) to be converted. A negative field width argument is taken as a - flag
13281 followed by a positive field width. A negative precision argument is taken as if the
13282 precision were omitted.
13284 The flag characters and their meanings are:
13285 - The result of the conversion is left-justified within the field. (It is right-justified if
13287 this flag is not specified.)</pre>
13288 + The result of a signed conversion always begins with a plus or minus sign. (It
13290 begins with a sign only when a negative value is converted if this flag is not</pre>
13297 specified.)<sup><a href="#note242"><b>242)</b></a></sup></pre>
13298 space If the first character of a signed conversion is not a sign, or if a signed conversion
13300 results in no characters, a space is prefixed to the result. If the space and + flags
13301 both appear, the space flag is ignored.</pre>
13302 # The result is converted to an ''alternative form''. For o conversion, it increases
13304 the precision, if and only if necessary, to force the first digit of the result to be a
13305 zero (if the value and precision are both 0, a single 0 is printed). For x (or X)
13306 conversion, a nonzero result has 0x (or 0X) prefixed to it. For a, A, e, E, f, F, g,
13307 and G conversions, the result of converting a floating-point number always
13308 contains a decimal-point character, even if no digits follow it. (Normally, a
13309 decimal-point character appears in the result of these conversions only if a digit
13310 follows it.) For g and G conversions, trailing zeros are not removed from the
13311 result. For other conversions, the behavior is undefined.</pre>
13312 0 For d, i, o, u, x, X, a, A, e, E, f, F, g, and G conversions, leading zeros
13315 (following any indication of sign or base) are used to pad to the field width rather
13316 than performing space padding, except when converting an infinity or NaN. If the
13317 0 and - flags both appear, the 0 flag is ignored. For d, i, o, u, x, and X
13318 conversions, if a precision is specified, the 0 flag is ignored. For other
13319 conversions, the behavior is undefined.</pre>
13320 The length modifiers and their meanings are:
13321 hh Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
13323 signed char or unsigned char argument (the argument will have
13324 been promoted according to the integer promotions, but its value shall be
13325 converted to signed char or unsigned char before printing); or that
13326 a following n conversion specifier applies to a pointer to a signed char
13328 h Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
13330 short int or unsigned short int argument (the argument will
13331 have been promoted according to the integer promotions, but its value shall
13332 be converted to short int or unsigned short int before printing);
13333 or that a following n conversion specifier applies to a pointer to a short
13334 int argument.</pre>
13335 l (ell) Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
13337 long int or unsigned long int argument; that a following n
13338 conversion specifier applies to a pointer to a long int argument; that a</pre>
13342 following c conversion specifier applies to a wint_t argument; that a
13343 following s conversion specifier applies to a pointer to a wchar_t
13344 argument; or has no effect on a following a, A, e, E, f, F, g, or G conversion
13346 ll (ell-ell) Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
13348 long long int or unsigned long long int argument; or that a
13349 following n conversion specifier applies to a pointer to a long long int
13351 j Specifies that a following d, i, o, u, x, or X conversion specifier applies to
13353 an intmax_t or uintmax_t argument; or that a following n conversion
13354 specifier applies to a pointer to an intmax_t argument.</pre>
13355 z Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
13357 size_t or the corresponding signed integer type argument; or that a
13358 following n conversion specifier applies to a pointer to a signed integer type
13359 corresponding to size_t argument.</pre>
13360 t Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
13362 ptrdiff_t or the corresponding unsigned integer type argument; or that a
13363 following n conversion specifier applies to a pointer to a ptrdiff_t
13365 L Specifies that a following a, A, e, E, f, F, g, or G conversion specifier
13367 applies to a long double argument.</pre>
13368 If a length modifier appears with any conversion specifier other than as specified above,
13369 the behavior is undefined.
13371 The conversion specifiers and their meanings are:
13372 d,i The int argument is converted to signed decimal in the style [-]dddd. The
13374 precision specifies the minimum number of digits to appear; if the value
13375 being converted can be represented in fewer digits, it is expanded with
13376 leading zeros. The default precision is 1. The result of converting a zero
13377 value with a precision of zero is no characters.</pre>
13378 o,u,x,X The unsigned int argument is converted to unsigned octal (o), unsigned
13381 decimal (u), or unsigned hexadecimal notation (x or X) in the style dddd; the
13382 letters abcdef are used for x conversion and the letters ABCDEF for X
13383 conversion. The precision specifies the minimum number of digits to appear;
13384 if the value being converted can be represented in fewer digits, it is expanded
13385 with leading zeros. The default precision is 1. The result of converting a
13386 zero value with a precision of zero is no characters.</pre>
13387 f,F A double argument representing a floating-point number is converted to
13389 decimal notation in the style [-]ddd.ddd, where the number of digits after
13390 the decimal-point character is equal to the precision specification. If the
13391 precision is missing, it is taken as 6; if the precision is zero and the # flag is
13392 not specified, no decimal-point character appears. If a decimal-point
13393 character appears, at least one digit appears before it. The value is rounded to
13394 the appropriate number of digits.
13395 A double argument representing an infinity is converted in one of the styles
13396 [-]inf or [-]infinity -- which style is implementation-defined. A
13397 double argument representing a NaN is converted in one of the styles
13398 [-]nan or [-]nan(n-char-sequence) -- which style, and the meaning of
13399 any n-char-sequence, is implementation-defined. The F conversion specifier
13400 produces INF, INFINITY, or NAN instead of inf, infinity, or nan,
13401 respectively.<sup><a href="#note243"><b>243)</b></a></sup></pre>
13402 e,E A double argument representing a floating-point number is converted in the
13404 style [-]d.ddd e(+-)dd, where there is one digit (which is nonzero if the
13405 argument is nonzero) before the decimal-point character and the number of
13406 digits after it is equal to the precision; if the precision is missing, it is taken as
13407 6; if the precision is zero and the # flag is not specified, no decimal-point
13408 character appears. The value is rounded to the appropriate number of digits.
13409 The E conversion specifier produces a number with E instead of e
13410 introducing the exponent. The exponent always contains at least two digits,
13411 and only as many more digits as necessary to represent the exponent. If the
13412 value is zero, the exponent is zero.
13413 A double argument representing an infinity or NaN is converted in the style
13414 of an f or F conversion specifier.</pre>
13415 g,G A double argument representing a floating-point number is converted in
13417 style f or e (or in style F or E in the case of a G conversion specifier),
13418 depending on the value converted and the precision. Let P equal the
13419 precision if nonzero, 6 if the precision is omitted, or 1 if the precision is zero.
13420 Then, if a conversion with style E would have an exponent of X :
13421 -- if P > X >= -4, the conversion is with style f (or F) and precision
13423 -- otherwise, the conversion is with style e (or E) and precision P - 1.
13424 Finally, unless the # flag is used, any trailing zeros are removed from the</pre>
13428 fractional portion of the result and the decimal-point character is removed if
13429 there is no fractional portion remaining.
13430 A double argument representing an infinity or NaN is converted in the style
13431 of an f or F conversion specifier.</pre>
13432 a,A A double argument representing a floating-point number is converted in the
13434 style [-]0xh.hhhh p(+-)d, where there is one hexadecimal digit (which is
13435 nonzero if the argument is a normalized floating-point number and is
13436 otherwise unspecified) before the decimal-point character<sup><a href="#note244"><b>244)</b></a></sup> and the number
13437 of hexadecimal digits after it is equal to the precision; if the precision is
13438 missing and FLT_RADIX is a power of 2, then the precision is sufficient for
13439 an exact representation of the value; if the precision is missing and
13440 FLT_RADIX is not a power of 2, then the precision is sufficient to
13441 distinguish<sup><a href="#note245"><b>245)</b></a></sup> values of type double, except that trailing zeros may be
13442 omitted; if the precision is zero and the # flag is not specified, no decimal-
13443 point character appears. The letters abcdef are used for a conversion and
13444 the letters ABCDEF for A conversion. The A conversion specifier produces a
13445 number with X and P instead of x and p. The exponent always contains at
13446 least one digit, and only as many more digits as necessary to represent the
13447 decimal exponent of 2. If the value is zero, the exponent is zero.
13448 A double argument representing an infinity or NaN is converted in the style
13449 of an f or F conversion specifier.</pre>
13450 c If no l length modifier is present, the int argument is converted to an
13452 unsigned char, and the resulting character is written.
13453 If an l length modifier is present, the wint_t argument is converted as if by
13454 an ls conversion specification with no precision and an argument that points
13455 to the initial element of a two-element array of wchar_t, the first element
13456 containing the wint_t argument to the lc conversion specification and the
13457 second a null wide character.</pre>
13458 s If no l length modifier is present, the argument shall be a pointer to the initial
13460 element of an array of character type.<sup><a href="#note246"><b>246)</b></a></sup> Characters from the array are</pre>
13465 written up to (but not including) the terminating null character. If the
13466 precision is specified, no more than that many bytes are written. If the
13467 precision is not specified or is greater than the size of the array, the array shall
13468 contain a null character.
13469 If an l length modifier is present, the argument shall be a pointer to the initial
13470 element of an array of wchar_t type. Wide characters from the array are
13471 converted to multibyte characters (each as if by a call to the wcrtomb
13472 function, with the conversion state described by an mbstate_t object
13473 initialized to zero before the first wide character is converted) up to and
13474 including a terminating null wide character. The resulting multibyte
13475 characters are written up to (but not including) the terminating null character
13476 (byte). If no precision is specified, the array shall contain a null wide
13477 character. If a precision is specified, no more than that many bytes are
13478 written (including shift sequences, if any), and the array shall contain a null
13479 wide character if, to equal the multibyte character sequence length given by
13480 the precision, the function would need to access a wide character one past the
13481 end of the array. In no case is a partial multibyte character written.<sup><a href="#note247"><b>247)</b></a></sup></pre>
13482 p The argument shall be a pointer to void. The value of the pointer is
13484 converted to a sequence of printing characters, in an implementation-defined
13486 n The argument shall be a pointer to signed integer into which is written the
13488 number of characters written to the output stream so far by this call to
13489 fprintf. No argument is converted, but one is consumed. If the conversion
13490 specification includes any flags, a field width, or a precision, the behavior is
13492 % A % character is written. No argument is converted. The complete
13495 conversion specification shall be %%.</pre>
13496 If a conversion specification is invalid, the behavior is undefined.<sup><a href="#note248"><b>248)</b></a></sup> If any argument is
13497 not the correct type for the corresponding conversion specification, the behavior is
13500 In no case does a nonexistent or small field width cause truncation of a field; if the result
13501 of a conversion is wider than the field width, the field is expanded to contain the
13509 For a and A conversions, if FLT_RADIX is a power of 2, the value is correctly rounded
13510 to a hexadecimal floating number with the given precision.
13511 Recommended practice
13513 For a and A conversions, if FLT_RADIX is not a power of 2 and the result is not exactly
13514 representable in the given precision, the result should be one of the two adjacent numbers
13515 in hexadecimal floating style with the given precision, with the extra stipulation that the
13516 error should have a correct sign for the current rounding direction.
13518 For e, E, f, F, g, and G conversions, if the number of significant decimal digits is at most
13519 DECIMAL_DIG, then the result should be correctly rounded.<sup><a href="#note249"><b>249)</b></a></sup> If the number of
13520 significant decimal digits is more than DECIMAL_DIG but the source value is exactly
13521 representable with DECIMAL_DIG digits, then the result should be an exact
13522 representation with trailing zeros. Otherwise, the source value is bounded by two
13523 adjacent decimal strings L < U, both having DECIMAL_DIG significant digits; the value
13524 of the resultant decimal string D should satisfy L <= D <= U, with the extra stipulation that
13525 the error should have a correct sign for the current rounding direction.
13528 The fprintf function returns the number of characters transmitted, or a negative value
13529 if an output or encoding error occurred.
13530 Environmental limits
13532 The number of characters that can be produced by any single conversion shall be at least
13535 EXAMPLE 1 To print a date and time in the form ''Sunday, July 3, 10:02'' followed by pi to five decimal
13538 #include <a href="#7.12"><math.h></a>
13539 #include <a href="#7.19"><stdio.h></a>
13541 char *weekday, *month; // pointers to strings
13542 int day, hour, min;
13543 fprintf(stdout, "%s, %s %d, %.2d:%.2d\n",
13544 weekday, month, day, hour, min);
13545 fprintf(stdout, "pi = %.5f\n", 4 * atan(1.0));</pre>
13548 EXAMPLE 2 In this example, multibyte characters do not have a state-dependent encoding, and the
13549 members of the extended character set that consist of more than one byte each consist of exactly two bytes,
13550 the first of which is denoted here by a and the second by an uppercase letter.
13557 Given the following wide string with length seven,
13559 static wchar_t wstr[] = L" X Yabc Z W";</pre>
13562 fprintf(stdout, "|1234567890123|\n");
13563 fprintf(stdout, "|%13ls|\n", wstr);
13564 fprintf(stdout, "|%-13.9ls|\n", wstr);
13565 fprintf(stdout, "|%13.10ls|\n", wstr);
13566 fprintf(stdout, "|%13.11ls|\n", wstr);
13567 fprintf(stdout, "|%13.15ls|\n", &wstr[2]);
13568 fprintf(stdout, "|%13lc|\n", (wint_t) wstr[5]);</pre>
13569 will print the following seven lines:
13579 <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>).
13582 <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.
13584 <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,
13585 include a minus sign.
13587 <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;
13588 the # and 0 flag characters have no effect.
13590 <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
13591 that subsequent digits align to nibble (4-bit) boundaries.
13593 <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
13594 FLT_RADIX and n is the number of base-b digits in the significand of the source type. A smaller p
13595 might suffice depending on the implementation's scheme for determining the digit to the left of the
13596 decimal-point character.
13598 <p><small><a name="note246" href="#note246">246)</a> No special provisions are made for multibyte characters.
13600 <p><small><a name="note247" href="#note247">247)</a> Redundant shift sequences may result if multibyte characters have a state-dependent encoding.
13602 <p><small><a name="note248" href="#note248">248)</a> See ''future library directions'' (<a href="#7.26.9">7.26.9</a>).
13604 <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
13605 given format specifier. The number of significant digits is determined by the format specifier, and in
13606 the case of fixed-point conversion by the source value as well.
13609 <h5><a name="7.19.6.2" href="#7.19.6.2">7.19.6.2 The fscanf function</a></h5>
13613 #include <a href="#7.19"><stdio.h></a>
13614 int fscanf(FILE * restrict stream,
13615 const char * restrict format, ...);</pre>
13616 <h6>Description</h6>
13618 The fscanf function reads input from the stream pointed to by stream, under control
13619 of the string pointed to by format that specifies the admissible input sequences and how
13620 they are to be converted for assignment, using subsequent arguments as pointers to the
13621 objects to receive the converted input. If there are insufficient arguments for the format,
13622 the behavior is undefined. If the format is exhausted while arguments remain, the excess
13623 arguments are evaluated (as always) but are otherwise ignored.
13625 The format shall be a multibyte character sequence, beginning and ending in its initial
13626 shift state. The format is composed of zero or more directives: one or more white-space
13627 characters, an ordinary multibyte character (neither % nor a white-space character), or a
13628 conversion specification. Each conversion specification is introduced by the character %.
13629 After the %, the following appear in sequence:
13631 <li> An optional assignment-suppressing character *.
13632 <li> An optional decimal integer greater than zero that specifies the maximum field width
13635 <li> An optional length modifier that specifies the size of the receiving object.
13636 <li> A conversion specifier character that specifies the type of conversion to be applied.
13639 The fscanf function executes each directive of the format in turn. If a directive fails, as
13640 detailed below, the function returns. Failures are described as input failures (due to the
13641 occurrence of an encoding error or the unavailability of input characters), or matching
13642 failures (due to inappropriate input).
13644 A directive composed of white-space character(s) is executed by reading input up to the
13645 first non-white-space character (which remains unread), or until no more characters can
13648 A directive that is an ordinary multibyte character is executed by reading the next
13649 characters of the stream. If any of those characters differ from the ones composing the
13650 directive, the directive fails and the differing and subsequent characters remain unread.
13651 Similarly, if end-of-file, an encoding error, or a read error prevents a character from being
13652 read, the directive fails.
13654 A directive that is a conversion specification defines a set of matching input sequences, as
13655 described below for each specifier. A conversion specification is executed in the
13658 Input white-space characters (as specified by the isspace function) are skipped, unless
13659 the specification includes a [, c, or n specifier.<sup><a href="#note250"><b>250)</b></a></sup>
13661 An input item is read from the stream, unless the specification includes an n specifier. An
13662 input item is defined as the longest sequence of input characters which does not exceed
13663 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>
13664 The first character, if any, after the input item remains unread. If the length of the input
13665 item is zero, the execution of the directive fails; this condition is a matching failure unless
13666 end-of-file, an encoding error, or a read error prevented input from the stream, in which
13667 case it is an input failure.
13669 Except in the case of a % specifier, the input item (or, in the case of a %n directive, the
13670 count of input characters) is converted to a type appropriate to the conversion specifier. If
13671 the input item is not a matching sequence, the execution of the directive fails: this
13672 condition is a matching failure. Unless assignment suppression was indicated by a *, the
13673 result of the conversion is placed in the object pointed to by the first argument following
13674 the format argument that has not already received a conversion result. If this object
13675 does not have an appropriate type, or if the result of the conversion cannot be represented
13679 in the object, the behavior is undefined.
13681 The length modifiers and their meanings are:
13682 hh Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
13684 to an argument with type pointer to signed char or unsigned char.</pre>
13685 h Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
13687 to an argument with type pointer to short int or unsigned short
13689 l (ell) Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
13691 to an argument with type pointer to long int or unsigned long
13692 int; that a following a, A, e, E, f, F, g, or G conversion specifier applies to
13693 an argument with type pointer to double; or that a following c, s, or [
13694 conversion specifier applies to an argument with type pointer to wchar_t.</pre>
13695 ll (ell-ell) Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
13697 to an argument with type pointer to long long int or unsigned
13698 long long int.</pre>
13699 j Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
13701 to an argument with type pointer to intmax_t or uintmax_t.</pre>
13702 z Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
13704 to an argument with type pointer to size_t or the corresponding signed
13705 integer type.</pre>
13706 t Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
13708 to an argument with type pointer to ptrdiff_t or the corresponding
13709 unsigned integer type.</pre>
13710 L Specifies that a following a, A, e, E, f, F, g, or G conversion specifier
13712 applies to an argument with type pointer to long double.</pre>
13713 If a length modifier appears with any conversion specifier other than as specified above,
13714 the behavior is undefined.
13716 The conversion specifiers and their meanings are:
13717 d Matches an optionally signed decimal integer, whose format is the same as
13719 expected for the subject sequence of the strtol function with the value 10
13720 for the base argument. The corresponding argument shall be a pointer to
13721 signed integer.</pre>
13722 i Matches an optionally signed integer, whose format is the same as expected
13725 for the subject sequence of the strtol function with the value 0 for the
13726 base argument. The corresponding argument shall be a pointer to signed
13728 o Matches an optionally signed octal integer, whose format is the same as
13730 expected for the subject sequence of the strtoul function with the value 8
13731 for the base argument. The corresponding argument shall be a pointer to
13732 unsigned integer.</pre>
13733 u Matches an optionally signed decimal integer, whose format is the same as
13735 expected for the subject sequence of the strtoul function with the value 10
13736 for the base argument. The corresponding argument shall be a pointer to
13737 unsigned integer.</pre>
13738 x Matches an optionally signed hexadecimal integer, whose format is the same
13740 as expected for the subject sequence of the strtoul function with the value
13741 16 for the base argument. The corresponding argument shall be a pointer to
13742 unsigned integer.</pre>
13743 a,e,f,g Matches an optionally signed floating-point number, infinity, or NaN, whose
13745 format is the same as expected for the subject sequence of the strtod
13746 function. The corresponding argument shall be a pointer to floating.</pre>
13747 c Matches a sequence of characters of exactly the number specified by the field
13749 width (1 if no field width is present in the directive).<sup><a href="#note252"><b>252)</b></a></sup>
13750 If no l length modifier is present, the corresponding argument shall be a
13751 pointer to the initial element of a character array large enough to accept the
13752 sequence. No null character is added.
13753 If an l length modifier is present, the input shall be a sequence of multibyte
13754 characters that begins in the initial shift state. Each multibyte character in the
13755 sequence is converted to a wide character as if by a call to the mbrtowc
13756 function, with the conversion state described by an mbstate_t object
13757 initialized to zero before the first multibyte character is converted. The
13758 corresponding argument shall be a pointer to the initial element of an array of
13759 wchar_t large enough to accept the resulting sequence of wide characters.
13760 No null wide character is added.</pre>
13761 s Matches a sequence of non-white-space characters.252)
13763 If no l length modifier is present, the corresponding argument shall be a
13764 pointer to the initial element of a character array large enough to accept the
13765 sequence and a terminating null character, which will be added automatically.
13766 If an l length modifier is present, the input shall be a sequence of multibyte</pre>
13771 characters that begins in the initial shift state. Each multibyte character is
13772 converted to a wide character as if by a call to the mbrtowc function, with
13773 the conversion state described by an mbstate_t object initialized to zero
13774 before the first multibyte character is converted. The corresponding argument
13775 shall be a pointer to the initial element of an array of wchar_t large enough
13776 to accept the sequence and the terminating null wide character, which will be
13777 added automatically.</pre>
13778 [ Matches a nonempty sequence of characters from a set of expected characters
13781 If no l length modifier is present, the corresponding argument shall be a
13782 pointer to the initial element of a character array large enough to accept the
13783 sequence and a terminating null character, which will be added automatically.
13784 If an l length modifier is present, the input shall be a sequence of multibyte
13785 characters that begins in the initial shift state. Each multibyte character is
13786 converted to a wide character as if by a call to the mbrtowc function, with
13787 the conversion state described by an mbstate_t object initialized to zero
13788 before the first multibyte character is converted. The corresponding argument
13789 shall be a pointer to the initial element of an array of wchar_t large enough
13790 to accept the sequence and the terminating null wide character, which will be
13791 added automatically.
13792 The conversion specifier includes all subsequent characters in the format
13793 string, up to and including the matching right bracket (]). The characters
13794 between the brackets (the scanlist) compose the scanset, unless the character
13795 after the left bracket is a circumflex (^), in which case the scanset contains all
13796 characters that do not appear in the scanlist between the circumflex and the
13797 right bracket. If the conversion specifier begins with [] or [^], the right
13798 bracket character is in the scanlist and the next following right bracket
13799 character is the matching right bracket that ends the specification; otherwise
13800 the first following right bracket character is the one that ends the
13801 specification. If a - character is in the scanlist and is not the first, nor the
13802 second where the first character is a ^, nor the last character, the behavior is
13803 implementation-defined.</pre>
13804 p Matches an implementation-defined set of sequences, which should be the
13807 same as the set of sequences that may be produced by the %p conversion of
13808 the fprintf function. The corresponding argument shall be a pointer to a
13809 pointer to void. The input item is converted to a pointer value in an
13810 implementation-defined manner. If the input item is a value converted earlier
13811 during the same program execution, the pointer that results shall compare
13812 equal to that value; otherwise the behavior of the %p conversion is undefined.</pre>
13813 n No input is consumed. The corresponding argument shall be a pointer to
13815 signed integer into which is to be written the number of characters read from
13816 the input stream so far by this call to the fscanf function. Execution of a
13817 %n directive does not increment the assignment count returned at the
13818 completion of execution of the fscanf function. No argument is converted,
13819 but one is consumed. If the conversion specification includes an assignment-
13820 suppressing character or a field width, the behavior is undefined.</pre>
13821 % Matches a single % character; no conversion or assignment occurs. The
13824 complete conversion specification shall be %%.</pre>
13825 If a conversion specification is invalid, the behavior is undefined.<sup><a href="#note253"><b>253)</b></a></sup>
13827 The conversion specifiers A, E, F, G, and X are also valid and behave the same as,
13828 respectively, a, e, f, g, and x.
13830 Trailing white space (including new-line characters) is left unread unless matched by a
13831 directive. The success of literal matches and suppressed assignments is not directly
13832 determinable other than via the %n directive.
13835 The fscanf function returns the value of the macro EOF if an input failure occurs
13836 before any conversion. Otherwise, the function returns the number of input items
13837 assigned, which can be fewer than provided for, or even zero, in the event of an early
13840 EXAMPLE 1 The call:
13842 #include <a href="#7.19"><stdio.h></a>
13844 int n, i; float x; char name[50];
13845 n = fscanf(stdin, "%d%f%s", &i, &x, name);</pre>
13846 with the input line:
13848 25 54.32E-1 thompson</pre>
13849 will assign to n the value 3, to i the value 25, to x the value 5.432, and to name the sequence
13853 EXAMPLE 2 The call:
13855 #include <a href="#7.19"><stdio.h></a>
13857 int i; float x; char name[50];
13858 fscanf(stdin, "%2d%f%*d %[0123456789]", &i, &x, name);</pre>
13865 56789 0123 56a72</pre>
13866 will assign to i the value 56 and to x the value 789.0, will skip 0123, and will assign to name the
13867 sequence 56\0. The next character read from the input stream will be a.
13870 EXAMPLE 3 To accept repeatedly from stdin a quantity, a unit of measure, and an item name:
13873 #include <a href="#7.19"><stdio.h></a>
13875 int count; float quant; char units[21], item[21];
13877 count = fscanf(stdin, "%f%20s of %20s", &quant, units, item);
13878 fscanf(stdin,"%*[^\n]");
13879 } while (!feof(stdin) && !ferror(stdin));</pre>
13880 If the stdin stream contains the following lines:
13883 -12.8degrees Celsius
13887 100ergs of energy</pre>
13888 the execution of the above example will be analogous to the following assignments:
13890 quant = 2; strcpy(units, "quarts"); strcpy(item, "oil");
13892 quant = -12.8; strcpy(units, "degrees");
13893 count = 2; // "C" fails to match "o"
13894 count = 0; // "l" fails to match "%f"
13895 quant = 10.0; strcpy(units, "LBS"); strcpy(item, "dirt");
13897 count = 0; // "100e" fails to match "%f"
13903 #include <a href="#7.19"><stdio.h></a>
13905 int d1, d2, n1, n2, i;
13906 i = sscanf("123", "%d%n%n%d", &d1, &n1, &n2, &d2);</pre>
13907 the value 123 is assigned to d1 and the value 3 to n1. Because %n can never get an input failure the value
13908 of 3 is also assigned to n2. The value of d2 is not affected. The value 1 is assigned to i.
13911 EXAMPLE 5 In these examples, multibyte characters do have a state-dependent encoding, and the
13912 members of the extended character set that consist of more than one byte each consist of exactly two bytes,
13913 the first of which is denoted here by a and the second by an uppercase letter, but are only recognized as
13914 such when in the alternate shift state. The shift sequences are denoted by (uparrow) and (downarrow), in which the first causes
13915 entry into the alternate shift state.
13920 #include <a href="#7.19"><stdio.h></a>
13923 fscanf(stdin, "a%s", str);</pre>
13924 with the input line:
13926 a(uparrow) X Y(downarrow) bc</pre>
13927 str will contain (uparrow) X Y(downarrow)\0 assuming that none of the bytes of the shift sequences (or of the multibyte
13928 characters, in the more general case) appears to be a single-byte white-space character.
13930 In contrast, after the call:
13932 #include <a href="#7.19"><stdio.h></a>
13933 #include <a href="#7.17"><stddef.h></a>
13936 fscanf(stdin, "a%ls", wstr);</pre>
13937 with the same input line, wstr will contain the two wide characters that correspond to X and Y and a
13938 terminating null wide character.
13942 #include <a href="#7.19"><stdio.h></a>
13943 #include <a href="#7.17"><stddef.h></a>
13946 fscanf(stdin, "a(uparrow) X(downarrow)%ls", wstr);</pre>
13947 with the same input line will return zero due to a matching failure against the (downarrow) sequence in the format
13950 Assuming that the first byte of the multibyte character X is the same as the first byte of the multibyte
13951 character Y, after the call:
13953 #include <a href="#7.19"><stdio.h></a>
13954 #include <a href="#7.17"><stddef.h></a>
13957 fscanf(stdin, "a(uparrow) Y(downarrow)%ls", wstr);</pre>
13958 with the same input line, zero will again be returned, but stdin will be left with a partially consumed
13959 multibyte character.
13961 <p><b> Forward references</b>: the strtod, strtof, and strtold functions (<a href="#7.20.1.3">7.20.1.3</a>), the
13962 strtol, strtoll, strtoul, and strtoull functions (<a href="#7.20.1.4">7.20.1.4</a>), conversion state
13963 (<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>).
13967 <p><small><a name="note250" href="#note250">250)</a> These white-space characters are not counted against a specified field width.
13969 <p><small><a name="note251" href="#note251">251)</a> fscanf pushes back at most one input character onto the input stream. Therefore, some sequences
13970 that are acceptable to strtod, strtol, etc., are unacceptable to fscanf.
13972 <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 [
13973 conversion specifiers -- the extent of the input field is determined on a byte-by-byte basis. The
13974 resulting field is nevertheless a sequence of multibyte characters that begins in the initial shift state.
13976 <p><small><a name="note253" href="#note253">253)</a> See ''future library directions'' (<a href="#7.26.9">7.26.9</a>).
13979 <h5><a name="7.19.6.3" href="#7.19.6.3">7.19.6.3 The printf function</a></h5>
13983 #include <a href="#7.19"><stdio.h></a>
13984 int printf(const char * restrict format, ...);</pre>
13985 <h6>Description</h6>
13987 The printf function is equivalent to fprintf with the argument stdout interposed
13988 before the arguments to printf.
13991 The printf function returns the number of characters transmitted, or a negative value if
13992 an output or encoding error occurred.
13994 <h5><a name="7.19.6.4" href="#7.19.6.4">7.19.6.4 The scanf function</a></h5>
13998 #include <a href="#7.19"><stdio.h></a>
13999 int scanf(const char * restrict format, ...);</pre>
14000 <h6>Description</h6>
14002 The scanf function is equivalent to fscanf with the argument stdin interposed
14003 before the arguments to scanf.
14006 The scanf function returns the value of the macro EOF if an input failure occurs before
14007 any conversion. Otherwise, the scanf function returns the number of input items
14008 assigned, which can be fewer than provided for, or even zero, in the event of an early
14011 <h5><a name="7.19.6.5" href="#7.19.6.5">7.19.6.5 The snprintf function</a></h5>
14015 #include <a href="#7.19"><stdio.h></a>
14016 int snprintf(char * restrict s, size_t n,
14017 const char * restrict format, ...);</pre>
14018 <h6>Description</h6>
14020 The snprintf function is equivalent to fprintf, except that the output is written into
14021 an array (specified by argument s) rather than to a stream. If n is zero, nothing is written,
14022 and s may be a null pointer. Otherwise, output characters beyond the n-1st are
14023 discarded rather than being written to the array, and a null character is written at the end
14024 of the characters actually written into the array. If copying takes place between objects
14025 that overlap, the behavior is undefined.
14029 The snprintf function returns the number of characters that would have been written
14030 had n been sufficiently large, not counting the terminating null character, or a negative
14031 value if an encoding error occurred. Thus, the null-terminated output has been
14032 completely written if and only if the returned value is nonnegative and less than n.
14034 <h5><a name="7.19.6.6" href="#7.19.6.6">7.19.6.6 The sprintf function</a></h5>
14038 #include <a href="#7.19"><stdio.h></a>
14039 int sprintf(char * restrict s,
14040 const char * restrict format, ...);</pre>
14041 <h6>Description</h6>
14043 The sprintf function is equivalent to fprintf, except that the output is written into
14044 an array (specified by the argument s) rather than to a stream. A null character is written
14045 at the end of the characters written; it is not counted as part of the returned value. If
14046 copying takes place between objects that overlap, the behavior is undefined.
14049 The sprintf function returns the number of characters written in the array, not
14050 counting the terminating null character, or a negative value if an encoding error occurred.
14052 <h5><a name="7.19.6.7" href="#7.19.6.7">7.19.6.7 The sscanf function</a></h5>
14056 #include <a href="#7.19"><stdio.h></a>
14057 int sscanf(const char * restrict s,
14058 const char * restrict format, ...);</pre>
14059 <h6>Description</h6>
14061 The sscanf function is equivalent to fscanf, except that input is obtained from a
14062 string (specified by the argument s) rather than from a stream. Reaching the end of the
14063 string is equivalent to encountering end-of-file for the fscanf function. If copying
14064 takes place between objects that overlap, the behavior is undefined.
14067 The sscanf function returns the value of the macro EOF if an input failure occurs
14068 before any conversion. Otherwise, the sscanf function returns the number of input
14069 items assigned, which can be fewer than provided for, or even zero, in the event of an
14070 early matching failure.
14073 <h5><a name="7.19.6.8" href="#7.19.6.8">7.19.6.8 The vfprintf function</a></h5>
14077 #include <a href="#7.15"><stdarg.h></a>
14078 #include <a href="#7.19"><stdio.h></a>
14079 int vfprintf(FILE * restrict stream,
14080 const char * restrict format,
14081 va_list arg);</pre>
14082 <h6>Description</h6>
14084 The vfprintf function is equivalent to fprintf, with the variable argument list
14085 replaced by arg, which shall have been initialized by the va_start macro (and
14086 possibly subsequent va_arg calls). The vfprintf function does not invoke the
14087 va_end macro.<sup><a href="#note254"><b>254)</b></a></sup>
14090 The vfprintf function returns the number of characters transmitted, or a negative
14091 value if an output or encoding error occurred.
14093 EXAMPLE The following shows the use of the vfprintf function in a general error-reporting routine.
14095 #include <a href="#7.15"><stdarg.h></a>
14096 #include <a href="#7.19"><stdio.h></a>
14097 void error(char *function_name, char *format, ...)
14100 va_start(args, format);
14101 // print out name of function causing error
14102 fprintf(stderr, "ERROR in %s: ", function_name);
14103 // print out remainder of message
14104 vfprintf(stderr, format, args);
14114 <p><small><a name="note254" href="#note254">254)</a> As the functions vfprintf, vfscanf, vprintf, vscanf, vsnprintf, vsprintf, and
14115 vsscanf invoke the va_arg macro, the value of arg after the return is indeterminate.
14118 <h5><a name="7.19.6.9" href="#7.19.6.9">7.19.6.9 The vfscanf function</a></h5>
14122 #include <a href="#7.15"><stdarg.h></a>
14123 #include <a href="#7.19"><stdio.h></a>
14124 int vfscanf(FILE * restrict stream,
14125 const char * restrict format,
14126 va_list arg);</pre>
14127 <h6>Description</h6>
14129 The vfscanf function is equivalent to fscanf, with the variable argument list
14130 replaced by arg, which shall have been initialized by the va_start macro (and
14131 possibly subsequent va_arg calls). The vfscanf function does not invoke the
14135 The vfscanf function returns the value of the macro EOF if an input failure occurs
14136 before any conversion. Otherwise, the vfscanf function returns the number of input
14137 items assigned, which can be fewer than provided for, or even zero, in the event of an
14138 early matching failure.
14140 <h5><a name="7.19.6.10" href="#7.19.6.10">7.19.6.10 The vprintf function</a></h5>
14144 #include <a href="#7.15"><stdarg.h></a>
14145 #include <a href="#7.19"><stdio.h></a>
14146 int vprintf(const char * restrict format,
14147 va_list arg);</pre>
14148 <h6>Description</h6>
14150 The vprintf function is equivalent to printf, with the variable argument list
14151 replaced by arg, which shall have been initialized by the va_start macro (and
14152 possibly subsequent va_arg calls). The vprintf function does not invoke the
14156 The vprintf function returns the number of characters transmitted, or a negative value
14157 if an output or encoding error occurred.
14160 <h5><a name="7.19.6.11" href="#7.19.6.11">7.19.6.11 The vscanf function</a></h5>
14164 #include <a href="#7.15"><stdarg.h></a>
14165 #include <a href="#7.19"><stdio.h></a>
14166 int vscanf(const char * restrict format,
14167 va_list arg);</pre>
14168 <h6>Description</h6>
14170 The vscanf function is equivalent to scanf, with the variable argument list replaced
14171 by arg, which shall have been initialized by the va_start macro (and possibly
14172 subsequent va_arg calls). The vscanf function does not invoke the va_end
14176 The vscanf function returns the value of the macro EOF if an input failure occurs
14177 before any conversion. Otherwise, the vscanf function returns the number of input
14178 items assigned, which can be fewer than provided for, or even zero, in the event of an
14179 early matching failure.
14181 <h5><a name="7.19.6.12" href="#7.19.6.12">7.19.6.12 The vsnprintf function</a></h5>
14185 #include <a href="#7.15"><stdarg.h></a>
14186 #include <a href="#7.19"><stdio.h></a>
14187 int vsnprintf(char * restrict s, size_t n,
14188 const char * restrict format,
14189 va_list arg);</pre>
14190 <h6>Description</h6>
14192 The vsnprintf function is equivalent to snprintf, with the variable argument list
14193 replaced by arg, which shall have been initialized by the va_start macro (and
14194 possibly subsequent va_arg calls). The vsnprintf function does not invoke the
14195 va_end macro.254) If copying takes place between objects that overlap, the behavior is
14199 The vsnprintf function returns the number of characters that would have been written
14200 had n been sufficiently large, not counting the terminating null character, or a negative
14201 value if an encoding error occurred. Thus, the null-terminated output has been
14202 completely written if and only if the returned value is nonnegative and less than n.
14205 <h5><a name="7.19.6.13" href="#7.19.6.13">7.19.6.13 The vsprintf function</a></h5>
14209 #include <a href="#7.15"><stdarg.h></a>
14210 #include <a href="#7.19"><stdio.h></a>
14211 int vsprintf(char * restrict s,
14212 const char * restrict format,
14213 va_list arg);</pre>
14214 <h6>Description</h6>
14216 The vsprintf function is equivalent to sprintf, with the variable argument list
14217 replaced by arg, which shall have been initialized by the va_start macro (and
14218 possibly subsequent va_arg calls). The vsprintf function does not invoke the
14219 va_end macro.254) If copying takes place between objects that overlap, the behavior is
14223 The vsprintf function returns the number of characters written in the array, not
14224 counting the terminating null character, or a negative value if an encoding error occurred.
14226 <h5><a name="7.19.6.14" href="#7.19.6.14">7.19.6.14 The vsscanf function</a></h5>
14230 #include <a href="#7.15"><stdarg.h></a>
14231 #include <a href="#7.19"><stdio.h></a>
14232 int vsscanf(const char * restrict s,
14233 const char * restrict format,
14234 va_list arg);</pre>
14235 <h6>Description</h6>
14237 The vsscanf function is equivalent to sscanf, with the variable argument list
14238 replaced by arg, which shall have been initialized by the va_start macro (and
14239 possibly subsequent va_arg calls). The vsscanf function does not invoke the
14243 The vsscanf function returns the value of the macro EOF if an input failure occurs
14244 before any conversion. Otherwise, the vsscanf function returns the number of input
14245 items assigned, which can be fewer than provided for, or even zero, in the event of an
14246 early matching failure.
14249 <h4><a name="7.19.7" href="#7.19.7">7.19.7 Character input/output functions</a></h4>
14251 <h5><a name="7.19.7.1" href="#7.19.7.1">7.19.7.1 The fgetc function</a></h5>
14255 #include <a href="#7.19"><stdio.h></a>
14256 int fgetc(FILE *stream);</pre>
14257 <h6>Description</h6>
14259 If the end-of-file indicator for the input stream pointed to by stream is not set and a
14260 next character is present, the fgetc function obtains that character as an unsigned
14261 char converted to an int and advances the associated file position indicator for the
14262 stream (if defined).
14265 If the end-of-file indicator for the stream is set, or if the stream is at end-of-file, the end-
14266 of-file indicator for the stream is set and the fgetc function returns EOF. Otherwise, the
14267 fgetc function returns the next character from the input stream pointed to by stream.
14268 If a read error occurs, the error indicator for the stream is set and the fgetc function
14269 returns EOF.<sup><a href="#note255"><b>255)</b></a></sup>
14272 <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.
14275 <h5><a name="7.19.7.2" href="#7.19.7.2">7.19.7.2 The fgets function</a></h5>
14279 #include <a href="#7.19"><stdio.h></a>
14280 char *fgets(char * restrict s, int n,
14281 FILE * restrict stream);</pre>
14282 <h6>Description</h6>
14284 The fgets function reads at most one less than the number of characters specified by n
14285 from the stream pointed to by stream into the array pointed to by s. No additional
14286 characters are read after a new-line character (which is retained) or after end-of-file. A
14287 null character is written immediately after the last character read into the array.
14290 The fgets function returns s if successful. If end-of-file is encountered and no
14291 characters have been read into the array, the contents of the array remain unchanged and a
14292 null pointer is returned. If a read error occurs during the operation, the array contents are
14293 indeterminate and a null pointer is returned.
14300 <h5><a name="7.19.7.3" href="#7.19.7.3">7.19.7.3 The fputc function</a></h5>
14304 #include <a href="#7.19"><stdio.h></a>
14305 int fputc(int c, FILE *stream);</pre>
14306 <h6>Description</h6>
14308 The fputc function writes the character specified by c (converted to an unsigned
14309 char) to the output stream pointed to by stream, at the position indicated by the
14310 associated file position indicator for the stream (if defined), and advances the indicator
14311 appropriately. If the file cannot support positioning requests, or if the stream was opened
14312 with append mode, the character is appended to the output stream.
14315 The fputc function returns the character written. If a write error occurs, the error
14316 indicator for the stream is set and fputc returns EOF.
14318 <h5><a name="7.19.7.4" href="#7.19.7.4">7.19.7.4 The fputs function</a></h5>
14322 #include <a href="#7.19"><stdio.h></a>
14323 int fputs(const char * restrict s,
14324 FILE * restrict stream);</pre>
14325 <h6>Description</h6>
14327 The fputs function writes the string pointed to by s to the stream pointed to by
14328 stream. The terminating null character is not written.
14331 The fputs function returns EOF if a write error occurs; otherwise it returns a
14334 <h5><a name="7.19.7.5" href="#7.19.7.5">7.19.7.5 The getc function</a></h5>
14338 #include <a href="#7.19"><stdio.h></a>
14339 int getc(FILE *stream);</pre>
14340 <h6>Description</h6>
14342 The getc function is equivalent to fgetc, except that if it is implemented as a macro, it
14343 may evaluate stream more than once, so the argument should never be an expression
14348 The getc function returns the next character from the input stream pointed to by
14349 stream. If the stream is at end-of-file, the end-of-file indicator for the stream is set and
14350 getc returns EOF. If a read error occurs, the error indicator for the stream is set and
14353 <h5><a name="7.19.7.6" href="#7.19.7.6">7.19.7.6 The getchar function</a></h5>
14357 #include <a href="#7.19"><stdio.h></a>
14358 int getchar(void);</pre>
14359 <h6>Description</h6>
14361 The getchar function is equivalent to getc with the argument stdin.
14364 The getchar function returns the next character from the input stream pointed to by
14365 stdin. If the stream is at end-of-file, the end-of-file indicator for the stream is set and
14366 getchar returns EOF. If a read error occurs, the error indicator for the stream is set and
14367 getchar returns EOF.
14369 <h5><a name="7.19.7.7" href="#7.19.7.7">7.19.7.7 The gets function</a></h5>
14373 #include <a href="#7.19"><stdio.h></a>
14374 char *gets(char *s);</pre>
14375 <h6>Description</h6>
14377 The gets function reads characters from the input stream pointed to by stdin, into the
14378 array pointed to by s, until end-of-file is encountered or a new-line character is read.
14379 Any new-line character is discarded, and a null character is written immediately after the
14380 last character read into the array.
14383 The gets function returns s if successful. If end-of-file is encountered and no
14384 characters have been read into the array, the contents of the array remain unchanged and a
14385 null pointer is returned. If a read error occurs during the operation, the array contents are
14386 indeterminate and a null pointer is returned.
14387 <p><b> Forward references</b>: future library directions (<a href="#7.26.9">7.26.9</a>).
14390 <h5><a name="7.19.7.8" href="#7.19.7.8">7.19.7.8 The putc function</a></h5>
14394 #include <a href="#7.19"><stdio.h></a>
14395 int putc(int c, FILE *stream);</pre>
14396 <h6>Description</h6>
14398 The putc function is equivalent to fputc, except that if it is implemented as a macro, it
14399 may evaluate stream more than once, so that argument should never be an expression
14403 The putc function returns the character written. If a write error occurs, the error
14404 indicator for the stream is set and putc returns EOF.
14406 <h5><a name="7.19.7.9" href="#7.19.7.9">7.19.7.9 The putchar function</a></h5>
14410 #include <a href="#7.19"><stdio.h></a>
14411 int putchar(int c);</pre>
14412 <h6>Description</h6>
14414 The putchar function is equivalent to putc with the second argument stdout.
14417 The putchar function returns the character written. If a write error occurs, the error
14418 indicator for the stream is set and putchar returns EOF.
14420 <h5><a name="7.19.7.10" href="#7.19.7.10">7.19.7.10 The puts function</a></h5>
14424 #include <a href="#7.19"><stdio.h></a>
14425 int puts(const char *s);</pre>
14426 <h6>Description</h6>
14428 The puts function writes the string pointed to by s to the stream pointed to by stdout,
14429 and appends a new-line character to the output. The terminating null character is not
14433 The puts function returns EOF if a write error occurs; otherwise it returns a nonnegative
14437 <h5><a name="7.19.7.11" href="#7.19.7.11">7.19.7.11 The ungetc function</a></h5>
14441 #include <a href="#7.19"><stdio.h></a>
14442 int ungetc(int c, FILE *stream);</pre>
14443 <h6>Description</h6>
14445 The ungetc function pushes the character specified by c (converted to an unsigned
14446 char) back onto the input stream pointed to by stream. Pushed-back characters will be
14447 returned by subsequent reads on that stream in the reverse order of their pushing. A
14448 successful intervening call (with the stream pointed to by stream) to a file positioning
14449 function (fseek, fsetpos, or rewind) discards any pushed-back characters for the
14450 stream. The external storage corresponding to the stream is unchanged.
14452 One character of pushback is guaranteed. If the ungetc function is called too many
14453 times on the same stream without an intervening read or file positioning operation on that
14454 stream, the operation may fail.
14456 If the value of c equals that of the macro EOF, the operation fails and the input stream is
14459 A successful call to the ungetc function clears the end-of-file indicator for the stream.
14460 The value of the file position indicator for the stream after reading or discarding all
14461 pushed-back characters shall be the same as it was before the characters were pushed
14462 back. For a text stream, the value of its file position indicator after a successful call to the
14463 ungetc function is unspecified until all pushed-back characters are read or discarded.
14464 For a binary stream, its file position indicator is decremented by each successful call to
14465 the ungetc function; if its value was zero before a call, it is indeterminate after the
14466 call.<sup><a href="#note256"><b>256)</b></a></sup>
14469 The ungetc function returns the character pushed back after conversion, or EOF if the
14471 <p><b> Forward references</b>: file positioning functions (<a href="#7.19.9">7.19.9</a>).
14479 <p><small><a name="note256" href="#note256">256)</a> See ''future library directions'' (<a href="#7.26.9">7.26.9</a>).
14482 <h4><a name="7.19.8" href="#7.19.8">7.19.8 Direct input/output functions</a></h4>
14484 <h5><a name="7.19.8.1" href="#7.19.8.1">7.19.8.1 The fread function</a></h5>
14488 #include <a href="#7.19"><stdio.h></a>
14489 size_t fread(void * restrict ptr,
14490 size_t size, size_t nmemb,
14491 FILE * restrict stream);</pre>
14492 <h6>Description</h6>
14494 The fread function reads, into the array pointed to by ptr, up to nmemb elements
14495 whose size is specified by size, from the stream pointed to by stream. For each
14496 object, size calls are made to the fgetc function and the results stored, in the order
14497 read, in an array of unsigned char exactly overlaying the object. The file position
14498 indicator for the stream (if defined) is advanced by the number of characters successfully
14499 read. If an error occurs, the resulting value of the file position indicator for the stream is
14500 indeterminate. If a partial element is read, its value is indeterminate.
14503 The fread function returns the number of elements successfully read, which may be
14504 less than nmemb if a read error or end-of-file is encountered. If size or nmemb is zero,
14505 fread returns zero and the contents of the array and the state of the stream remain
14508 <h5><a name="7.19.8.2" href="#7.19.8.2">7.19.8.2 The fwrite function</a></h5>
14512 #include <a href="#7.19"><stdio.h></a>
14513 size_t fwrite(const void * restrict ptr,
14514 size_t size, size_t nmemb,
14515 FILE * restrict stream);</pre>
14516 <h6>Description</h6>
14518 The fwrite function writes, from the array pointed to by ptr, up to nmemb elements
14519 whose size is specified by size, to the stream pointed to by stream. For each object,
14520 size calls are made to the fputc function, taking the values (in order) from an array of
14521 unsigned char exactly overlaying the object. The file position indicator for the
14522 stream (if defined) is advanced by the number of characters successfully written. If an
14523 error occurs, the resulting value of the file position indicator for the stream is
14528 The fwrite function returns the number of elements successfully written, which will be
14529 less than nmemb only if a write error is encountered. If size or nmemb is zero,
14530 fwrite returns zero and the state of the stream remains unchanged.
14532 <h4><a name="7.19.9" href="#7.19.9">7.19.9 File positioning functions</a></h4>
14534 <h5><a name="7.19.9.1" href="#7.19.9.1">7.19.9.1 The fgetpos function</a></h5>
14538 #include <a href="#7.19"><stdio.h></a>
14539 int fgetpos(FILE * restrict stream,
14540 fpos_t * restrict pos);</pre>
14541 <h6>Description</h6>
14543 The fgetpos function stores the current values of the parse state (if any) and file
14544 position indicator for the stream pointed to by stream in the object pointed to by pos.
14545 The values stored contain unspecified information usable by the fsetpos function for
14546 repositioning the stream to its position at the time of the call to the fgetpos function.
14549 If successful, the fgetpos function returns zero; on failure, the fgetpos function
14550 returns nonzero and stores an implementation-defined positive value in errno.
14551 <p><b> Forward references</b>: the fsetpos function (<a href="#7.19.9.3">7.19.9.3</a>).
14553 <h5><a name="7.19.9.2" href="#7.19.9.2">7.19.9.2 The fseek function</a></h5>
14557 #include <a href="#7.19"><stdio.h></a>
14558 int fseek(FILE *stream, long int offset, int whence);</pre>
14559 <h6>Description</h6>
14561 The fseek function sets the file position indicator for the stream pointed to by stream.
14562 If a read or write error occurs, the error indicator for the stream is set and fseek fails.
14564 For a binary stream, the new position, measured in characters from the beginning of the
14565 file, is obtained by adding offset to the position specified by whence. The specified
14566 position is the beginning of the file if whence is SEEK_SET, the current value of the file
14567 position indicator if SEEK_CUR, or end-of-file if SEEK_END. A binary stream need not
14568 meaningfully support fseek calls with a whence value of SEEK_END.
14570 For a text stream, either offset shall be zero, or offset shall be a value returned by
14571 an earlier successful call to the ftell function on a stream associated with the same file
14572 and whence shall be SEEK_SET.
14575 After determining the new position, a successful call to the fseek function undoes any
14576 effects of the ungetc function on the stream, clears the end-of-file indicator for the
14577 stream, and then establishes the new position. After a successful fseek call, the next
14578 operation on an update stream may be either input or output.
14581 The fseek function returns nonzero only for a request that cannot be satisfied.
14582 <p><b> Forward references</b>: the ftell function (<a href="#7.19.9.4">7.19.9.4</a>).
14584 <h5><a name="7.19.9.3" href="#7.19.9.3">7.19.9.3 The fsetpos function</a></h5>
14588 #include <a href="#7.19"><stdio.h></a>
14589 int fsetpos(FILE *stream, const fpos_t *pos);</pre>
14590 <h6>Description</h6>
14592 The fsetpos function sets the mbstate_t object (if any) and file position indicator
14593 for the stream pointed to by stream according to the value of the object pointed to by
14594 pos, which shall be a value obtained from an earlier successful call to the fgetpos
14595 function on a stream associated with the same file. If a read or write error occurs, the
14596 error indicator for the stream is set and fsetpos fails.
14598 A successful call to the fsetpos function undoes any effects of the ungetc function
14599 on the stream, clears the end-of-file indicator for the stream, and then establishes the new
14600 parse state and position. After a successful fsetpos call, the next operation on an
14601 update stream may be either input or output.
14604 If successful, the fsetpos function returns zero; on failure, the fsetpos function
14605 returns nonzero and stores an implementation-defined positive value in errno.
14607 <h5><a name="7.19.9.4" href="#7.19.9.4">7.19.9.4 The ftell function</a></h5>
14611 #include <a href="#7.19"><stdio.h></a>
14612 long int ftell(FILE *stream);</pre>
14613 <h6>Description</h6>
14615 The ftell function obtains the current value of the file position indicator for the stream
14616 pointed to by stream. For a binary stream, the value is the number of characters from
14617 the beginning of the file. For a text stream, its file position indicator contains unspecified
14618 information, usable by the fseek function for returning the file position indicator for the
14619 stream to its position at the time of the ftell call; the difference between two such
14620 return values is not necessarily a meaningful measure of the number of characters written
14625 If successful, the ftell function returns the current value of the file position indicator
14626 for the stream. On failure, the ftell function returns -1L and stores an
14627 implementation-defined positive value in errno.
14629 <h5><a name="7.19.9.5" href="#7.19.9.5">7.19.9.5 The rewind function</a></h5>
14633 #include <a href="#7.19"><stdio.h></a>
14634 void rewind(FILE *stream);</pre>
14635 <h6>Description</h6>
14637 The rewind function sets the file position indicator for the stream pointed to by
14638 stream to the beginning of the file. It is equivalent to
14640 (void)fseek(stream, 0L, SEEK_SET)</pre>
14641 except that the error indicator for the stream is also cleared.
14644 The rewind function returns no value.
14646 <h4><a name="7.19.10" href="#7.19.10">7.19.10 Error-handling functions</a></h4>
14648 <h5><a name="7.19.10.1" href="#7.19.10.1">7.19.10.1 The clearerr function</a></h5>
14652 #include <a href="#7.19"><stdio.h></a>
14653 void clearerr(FILE *stream);</pre>
14654 <h6>Description</h6>
14656 The clearerr function clears the end-of-file and error indicators for the stream pointed
14660 The clearerr function returns no value.
14663 <h5><a name="7.19.10.2" href="#7.19.10.2">7.19.10.2 The feof function</a></h5>
14667 #include <a href="#7.19"><stdio.h></a>
14668 int feof(FILE *stream);</pre>
14669 <h6>Description</h6>
14671 The feof function tests the end-of-file indicator for the stream pointed to by stream.
14674 The feof function returns nonzero if and only if the end-of-file indicator is set for
14677 <h5><a name="7.19.10.3" href="#7.19.10.3">7.19.10.3 The ferror function</a></h5>
14681 #include <a href="#7.19"><stdio.h></a>
14682 int ferror(FILE *stream);</pre>
14683 <h6>Description</h6>
14685 The ferror function tests the error indicator for the stream pointed to by stream.
14688 The ferror function returns nonzero if and only if the error indicator is set for
14691 <h5><a name="7.19.10.4" href="#7.19.10.4">7.19.10.4 The perror function</a></h5>
14695 #include <a href="#7.19"><stdio.h></a>
14696 void perror(const char *s);</pre>
14697 <h6>Description</h6>
14699 The perror function maps the error number in the integer expression errno to an
14700 error message. It writes a sequence of characters to the standard error stream thus: first
14701 (if s is not a null pointer and the character pointed to by s is not the null character), the
14702 string pointed to by s followed by a colon (:) and a space; then an appropriate error
14703 message string followed by a new-line character. The contents of the error message
14704 strings are the same as those returned by the strerror function with argument errno.
14707 The perror function returns no value.
14708 <p><b> Forward references</b>: the strerror function (<a href="#7.21.6.2">7.21.6.2</a>).
14711 <h3><a name="7.20" href="#7.20">7.20 General utilities <stdlib.h></a></h3>
14713 The header <a href="#7.20"><stdlib.h></a> declares five types and several functions of general utility, and
14714 defines several macros.<sup><a href="#note257"><b>257)</b></a></sup>
14716 The types declared are size_t and wchar_t (both described in <a href="#7.17">7.17</a>),
14719 which is a structure type that is the type of the value returned by the div function,
14722 which is a structure type that is the type of the value returned by the ldiv function, and
14725 which is a structure type that is the type of the value returned by the lldiv function.
14727 The macros defined are NULL (described in <a href="#7.17">7.17</a>);
14733 which expand to integer constant expressions that can be used as the argument to the
14734 exit function to return unsuccessful or successful termination status, respectively, to the
14738 which expands to an integer constant expression that is the maximum value returned by
14739 the rand function; and
14742 which expands to a positive integer expression with type size_t that is the maximum
14743 number of bytes in a multibyte character for the extended character set specified by the
14744 current locale (category LC_CTYPE), which is never greater than MB_LEN_MAX.
14752 <p><small><a name="note257" href="#note257">257)</a> See ''future library directions'' (<a href="#7.26.10">7.26.10</a>).
14755 <h4><a name="7.20.1" href="#7.20.1">7.20.1 Numeric conversion functions</a></h4>
14757 The functions atof, atoi, atol, and atoll need not affect the value of the integer
14758 expression errno on an error. If the value of the result cannot be represented, the
14759 behavior is undefined.
14761 <h5><a name="7.20.1.1" href="#7.20.1.1">7.20.1.1 The atof function</a></h5>
14765 #include <a href="#7.20"><stdlib.h></a>
14766 double atof(const char *nptr);</pre>
14767 <h6>Description</h6>
14769 The atof function converts the initial portion of the string pointed to by nptr to
14770 double representation. Except for the behavior on error, it is equivalent to
14772 strtod(nptr, (char **)NULL)</pre>
14775 The atof function returns the converted value.
14776 <p><b> Forward references</b>: the strtod, strtof, and strtold functions (<a href="#7.20.1.3">7.20.1.3</a>).
14778 <h5><a name="7.20.1.2" href="#7.20.1.2">7.20.1.2 The atoi, atol, and atoll functions</a></h5>
14782 #include <a href="#7.20"><stdlib.h></a>
14783 int atoi(const char *nptr);
14784 long int atol(const char *nptr);
14785 long long int atoll(const char *nptr);</pre>
14786 <h6>Description</h6>
14788 The atoi, atol, and atoll functions convert the initial portion of the string pointed
14789 to by nptr to int, long int, and long long int representation, respectively.
14790 Except for the behavior on error, they are equivalent to
14792 atoi: (int)strtol(nptr, (char **)NULL, 10)
14793 atol: strtol(nptr, (char **)NULL, 10)
14794 atoll: strtoll(nptr, (char **)NULL, 10)</pre>
14797 The atoi, atol, and atoll functions return the converted value.
14798 <p><b> Forward references</b>: the strtol, strtoll, strtoul, and strtoull functions
14799 (<a href="#7.20.1.4">7.20.1.4</a>).
14802 <h5><a name="7.20.1.3" href="#7.20.1.3">7.20.1.3 The strtod, strtof, and strtold functions</a></h5>
14806 #include <a href="#7.20"><stdlib.h></a>
14807 double strtod(const char * restrict nptr,
14808 char ** restrict endptr);
14809 float strtof(const char * restrict nptr,
14810 char ** restrict endptr);
14811 long double strtold(const char * restrict nptr,
14812 char ** restrict endptr);</pre>
14813 <h6>Description</h6>
14815 The strtod, strtof, and strtold functions convert the initial portion of the string
14816 pointed to by nptr to double, float, and long double representation,
14817 respectively. First, they decompose the input string into three parts: an initial, possibly
14818 empty, sequence of white-space characters (as specified by the isspace function), a
14819 subject sequence resembling a floating-point constant or representing an infinity or NaN;
14820 and a final string of one or more unrecognized characters, including the terminating null
14821 character of the input string. Then, they attempt to convert the subject sequence to a
14822 floating-point number, and return the result.
14824 The expected form of the subject sequence is an optional plus or minus sign, then one of
14827 <li> a nonempty sequence of decimal digits optionally containing a decimal-point
14828 character, then an optional exponent part as defined in <a href="#6.4.4.2">6.4.4.2</a>;
14829 <li> a 0x or 0X, then a nonempty sequence of hexadecimal digits optionally containing a
14830 decimal-point character, then an optional binary exponent part as defined in <a href="#6.4.4.2">6.4.4.2</a>;
14831 <li> INF or INFINITY, ignoring case
14832 <li> NAN or NAN(n-char-sequenceopt), ignoring case in the NAN part, where:
14837 n-char-sequence digit
14838 n-char-sequence nondigit</pre>
14840 The subject sequence is defined as the longest initial subsequence of the input string,
14841 starting with the first non-white-space character, that is of the expected form. The subject
14842 sequence contains no characters if the input string is not of the expected form.
14844 If the subject sequence has the expected form for a floating-point number, the sequence of
14845 characters starting with the first digit or the decimal-point character (whichever occurs
14846 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
14848 decimal-point character is used in place of a period, and that if neither an exponent part
14849 nor a decimal-point character appears in a decimal floating point number, or if a binary
14850 exponent part does not appear in a hexadecimal floating point number, an exponent part
14851 of the appropriate type with value zero is assumed to follow the last digit in the string. If
14852 the subject sequence begins with a minus sign, the sequence is interpreted as negated.<sup><a href="#note258"><b>258)</b></a></sup>
14853 A character sequence INF or INFINITY is interpreted as an infinity, if representable in
14854 the return type, else like a floating constant that is too large for the range of the return
14855 type. A character sequence NAN or NAN(n-char-sequenceopt), is interpreted as a quiet
14856 NaN, if supported in the return type, else like a subject sequence part that does not have
14857 the expected form; the meaning of the n-char sequences is implementation-defined.<sup><a href="#note259"><b>259)</b></a></sup> A
14858 pointer to the final string is stored in the object pointed to by endptr, provided that
14859 endptr is not a null pointer.
14861 If the subject sequence has the hexadecimal form and FLT_RADIX is a power of 2, the
14862 value resulting from the conversion is correctly rounded.
14864 In other than the "C" locale, additional locale-specific subject sequence forms may be
14867 If the subject sequence is empty or does not have the expected form, no conversion is
14868 performed; the value of nptr is stored in the object pointed to by endptr, provided
14869 that endptr is not a null pointer.
14870 Recommended practice
14872 If the subject sequence has the hexadecimal form, FLT_RADIX is not a power of 2, and
14873 the result is not exactly representable, the result should be one of the two numbers in the
14874 appropriate internal format that are adjacent to the hexadecimal floating source value,
14875 with the extra stipulation that the error should have a correct sign for the current rounding
14878 If the subject sequence has the decimal form and at most DECIMAL_DIG (defined in
14879 <a href="#7.7"><float.h></a>) significant digits, the result should be correctly rounded. If the subject
14880 sequence D has the decimal form and more than DECIMAL_DIG significant digits,
14881 consider the two bounding, adjacent decimal strings L and U, both having
14882 DECIMAL_DIG significant digits, such that the values of L, D, and U satisfy L <= D <= U.
14883 The result should be one of the (equal or adjacent) values that would be obtained by
14884 correctly rounding L and U according to the current rounding direction, with the extra
14887 stipulation that the error with respect to D should have a correct sign for the current
14888 rounding direction.<sup><a href="#note260"><b>260)</b></a></sup>
14891 The functions return the converted value, if any. If no conversion could be performed,
14892 zero is returned. If the correct value is outside the range of representable values, plus or
14893 minus HUGE_VAL, HUGE_VALF, or HUGE_VALL is returned (according to the return
14894 type and sign of the value), and the value of the macro ERANGE is stored in errno. If
14895 the result underflows (<a href="#7.12.1">7.12.1</a>), the functions return a value whose magnitude is no greater
14896 than the smallest normalized positive number in the return type; whether errno acquires
14897 the value ERANGE is implementation-defined.
14900 <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
14901 negating the value resulting from converting the corresponding unsigned sequence (see <a href="#F.5">F.5</a>); the two
14902 methods may yield different results if rounding is toward positive or negative infinity. In either case,
14903 the functions honor the sign of zero if floating-point arithmetic supports signed zeros.
14905 <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
14906 the NaN's significand.
14908 <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
14909 to the same internal floating value, but if not will round to adjacent values.
14912 <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>
14916 #include <a href="#7.20"><stdlib.h></a>
14918 const char * restrict nptr,
14919 char ** restrict endptr,
14921 long long int strtoll(
14922 const char * restrict nptr,
14923 char ** restrict endptr,
14925 unsigned long int strtoul(
14926 const char * restrict nptr,
14927 char ** restrict endptr,
14929 unsigned long long int strtoull(
14930 const char * restrict nptr,
14931 char ** restrict endptr,
14933 <h6>Description</h6>
14935 The strtol, strtoll, strtoul, and strtoull functions convert the initial
14936 portion of the string pointed to by nptr to long int, long long int, unsigned
14937 long int, and unsigned long long int representation, respectively. First,
14938 they decompose the input string into three parts: an initial, possibly empty, sequence of
14939 white-space characters (as specified by the isspace function), a subject sequence
14943 resembling an integer represented in some radix determined by the value of base, and a
14944 final string of one or more unrecognized characters, including the terminating null
14945 character of the input string. Then, they attempt to convert the subject sequence to an
14946 integer, and return the result.
14948 If the value of base is zero, the expected form of the subject sequence is that of an
14949 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
14950 not including an integer suffix. If the value of base is between 2 and 36 (inclusive), the
14951 expected form of the subject sequence is a sequence of letters and digits representing an
14952 integer with the radix specified by base, optionally preceded by a plus or minus sign,
14953 but not including an integer suffix. The letters from a (or A) through z (or Z) are
14954 ascribed the values 10 through 35; only letters and digits whose ascribed values are less
14955 than that of base are permitted. If the value of base is 16, the characters 0x or 0X may
14956 optionally precede the sequence of letters and digits, following the sign if present.
14958 The subject sequence is defined as the longest initial subsequence of the input string,
14959 starting with the first non-white-space character, that is of the expected form. The subject
14960 sequence contains no characters if the input string is empty or consists entirely of white
14961 space, or if the first non-white-space character is other than a sign or a permissible letter
14964 If the subject sequence has the expected form and the value of base is zero, the sequence
14965 of characters starting with the first digit is interpreted as an integer constant according to
14966 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
14967 is between 2 and 36, it is used as the base for conversion, ascribing to each letter its value
14968 as given above. If the subject sequence begins with a minus sign, the value resulting from
14969 the conversion is negated (in the return type). A pointer to the final string is stored in the
14970 object pointed to by endptr, provided that endptr is not a null pointer.
14972 In other than the "C" locale, additional locale-specific subject sequence forms may be
14975 If the subject sequence is empty or does not have the expected form, no conversion is
14976 performed; the value of nptr is stored in the object pointed to by endptr, provided
14977 that endptr is not a null pointer.
14980 The strtol, strtoll, strtoul, and strtoull functions return the converted
14981 value, if any. If no conversion could be performed, zero is returned. If the correct value
14982 is outside the range of representable values, LONG_MIN, LONG_MAX, LLONG_MIN,
14983 LLONG_MAX, ULONG_MAX, or ULLONG_MAX is returned (according to the return type
14984 and sign of the value, if any), and the value of the macro ERANGE is stored in errno.
14987 <h4><a name="7.20.2" href="#7.20.2">7.20.2 Pseudo-random sequence generation functions</a></h4>
14989 <h5><a name="7.20.2.1" href="#7.20.2.1">7.20.2.1 The rand function</a></h5>
14993 #include <a href="#7.20"><stdlib.h></a>
14994 int rand(void);</pre>
14995 <h6>Description</h6>
14997 The rand function computes a sequence of pseudo-random integers in the range 0 to
15000 The implementation shall behave as if no library function calls the rand function.
15003 The rand function returns a pseudo-random integer.
15004 Environmental limits
15006 The value of the RAND_MAX macro shall be at least 32767.
15008 <h5><a name="7.20.2.2" href="#7.20.2.2">7.20.2.2 The srand function</a></h5>
15012 #include <a href="#7.20"><stdlib.h></a>
15013 void srand(unsigned int seed);</pre>
15014 <h6>Description</h6>
15016 The srand function uses the argument as a seed for a new sequence of pseudo-random
15017 numbers to be returned by subsequent calls to rand. If srand is then called with the
15018 same seed value, the sequence of pseudo-random numbers shall be repeated. If rand is
15019 called before any calls to srand have been made, the same sequence shall be generated
15020 as when srand is first called with a seed value of 1.
15022 The implementation shall behave as if no library function calls the srand function.
15025 The srand function returns no value.
15027 EXAMPLE The following functions define a portable implementation of rand and srand.
15030 static unsigned long int next = 1;
15031 int rand(void) // RAND_MAX assumed to be 32767
15033 next = next * 1103515245 + 12345;
15034 return (unsigned int)(next/65536) % 32768;
15036 void srand(unsigned int seed)
15042 <h4><a name="7.20.3" href="#7.20.3">7.20.3 Memory management functions</a></h4>
15044 The order and contiguity of storage allocated by successive calls to the calloc,
15045 malloc, and realloc functions is unspecified. The pointer returned if the allocation
15046 succeeds is suitably aligned so that it may be assigned to a pointer to any type of object
15047 and then used to access such an object or an array of such objects in the space allocated
15048 (until the space is explicitly deallocated). The lifetime of an allocated object extends
15049 from the allocation until the deallocation. Each such allocation shall yield a pointer to an
15050 object disjoint from any other object. The pointer returned points to the start (lowest byte
15051 address) of the allocated space. If the space cannot be allocated, a null pointer is
15052 returned. If the size of the space requested is zero, the behavior is implementation-
15053 defined: either a null pointer is returned, or the behavior is as if the size were some
15054 nonzero value, except that the returned pointer shall not be used to access an object.
15056 <h5><a name="7.20.3.1" href="#7.20.3.1">7.20.3.1 The calloc function</a></h5>
15060 #include <a href="#7.20"><stdlib.h></a>
15061 void *calloc(size_t nmemb, size_t size);</pre>
15062 <h6>Description</h6>
15064 The calloc function allocates space for an array of nmemb objects, each of whose size
15065 is size. The space is initialized to all bits zero.<sup><a href="#note261"><b>261)</b></a></sup>
15068 The calloc function returns either a null pointer or a pointer to the allocated space.
15071 <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
15075 <h5><a name="7.20.3.2" href="#7.20.3.2">7.20.3.2 The free function</a></h5>
15079 #include <a href="#7.20"><stdlib.h></a>
15080 void free(void *ptr);</pre>
15081 <h6>Description</h6>
15083 The free function causes the space pointed to by ptr to be deallocated, that is, made
15084 available for further allocation. If ptr is a null pointer, no action occurs. Otherwise, if
15085 the argument does not match a pointer earlier returned by the calloc, malloc, or
15089 realloc function, or if the space has been deallocated by a call to free or realloc,
15090 the behavior is undefined.
15093 The free function returns no value.
15095 <h5><a name="7.20.3.3" href="#7.20.3.3">7.20.3.3 The malloc function</a></h5>
15099 #include <a href="#7.20"><stdlib.h></a>
15100 void *malloc(size_t size);</pre>
15101 <h6>Description</h6>
15103 The malloc function allocates space for an object whose size is specified by size and
15104 whose value is indeterminate.
15107 The malloc function returns either a null pointer or a pointer to the allocated space.
15109 <h5><a name="7.20.3.4" href="#7.20.3.4">7.20.3.4 The realloc function</a></h5>
15113 #include <a href="#7.20"><stdlib.h></a>
15114 void *realloc(void *ptr, size_t size);</pre>
15115 <h6>Description</h6>
15117 The realloc function deallocates the old object pointed to by ptr and returns a
15118 pointer to a new object that has the size specified by size. The contents of the new
15119 object shall be the same as that of the old object prior to deallocation, up to the lesser of
15120 the new and old sizes. Any bytes in the new object beyond the size of the old object have
15121 indeterminate values.
15123 If ptr is a null pointer, the realloc function behaves like the malloc function for the
15124 specified size. Otherwise, if ptr does not match a pointer earlier returned by the
15125 calloc, malloc, or realloc function, or if the space has been deallocated by a call
15126 to the free or realloc function, the behavior is undefined. If memory for the new
15127 object cannot be allocated, the old object is not deallocated and its value is unchanged.
15130 The realloc function returns a pointer to the new object (which may have the same
15131 value as a pointer to the old object), or a null pointer if the new object could not be
15135 <h4><a name="7.20.4" href="#7.20.4">7.20.4 Communication with the environment</a></h4>
15137 <h5><a name="7.20.4.1" href="#7.20.4.1">7.20.4.1 The abort function</a></h5>
15141 #include <a href="#7.20"><stdlib.h></a>
15142 void abort(void);</pre>
15143 <h6>Description</h6>
15145 The abort function causes abnormal program termination to occur, unless the signal
15146 SIGABRT is being caught and the signal handler does not return. Whether open streams
15147 with unwritten buffered data are flushed, open streams are closed, or temporary files are
15148 removed is implementation-defined. An implementation-defined form of the status
15149 unsuccessful termination is returned to the host environment by means of the function
15150 call raise(SIGABRT).
15153 The abort function does not return to its caller.
15155 <h5><a name="7.20.4.2" href="#7.20.4.2">7.20.4.2 The atexit function</a></h5>
15159 #include <a href="#7.20"><stdlib.h></a>
15160 int atexit(void (*func)(void));</pre>
15161 <h6>Description</h6>
15163 The atexit function registers the function pointed to by func, to be called without
15164 arguments at normal program termination.
15165 Environmental limits
15167 The implementation shall support the registration of at least 32 functions.
15170 The atexit function returns zero if the registration succeeds, nonzero if it fails.
15171 <p><b> Forward references</b>: the exit function (<a href="#7.20.4.3">7.20.4.3</a>).
15173 <h5><a name="7.20.4.3" href="#7.20.4.3">7.20.4.3 The exit function</a></h5>
15177 #include <a href="#7.20"><stdlib.h></a>
15178 void exit(int status);</pre>
15179 <h6>Description</h6>
15181 The exit function causes normal program termination to occur. If more than one call to
15182 the exit function is executed by a program, the behavior is undefined.
15185 First, all functions registered by the atexit function are called, in the reverse order of
15186 their registration,<sup><a href="#note262"><b>262)</b></a></sup> except that a function is called after any previously registered
15187 functions that had already been called at the time it was registered. If, during the call to
15188 any such function, a call to the longjmp function is made that would terminate the call
15189 to the registered function, the behavior is undefined.
15191 Next, all open streams with unwritten buffered data are flushed, all open streams are
15192 closed, and all files created by the tmpfile function are removed.
15194 Finally, control is returned to the host environment. If the value of status is zero or
15195 EXIT_SUCCESS, an implementation-defined form of the status successful termination is
15196 returned. If the value of status is EXIT_FAILURE, an implementation-defined form
15197 of the status unsuccessful termination is returned. Otherwise the status returned is
15198 implementation-defined.
15201 The exit function cannot return to its caller.
15204 <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
15205 other registered functions.
15208 <h5><a name="7.20.4.4" href="#7.20.4.4">7.20.4.4 The _Exit function</a></h5>
15212 #include <a href="#7.20"><stdlib.h></a>
15213 void _Exit(int status);</pre>
15214 <h6>Description</h6>
15216 The _Exit function causes normal program termination to occur and control to be
15217 returned to the host environment. No functions registered by the atexit function or
15218 signal handlers registered by the signal function are called. The status returned to the
15219 host environment is determined in the same way as for the exit function (<a href="#7.20.4.3">7.20.4.3</a>).
15220 Whether open streams with unwritten buffered data are flushed, open streams are closed,
15221 or temporary files are removed is implementation-defined.
15224 The _Exit function cannot return to its caller.
15231 <h5><a name="7.20.4.5" href="#7.20.4.5">7.20.4.5 The getenv function</a></h5>
15235 #include <a href="#7.20"><stdlib.h></a>
15236 char *getenv(const char *name);</pre>
15237 <h6>Description</h6>
15239 The getenv function searches an environment list, provided by the host environment,
15240 for a string that matches the string pointed to by name. The set of environment names
15241 and the method for altering the environment list are implementation-defined.
15243 The implementation shall behave as if no library function calls the getenv function.
15246 The getenv function returns a pointer to a string associated with the matched list
15247 member. The string pointed to shall not be modified by the program, but may be
15248 overwritten by a subsequent call to the getenv function. If the specified name cannot
15249 be found, a null pointer is returned.
15251 <h5><a name="7.20.4.6" href="#7.20.4.6">7.20.4.6 The system function</a></h5>
15255 #include <a href="#7.20"><stdlib.h></a>
15256 int system(const char *string);</pre>
15257 <h6>Description</h6>
15259 If string is a null pointer, the system function determines whether the host
15260 environment has a command processor. If string is not a null pointer, the system
15261 function passes the string pointed to by string to that command processor to be
15262 executed in a manner which the implementation shall document; this might then cause the
15263 program calling system to behave in a non-conforming manner or to terminate.
15266 If the argument is a null pointer, the system function returns nonzero only if a
15267 command processor is available. If the argument is not a null pointer, and the system
15268 function does return, it returns an implementation-defined value.
15271 <h4><a name="7.20.5" href="#7.20.5">7.20.5 Searching and sorting utilities</a></h4>
15273 These utilities make use of a comparison function to search or sort arrays of unspecified
15274 type. Where an argument declared as size_t nmemb specifies the length of the array
15275 for a function, nmemb can have the value zero on a call to that function; the comparison
15276 function is not called, a search finds no matching element, and sorting performs no
15277 rearrangement. Pointer arguments on such a call shall still have valid values, as described
15278 in <a href="#7.1.4">7.1.4</a>.
15280 The implementation shall ensure that the second argument of the comparison function
15281 (when called from bsearch), or both arguments (when called from qsort), are
15282 pointers to elements of the array.<sup><a href="#note263"><b>263)</b></a></sup> The first argument when called from bsearch
15285 The comparison function shall not alter the contents of the array. The implementation
15286 may reorder elements of the array between calls to the comparison function, but shall not
15287 alter the contents of any individual element.
15289 When the same objects (consisting of size bytes, irrespective of their current positions
15290 in the array) are passed more than once to the comparison function, the results shall be
15291 consistent with one another. That is, for qsort they shall define a total ordering on the
15292 array, and for bsearch the same object shall always compare the same way with the
15295 A sequence point occurs immediately before and immediately after each call to the
15296 comparison function, and also between any call to the comparison function and any
15297 movement of the objects passed as arguments to that call.
15300 <p><small><a name="note263" href="#note263">263)</a> That is, if the value passed is p, then the following expressions are always nonzero:
15303 ((char *)p - (char *)base) % size == 0
15304 (char *)p >= (char *)base
15305 (char *)p < (char *)base + nmemb * size</pre>
15308 <h5><a name="7.20.5.1" href="#7.20.5.1">7.20.5.1 The bsearch function</a></h5>
15312 #include <a href="#7.20"><stdlib.h></a>
15313 void *bsearch(const void *key, const void *base,
15314 size_t nmemb, size_t size,
15315 int (*compar)(const void *, const void *));</pre>
15316 <h6>Description</h6>
15318 The bsearch function searches an array of nmemb objects, the initial element of which
15319 is pointed to by base, for an element that matches the object pointed to by key. The
15323 size of each element of the array is specified by size.
15325 The comparison function pointed to by compar is called with two arguments that point
15326 to the key object and to an array element, in that order. The function shall return an
15327 integer less than, equal to, or greater than zero if the key object is considered,
15328 respectively, to be less than, to match, or to be greater than the array element. The array
15329 shall consist of: all the elements that compare less than, all the elements that compare
15330 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>
15333 The bsearch function returns a pointer to a matching element of the array, or a null
15334 pointer if no match is found. If two elements compare as equal, which element is
15335 matched is unspecified.
15338 <p><small><a name="note264" href="#note264">264)</a> In practice, the entire array is sorted according to the comparison function.
15341 <h5><a name="7.20.5.2" href="#7.20.5.2">7.20.5.2 The qsort function</a></h5>
15345 #include <a href="#7.20"><stdlib.h></a>
15346 void qsort(void *base, size_t nmemb, size_t size,
15347 int (*compar)(const void *, const void *));</pre>
15348 <h6>Description</h6>
15350 The qsort function sorts an array of nmemb objects, the initial element of which is
15351 pointed to by base. The size of each object is specified by size.
15353 The contents of the array are sorted into ascending order according to a comparison
15354 function pointed to by compar, which is called with two arguments that point to the
15355 objects being compared. The function shall return an integer less than, equal to, or
15356 greater than zero if the first argument is considered to be respectively less than, equal to,
15357 or greater than the second.
15359 If two elements compare as equal, their order in the resulting sorted array is unspecified.
15362 The qsort function returns no value.
15369 <h4><a name="7.20.6" href="#7.20.6">7.20.6 Integer arithmetic functions</a></h4>
15371 <h5><a name="7.20.6.1" href="#7.20.6.1">7.20.6.1 The abs, labs and llabs functions</a></h5>
15375 #include <a href="#7.20"><stdlib.h></a>
15377 long int labs(long int j);
15378 long long int llabs(long long int j);</pre>
15379 <h6>Description</h6>
15381 The abs, labs, and llabs functions compute the absolute value of an integer j. If the
15382 result cannot be represented, the behavior is undefined.<sup><a href="#note265"><b>265)</b></a></sup>
15385 The abs, labs, and llabs, functions return the absolute value.
15388 <p><small><a name="note265" href="#note265">265)</a> The absolute value of the most negative number cannot be represented in two's complement.
15391 <h5><a name="7.20.6.2" href="#7.20.6.2">7.20.6.2 The div, ldiv, and lldiv functions</a></h5>
15395 #include <a href="#7.20"><stdlib.h></a>
15396 div_t div(int numer, int denom);
15397 ldiv_t ldiv(long int numer, long int denom);
15398 lldiv_t lldiv(long long int numer, long long int denom);</pre>
15399 <h6>Description</h6>
15401 The div, ldiv, and lldiv, functions compute numer / denom and numer %
15402 denom in a single operation.
15405 The div, ldiv, and lldiv functions return a structure of type div_t, ldiv_t, and
15406 lldiv_t, respectively, comprising both the quotient and the remainder. The structures
15407 shall contain (in either order) the members quot (the quotient) and rem (the remainder),
15408 each of which has the same type as the arguments numer and denom. If either part of
15409 the result cannot be represented, the behavior is undefined.
15416 <h4><a name="7.20.7" href="#7.20.7">7.20.7 Multibyte/wide character conversion functions</a></h4>
15418 The behavior of the multibyte character functions is affected by the LC_CTYPE category
15419 of the current locale. For a state-dependent encoding, each function is placed into its
15420 initial conversion state by a call for which its character pointer argument, s, is a null
15421 pointer. Subsequent calls with s as other than a null pointer cause the internal conversion
15422 state of the function to be altered as necessary. A call with s as a null pointer causes
15423 these functions to return a nonzero value if encodings have state dependency, and zero
15424 otherwise.<sup><a href="#note266"><b>266)</b></a></sup> Changing the LC_CTYPE category causes the conversion state of these
15425 functions to be indeterminate.
15428 <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
15429 character codes, but are grouped with an adjacent multibyte character.
15432 <h5><a name="7.20.7.1" href="#7.20.7.1">7.20.7.1 The mblen function</a></h5>
15436 #include <a href="#7.20"><stdlib.h></a>
15437 int mblen(const char *s, size_t n);</pre>
15438 <h6>Description</h6>
15440 If s is not a null pointer, the mblen function determines the number of bytes contained
15441 in the multibyte character pointed to by s. Except that the conversion state of the
15442 mbtowc function is not affected, it is equivalent to
15445 mbtowc((wchar_t *)0, s, n);</pre>
15446 The implementation shall behave as if no library function calls the mblen function.
15449 If s is a null pointer, the mblen function returns a nonzero or zero value, if multibyte
15450 character encodings, respectively, do or do not have state-dependent encodings. If s is
15451 not a null pointer, the mblen function either returns 0 (if s points to the null character),
15452 or returns the number of bytes that are contained in the multibyte character (if the next n
15453 or fewer bytes form a valid multibyte character), or returns -1 (if they do not form a valid
15454 multibyte character).
15455 <p><b> Forward references</b>: the mbtowc function (<a href="#7.20.7.2">7.20.7.2</a>).
15462 <h5><a name="7.20.7.2" href="#7.20.7.2">7.20.7.2 The mbtowc function</a></h5>
15466 #include <a href="#7.20"><stdlib.h></a>
15467 int mbtowc(wchar_t * restrict pwc,
15468 const char * restrict s,
15470 <h6>Description</h6>
15472 If s is not a null pointer, the mbtowc function inspects at most n bytes beginning with
15473 the byte pointed to by s to determine the number of bytes needed to complete the next
15474 multibyte character (including any shift sequences). If the function determines that the
15475 next multibyte character is complete and valid, it determines the value of the
15476 corresponding wide character and then, if pwc is not a null pointer, stores that value in
15477 the object pointed to by pwc. If the corresponding wide character is the null wide
15478 character, the function is left in the initial conversion state.
15480 The implementation shall behave as if no library function calls the mbtowc function.
15483 If s is a null pointer, the mbtowc function returns a nonzero or zero value, if multibyte
15484 character encodings, respectively, do or do not have state-dependent encodings. If s is
15485 not a null pointer, the mbtowc function either returns 0 (if s points to the null character),
15486 or returns the number of bytes that are contained in the converted multibyte character (if
15487 the next n or fewer bytes form a valid multibyte character), or returns -1 (if they do not
15488 form a valid multibyte character).
15490 In no case will the value returned be greater than n or the value of the MB_CUR_MAX
15493 <h5><a name="7.20.7.3" href="#7.20.7.3">7.20.7.3 The wctomb function</a></h5>
15497 #include <a href="#7.20"><stdlib.h></a>
15498 int wctomb(char *s, wchar_t wc);</pre>
15499 <h6>Description</h6>
15501 The wctomb function determines the number of bytes needed to represent the multibyte
15502 character corresponding to the wide character given by wc (including any shift
15503 sequences), and stores the multibyte character representation in the array whose first
15504 element is pointed to by s (if s is not a null pointer). At most MB_CUR_MAX characters
15505 are stored. If wc is a null wide character, a null byte is stored, preceded by any shift
15506 sequence needed to restore the initial shift state, and the function is left in the initial
15510 The implementation shall behave as if no library function calls the wctomb function.
15513 If s is a null pointer, the wctomb function returns a nonzero or zero value, if multibyte
15514 character encodings, respectively, do or do not have state-dependent encodings. If s is
15515 not a null pointer, the wctomb function returns -1 if the value of wc does not correspond
15516 to a valid multibyte character, or returns the number of bytes that are contained in the
15517 multibyte character corresponding to the value of wc.
15519 In no case will the value returned be greater than the value of the MB_CUR_MAX macro.
15521 <h4><a name="7.20.8" href="#7.20.8">7.20.8 Multibyte/wide string conversion functions</a></h4>
15523 The behavior of the multibyte string functions is affected by the LC_CTYPE category of
15524 the current locale.
15526 <h5><a name="7.20.8.1" href="#7.20.8.1">7.20.8.1 The mbstowcs function</a></h5>
15530 #include <a href="#7.20"><stdlib.h></a>
15531 size_t mbstowcs(wchar_t * restrict pwcs,
15532 const char * restrict s,
15534 <h6>Description</h6>
15536 The mbstowcs function converts a sequence of multibyte characters that begins in the
15537 initial shift state from the array pointed to by s into a sequence of corresponding wide
15538 characters and stores not more than n wide characters into the array pointed to by pwcs.
15539 No multibyte characters that follow a null character (which is converted into a null wide
15540 character) will be examined or converted. Each multibyte character is converted as if by
15541 a call to the mbtowc function, except that the conversion state of the mbtowc function is
15544 No more than n elements will be modified in the array pointed to by pwcs. If copying
15545 takes place between objects that overlap, the behavior is undefined.
15548 If an invalid multibyte character is encountered, the mbstowcs function returns
15549 (size_t)(-1). Otherwise, the mbstowcs function returns the number of array
15550 elements modified, not including a terminating null wide character, if any.<sup><a href="#note267"><b>267)</b></a></sup>
15558 <p><small><a name="note267" href="#note267">267)</a> The array will not be null-terminated if the value returned is n.
15561 <h5><a name="7.20.8.2" href="#7.20.8.2">7.20.8.2 The wcstombs function</a></h5>
15565 #include <a href="#7.20"><stdlib.h></a>
15566 size_t wcstombs(char * restrict s,
15567 const wchar_t * restrict pwcs,
15569 <h6>Description</h6>
15571 The wcstombs function converts a sequence of wide characters from the array pointed
15572 to by pwcs into a sequence of corresponding multibyte characters that begins in the
15573 initial shift state, and stores these multibyte characters into the array pointed to by s,
15574 stopping if a multibyte character would exceed the limit of n total bytes or if a null
15575 character is stored. Each wide character is converted as if by a call to the wctomb
15576 function, except that the conversion state of the wctomb function is not affected.
15578 No more than n bytes will be modified in the array pointed to by s. If copying takes place
15579 between objects that overlap, the behavior is undefined.
15582 If a wide character is encountered that does not correspond to a valid multibyte character,
15583 the wcstombs function returns (size_t)(-1). Otherwise, the wcstombs function
15584 returns the number of bytes modified, not including a terminating null character, if
15588 <h3><a name="7.21" href="#7.21">7.21 String handling <string.h></a></h3>
15590 <h4><a name="7.21.1" href="#7.21.1">7.21.1 String function conventions</a></h4>
15592 The header <a href="#7.21"><string.h></a> declares one type and several functions, and defines one
15593 macro useful for manipulating arrays of character type and other objects treated as arrays
15594 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
15595 <a href="#7.17">7.17</a>). Various methods are used for determining the lengths of the arrays, but in all cases
15596 a char * or void * argument points to the initial (lowest addressed) character of the
15597 array. If an array is accessed beyond the end of an object, the behavior is undefined.
15599 Where an argument declared as size_t n specifies the length of the array for a
15600 function, n can have the value zero on a call to that function. Unless explicitly stated
15601 otherwise in the description of a particular function in this subclause, pointer arguments
15602 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
15603 function that locates a character finds no occurrence, a function that compares two
15604 character sequences returns zero, and a function that copies characters copies zero
15607 For all functions in this subclause, each character shall be interpreted as if it had the type
15608 unsigned char (and therefore every possible object representation is valid and has a
15612 <p><small><a name="note268" href="#note268">268)</a> See ''future library directions'' (<a href="#7.26.11">7.26.11</a>).
15615 <h4><a name="7.21.2" href="#7.21.2">7.21.2 Copying functions</a></h4>
15617 <h5><a name="7.21.2.1" href="#7.21.2.1">7.21.2.1 The memcpy function</a></h5>
15621 #include <a href="#7.21"><string.h></a>
15622 void *memcpy(void * restrict s1,
15623 const void * restrict s2,
15625 <h6>Description</h6>
15627 The memcpy function copies n characters from the object pointed to by s2 into the
15628 object pointed to by s1. If copying takes place between objects that overlap, the behavior
15632 The memcpy function returns the value of s1.
15639 <h5><a name="7.21.2.2" href="#7.21.2.2">7.21.2.2 The memmove function</a></h5>
15643 #include <a href="#7.21"><string.h></a>
15644 void *memmove(void *s1, const void *s2, size_t n);</pre>
15645 <h6>Description</h6>
15647 The memmove function copies n characters from the object pointed to by s2 into the
15648 object pointed to by s1. Copying takes place as if the n characters from the object
15649 pointed to by s2 are first copied into a temporary array of n characters that does not
15650 overlap the objects pointed to by s1 and s2, and then the n characters from the
15651 temporary array are copied into the object pointed to by s1.
15654 The memmove function returns the value of s1.
15656 <h5><a name="7.21.2.3" href="#7.21.2.3">7.21.2.3 The strcpy function</a></h5>
15660 #include <a href="#7.21"><string.h></a>
15661 char *strcpy(char * restrict s1,
15662 const char * restrict s2);</pre>
15663 <h6>Description</h6>
15665 The strcpy function copies the string pointed to by s2 (including the terminating null
15666 character) into the array pointed to by s1. If copying takes place between objects that
15667 overlap, the behavior is undefined.
15670 The strcpy function returns the value of s1.
15672 <h5><a name="7.21.2.4" href="#7.21.2.4">7.21.2.4 The strncpy function</a></h5>
15676 #include <a href="#7.21"><string.h></a>
15677 char *strncpy(char * restrict s1,
15678 const char * restrict s2,
15680 <h6>Description</h6>
15682 The strncpy function copies not more than n characters (characters that follow a null
15683 character are not copied) from the array pointed to by s2 to the array pointed to by
15685 s1.<sup><a href="#note269"><b>269)</b></a></sup> If copying takes place between objects that overlap, the behavior is undefined.
15687 If the array pointed to by s2 is a string that is shorter than n characters, null characters
15688 are appended to the copy in the array pointed to by s1, until n characters in all have been
15692 The strncpy function returns the value of s1.
15695 <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
15696 not be null-terminated.
15699 <h4><a name="7.21.3" href="#7.21.3">7.21.3 Concatenation functions</a></h4>
15701 <h5><a name="7.21.3.1" href="#7.21.3.1">7.21.3.1 The strcat function</a></h5>
15705 #include <a href="#7.21"><string.h></a>
15706 char *strcat(char * restrict s1,
15707 const char * restrict s2);</pre>
15708 <h6>Description</h6>
15710 The strcat function appends a copy of the string pointed to by s2 (including the
15711 terminating null character) to the end of the string pointed to by s1. The initial character
15712 of s2 overwrites the null character at the end of s1. If copying takes place between
15713 objects that overlap, the behavior is undefined.
15716 The strcat function returns the value of s1.
15718 <h5><a name="7.21.3.2" href="#7.21.3.2">7.21.3.2 The strncat function</a></h5>
15722 #include <a href="#7.21"><string.h></a>
15723 char *strncat(char * restrict s1,
15724 const char * restrict s2,
15726 <h6>Description</h6>
15728 The strncat function appends not more than n characters (a null character and
15729 characters that follow it are not appended) from the array pointed to by s2 to the end of
15730 the string pointed to by s1. The initial character of s2 overwrites the null character at the
15731 end of s1. A terminating null character is always appended to the result.<sup><a href="#note270"><b>270)</b></a></sup> If copying
15734 takes place between objects that overlap, the behavior is undefined.
15737 The strncat function returns the value of s1.
15738 <p><b> Forward references</b>: the strlen function (<a href="#7.21.6.3">7.21.6.3</a>).
15741 <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
15745 <h4><a name="7.21.4" href="#7.21.4">7.21.4 Comparison functions</a></h4>
15747 The sign of a nonzero value returned by the comparison functions memcmp, strcmp,
15748 and strncmp is determined by the sign of the difference between the values of the first
15749 pair of characters (both interpreted as unsigned char) that differ in the objects being
15752 <h5><a name="7.21.4.1" href="#7.21.4.1">7.21.4.1 The memcmp function</a></h5>
15756 #include <a href="#7.21"><string.h></a>
15757 int memcmp(const void *s1, const void *s2, size_t n);</pre>
15758 <h6>Description</h6>
15760 The memcmp function compares the first n characters of the object pointed to by s1 to
15761 the first n characters of the object pointed to by s2.<sup><a href="#note271"><b>271)</b></a></sup>
15764 The memcmp function returns an integer greater than, equal to, or less than zero,
15765 accordingly as the object pointed to by s1 is greater than, equal to, or less than the object
15769 <p><small><a name="note271" href="#note271">271)</a> The contents of ''holes'' used as padding for purposes of alignment within structure objects are
15770 indeterminate. Strings shorter than their allocated space and unions may also cause problems in
15774 <h5><a name="7.21.4.2" href="#7.21.4.2">7.21.4.2 The strcmp function</a></h5>
15778 #include <a href="#7.21"><string.h></a>
15779 int strcmp(const char *s1, const char *s2);</pre>
15780 <h6>Description</h6>
15782 The strcmp function compares the string pointed to by s1 to the string pointed to by
15786 The strcmp function returns an integer greater than, equal to, or less than zero,
15787 accordingly as the string pointed to by s1 is greater than, equal to, or less than the string
15792 <h5><a name="7.21.4.3" href="#7.21.4.3">7.21.4.3 The strcoll function</a></h5>
15796 #include <a href="#7.21"><string.h></a>
15797 int strcoll(const char *s1, const char *s2);</pre>
15798 <h6>Description</h6>
15800 The strcoll function compares the string pointed to by s1 to the string pointed to by
15801 s2, both interpreted as appropriate to the LC_COLLATE category of the current locale.
15804 The strcoll function returns an integer greater than, equal to, or less than zero,
15805 accordingly as the string pointed to by s1 is greater than, equal to, or less than the string
15806 pointed to by s2 when both are interpreted as appropriate to the current locale.
15808 <h5><a name="7.21.4.4" href="#7.21.4.4">7.21.4.4 The strncmp function</a></h5>
15812 #include <a href="#7.21"><string.h></a>
15813 int strncmp(const char *s1, const char *s2, size_t n);</pre>
15814 <h6>Description</h6>
15816 The strncmp function compares not more than n characters (characters that follow a
15817 null character are not compared) from the array pointed to by s1 to the array pointed to
15821 The strncmp function returns an integer greater than, equal to, or less than zero,
15822 accordingly as the possibly null-terminated array pointed to by s1 is greater than, equal
15823 to, or less than the possibly null-terminated array pointed to by s2.
15825 <h5><a name="7.21.4.5" href="#7.21.4.5">7.21.4.5 The strxfrm function</a></h5>
15829 #include <a href="#7.21"><string.h></a>
15830 size_t strxfrm(char * restrict s1,
15831 const char * restrict s2,
15833 <h6>Description</h6>
15835 The strxfrm function transforms the string pointed to by s2 and places the resulting
15836 string into the array pointed to by s1. The transformation is such that if the strcmp
15837 function is applied to two transformed strings, it returns a value greater than, equal to, or
15839 less than zero, corresponding to the result of the strcoll function applied to the same
15840 two original strings. No more than n characters are placed into the resulting array
15841 pointed to by s1, including the terminating null character. If n is zero, s1 is permitted to
15842 be a null pointer. If copying takes place between objects that overlap, the behavior is
15846 The strxfrm function returns the length of the transformed string (not including the
15847 terminating null character). If the value returned is n or more, the contents of the array
15848 pointed to by s1 are indeterminate.
15850 EXAMPLE The value of the following expression is the size of the array needed to hold the
15851 transformation of the string pointed to by s.
15853 1 + strxfrm(NULL, s, 0)</pre>
15856 <h4><a name="7.21.5" href="#7.21.5">7.21.5 Search functions</a></h4>
15858 <h5><a name="7.21.5.1" href="#7.21.5.1">7.21.5.1 The memchr function</a></h5>
15862 #include <a href="#7.21"><string.h></a>
15863 void *memchr(const void *s, int c, size_t n);</pre>
15864 <h6>Description</h6>
15866 The memchr function locates the first occurrence of c (converted to an unsigned
15867 char) in the initial n characters (each interpreted as unsigned char) of the object
15871 The memchr function returns a pointer to the located character, or a null pointer if the
15872 character does not occur in the object.
15874 <h5><a name="7.21.5.2" href="#7.21.5.2">7.21.5.2 The strchr function</a></h5>
15878 #include <a href="#7.21"><string.h></a>
15879 char *strchr(const char *s, int c);</pre>
15880 <h6>Description</h6>
15882 The strchr function locates the first occurrence of c (converted to a char) in the
15883 string pointed to by s. The terminating null character is considered to be part of the
15887 The strchr function returns a pointer to the located character, or a null pointer if the
15888 character does not occur in the string.
15891 <h5><a name="7.21.5.3" href="#7.21.5.3">7.21.5.3 The strcspn function</a></h5>
15895 #include <a href="#7.21"><string.h></a>
15896 size_t strcspn(const char *s1, const char *s2);</pre>
15897 <h6>Description</h6>
15899 The strcspn function computes the length of the maximum initial segment of the string
15900 pointed to by s1 which consists entirely of characters not from the string pointed to by
15904 The strcspn function returns the length of the segment.
15906 <h5><a name="7.21.5.4" href="#7.21.5.4">7.21.5.4 The strpbrk function</a></h5>
15910 #include <a href="#7.21"><string.h></a>
15911 char *strpbrk(const char *s1, const char *s2);</pre>
15912 <h6>Description</h6>
15914 The strpbrk function locates the first occurrence in the string pointed to by s1 of any
15915 character from the string pointed to by s2.
15918 The strpbrk function returns a pointer to the character, or a null pointer if no character
15919 from s2 occurs in s1.
15921 <h5><a name="7.21.5.5" href="#7.21.5.5">7.21.5.5 The strrchr function</a></h5>
15925 #include <a href="#7.21"><string.h></a>
15926 char *strrchr(const char *s, int c);</pre>
15927 <h6>Description</h6>
15929 The strrchr function locates the last occurrence of c (converted to a char) in the
15930 string pointed to by s. The terminating null character is considered to be part of the
15934 The strrchr function returns a pointer to the character, or a null pointer if c does not
15935 occur in the string.
15938 <h5><a name="7.21.5.6" href="#7.21.5.6">7.21.5.6 The strspn function</a></h5>
15942 #include <a href="#7.21"><string.h></a>
15943 size_t strspn(const char *s1, const char *s2);</pre>
15944 <h6>Description</h6>
15946 The strspn function computes the length of the maximum initial segment of the string
15947 pointed to by s1 which consists entirely of characters from the string pointed to by s2.
15950 The strspn function returns the length of the segment.
15952 <h5><a name="7.21.5.7" href="#7.21.5.7">7.21.5.7 The strstr function</a></h5>
15956 #include <a href="#7.21"><string.h></a>
15957 char *strstr(const char *s1, const char *s2);</pre>
15958 <h6>Description</h6>
15960 The strstr function locates the first occurrence in the string pointed to by s1 of the
15961 sequence of characters (excluding the terminating null character) in the string pointed to
15965 The strstr function returns a pointer to the located string, or a null pointer if the string
15966 is not found. If s2 points to a string with zero length, the function returns s1.
15968 <h5><a name="7.21.5.8" href="#7.21.5.8">7.21.5.8 The strtok function</a></h5>
15972 #include <a href="#7.21"><string.h></a>
15973 char *strtok(char * restrict s1,
15974 const char * restrict s2);</pre>
15975 <h6>Description</h6>
15977 A sequence of calls to the strtok function breaks the string pointed to by s1 into a
15978 sequence of tokens, each of which is delimited by a character from the string pointed to
15979 by s2. The first call in the sequence has a non-null first argument; subsequent calls in the
15980 sequence have a null first argument. The separator string pointed to by s2 may be
15981 different from call to call.
15983 The first call in the sequence searches the string pointed to by s1 for the first character
15984 that is not contained in the current separator string pointed to by s2. If no such character
15985 is found, then there are no tokens in the string pointed to by s1 and the strtok function
15987 returns a null pointer. If such a character is found, it is the start of the first token.
15989 The strtok function then searches from there for a character that is contained in the
15990 current separator string. If no such character is found, the current token extends to the
15991 end of the string pointed to by s1, and subsequent searches for a token will return a null
15992 pointer. If such a character is found, it is overwritten by a null character, which
15993 terminates the current token. The strtok function saves a pointer to the following
15994 character, from which the next search for a token will start.
15996 Each subsequent call, with a null pointer as the value of the first argument, starts
15997 searching from the saved pointer and behaves as described above.
15999 The implementation shall behave as if no library function calls the strtok function.
16002 The strtok function returns a pointer to the first character of a token, or a null pointer
16003 if there is no token.
16007 #include <a href="#7.21"><string.h></a>
16008 static char str[] = "?a???b,,,#c";
16010 t = strtok(str, "?"); // t points to the token "a"
16011 t = strtok(NULL, ","); // t points to the token "??b"
16012 t = strtok(NULL, "#,"); // t points to the token "c"
16013 t = strtok(NULL, "?"); // t is a null pointer</pre>
16016 <h4><a name="7.21.6" href="#7.21.6">7.21.6 Miscellaneous functions</a></h4>
16018 <h5><a name="7.21.6.1" href="#7.21.6.1">7.21.6.1 The memset function</a></h5>
16022 #include <a href="#7.21"><string.h></a>
16023 void *memset(void *s, int c, size_t n);</pre>
16024 <h6>Description</h6>
16026 The memset function copies the value of c (converted to an unsigned char) into
16027 each of the first n characters of the object pointed to by s.
16030 The memset function returns the value of s.
16033 <h5><a name="7.21.6.2" href="#7.21.6.2">7.21.6.2 The strerror function</a></h5>
16037 #include <a href="#7.21"><string.h></a>
16038 char *strerror(int errnum);</pre>
16039 <h6>Description</h6>
16041 The strerror function maps the number in errnum to a message string. Typically,
16042 the values for errnum come from errno, but strerror shall map any value of type
16045 The implementation shall behave as if no library function calls the strerror function.
16048 The strerror function returns a pointer to the string, the contents of which are locale-
16049 specific. The array pointed to shall not be modified by the program, but may be
16050 overwritten by a subsequent call to the strerror function.
16052 <h5><a name="7.21.6.3" href="#7.21.6.3">7.21.6.3 The strlen function</a></h5>
16056 #include <a href="#7.21"><string.h></a>
16057 size_t strlen(const char *s);</pre>
16058 <h6>Description</h6>
16060 The strlen function computes the length of the string pointed to by s.
16063 The strlen function returns the number of characters that precede the terminating null
16067 <h3><a name="7.22" href="#7.22">7.22 Type-generic math <tgmath.h></a></h3>
16069 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
16070 defines several type-generic macros.
16072 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
16073 double) suffix, several have one or more parameters whose corresponding real type is
16074 double. For each such function, except modf, there is a corresponding type-generic
16075 macro.<sup><a href="#note272"><b>272)</b></a></sup> The parameters whose corresponding real type is double in the function
16076 synopsis are generic parameters. Use of the macro invokes a function whose
16077 corresponding real type and type domain are determined by the arguments for the generic
16078 parameters.<sup><a href="#note273"><b>273)</b></a></sup>
16080 Use of the macro invokes a function whose generic parameters have the corresponding
16081 real type determined as follows:
16083 <li> First, if any argument for generic parameters has type long double, the type
16084 determined is long double.
16085 <li> Otherwise, if any argument for generic parameters has type double or is of integer
16086 type, the type determined is double.
16087 <li> Otherwise, the type determined is float.
16090 For each unsuffixed function in <a href="#7.12"><math.h></a> for which there is a function in
16091 <a href="#7.3"><complex.h></a> with the same name except for a c prefix, the corresponding type-
16092 generic macro (for both functions) has the same name as the function in <a href="#7.12"><math.h></a>. The
16093 corresponding type-generic macro for fabs and cabs is fabs.
16100 <a href="#7.12"><math.h></a> <a href="#7.3"><complex.h></a> type-generic
16101 function function macro
16118 fabs cabs fabs</pre>
16119 If at least one argument for a generic parameter is complex, then use of the macro invokes
16120 a complex function; otherwise, use of the macro invokes a real function.
16122 For each unsuffixed function in <a href="#7.12"><math.h></a> without a c-prefixed counterpart in
16123 <a href="#7.3"><complex.h></a> (except modf), the corresponding type-generic macro has the same
16124 name as the function. These type-generic macros are:
16126 atan2 fma llround remainder
16127 cbrt fmax log10 remquo
16128 ceil fmin log1p rint
16129 copysign fmod log2 round
16130 erf frexp logb scalbn
16131 erfc hypot lrint scalbln
16132 exp2 ilogb lround tgamma
16133 expm1 ldexp nearbyint trunc
16134 fdim lgamma nextafter
16135 floor llrint nexttoward</pre>
16136 If all arguments for generic parameters are real, then use of the macro invokes a real
16137 function; otherwise, use of the macro results in undefined behavior.
16139 For each unsuffixed function in <a href="#7.3"><complex.h></a> that is not a c-prefixed counterpart to a
16140 function in <a href="#7.12"><math.h></a>, the corresponding type-generic macro has the same name as the
16141 function. These type-generic macros are:
16146 Use of the macro with any real or complex argument invokes a complex function.
16148 EXAMPLE With the declarations
16150 #include <a href="#7.22"><tgmath.h></a>
16157 long double complex ldc;</pre>
16158 functions invoked by use of type-generic macros are shown in the following table:
16162 exp(n) exp(n), the function
16164 sin(d) sin(d), the function
16168 pow(ldc, f) cpowl(ldc, f)
16169 remainder(n, n) remainder(n, n), the function
16170 nextafter(d, f) nextafter(d, f), the function
16171 nexttoward(f, ld) nexttowardf(f, ld)
16172 copysign(n, ld) copysignl(n, ld)
16173 ceil(fc) undefined behavior
16174 rint(dc) undefined behavior
16175 fmax(ldc, ld) undefined behavior
16176 carg(n) carg(n), the function
16178 creal(d) creal(d), the function
16179 cimag(ld) cimagl(ld)
16181 carg(dc) carg(dc), the function
16182 cproj(ldc) cprojl(ldc)</pre>
16185 <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
16186 make available the corresponding ordinary function.
16188 <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,
16189 the behavior is undefined.
16192 <h3><a name="7.23" href="#7.23">7.23 Date and time <time.h></a></h3>
16194 <h4><a name="7.23.1" href="#7.23.1">7.23.1 Components of time</a></h4>
16196 The header <a href="#7.23"><time.h></a> defines two macros, and declares several types and functions for
16197 manipulating time. Many functions deal with a calendar time that represents the current
16198 date (according to the Gregorian calendar) and time. Some functions deal with local
16199 time, which is the calendar time expressed for some specific time zone, and with Daylight
16200 Saving Time, which is a temporary change in the algorithm for determining local time.
16201 The local time zone and Daylight Saving Time are implementation-defined.
16203 The macros defined are NULL (described in <a href="#7.17">7.17</a>); and
16205 CLOCKS_PER_SEC</pre>
16206 which expands to an expression with type clock_t (described below) that is the
16207 number per second of the value returned by the clock function.
16209 The types declared are size_t (described in <a href="#7.17">7.17</a>);
16215 which are arithmetic types capable of representing times; and
16218 which holds the components of a calendar time, called the broken-down time.
16220 The range and precision of times representable in clock_t and time_t are
16221 implementation-defined. The tm structure shall contain at least the following members,
16222 in any order. The semantics of the members and their normal ranges are expressed in the
16223 comments.<sup><a href="#note274"><b>274)</b></a></sup>
16225 int tm_sec; // seconds after the minute -- [0, 60]
16226 int tm_min; // minutes after the hour -- [0, 59]
16227 int tm_hour; // hours since midnight -- [0, 23]
16228 int tm_mday; // day of the month -- [1, 31]
16229 int tm_mon; // months since January -- [0, 11]
16230 int tm_year; // years since 1900
16231 int tm_wday; // days since Sunday -- [0, 6]
16232 int tm_yday; // days since January 1 -- [0, 365]
16233 int tm_isdst; // Daylight Saving Time flag</pre>
16238 The value of tm_isdst is positive if Daylight Saving Time is in effect, zero if Daylight
16239 Saving Time is not in effect, and negative if the information is not available.
16242 <p><small><a name="note274" href="#note274">274)</a> The range [0, 60] for tm_sec allows for a positive leap second.
16245 <h4><a name="7.23.2" href="#7.23.2">7.23.2 Time manipulation functions</a></h4>
16247 <h5><a name="7.23.2.1" href="#7.23.2.1">7.23.2.1 The clock function</a></h5>
16251 #include <a href="#7.23"><time.h></a>
16252 clock_t clock(void);</pre>
16253 <h6>Description</h6>
16255 The clock function determines the processor time used.
16258 The clock function returns the implementation's best approximation to the processor
16259 time used by the program since the beginning of an implementation-defined era related
16260 only to the program invocation. To determine the time in seconds, the value returned by
16261 the clock function should be divided by the value of the macro CLOCKS_PER_SEC. If
16262 the processor time used is not available or its value cannot be represented, the function
16263 returns the value (clock_t)(-1).<sup><a href="#note275"><b>275)</b></a></sup>
16266 <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
16267 the program and its return value subtracted from the value returned by subsequent calls.
16270 <h5><a name="7.23.2.2" href="#7.23.2.2">7.23.2.2 The difftime function</a></h5>
16274 #include <a href="#7.23"><time.h></a>
16275 double difftime(time_t time1, time_t time0);</pre>
16276 <h6>Description</h6>
16278 The difftime function computes the difference between two calendar times: time1 -
16282 The difftime function returns the difference expressed in seconds as a double.
16289 <h5><a name="7.23.2.3" href="#7.23.2.3">7.23.2.3 The mktime function</a></h5>
16293 #include <a href="#7.23"><time.h></a>
16294 time_t mktime(struct tm *timeptr);</pre>
16295 <h6>Description</h6>
16297 The mktime function converts the broken-down time, expressed as local time, in the
16298 structure pointed to by timeptr into a calendar time value with the same encoding as
16299 that of the values returned by the time function. The original values of the tm_wday
16300 and tm_yday components of the structure are ignored, and the original values of the
16301 other components are not restricted to the ranges indicated above.<sup><a href="#note276"><b>276)</b></a></sup> On successful
16302 completion, the values of the tm_wday and tm_yday components of the structure are
16303 set appropriately, and the other components are set to represent the specified calendar
16304 time, but with their values forced to the ranges indicated above; the final value of
16305 tm_mday is not set until tm_mon and tm_year are determined.
16308 The mktime function returns the specified calendar time encoded as a value of type
16309 time_t. If the calendar time cannot be represented, the function returns the value
16312 EXAMPLE What day of the week is July 4, 2001?
16314 #include <a href="#7.19"><stdio.h></a>
16315 #include <a href="#7.23"><time.h></a>
16316 static const char *const wday[] = {
16317 "Sunday", "Monday", "Tuesday", "Wednesday",
16318 "Thursday", "Friday", "Saturday", "-unknown-"
16320 struct tm time_str;
16328 time_str.tm_year = 2001 - 1900;
16329 time_str.tm_mon = 7 - 1;
16330 time_str.tm_mday = 4;
16331 time_str.tm_hour = 0;
16332 time_str.tm_min = 0;
16333 time_str.tm_sec = 1;
16334 time_str.tm_isdst = -1;
16335 if (mktime(&time_str) == (time_t)(-1))
16336 time_str.tm_wday = 7;
16337 printf("%s\n", wday[time_str.tm_wday]);</pre>
16341 <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
16342 Daylight Saving Time, respectively, is or is not in effect for the specified time. A negative value
16343 causes it to attempt to determine whether Daylight Saving Time is in effect for the specified time.
16346 <h5><a name="7.23.2.4" href="#7.23.2.4">7.23.2.4 The time function</a></h5>
16350 #include <a href="#7.23"><time.h></a>
16351 time_t time(time_t *timer);</pre>
16352 <h6>Description</h6>
16354 The time function determines the current calendar time. The encoding of the value is
16358 The time function returns the implementation's best approximation to the current
16359 calendar time. The value (time_t)(-1) is returned if the calendar time is not
16360 available. If timer is not a null pointer, the return value is also assigned to the object it
16363 <h4><a name="7.23.3" href="#7.23.3">7.23.3 Time conversion functions</a></h4>
16365 Except for the strftime function, these functions each return a pointer to one of two
16366 types of static objects: a broken-down time structure or an array of char. Execution of
16367 any of the functions that return a pointer to one of these object types may overwrite the
16368 information in any object of the same type pointed to by the value returned from any
16369 previous call to any of them. The implementation shall behave as if no other library
16370 functions call these functions.
16372 <h5><a name="7.23.3.1" href="#7.23.3.1">7.23.3.1 The asctime function</a></h5>
16376 #include <a href="#7.23"><time.h></a>
16377 char *asctime(const struct tm *timeptr);</pre>
16378 <h6>Description</h6>
16380 The asctime function converts the broken-down time in the structure pointed to by
16381 timeptr into a string in the form
16384 Sun Sep 16 01:03:52 1973\n\0</pre>
16385 using the equivalent of the following algorithm.
16386 char *asctime(const struct tm *timeptr)
16389 static const char wday_name[7][3] = {
16390 "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"
16392 static const char mon_name[12][3] = {
16393 "Jan", "Feb", "Mar", "Apr", "May", "Jun",
16394 "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
16396 static char result[26];
16397 sprintf(result, "%.3s %.3s%3d %.2d:%.2d:%.2d %d\n",
16398 wday_name[timeptr->tm_wday],
16399 mon_name[timeptr->tm_mon],
16400 timeptr->tm_mday, timeptr->tm_hour,
16401 timeptr->tm_min, timeptr->tm_sec,
16402 1900 + timeptr->tm_year);
16403 return result;</pre>
16407 The asctime function returns a pointer to the string.
16409 <h5><a name="7.23.3.2" href="#7.23.3.2">7.23.3.2 The ctime function</a></h5>
16413 #include <a href="#7.23"><time.h></a>
16414 char *ctime(const time_t *timer);</pre>
16415 <h6>Description</h6>
16417 The ctime function converts the calendar time pointed to by timer to local time in the
16418 form of a string. It is equivalent to
16420 asctime(localtime(timer))</pre>
16423 The ctime function returns the pointer returned by the asctime function with that
16424 broken-down time as argument.
16425 <p><b> Forward references</b>: the localtime function (<a href="#7.23.3.4">7.23.3.4</a>).
16428 <h5><a name="7.23.3.3" href="#7.23.3.3">7.23.3.3 The gmtime function</a></h5>
16432 #include <a href="#7.23"><time.h></a>
16433 struct tm *gmtime(const time_t *timer);</pre>
16434 <h6>Description</h6>
16436 The gmtime function converts the calendar time pointed to by timer into a broken-
16437 down time, expressed as UTC.
16440 The gmtime function returns a pointer to the broken-down time, or a null pointer if the
16441 specified time cannot be converted to UTC.
16443 <h5><a name="7.23.3.4" href="#7.23.3.4">7.23.3.4 The localtime function</a></h5>
16447 #include <a href="#7.23"><time.h></a>
16448 struct tm *localtime(const time_t *timer);</pre>
16449 <h6>Description</h6>
16451 The localtime function converts the calendar time pointed to by timer into a
16452 broken-down time, expressed as local time.
16455 The localtime function returns a pointer to the broken-down time, or a null pointer if
16456 the specified time cannot be converted to local time.
16458 <h5><a name="7.23.3.5" href="#7.23.3.5">7.23.3.5 The strftime function</a></h5>
16462 #include <a href="#7.23"><time.h></a>
16463 size_t strftime(char * restrict s,
16465 const char * restrict format,
16466 const struct tm * restrict timeptr);</pre>
16467 <h6>Description</h6>
16469 The strftime function places characters into the array pointed to by s as controlled by
16470 the string pointed to by format. The format shall be a multibyte character sequence,
16471 beginning and ending in its initial shift state. The format string consists of zero or
16472 more conversion specifiers and ordinary multibyte characters. A conversion specifier
16473 consists of a % character, possibly followed by an E or O modifier character (described
16474 below), followed by a character that determines the behavior of the conversion specifier.
16475 All ordinary multibyte characters (including the terminating null character) are copied
16477 unchanged into the array. If copying takes place between objects that overlap, the
16478 behavior is undefined. No more than maxsize characters are placed into the array.
16480 Each conversion specifier is replaced by appropriate characters as described in the
16481 following list. The appropriate characters are determined using the LC_TIME category
16482 of the current locale and by the values of zero or more members of the broken-down time
16483 structure pointed to by timeptr, as specified in brackets in the description. If any of
16484 the specified values is outside the normal range, the characters stored are unspecified.
16485 %a is replaced by the locale's abbreviated weekday name. [tm_wday]
16486 %A is replaced by the locale's full weekday name. [tm_wday]
16487 %b is replaced by the locale's abbreviated month name. [tm_mon]
16488 %B is replaced by the locale's full month name. [tm_mon]
16489 %c is replaced by the locale's appropriate date and time representation. [all specified
16491 in <a href="#7.23.1">7.23.1</a>]</pre>
16492 %C is replaced by the year divided by 100 and truncated to an integer, as a decimal
16494 number (00-99). [tm_year]</pre>
16495 %d is replaced by the day of the month as a decimal number (01-31). [tm_mday]
16496 %D is equivalent to ''%m/%d/%y''. [tm_mon, tm_mday, tm_year]
16497 %e is replaced by the day of the month as a decimal number (1-31); a single digit is
16499 preceded by a space. [tm_mday]</pre>
16500 %F is equivalent to ''%Y-%m-%d'' (the ISO 8601 date format). [tm_year, tm_mon,
16503 %g is replaced by the last 2 digits of the week-based year (see below) as a decimal
16505 number (00-99). [tm_year, tm_wday, tm_yday]</pre>
16506 %G is replaced by the week-based year (see below) as a decimal number (e.g., 1997).
16508 [tm_year, tm_wday, tm_yday]</pre>
16509 %h is equivalent to ''%b''. [tm_mon]
16510 %H is replaced by the hour (24-hour clock) as a decimal number (00-23). [tm_hour]
16511 %I is replaced by the hour (12-hour clock) as a decimal number (01-12). [tm_hour]
16512 %j is replaced by the day of the year as a decimal number (001-366). [tm_yday]
16513 %m is replaced by the month as a decimal number (01-12). [tm_mon]
16514 %M is replaced by the minute as a decimal number (00-59). [tm_min]
16515 %n is replaced by a new-line character.
16516 %p is replaced by the locale's equivalent of the AM/PM designations associated with a
16518 12-hour clock. [tm_hour]</pre>
16519 %r is replaced by the locale's 12-hour clock time. [tm_hour, tm_min, tm_sec]
16520 %R is equivalent to ''%H:%M''. [tm_hour, tm_min]
16521 %S is replaced by the second as a decimal number (00-60). [tm_sec]
16522 %t is replaced by a horizontal-tab character.
16523 %T is equivalent to ''%H:%M:%S'' (the ISO 8601 time format). [tm_hour, tm_min,
16527 %u is replaced by the ISO 8601 weekday as a decimal number (1-7), where Monday
16529 is 1. [tm_wday]</pre>
16530 %U is replaced by the week number of the year (the first Sunday as the first day of week
16532 1) as a decimal number (00-53). [tm_year, tm_wday, tm_yday]</pre>
16533 %V is replaced by the ISO 8601 week number (see below) as a decimal number
16535 (01-53). [tm_year, tm_wday, tm_yday]</pre>
16536 %w is replaced by the weekday as a decimal number (0-6), where Sunday is 0.
16539 %W is replaced by the week number of the year (the first Monday as the first day of
16541 week 1) as a decimal number (00-53). [tm_year, tm_wday, tm_yday]</pre>
16542 %x is replaced by the locale's appropriate date representation. [all specified in <a href="#7.23.1">7.23.1</a>]
16543 %X is replaced by the locale's appropriate time representation. [all specified in <a href="#7.23.1">7.23.1</a>]
16544 %y is replaced by the last 2 digits of the year as a decimal number (00-99).
16547 %Y is replaced by the year as a decimal number (e.g., 1997). [tm_year]
16548 %z is replaced by the offset from UTC in the ISO 8601 format ''-0430'' (meaning 4
16550 hours 30 minutes behind UTC, west of Greenwich), or by no characters if no time
16551 zone is determinable. [tm_isdst]</pre>
16552 %Z is replaced by the locale's time zone name or abbreviation, or by no characters if no
16554 time zone is determinable. [tm_isdst]</pre>
16555 %% is replaced by %.
16557 Some conversion specifiers can be modified by the inclusion of an E or O modifier
16558 character to indicate an alternative format or specification. If the alternative format or
16559 specification does not exist for the current locale, the modifier is ignored.
16560 %Ec is replaced by the locale's alternative date and time representation.
16561 %EC is replaced by the name of the base year (period) in the locale's alternative
16563 representation.</pre>
16564 %Ex is replaced by the locale's alternative date representation.
16565 %EX is replaced by the locale's alternative time representation.
16566 %Ey is replaced by the offset from %EC (year only) in the locale's alternative
16568 representation.</pre>
16569 %EY is replaced by the locale's full alternative year representation.
16570 %Od is replaced by the day of the month, using the locale's alternative numeric symbols
16572 (filled as needed with leading zeros, or with leading spaces if there is no alternative
16573 symbol for zero).</pre>
16574 %Oe is replaced by the day of the month, using the locale's alternative numeric symbols
16576 (filled as needed with leading spaces).</pre>
16577 %OH is replaced by the hour (24-hour clock), using the locale's alternative numeric
16581 %OI is replaced by the hour (12-hour clock), using the locale's alternative numeric
16584 %Om is replaced by the month, using the locale's alternative numeric symbols.
16585 %OM is replaced by the minutes, using the locale's alternative numeric symbols.
16586 %OS is replaced by the seconds, using the locale's alternative numeric symbols.
16587 %Ou is replaced by the ISO 8601 weekday as a number in the locale's alternative
16589 representation, where Monday is 1.</pre>
16590 %OU is replaced by the week number, using the locale's alternative numeric symbols.
16591 %OV is replaced by the ISO 8601 week number, using the locale's alternative numeric
16594 %Ow is replaced by the weekday as a number, using the locale's alternative numeric
16597 %OW is replaced by the week number of the year, using the locale's alternative numeric
16600 %Oy is replaced by the last 2 digits of the year, using the locale's alternative numeric
16604 %g, %G, and %V give values according to the ISO 8601 week-based year. In this system,
16605 weeks begin on a Monday and week 1 of the year is the week that includes January 4th,
16606 which is also the week that includes the first Thursday of the year, and is also the first
16607 week that contains at least four days in the year. If the first Monday of January is the
16608 2nd, 3rd, or 4th, the preceding days are part of the last week of the preceding year; thus,
16609 for Saturday 2nd January 1999, %G is replaced by 1998 and %V is replaced by 53. If
16610 December 29th, 30th, or 31st is a Monday, it and any following days are part of week 1 of
16611 the following year. Thus, for Tuesday 30th December 1997, %G is replaced by 1998 and
16612 %V is replaced by 01.
16614 If a conversion specifier is not one of the above, the behavior is undefined.
16616 In the "C" locale, the E and O modifiers are ignored and the replacement strings for the
16617 following specifiers are:
16618 %a the first three characters of %A.
16619 %A one of ''Sunday'', ''Monday'', ... , ''Saturday''.
16620 %b the first three characters of %B.
16621 %B one of ''January'', ''February'', ... , ''December''.
16622 %c equivalent to ''%a %b %e %T %Y''.
16623 %p one of ''AM'' or ''PM''.
16624 %r equivalent to ''%I:%M:%S %p''.
16625 %x equivalent to ''%m/%d/%y''.
16626 %X equivalent to %T.
16627 %Z implementation-defined.
16631 If the total number of resulting characters including the terminating null character is not
16632 more than maxsize, the strftime function returns the number of characters placed
16633 into the array pointed to by s not including the terminating null character. Otherwise,
16634 zero is returned and the contents of the array are indeterminate.
16637 <h3><a name="7.24" href="#7.24">7.24 Extended multibyte and wide character utilities <wchar.h></a></h3>
16639 <h4><a name="7.24.1" href="#7.24.1">7.24.1 Introduction</a></h4>
16641 The header <a href="#7.24"><wchar.h></a> declares four data types, one tag, four macros, and many
16642 functions.<sup><a href="#note277"><b>277)</b></a></sup>
16644 The types declared are wchar_t and size_t (both described in <a href="#7.17">7.17</a>);
16647 which is an object type other than an array type that can hold the conversion state
16648 information necessary to convert between sequences of multibyte characters and wide
16652 which is an integer type unchanged by default argument promotions that can hold any
16653 value corresponding to members of the extended character set, as well as at least one
16654 value that does not correspond to any member of the extended character set (see WEOF
16655 below);<sup><a href="#note278"><b>278)</b></a></sup> and
16658 which is declared as an incomplete structure type (the contents are described in <a href="#7.23.1">7.23.1</a>).
16660 The macros defined are NULL (described in <a href="#7.17">7.17</a>); WCHAR_MIN and WCHAR_MAX
16661 (described in <a href="#7.18.3">7.18.3</a>); and
16664 which expands to a constant expression of type wint_t whose value does not
16665 correspond to any member of the extended character set.<sup><a href="#note279"><b>279)</b></a></sup> It is accepted (and returned)
16666 by several functions in this subclause to indicate end-of-file, that is, no more input from a
16667 stream. It is also used as a wide character value that does not correspond to any member
16668 of the extended character set.
16670 The functions declared are grouped as follows:
16672 <li> Functions that perform input and output of wide characters, or multibyte characters,
16674 <li> Functions that provide wide string numeric conversion;
16675 <li> Functions that perform general wide string manipulation;
16679 <li> Functions for wide string date and time conversion; and
16680 <li> Functions that provide extended capabilities for conversion between multibyte and
16681 wide character sequences.
16684 Unless explicitly stated otherwise, if the execution of a function described in this
16685 subclause causes copying to take place between objects that overlap, the behavior is
16689 <p><small><a name="note277" href="#note277">277)</a> See ''future library directions'' (<a href="#7.26.12">7.26.12</a>).
16691 <p><small><a name="note278" href="#note278">278)</a> wchar_t and wint_t can be the same integer type.
16693 <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.
16696 <h4><a name="7.24.2" href="#7.24.2">7.24.2 Formatted wide character input/output functions</a></h4>
16698 The formatted wide character input/output functions shall behave as if there is a sequence
16699 point after the actions associated with each specifier.<sup><a href="#note280"><b>280)</b></a></sup>
16702 <p><small><a name="note280" href="#note280">280)</a> The fwprintf functions perform writes to memory for the %n specifier.
16705 <h5><a name="7.24.2.1" href="#7.24.2.1">7.24.2.1 The fwprintf function</a></h5>
16709 #include <a href="#7.19"><stdio.h></a>
16710 #include <a href="#7.24"><wchar.h></a>
16711 int fwprintf(FILE * restrict stream,
16712 const wchar_t * restrict format, ...);</pre>
16713 <h6>Description</h6>
16715 The fwprintf function writes output to the stream pointed to by stream, under
16716 control of the wide string pointed to by format that specifies how subsequent arguments
16717 are converted for output. If there are insufficient arguments for the format, the behavior
16718 is undefined. If the format is exhausted while arguments remain, the excess arguments
16719 are evaluated (as always) but are otherwise ignored. The fwprintf function returns
16720 when the end of the format string is encountered.
16722 The format is composed of zero or more directives: ordinary wide characters (not %),
16723 which are copied unchanged to the output stream; and conversion specifications, each of
16724 which results in fetching zero or more subsequent arguments, converting them, if
16725 applicable, according to the corresponding conversion specifier, and then writing the
16726 result to the output stream.
16728 Each conversion specification is introduced by the wide character %. After the %, the
16729 following appear in sequence:
16731 <li> Zero or more flags (in any order) that modify the meaning of the conversion
16733 <li> An optional minimum field width. If the converted value has fewer wide characters
16734 than the field width, it is padded with spaces (by default) on the left (or right, if the
16738 left adjustment flag, described later, has been given) to the field width. The field
16739 width takes the form of an asterisk * (described later) or a nonnegative decimal
16740 integer.<sup><a href="#note281"><b>281)</b></a></sup>
16741 <li> An optional precision that gives the minimum number of digits to appear for the d, i,
16742 o, u, x, and X conversions, the number of digits to appear after the decimal-point
16743 wide character for a, A, e, E, f, and F conversions, the maximum number of
16744 significant digits for the g and G conversions, or the maximum number of wide
16745 characters to be written for s conversions. The precision takes the form of a period
16746 (.) followed either by an asterisk * (described later) or by an optional decimal
16747 integer; if only the period is specified, the precision is taken as zero. If a precision
16748 appears with any other conversion specifier, the behavior is undefined.
16749 <li> An optional length modifier that specifies the size of the argument.
16750 <li> A conversion specifier wide character that specifies the type of conversion to be
16754 As noted above, a field width, or precision, or both, may be indicated by an asterisk. In
16755 this case, an int argument supplies the field width or precision. The arguments
16756 specifying field width, or precision, or both, shall appear (in that order) before the
16757 argument (if any) to be converted. A negative field width argument is taken as a - flag
16758 followed by a positive field width. A negative precision argument is taken as if the
16759 precision were omitted.
16761 The flag wide characters and their meanings are:
16762 - The result of the conversion is left-justified within the field. (It is right-justified if
16764 this flag is not specified.)</pre>
16765 + The result of a signed conversion always begins with a plus or minus sign. (It
16767 begins with a sign only when a negative value is converted if this flag is not
16768 specified.)<sup><a href="#note282"><b>282)</b></a></sup></pre>
16769 space If the first wide character of a signed conversion is not a sign, or if a signed
16771 conversion results in no wide characters, a space is prefixed to the result. If the
16772 space and + flags both appear, the space flag is ignored.</pre>
16773 # The result is converted to an ''alternative form''. For o conversion, it increases
16775 the precision, if and only if necessary, to force the first digit of the result to be a
16776 zero (if the value and precision are both 0, a single 0 is printed). For x (or X)
16777 conversion, a nonzero result has 0x (or 0X) prefixed to it. For a, A, e, E, f, F, g,</pre>
16781 and G conversions, the result of converting a floating-point number always
16782 contains a decimal-point wide character, even if no digits follow it. (Normally, a
16783 decimal-point wide character appears in the result of these conversions only if a
16784 digit follows it.) For g and G conversions, trailing zeros are not removed from the
16785 result. For other conversions, the behavior is undefined.</pre>
16786 0 For d, i, o, u, x, X, a, A, e, E, f, F, g, and G conversions, leading zeros
16789 (following any indication of sign or base) are used to pad to the field width rather
16790 than performing space padding, except when converting an infinity or NaN. If the
16791 0 and - flags both appear, the 0 flag is ignored. For d, i, o, u, x, and X
16792 conversions, if a precision is specified, the 0 flag is ignored. For other
16793 conversions, the behavior is undefined.</pre>
16794 The length modifiers and their meanings are:
16795 hh Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
16797 signed char or unsigned char argument (the argument will have
16798 been promoted according to the integer promotions, but its value shall be
16799 converted to signed char or unsigned char before printing); or that
16800 a following n conversion specifier applies to a pointer to a signed char
16802 h Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
16804 short int or unsigned short int argument (the argument will
16805 have been promoted according to the integer promotions, but its value shall
16806 be converted to short int or unsigned short int before printing);
16807 or that a following n conversion specifier applies to a pointer to a short
16808 int argument.</pre>
16809 l (ell) Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
16811 long int or unsigned long int argument; that a following n
16812 conversion specifier applies to a pointer to a long int argument; that a
16813 following c conversion specifier applies to a wint_t argument; that a
16814 following s conversion specifier applies to a pointer to a wchar_t
16815 argument; or has no effect on a following a, A, e, E, f, F, g, or G conversion
16817 ll (ell-ell) Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
16819 long long int or unsigned long long int argument; or that a
16820 following n conversion specifier applies to a pointer to a long long int
16822 j Specifies that a following d, i, o, u, x, or X conversion specifier applies to
16825 an intmax_t or uintmax_t argument; or that a following n conversion
16826 specifier applies to a pointer to an intmax_t argument.</pre>
16827 z Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
16829 size_t or the corresponding signed integer type argument; or that a
16830 following n conversion specifier applies to a pointer to a signed integer type
16831 corresponding to size_t argument.</pre>
16832 t Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
16834 ptrdiff_t or the corresponding unsigned integer type argument; or that a
16835 following n conversion specifier applies to a pointer to a ptrdiff_t
16837 L Specifies that a following a, A, e, E, f, F, g, or G conversion specifier
16839 applies to a long double argument.</pre>
16840 If a length modifier appears with any conversion specifier other than as specified above,
16841 the behavior is undefined.
16843 The conversion specifiers and their meanings are:
16844 d,i The int argument is converted to signed decimal in the style [-]dddd. The
16846 precision specifies the minimum number of digits to appear; if the value
16847 being converted can be represented in fewer digits, it is expanded with
16848 leading zeros. The default precision is 1. The result of converting a zero
16849 value with a precision of zero is no wide characters.</pre>
16850 o,u,x,X The unsigned int argument is converted to unsigned octal (o), unsigned
16852 decimal (u), or unsigned hexadecimal notation (x or X) in the style dddd; the
16853 letters abcdef are used for x conversion and the letters ABCDEF for X
16854 conversion. The precision specifies the minimum number of digits to appear;
16855 if the value being converted can be represented in fewer digits, it is expanded
16856 with leading zeros. The default precision is 1. The result of converting a
16857 zero value with a precision of zero is no wide characters.</pre>
16858 f,F A double argument representing a floating-point number is converted to
16861 decimal notation in the style [-]ddd.ddd, where the number of digits after
16862 the decimal-point wide character is equal to the precision specification. If the
16863 precision is missing, it is taken as 6; if the precision is zero and the # flag is
16864 not specified, no decimal-point wide character appears. If a decimal-point
16865 wide character appears, at least one digit appears before it. The value is
16866 rounded to the appropriate number of digits.
16867 A double argument representing an infinity is converted in one of the styles
16868 [-]inf or [-]infinity -- which style is implementation-defined. A
16869 double argument representing a NaN is converted in one of the styles
16870 [-]nan or [-]nan(n-wchar-sequence) -- which style, and the meaning of
16871 any n-wchar-sequence, is implementation-defined. The F conversion
16872 specifier produces INF, INFINITY, or NAN instead of inf, infinity, or
16873 nan, respectively.<sup><a href="#note283"><b>283)</b></a></sup></pre>
16874 e,E A double argument representing a floating-point number is converted in the
16876 style [-]d.ddd e(+-)dd, where there is one digit (which is nonzero if the
16877 argument is nonzero) before the decimal-point wide character and the number
16878 of digits after it is equal to the precision; if the precision is missing, it is taken
16879 as 6; if the precision is zero and the # flag is not specified, no decimal-point
16880 wide character appears. The value is rounded to the appropriate number of
16881 digits. The E conversion specifier produces a number with E instead of e
16882 introducing the exponent. The exponent always contains at least two digits,
16883 and only as many more digits as necessary to represent the exponent. If the
16884 value is zero, the exponent is zero.
16885 A double argument representing an infinity or NaN is converted in the style
16886 of an f or F conversion specifier.</pre>
16887 g,G A double argument representing a floating-point number is converted in
16889 style f or e (or in style F or E in the case of a G conversion specifier),
16890 depending on the value converted and the precision. Let P equal the
16891 precision if nonzero, 6 if the precision is omitted, or 1 if the precision is zero.
16892 Then, if a conversion with style E would have an exponent of X :
16893 -- if P > X >= -4, the conversion is with style f (or F) and precision
16895 -- otherwise, the conversion is with style e (or E) and precision P - 1.
16896 Finally, unless the # flag is used, any trailing zeros are removed from the
16897 fractional portion of the result and the decimal-point wide character is
16898 removed if there is no fractional portion remaining.
16899 A double argument representing an infinity or NaN is converted in the style
16900 of an f or F conversion specifier.</pre>
16901 a,A A double argument representing a floating-point number is converted in the
16903 style [-]0xh.hhhh p(+-)d, where there is one hexadecimal digit (which is
16904 nonzero if the argument is a normalized floating-point number and is
16905 otherwise unspecified) before the decimal-point wide character<sup><a href="#note284"><b>284)</b></a></sup> and the
16906 number of hexadecimal digits after it is equal to the precision; if the precision
16907 is missing and FLT_RADIX is a power of 2, then the precision is sufficient</pre>
16912 for an exact representation of the value; if the precision is missing and
16913 FLT_RADIX is not a power of 2, then the precision is sufficient to
16914 distinguish<sup><a href="#note285"><b>285)</b></a></sup> values of type double, except that trailing zeros may be
16915 omitted; if the precision is zero and the # flag is not specified, no decimal-
16916 point wide character appears. The letters abcdef are used for a conversion
16917 and the letters ABCDEF for A conversion. The A conversion specifier
16918 produces a number with X and P instead of x and p. The exponent always
16919 contains at least one digit, and only as many more digits as necessary to
16920 represent the decimal exponent of 2. If the value is zero, the exponent is
16922 A double argument representing an infinity or NaN is converted in the style
16923 of an f or F conversion specifier.</pre>
16924 c If no l length modifier is present, the int argument is converted to a wide
16926 character as if by calling btowc and the resulting wide character is written.
16927 If an l length modifier is present, the wint_t argument is converted to
16928 wchar_t and written.</pre>
16929 s If no l length modifier is present, the argument shall be a pointer to the initial
16931 element of a character array containing a multibyte character sequence
16932 beginning in the initial shift state. Characters from the array are converted as
16933 if by repeated calls to the mbrtowc function, with the conversion state
16934 described by an mbstate_t object initialized to zero before the first
16935 multibyte character is converted, and written up to (but not including) the
16936 terminating null wide character. If the precision is specified, no more than
16937 that many wide characters are written. If the precision is not specified or is
16938 greater than the size of the converted array, the converted array shall contain a
16939 null wide character.
16940 If an l length modifier is present, the argument shall be a pointer to the initial
16941 element of an array of wchar_t type. Wide characters from the array are
16942 written up to (but not including) a terminating null wide character. If the
16943 precision is specified, no more than that many wide characters are written. If
16944 the precision is not specified or is greater than the size of the array, the array
16945 shall contain a null wide character.</pre>
16946 p The argument shall be a pointer to void. The value of the pointer is
16948 converted to a sequence of printing wide characters, in an implementation-</pre>
16952 defined manner.</pre>
16953 n The argument shall be a pointer to signed integer into which is written the
16955 number of wide characters written to the output stream so far by this call to
16956 fwprintf. No argument is converted, but one is consumed. If the
16957 conversion specification includes any flags, a field width, or a precision, the
16958 behavior is undefined.</pre>
16959 % A % wide character is written. No argument is converted. The complete
16962 conversion specification shall be %%.</pre>
16963 If a conversion specification is invalid, the behavior is undefined.<sup><a href="#note286"><b>286)</b></a></sup> If any argument is
16964 not the correct type for the corresponding conversion specification, the behavior is
16967 In no case does a nonexistent or small field width cause truncation of a field; if the result
16968 of a conversion is wider than the field width, the field is expanded to contain the
16971 For a and A conversions, if FLT_RADIX is a power of 2, the value is correctly rounded
16972 to a hexadecimal floating number with the given precision.
16973 Recommended practice
16975 For a and A conversions, if FLT_RADIX is not a power of 2 and the result is not exactly
16976 representable in the given precision, the result should be one of the two adjacent numbers
16977 in hexadecimal floating style with the given precision, with the extra stipulation that the
16978 error should have a correct sign for the current rounding direction.
16980 For e, E, f, F, g, and G conversions, if the number of significant decimal digits is at most
16981 DECIMAL_DIG, then the result should be correctly rounded.<sup><a href="#note287"><b>287)</b></a></sup> If the number of
16982 significant decimal digits is more than DECIMAL_DIG but the source value is exactly
16983 representable with DECIMAL_DIG digits, then the result should be an exact
16984 representation with trailing zeros. Otherwise, the source value is bounded by two
16985 adjacent decimal strings L < U, both having DECIMAL_DIG significant digits; the value
16986 of the resultant decimal string D should satisfy L <= D <= U, with the extra stipulation that
16987 the error should have a correct sign for the current rounding direction.
16990 The fwprintf function returns the number of wide characters transmitted, or a negative
16991 value if an output or encoding error occurred.
16994 Environmental limits
16996 The number of wide characters that can be produced by any single conversion shall be at
16999 EXAMPLE To print a date and time in the form ''Sunday, July 3, 10:02'' followed by pi to five decimal
17002 #include <a href="#7.12"><math.h></a>
17003 #include <a href="#7.19"><stdio.h></a>
17004 #include <a href="#7.24"><wchar.h></a>
17006 wchar_t *weekday, *month; // pointers to wide strings
17007 int day, hour, min;
17008 fwprintf(stdout, L"%ls, %ls %d, %.2d:%.2d\n",
17009 weekday, month, day, hour, min);
17010 fwprintf(stdout, L"pi = %.5f\n", 4 * atan(1.0));</pre>
17012 <p><b> Forward references</b>: the btowc function (<a href="#7.24.6.1.1">7.24.6.1.1</a>), the mbrtowc function
17013 (<a href="#7.24.6.3.2">7.24.6.3.2</a>).
17016 <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.
17018 <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,
17019 include a minus sign.
17021 <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
17022 meaning; the # and 0 flag wide characters have no effect.
17024 <p><small><a name="note284" href="#note284">284)</a> Binary implementations can choose the hexadecimal digit to the left of the decimal-point wide
17025 character so that subsequent digits align to nibble (4-bit) boundaries.
17027 <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
17028 FLT_RADIX and n is the number of base-b digits in the significand of the source type. A smaller p
17029 might suffice depending on the implementation's scheme for determining the digit to the left of the
17030 decimal-point wide character.
17032 <p><small><a name="note286" href="#note286">286)</a> See ''future library directions'' (<a href="#7.26.12">7.26.12</a>).
17034 <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
17035 given format specifier. The number of significant digits is determined by the format specifier, and in
17036 the case of fixed-point conversion by the source value as well.
17039 <h5><a name="7.24.2.2" href="#7.24.2.2">7.24.2.2 The fwscanf function</a></h5>
17043 #include <a href="#7.19"><stdio.h></a>
17044 #include <a href="#7.24"><wchar.h></a>
17045 int fwscanf(FILE * restrict stream,
17046 const wchar_t * restrict format, ...);</pre>
17047 <h6>Description</h6>
17049 The fwscanf function reads input from the stream pointed to by stream, under
17050 control of the wide string pointed to by format that specifies the admissible input
17051 sequences and how they are to be converted for assignment, using subsequent arguments
17052 as pointers to the objects to receive the converted input. If there are insufficient
17053 arguments for the format, the behavior is undefined. If the format is exhausted while
17054 arguments remain, the excess arguments are evaluated (as always) but are otherwise
17057 The format is composed of zero or more directives: one or more white-space wide
17058 characters, an ordinary wide character (neither % nor a white-space wide character), or a
17059 conversion specification. Each conversion specification is introduced by the wide
17060 character %. After the %, the following appear in sequence:
17062 <li> An optional assignment-suppressing wide character *.
17063 <li> An optional decimal integer greater than zero that specifies the maximum field width
17064 (in wide characters).
17066 <li> An optional length modifier that specifies the size of the receiving object.
17067 <li> A conversion specifier wide character that specifies the type of conversion to be
17071 The fwscanf function executes each directive of the format in turn. If a directive fails,
17072 as detailed below, the function returns. Failures are described as input failures (due to the
17073 occurrence of an encoding error or the unavailability of input characters), or matching
17074 failures (due to inappropriate input).
17076 A directive composed of white-space wide character(s) is executed by reading input up to
17077 the first non-white-space wide character (which remains unread), or until no more wide
17078 characters can be read.
17080 A directive that is an ordinary wide character is executed by reading the next wide
17081 character of the stream. If that wide character differs from the directive, the directive
17082 fails and the differing and subsequent wide characters remain unread. Similarly, if end-
17083 of-file, an encoding error, or a read error prevents a wide character from being read, the
17086 A directive that is a conversion specification defines a set of matching input sequences, as
17087 described below for each specifier. A conversion specification is executed in the
17090 Input white-space wide characters (as specified by the iswspace function) are skipped,
17091 unless the specification includes a [, c, or n specifier.<sup><a href="#note288"><b>288)</b></a></sup>
17093 An input item is read from the stream, unless the specification includes an n specifier. An
17094 input item is defined as the longest sequence of input wide characters which does not
17095 exceed any specified field width and which is, or is a prefix of, a matching input
17096 sequence.<sup><a href="#note289"><b>289)</b></a></sup> The first wide character, if any, after the input item remains unread. If the
17097 length of the input item is zero, the execution of the directive fails; this condition is a
17098 matching failure unless end-of-file, an encoding error, or a read error prevented input
17099 from the stream, in which case it is an input failure.
17101 Except in the case of a % specifier, the input item (or, in the case of a %n directive, the
17102 count of input wide characters) is converted to a type appropriate to the conversion
17103 specifier. If the input item is not a matching sequence, the execution of the directive fails:
17104 this condition is a matching failure. Unless assignment suppression was indicated by a *,
17105 the result of the conversion is placed in the object pointed to by the first argument
17106 following the format argument that has not already received a conversion result. If this
17110 object does not have an appropriate type, or if the result of the conversion cannot be
17111 represented in the object, the behavior is undefined.
17113 The length modifiers and their meanings are:
17114 hh Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
17116 to an argument with type pointer to signed char or unsigned char.</pre>
17117 h Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
17119 to an argument with type pointer to short int or unsigned short
17121 l (ell) Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
17123 to an argument with type pointer to long int or unsigned long
17124 int; that a following a, A, e, E, f, F, g, or G conversion specifier applies to
17125 an argument with type pointer to double; or that a following c, s, or [
17126 conversion specifier applies to an argument with type pointer to wchar_t.</pre>
17127 ll (ell-ell) Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
17129 to an argument with type pointer to long long int or unsigned
17130 long long int.</pre>
17131 j Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
17133 to an argument with type pointer to intmax_t or uintmax_t.</pre>
17134 z Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
17136 to an argument with type pointer to size_t or the corresponding signed
17137 integer type.</pre>
17138 t Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
17140 to an argument with type pointer to ptrdiff_t or the corresponding
17141 unsigned integer type.</pre>
17142 L Specifies that a following a, A, e, E, f, F, g, or G conversion specifier
17144 applies to an argument with type pointer to long double.</pre>
17145 If a length modifier appears with any conversion specifier other than as specified above,
17146 the behavior is undefined.
17148 The conversion specifiers and their meanings are:
17149 d Matches an optionally signed decimal integer, whose format is the same as
17151 expected for the subject sequence of the wcstol function with the value 10
17152 for the base argument. The corresponding argument shall be a pointer to
17153 signed integer.</pre>
17154 i Matches an optionally signed integer, whose format is the same as expected
17157 for the subject sequence of the wcstol function with the value 0 for the
17158 base argument. The corresponding argument shall be a pointer to signed
17160 o Matches an optionally signed octal integer, whose format is the same as
17162 expected for the subject sequence of the wcstoul function with the value 8
17163 for the base argument. The corresponding argument shall be a pointer to
17164 unsigned integer.</pre>
17165 u Matches an optionally signed decimal integer, whose format is the same as
17167 expected for the subject sequence of the wcstoul function with the value 10
17168 for the base argument. The corresponding argument shall be a pointer to
17169 unsigned integer.</pre>
17170 x Matches an optionally signed hexadecimal integer, whose format is the same
17172 as expected for the subject sequence of the wcstoul function with the value
17173 16 for the base argument. The corresponding argument shall be a pointer to
17174 unsigned integer.</pre>
17175 a,e,f,g Matches an optionally signed floating-point number, infinity, or NaN, whose
17177 format is the same as expected for the subject sequence of the wcstod
17178 function. The corresponding argument shall be a pointer to floating.</pre>
17179 c Matches a sequence of wide characters of exactly the number specified by the
17181 field width (1 if no field width is present in the directive).
17182 If no l length modifier is present, characters from the input field are
17183 converted as if by repeated calls to the wcrtomb function, with the
17184 conversion state described by an mbstate_t object initialized to zero
17185 before the first wide character is converted. The corresponding argument
17186 shall be a pointer to the initial element of a character array large enough to
17187 accept the sequence. No null character is added.
17188 If an l length modifier is present, the corresponding argument shall be a
17189 pointer to the initial element of an array of wchar_t large enough to accept
17190 the sequence. No null wide character is added.</pre>
17191 s Matches a sequence of non-white-space wide characters.
17194 If no l length modifier is present, characters from the input field are
17195 converted as if by repeated calls to the wcrtomb function, with the
17196 conversion state described by an mbstate_t object initialized to zero
17197 before the first wide character is converted. The corresponding argument
17198 shall be a pointer to the initial element of a character array large enough to
17199 accept the sequence and a terminating null character, which will be added
17201 If an l length modifier is present, the corresponding argument shall be a
17202 pointer to the initial element of an array of wchar_t large enough to accept
17203 the sequence and the terminating null wide character, which will be added
17204 automatically.</pre>
17205 [ Matches a nonempty sequence of wide characters from a set of expected
17207 characters (the scanset).
17208 If no l length modifier is present, characters from the input field are
17209 converted as if by repeated calls to the wcrtomb function, with the
17210 conversion state described by an mbstate_t object initialized to zero
17211 before the first wide character is converted. The corresponding argument
17212 shall be a pointer to the initial element of a character array large enough to
17213 accept the sequence and a terminating null character, which will be added
17215 If an l length modifier is present, the corresponding argument shall be a
17216 pointer to the initial element of an array of wchar_t large enough to accept
17217 the sequence and the terminating null wide character, which will be added
17219 The conversion specifier includes all subsequent wide characters in the
17220 format string, up to and including the matching right bracket (]). The wide
17221 characters between the brackets (the scanlist) compose the scanset, unless the
17222 wide character after the left bracket is a circumflex (^), in which case the
17223 scanset contains all wide characters that do not appear in the scanlist between
17224 the circumflex and the right bracket. If the conversion specifier begins with
17225 [] or [^], the right bracket wide character is in the scanlist and the next
17226 following right bracket wide character is the matching right bracket that ends
17227 the specification; otherwise the first following right bracket wide character is
17228 the one that ends the specification. If a - wide character is in the scanlist and
17229 is not the first, nor the second where the first wide character is a ^, nor the
17230 last character, the behavior is implementation-defined.</pre>
17231 p Matches an implementation-defined set of sequences, which should be the
17233 same as the set of sequences that may be produced by the %p conversion of
17234 the fwprintf function. The corresponding argument shall be a pointer to a
17235 pointer to void. The input item is converted to a pointer value in an
17236 implementation-defined manner. If the input item is a value converted earlier
17237 during the same program execution, the pointer that results shall compare
17238 equal to that value; otherwise the behavior of the %p conversion is undefined.</pre>
17239 n No input is consumed. The corresponding argument shall be a pointer to
17242 signed integer into which is to be written the number of wide characters read
17243 from the input stream so far by this call to the fwscanf function. Execution
17244 of a %n directive does not increment the assignment count returned at the
17245 completion of execution of the fwscanf function. No argument is
17246 converted, but one is consumed. If the conversion specification includes an
17247 assignment-suppressing wide character or a field width, the behavior is
17249 % Matches a single % wide character; no conversion or assignment occurs. The
17252 complete conversion specification shall be %%.</pre>
17253 If a conversion specification is invalid, the behavior is undefined.<sup><a href="#note290"><b>290)</b></a></sup>
17255 The conversion specifiers A, E, F, G, and X are also valid and behave the same as,
17256 respectively, a, e, f, g, and x.
17258 Trailing white space (including new-line wide characters) is left unread unless matched
17259 by a directive. The success of literal matches and suppressed assignments is not directly
17260 determinable other than via the %n directive.
17263 The fwscanf function returns the value of the macro EOF if an input failure occurs
17264 before any conversion. Otherwise, the function returns the number of input items
17265 assigned, which can be fewer than provided for, or even zero, in the event of an early
17268 EXAMPLE 1 The call:
17270 #include <a href="#7.19"><stdio.h></a>
17271 #include <a href="#7.24"><wchar.h></a>
17273 int n, i; float x; wchar_t name[50];
17274 n = fwscanf(stdin, L"%d%f%ls", &i, &x, name);</pre>
17275 with the input line:
17277 25 54.32E-1 thompson</pre>
17278 will assign to n the value 3, to i the value 25, to x the value 5.432, and to name the sequence
17282 EXAMPLE 2 The call:
17284 #include <a href="#7.19"><stdio.h></a>
17285 #include <a href="#7.24"><wchar.h></a>
17287 int i; float x; double y;
17288 fwscanf(stdin, L"%2d%f%*d %lf", &i, &x, &y);</pre>
17291 56789 0123 56a72</pre>
17292 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
17293 56.0. The next wide character read from the input stream will be a.
17297 <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
17298 wcstol, wcstoll, wcstoul, and wcstoull functions (<a href="#7.24.4.1.2">7.24.4.1.2</a>), the wcrtomb
17299 function (<a href="#7.24.6.3.3">7.24.6.3.3</a>).
17302 <p><small><a name="note288" href="#note288">288)</a> These white-space wide characters are not counted against a specified field width.
17304 <p><small><a name="note289" href="#note289">289)</a> fwscanf pushes back at most one input wide character onto the input stream. Therefore, some
17305 sequences that are acceptable to wcstod, wcstol, etc., are unacceptable to fwscanf.
17307 <p><small><a name="note290" href="#note290">290)</a> See ''future library directions'' (<a href="#7.26.12">7.26.12</a>).
17310 <h5><a name="7.24.2.3" href="#7.24.2.3">7.24.2.3 The swprintf function</a></h5>
17314 #include <a href="#7.24"><wchar.h></a>
17315 int swprintf(wchar_t * restrict s,
17317 const wchar_t * restrict format, ...);</pre>
17318 <h6>Description</h6>
17320 The swprintf function is equivalent to fwprintf, except that the argument s
17321 specifies an array of wide characters into which the generated output is to be written,
17322 rather than written to a stream. No more than n wide characters are written, including a
17323 terminating null wide character, which is always added (unless n is zero).
17326 The swprintf function returns the number of wide characters written in the array, not
17327 counting the terminating null wide character, or a negative value if an encoding error
17328 occurred or if n or more wide characters were requested to be written.
17330 <h5><a name="7.24.2.4" href="#7.24.2.4">7.24.2.4 The swscanf function</a></h5>
17334 #include <a href="#7.24"><wchar.h></a>
17335 int swscanf(const wchar_t * restrict s,
17336 const wchar_t * restrict format, ...);</pre>
17337 <h6>Description</h6>
17339 The swscanf function is equivalent to fwscanf, except that the argument s specifies a
17340 wide string from which the input is to be obtained, rather than from a stream. Reaching
17341 the end of the wide string is equivalent to encountering end-of-file for the fwscanf
17345 The swscanf function returns the value of the macro EOF if an input failure occurs
17346 before any conversion. Otherwise, the swscanf function returns the number of input
17347 items assigned, which can be fewer than provided for, or even zero, in the event of an
17348 early matching failure.
17351 <h5><a name="7.24.2.5" href="#7.24.2.5">7.24.2.5 The vfwprintf function</a></h5>
17355 #include <a href="#7.15"><stdarg.h></a>
17356 #include <a href="#7.19"><stdio.h></a>
17357 #include <a href="#7.24"><wchar.h></a>
17358 int vfwprintf(FILE * restrict stream,
17359 const wchar_t * restrict format,
17360 va_list arg);</pre>
17361 <h6>Description</h6>
17363 The vfwprintf function is equivalent to fwprintf, with the variable argument list
17364 replaced by arg, which shall have been initialized by the va_start macro (and
17365 possibly subsequent va_arg calls). The vfwprintf function does not invoke the
17366 va_end macro.<sup><a href="#note291"><b>291)</b></a></sup>
17369 The vfwprintf function returns the number of wide characters transmitted, or a
17370 negative value if an output or encoding error occurred.
17372 EXAMPLE The following shows the use of the vfwprintf function in a general error-reporting
17375 #include <a href="#7.15"><stdarg.h></a>
17376 #include <a href="#7.19"><stdio.h></a>
17377 #include <a href="#7.24"><wchar.h></a>
17378 void error(char *function_name, wchar_t *format, ...)
17381 va_start(args, format);
17382 // print out name of function causing error
17383 fwprintf(stderr, L"ERROR in %s: ", function_name);
17384 // print out remainder of message
17385 vfwprintf(stderr, format, args);
17395 <p><small><a name="note291" href="#note291">291)</a> As the functions vfwprintf, vswprintf, vfwscanf, vwprintf, vwscanf, and vswscanf
17396 invoke the va_arg macro, the value of arg after the return is indeterminate.
17399 <h5><a name="7.24.2.6" href="#7.24.2.6">7.24.2.6 The vfwscanf function</a></h5>
17403 #include <a href="#7.15"><stdarg.h></a>
17404 #include <a href="#7.19"><stdio.h></a>
17405 #include <a href="#7.24"><wchar.h></a>
17406 int vfwscanf(FILE * restrict stream,
17407 const wchar_t * restrict format,
17408 va_list arg);</pre>
17409 <h6>Description</h6>
17411 The vfwscanf function is equivalent to fwscanf, with the variable argument list
17412 replaced by arg, which shall have been initialized by the va_start macro (and
17413 possibly subsequent va_arg calls). The vfwscanf function does not invoke the
17417 The vfwscanf function returns the value of the macro EOF if an input failure occurs
17418 before any conversion. Otherwise, the vfwscanf function returns the number of input
17419 items assigned, which can be fewer than provided for, or even zero, in the event of an
17420 early matching failure.
17422 <h5><a name="7.24.2.7" href="#7.24.2.7">7.24.2.7 The vswprintf function</a></h5>
17426 #include <a href="#7.15"><stdarg.h></a>
17427 #include <a href="#7.24"><wchar.h></a>
17428 int vswprintf(wchar_t * restrict s,
17430 const wchar_t * restrict format,
17431 va_list arg);</pre>
17432 <h6>Description</h6>
17434 The vswprintf function is equivalent to swprintf, with the variable argument list
17435 replaced by arg, which shall have been initialized by the va_start macro (and
17436 possibly subsequent va_arg calls). The vswprintf function does not invoke the
17440 The vswprintf function returns the number of wide characters written in the array, not
17441 counting the terminating null wide character, or a negative value if an encoding error
17442 occurred or if n or more wide characters were requested to be generated.
17445 <h5><a name="7.24.2.8" href="#7.24.2.8">7.24.2.8 The vswscanf function</a></h5>
17449 #include <a href="#7.15"><stdarg.h></a>
17450 #include <a href="#7.24"><wchar.h></a>
17451 int vswscanf(const wchar_t * restrict s,
17452 const wchar_t * restrict format,
17453 va_list arg);</pre>
17454 <h6>Description</h6>
17456 The vswscanf function is equivalent to swscanf, with the variable argument list
17457 replaced by arg, which shall have been initialized by the va_start macro (and
17458 possibly subsequent va_arg calls). The vswscanf function does not invoke the
17462 The vswscanf function returns the value of the macro EOF if an input failure occurs
17463 before any conversion. Otherwise, the vswscanf function returns the number of input
17464 items assigned, which can be fewer than provided for, or even zero, in the event of an
17465 early matching failure.
17467 <h5><a name="7.24.2.9" href="#7.24.2.9">7.24.2.9 The vwprintf function</a></h5>
17471 #include <a href="#7.15"><stdarg.h></a>
17472 #include <a href="#7.24"><wchar.h></a>
17473 int vwprintf(const wchar_t * restrict format,
17474 va_list arg);</pre>
17475 <h6>Description</h6>
17477 The vwprintf function is equivalent to wprintf, with the variable argument list
17478 replaced by arg, which shall have been initialized by the va_start macro (and
17479 possibly subsequent va_arg calls). The vwprintf function does not invoke the
17483 The vwprintf function returns the number of wide characters transmitted, or a negative
17484 value if an output or encoding error occurred.
17487 <h5><a name="7.24.2.10" href="#7.24.2.10">7.24.2.10 The vwscanf function</a></h5>
17491 #include <a href="#7.15"><stdarg.h></a>
17492 #include <a href="#7.24"><wchar.h></a>
17493 int vwscanf(const wchar_t * restrict format,
17494 va_list arg);</pre>
17495 <h6>Description</h6>
17497 The vwscanf function is equivalent to wscanf, with the variable argument list
17498 replaced by arg, which shall have been initialized by the va_start macro (and
17499 possibly subsequent va_arg calls). The vwscanf function does not invoke the
17503 The vwscanf function returns the value of the macro EOF if an input failure occurs
17504 before any conversion. Otherwise, the vwscanf function returns the number of input
17505 items assigned, which can be fewer than provided for, or even zero, in the event of an
17506 early matching failure.
17508 <h5><a name="7.24.2.11" href="#7.24.2.11">7.24.2.11 The wprintf function</a></h5>
17512 #include <a href="#7.24"><wchar.h></a>
17513 int wprintf(const wchar_t * restrict format, ...);</pre>
17514 <h6>Description</h6>
17516 The wprintf function is equivalent to fwprintf with the argument stdout
17517 interposed before the arguments to wprintf.
17520 The wprintf function returns the number of wide characters transmitted, or a negative
17521 value if an output or encoding error occurred.
17523 <h5><a name="7.24.2.12" href="#7.24.2.12">7.24.2.12 The wscanf function</a></h5>
17527 #include <a href="#7.24"><wchar.h></a>
17528 int wscanf(const wchar_t * restrict format, ...);</pre>
17529 <h6>Description</h6>
17531 The wscanf function is equivalent to fwscanf with the argument stdin interposed
17532 before the arguments to wscanf.
17536 The wscanf function returns the value of the macro EOF if an input failure occurs
17537 before any conversion. Otherwise, the wscanf function returns the number of input
17538 items assigned, which can be fewer than provided for, or even zero, in the event of an
17539 early matching failure.
17541 <h4><a name="7.24.3" href="#7.24.3">7.24.3 Wide character input/output functions</a></h4>
17543 <h5><a name="7.24.3.1" href="#7.24.3.1">7.24.3.1 The fgetwc function</a></h5>
17547 #include <a href="#7.19"><stdio.h></a>
17548 #include <a href="#7.24"><wchar.h></a>
17549 wint_t fgetwc(FILE *stream);</pre>
17550 <h6>Description</h6>
17552 If the end-of-file indicator for the input stream pointed to by stream is not set and a
17553 next wide character is present, the fgetwc function obtains that wide character as a
17554 wchar_t converted to a wint_t and advances the associated file position indicator for
17555 the stream (if defined).
17558 If the end-of-file indicator for the stream is set, or if the stream is at end-of-file, the end-
17559 of-file indicator for the stream is set and the fgetwc function returns WEOF. Otherwise,
17560 the fgetwc function returns the next wide character from the input stream pointed to by
17561 stream. If a read error occurs, the error indicator for the stream is set and the fgetwc
17562 function returns WEOF. If an encoding error occurs (including too few bytes), the value of
17563 the macro EILSEQ is stored in errno and the fgetwc function returns WEOF.<sup><a href="#note292"><b>292)</b></a></sup>
17566 <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.
17567 Also, errno will be set to EILSEQ by input/output functions only if an encoding error occurs.
17570 <h5><a name="7.24.3.2" href="#7.24.3.2">7.24.3.2 The fgetws function</a></h5>
17574 #include <a href="#7.19"><stdio.h></a>
17575 #include <a href="#7.24"><wchar.h></a>
17576 wchar_t *fgetws(wchar_t * restrict s,
17577 int n, FILE * restrict stream);</pre>
17578 <h6>Description</h6>
17580 The fgetws function reads at most one less than the number of wide characters
17581 specified by n from the stream pointed to by stream into the array pointed to by s. No
17585 additional wide characters are read after a new-line wide character (which is retained) or
17586 after end-of-file. A null wide character is written immediately after the last wide
17587 character read into the array.
17590 The fgetws function returns s if successful. If end-of-file is encountered and no
17591 characters have been read into the array, the contents of the array remain unchanged and a
17592 null pointer is returned. If a read or encoding error occurs during the operation, the array
17593 contents are indeterminate and a null pointer is returned.
17595 <h5><a name="7.24.3.3" href="#7.24.3.3">7.24.3.3 The fputwc function</a></h5>
17599 #include <a href="#7.19"><stdio.h></a>
17600 #include <a href="#7.24"><wchar.h></a>
17601 wint_t fputwc(wchar_t c, FILE *stream);</pre>
17602 <h6>Description</h6>
17604 The fputwc function writes the wide character specified by c to the output stream
17605 pointed to by stream, at the position indicated by the associated file position indicator
17606 for the stream (if defined), and advances the indicator appropriately. If the file cannot
17607 support positioning requests, or if the stream was opened with append mode, the
17608 character is appended to the output stream.
17611 The fputwc function returns the wide character written. If a write error occurs, the
17612 error indicator for the stream is set and fputwc returns WEOF. If an encoding error
17613 occurs, the value of the macro EILSEQ is stored in errno and fputwc returns WEOF.
17615 <h5><a name="7.24.3.4" href="#7.24.3.4">7.24.3.4 The fputws function</a></h5>
17619 #include <a href="#7.19"><stdio.h></a>
17620 #include <a href="#7.24"><wchar.h></a>
17621 int fputws(const wchar_t * restrict s,
17622 FILE * restrict stream);</pre>
17623 <h6>Description</h6>
17625 The fputws function writes the wide string pointed to by s to the stream pointed to by
17626 stream. The terminating null wide character is not written.
17629 The fputws function returns EOF if a write or encoding error occurs; otherwise, it
17630 returns a nonnegative value.
17633 <h5><a name="7.24.3.5" href="#7.24.3.5">7.24.3.5 The fwide function</a></h5>
17637 #include <a href="#7.19"><stdio.h></a>
17638 #include <a href="#7.24"><wchar.h></a>
17639 int fwide(FILE *stream, int mode);</pre>
17640 <h6>Description</h6>
17642 The fwide function determines the orientation of the stream pointed to by stream. If
17643 mode is greater than zero, the function first attempts to make the stream wide oriented. If
17644 mode is less than zero, the function first attempts to make the stream byte oriented.<sup><a href="#note293"><b>293)</b></a></sup>
17645 Otherwise, mode is zero and the function does not alter the orientation of the stream.
17648 The fwide function returns a value greater than zero if, after the call, the stream has
17649 wide orientation, a value less than zero if the stream has byte orientation, or zero if the
17650 stream has no orientation.
17653 <p><small><a name="note293" href="#note293">293)</a> If the orientation of the stream has already been determined, fwide does not change it.
17656 <h5><a name="7.24.3.6" href="#7.24.3.6">7.24.3.6 The getwc function</a></h5>
17660 #include <a href="#7.19"><stdio.h></a>
17661 #include <a href="#7.24"><wchar.h></a>
17662 wint_t getwc(FILE *stream);</pre>
17663 <h6>Description</h6>
17665 The getwc function is equivalent to fgetwc, except that if it is implemented as a
17666 macro, it may evaluate stream more than once, so the argument should never be an
17667 expression with side effects.
17670 The getwc function returns the next wide character from the input stream pointed to by
17673 <h5><a name="7.24.3.7" href="#7.24.3.7">7.24.3.7 The getwchar function</a></h5>
17677 #include <a href="#7.24"><wchar.h></a>
17678 wint_t getwchar(void);</pre>
17684 <h6>Description</h6>
17686 The getwchar function is equivalent to getwc with the argument stdin.
17689 The getwchar function returns the next wide character from the input stream pointed to
17692 <h5><a name="7.24.3.8" href="#7.24.3.8">7.24.3.8 The putwc function</a></h5>
17696 #include <a href="#7.19"><stdio.h></a>
17697 #include <a href="#7.24"><wchar.h></a>
17698 wint_t putwc(wchar_t c, FILE *stream);</pre>
17699 <h6>Description</h6>
17701 The putwc function is equivalent to fputwc, except that if it is implemented as a
17702 macro, it may evaluate stream more than once, so that argument should never be an
17703 expression with side effects.
17706 The putwc function returns the wide character written, or WEOF.
17708 <h5><a name="7.24.3.9" href="#7.24.3.9">7.24.3.9 The putwchar function</a></h5>
17712 #include <a href="#7.24"><wchar.h></a>
17713 wint_t putwchar(wchar_t c);</pre>
17714 <h6>Description</h6>
17716 The putwchar function is equivalent to putwc with the second argument stdout.
17719 The putwchar function returns the character written, or WEOF.
17721 <h5><a name="7.24.3.10" href="#7.24.3.10">7.24.3.10 The ungetwc function</a></h5>
17725 #include <a href="#7.19"><stdio.h></a>
17726 #include <a href="#7.24"><wchar.h></a>
17727 wint_t ungetwc(wint_t c, FILE *stream);</pre>
17728 <h6>Description</h6>
17730 The ungetwc function pushes the wide character specified by c back onto the input
17731 stream pointed to by stream. Pushed-back wide characters will be returned by
17732 subsequent reads on that stream in the reverse order of their pushing. A successful
17734 intervening call (with the stream pointed to by stream) to a file positioning function
17735 (fseek, fsetpos, or rewind) discards any pushed-back wide characters for the
17736 stream. The external storage corresponding to the stream is unchanged.
17738 One wide character of pushback is guaranteed, even if the call to the ungetwc function
17739 follows just after a call to a formatted wide character input function fwscanf,
17740 vfwscanf, vwscanf, or wscanf. If the ungetwc function is called too many times
17741 on the same stream without an intervening read or file positioning operation on that
17742 stream, the operation may fail.
17744 If the value of c equals that of the macro WEOF, the operation fails and the input stream is
17747 A successful call to the ungetwc function clears the end-of-file indicator for the stream.
17748 The value of the file position indicator for the stream after reading or discarding all
17749 pushed-back wide characters is the same as it was before the wide characters were pushed
17750 back. For a text or binary stream, the value of its file position indicator after a successful
17751 call to the ungetwc function is unspecified until all pushed-back wide characters are
17755 The ungetwc function returns the wide character pushed back, or WEOF if the operation
17758 <h4><a name="7.24.4" href="#7.24.4">7.24.4 General wide string utilities</a></h4>
17760 The header <a href="#7.24"><wchar.h></a> declares a number of functions useful for wide string
17761 manipulation. Various methods are used for determining the lengths of the arrays, but in
17762 all cases a wchar_t * argument points to the initial (lowest addressed) element of the
17763 array. If an array is accessed beyond the end of an object, the behavior is undefined.
17765 Where an argument declared as size_t n determines the length of the array for a
17766 function, n can have the value zero on a call to that function. Unless explicitly stated
17767 otherwise in the description of a particular function in this subclause, pointer arguments
17768 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
17769 function that locates a wide character finds no occurrence, a function that compares two
17770 wide character sequences returns zero, and a function that copies wide characters copies
17771 zero wide characters.
17774 <h5><a name="7.24.4.1" href="#7.24.4.1">7.24.4.1 Wide string numeric conversion functions</a></h5>
17776 <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>
17780 #include <a href="#7.24"><wchar.h></a>
17781 double wcstod(const wchar_t * restrict nptr,
17782 wchar_t ** restrict endptr);
17783 float wcstof(const wchar_t * restrict nptr,
17784 wchar_t ** restrict endptr);
17785 long double wcstold(const wchar_t * restrict nptr,
17786 wchar_t ** restrict endptr);</pre>
17787 <h6>Description</h6>
17789 The wcstod, wcstof, and wcstold functions convert the initial portion of the wide
17790 string pointed to by nptr to double, float, and long double representation,
17791 respectively. First, they decompose the input string into three parts: an initial, possibly
17792 empty, sequence of white-space wide characters (as specified by the iswspace
17793 function), a subject sequence resembling a floating-point constant or representing an
17794 infinity or NaN; and a final wide string of one or more unrecognized wide characters,
17795 including the terminating null wide character of the input wide string. Then, they attempt
17796 to convert the subject sequence to a floating-point number, and return the result.
17798 The expected form of the subject sequence is an optional plus or minus sign, then one of
17801 <li> a nonempty sequence of decimal digits optionally containing a decimal-point wide
17802 character, then an optional exponent part as defined for the corresponding single-byte
17803 characters in <a href="#6.4.4.2">6.4.4.2</a>;
17804 <li> a 0x or 0X, then a nonempty sequence of hexadecimal digits optionally containing a
17805 decimal-point wide character, then an optional binary exponent part as defined in
17806 <a href="#6.4.4.2">6.4.4.2</a>;
17807 <li> INF or INFINITY, or any other wide string equivalent except for case
17808 <li> NAN or NAN(n-wchar-sequenceopt), or any other wide string equivalent except for
17809 case in the NAN part, where:
17814 n-wchar-sequence digit
17815 n-wchar-sequence nondigit</pre>
17817 The subject sequence is defined as the longest initial subsequence of the input wide
17818 string, starting with the first non-white-space wide character, that is of the expected form.
17820 The subject sequence contains no wide characters if the input wide string is not of the
17823 If the subject sequence has the expected form for a floating-point number, the sequence of
17824 wide characters starting with the first digit or the decimal-point wide character
17825 (whichever occurs first) is interpreted as a floating constant according to the rules of
17826 <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
17827 if neither an exponent part nor a decimal-point wide character appears in a decimal
17828 floating point number, or if a binary exponent part does not appear in a hexadecimal
17829 floating point number, an exponent part of the appropriate type with value zero is
17830 assumed to follow the last digit in the string. If the subject sequence begins with a minus
17831 sign, the sequence is interpreted as negated.<sup><a href="#note294"><b>294)</b></a></sup> A wide character sequence INF or
17832 INFINITY is interpreted as an infinity, if representable in the return type, else like a
17833 floating constant that is too large for the range of the return type. A wide character
17834 sequence NAN or NAN(n-wchar-sequenceopt) is interpreted as a quiet NaN, if supported
17835 in the return type, else like a subject sequence part that does not have the expected form;
17836 the meaning of the n-wchar sequences is implementation-defined.<sup><a href="#note295"><b>295)</b></a></sup> A pointer to the
17837 final wide string is stored in the object pointed to by endptr, provided that endptr is
17838 not a null pointer.
17840 If the subject sequence has the hexadecimal form and FLT_RADIX is a power of 2, the
17841 value resulting from the conversion is correctly rounded.
17843 In other than the "C" locale, additional locale-specific subject sequence forms may be
17846 If the subject sequence is empty or does not have the expected form, no conversion is
17847 performed; the value of nptr is stored in the object pointed to by endptr, provided
17848 that endptr is not a null pointer.
17849 Recommended practice
17851 If the subject sequence has the hexadecimal form, FLT_RADIX is not a power of 2, and
17852 the result is not exactly representable, the result should be one of the two numbers in the
17853 appropriate internal format that are adjacent to the hexadecimal floating source value,
17854 with the extra stipulation that the error should have a correct sign for the current rounding
17861 If the subject sequence has the decimal form and at most DECIMAL_DIG (defined in
17862 <a href="#7.7"><float.h></a>) significant digits, the result should be correctly rounded. If the subject
17863 sequence D has the decimal form and more than DECIMAL_DIG significant digits,
17864 consider the two bounding, adjacent decimal strings L and U, both having
17865 DECIMAL_DIG significant digits, such that the values of L, D, and U satisfy L <= D <= U.
17866 The result should be one of the (equal or adjacent) values that would be obtained by
17867 correctly rounding L and U according to the current rounding direction, with the extra
17868 stipulation that the error with respect to D should have a correct sign for the current
17869 rounding direction.<sup><a href="#note296"><b>296)</b></a></sup>
17872 The functions return the converted value, if any. If no conversion could be performed,
17873 zero is returned. If the correct value is outside the range of representable values, plus or
17874 minus HUGE_VAL, HUGE_VALF, or HUGE_VALL is returned (according to the return
17875 type and sign of the value), and the value of the macro ERANGE is stored in errno. If
17876 the result underflows (<a href="#7.12.1">7.12.1</a>), the functions return a value whose magnitude is no greater
17877 than the smallest normalized positive number in the return type; whether errno acquires
17878 the value ERANGE is implementation-defined.
17886 <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
17887 negating the value resulting from converting the corresponding unsigned sequence (see <a href="#F.5">F.5</a>); the two
17888 methods may yield different results if rounding is toward positive or negative infinity. In either case,
17889 the functions honor the sign of zero if floating-point arithmetic supports signed zeros.
17891 <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
17892 the NaN's significand.
17894 <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
17895 to the same internal floating value, but if not will round to adjacent values.
17898 <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>
17902 #include <a href="#7.24"><wchar.h></a>
17904 const wchar_t * restrict nptr,
17905 wchar_t ** restrict endptr,
17907 long long int wcstoll(
17908 const wchar_t * restrict nptr,
17909 wchar_t ** restrict endptr,
17911 unsigned long int wcstoul(
17912 const wchar_t * restrict nptr,
17913 wchar_t ** restrict endptr,
17915 unsigned long long int wcstoull(
17916 const wchar_t * restrict nptr,
17917 wchar_t ** restrict endptr,
17919 <h6>Description</h6>
17921 The wcstol, wcstoll, wcstoul, and wcstoull functions convert the initial
17922 portion of the wide string pointed to by nptr to long int, long long int,
17923 unsigned long int, and unsigned long long int representation,
17924 respectively. First, they decompose the input string into three parts: an initial, possibly
17925 empty, sequence of white-space wide characters (as specified by the iswspace
17926 function), a subject sequence resembling an integer represented in some radix determined
17927 by the value of base, and a final wide string of one or more unrecognized wide
17928 characters, including the terminating null wide character of the input wide string. Then,
17929 they attempt to convert the subject sequence to an integer, and return the result.
17931 If the value of base is zero, the expected form of the subject sequence is that of an
17932 integer constant as described for the corresponding single-byte characters in <a href="#6.4.4.1">6.4.4.1</a>,
17933 optionally preceded by a plus or minus sign, but not including an integer suffix. If the
17934 value of base is between 2 and 36 (inclusive), the expected form of the subject sequence
17935 is a sequence of letters and digits representing an integer with the radix specified by
17936 base, optionally preceded by a plus or minus sign, but not including an integer suffix.
17937 The letters from a (or A) through z (or Z) are ascribed the values 10 through 35; only
17938 letters and digits whose ascribed values are less than that of base are permitted. If the
17939 value of base is 16, the wide characters 0x or 0X may optionally precede the sequence
17940 of letters and digits, following the sign if present.
17943 The subject sequence is defined as the longest initial subsequence of the input wide
17944 string, starting with the first non-white-space wide character, that is of the expected form.
17945 The subject sequence contains no wide characters if the input wide string is empty or
17946 consists entirely of white space, or if the first non-white-space wide character is other
17947 than a sign or a permissible letter or digit.
17949 If the subject sequence has the expected form and the value of base is zero, the sequence
17950 of wide characters starting with the first digit is interpreted as an integer constant
17951 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
17952 value of base is between 2 and 36, it is used as the base for conversion, ascribing to each
17953 letter its value as given above. If the subject sequence begins with a minus sign, the value
17954 resulting from the conversion is negated (in the return type). A pointer to the final wide
17955 string is stored in the object pointed to by endptr, provided that endptr is not a null
17958 In other than the "C" locale, additional locale-specific subject sequence forms may be
17961 If the subject sequence is empty or does not have the expected form, no conversion is
17962 performed; the value of nptr is stored in the object pointed to by endptr, provided
17963 that endptr is not a null pointer.
17966 The wcstol, wcstoll, wcstoul, and wcstoull functions return the converted
17967 value, if any. If no conversion could be performed, zero is returned. If the correct value
17968 is outside the range of representable values, LONG_MIN, LONG_MAX, LLONG_MIN,
17969 LLONG_MAX, ULONG_MAX, or ULLONG_MAX is returned (according to the return type
17970 sign of the value, if any), and the value of the macro ERANGE is stored in errno.
17972 <h5><a name="7.24.4.2" href="#7.24.4.2">7.24.4.2 Wide string copying functions</a></h5>
17974 <h5><a name="7.24.4.2.1" href="#7.24.4.2.1">7.24.4.2.1 The wcscpy function</a></h5>
17978 #include <a href="#7.24"><wchar.h></a>
17979 wchar_t *wcscpy(wchar_t * restrict s1,
17980 const wchar_t * restrict s2);</pre>
17981 <h6>Description</h6>
17983 The wcscpy function copies the wide string pointed to by s2 (including the terminating
17984 null wide character) into the array pointed to by s1.
17987 The wcscpy function returns the value of s1.
17990 <h5><a name="7.24.4.2.2" href="#7.24.4.2.2">7.24.4.2.2 The wcsncpy function</a></h5>
17994 #include <a href="#7.24"><wchar.h></a>
17995 wchar_t *wcsncpy(wchar_t * restrict s1,
17996 const wchar_t * restrict s2,
17998 <h6>Description</h6>
18000 The wcsncpy function copies not more than n wide characters (those that follow a null
18001 wide character are not copied) from the array pointed to by s2 to the array pointed to by
18002 s1.<sup><a href="#note297"><b>297)</b></a></sup>
18004 If the array pointed to by s2 is a wide string that is shorter than n wide characters, null
18005 wide characters are appended to the copy in the array pointed to by s1, until n wide
18006 characters in all have been written.
18009 The wcsncpy function returns the value of s1.
18012 <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
18013 result will not be null-terminated.
18016 <h5><a name="7.24.4.2.3" href="#7.24.4.2.3">7.24.4.2.3 The wmemcpy function</a></h5>
18020 #include <a href="#7.24"><wchar.h></a>
18021 wchar_t *wmemcpy(wchar_t * restrict s1,
18022 const wchar_t * restrict s2,
18024 <h6>Description</h6>
18026 The wmemcpy function copies n wide characters from the object pointed to by s2 to the
18027 object pointed to by s1.
18030 The wmemcpy function returns the value of s1.
18037 <h5><a name="7.24.4.2.4" href="#7.24.4.2.4">7.24.4.2.4 The wmemmove function</a></h5>
18041 #include <a href="#7.24"><wchar.h></a>
18042 wchar_t *wmemmove(wchar_t *s1, const wchar_t *s2,
18044 <h6>Description</h6>
18046 The wmemmove function copies n wide characters from the object pointed to by s2 to
18047 the object pointed to by s1. Copying takes place as if the n wide characters from the
18048 object pointed to by s2 are first copied into a temporary array of n wide characters that
18049 does not overlap the objects pointed to by s1 or s2, and then the n wide characters from
18050 the temporary array are copied into the object pointed to by s1.
18053 The wmemmove function returns the value of s1.
18055 <h5><a name="7.24.4.3" href="#7.24.4.3">7.24.4.3 Wide string concatenation functions</a></h5>
18057 <h5><a name="7.24.4.3.1" href="#7.24.4.3.1">7.24.4.3.1 The wcscat function</a></h5>
18061 #include <a href="#7.24"><wchar.h></a>
18062 wchar_t *wcscat(wchar_t * restrict s1,
18063 const wchar_t * restrict s2);</pre>
18064 <h6>Description</h6>
18066 The wcscat function appends a copy of the wide string pointed to by s2 (including the
18067 terminating null wide character) to the end of the wide string pointed to by s1. The initial
18068 wide character of s2 overwrites the null wide character at the end of s1.
18071 The wcscat function returns the value of s1.
18073 <h5><a name="7.24.4.3.2" href="#7.24.4.3.2">7.24.4.3.2 The wcsncat function</a></h5>
18077 #include <a href="#7.24"><wchar.h></a>
18078 wchar_t *wcsncat(wchar_t * restrict s1,
18079 const wchar_t * restrict s2,
18081 <h6>Description</h6>
18083 The wcsncat function appends not more than n wide characters (a null wide character
18084 and those that follow it are not appended) from the array pointed to by s2 to the end of
18086 the wide string pointed to by s1. The initial wide character of s2 overwrites the null
18087 wide character at the end of s1. A terminating null wide character is always appended to
18088 the result.<sup><a href="#note298"><b>298)</b></a></sup>
18091 The wcsncat function returns the value of s1.
18094 <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
18098 <h5><a name="7.24.4.4" href="#7.24.4.4">7.24.4.4 Wide string comparison functions</a></h5>
18100 Unless explicitly stated otherwise, the functions described in this subclause order two
18101 wide characters the same way as two integers of the underlying integer type designated
18104 <h5><a name="7.24.4.4.1" href="#7.24.4.4.1">7.24.4.4.1 The wcscmp function</a></h5>
18108 #include <a href="#7.24"><wchar.h></a>
18109 int wcscmp(const wchar_t *s1, const wchar_t *s2);</pre>
18110 <h6>Description</h6>
18112 The wcscmp function compares the wide string pointed to by s1 to the wide string
18116 The wcscmp function returns an integer greater than, equal to, or less than zero,
18117 accordingly as the wide string pointed to by s1 is greater than, equal to, or less than the
18118 wide string pointed to by s2.
18120 <h5><a name="7.24.4.4.2" href="#7.24.4.4.2">7.24.4.4.2 The wcscoll function</a></h5>
18124 #include <a href="#7.24"><wchar.h></a>
18125 int wcscoll(const wchar_t *s1, const wchar_t *s2);</pre>
18126 <h6>Description</h6>
18128 The wcscoll function compares the wide string pointed to by s1 to the wide string
18129 pointed to by s2, both interpreted as appropriate to the LC_COLLATE category of the
18133 The wcscoll function returns an integer greater than, equal to, or less than zero,
18134 accordingly as the wide string pointed to by s1 is greater than, equal to, or less than the
18138 wide string pointed to by s2 when both are interpreted as appropriate to the current
18141 <h5><a name="7.24.4.4.3" href="#7.24.4.4.3">7.24.4.4.3 The wcsncmp function</a></h5>
18145 #include <a href="#7.24"><wchar.h></a>
18146 int wcsncmp(const wchar_t *s1, const wchar_t *s2,
18148 <h6>Description</h6>
18150 The wcsncmp function compares not more than n wide characters (those that follow a
18151 null wide character are not compared) from the array pointed to by s1 to the array
18155 The wcsncmp function returns an integer greater than, equal to, or less than zero,
18156 accordingly as the possibly null-terminated array pointed to by s1 is greater than, equal
18157 to, or less than the possibly null-terminated array pointed to by s2.
18159 <h5><a name="7.24.4.4.4" href="#7.24.4.4.4">7.24.4.4.4 The wcsxfrm function</a></h5>
18163 #include <a href="#7.24"><wchar.h></a>
18164 size_t wcsxfrm(wchar_t * restrict s1,
18165 const wchar_t * restrict s2,
18167 <h6>Description</h6>
18169 The wcsxfrm function transforms the wide string pointed to by s2 and places the
18170 resulting wide string into the array pointed to by s1. The transformation is such that if
18171 the wcscmp function is applied to two transformed wide strings, it returns a value greater
18172 than, equal to, or less than zero, corresponding to the result of the wcscoll function
18173 applied to the same two original wide strings. No more than n wide characters are placed
18174 into the resulting array pointed to by s1, including the terminating null wide character. If
18175 n is zero, s1 is permitted to be a null pointer.
18178 The wcsxfrm function returns the length of the transformed wide string (not including
18179 the terminating null wide character). If the value returned is n or greater, the contents of
18180 the array pointed to by s1 are indeterminate.
18182 EXAMPLE The value of the following expression is the length of the array needed to hold the
18183 transformation of the wide string pointed to by s:
18186 1 + wcsxfrm(NULL, s, 0)</pre>
18189 <h5><a name="7.24.4.4.5" href="#7.24.4.4.5">7.24.4.4.5 The wmemcmp function</a></h5>
18193 #include <a href="#7.24"><wchar.h></a>
18194 int wmemcmp(const wchar_t *s1, const wchar_t *s2,
18196 <h6>Description</h6>
18198 The wmemcmp function compares the first n wide characters of the object pointed to by
18199 s1 to the first n wide characters of the object pointed to by s2.
18202 The wmemcmp function returns an integer greater than, equal to, or less than zero,
18203 accordingly as the object pointed to by s1 is greater than, equal to, or less than the object
18206 <h5><a name="7.24.4.5" href="#7.24.4.5">7.24.4.5 Wide string search functions</a></h5>
18208 <h5><a name="7.24.4.5.1" href="#7.24.4.5.1">7.24.4.5.1 The wcschr function</a></h5>
18212 #include <a href="#7.24"><wchar.h></a>
18213 wchar_t *wcschr(const wchar_t *s, wchar_t c);</pre>
18214 <h6>Description</h6>
18216 The wcschr function locates the first occurrence of c in the wide string pointed to by s.
18217 The terminating null wide character is considered to be part of the wide string.
18220 The wcschr function returns a pointer to the located wide character, or a null pointer if
18221 the wide character does not occur in the wide string.
18223 <h5><a name="7.24.4.5.2" href="#7.24.4.5.2">7.24.4.5.2 The wcscspn function</a></h5>
18227 #include <a href="#7.24"><wchar.h></a>
18228 size_t wcscspn(const wchar_t *s1, const wchar_t *s2);</pre>
18229 <h6>Description</h6>
18231 The wcscspn function computes the length of the maximum initial segment of the wide
18232 string pointed to by s1 which consists entirely of wide characters not from the wide
18233 string pointed to by s2.
18237 The wcscspn function returns the length of the segment.
18239 <h5><a name="7.24.4.5.3" href="#7.24.4.5.3">7.24.4.5.3 The wcspbrk function</a></h5>
18243 #include <a href="#7.24"><wchar.h></a>
18244 wchar_t *wcspbrk(const wchar_t *s1, const wchar_t *s2);</pre>
18245 <h6>Description</h6>
18247 The wcspbrk function locates the first occurrence in the wide string pointed to by s1 of
18248 any wide character from the wide string pointed to by s2.
18251 The wcspbrk function returns a pointer to the wide character in s1, or a null pointer if
18252 no wide character from s2 occurs in s1.
18254 <h5><a name="7.24.4.5.4" href="#7.24.4.5.4">7.24.4.5.4 The wcsrchr function</a></h5>
18258 #include <a href="#7.24"><wchar.h></a>
18259 wchar_t *wcsrchr(const wchar_t *s, wchar_t c);</pre>
18260 <h6>Description</h6>
18262 The wcsrchr function locates the last occurrence of c in the wide string pointed to by
18263 s. The terminating null wide character is considered to be part of the wide string.
18266 The wcsrchr function returns a pointer to the wide character, or a null pointer if c does
18267 not occur in the wide string.
18269 <h5><a name="7.24.4.5.5" href="#7.24.4.5.5">7.24.4.5.5 The wcsspn function</a></h5>
18273 #include <a href="#7.24"><wchar.h></a>
18274 size_t wcsspn(const wchar_t *s1, const wchar_t *s2);</pre>
18275 <h6>Description</h6>
18277 The wcsspn function computes the length of the maximum initial segment of the wide
18278 string pointed to by s1 which consists entirely of wide characters from the wide string
18282 The wcsspn function returns the length of the segment.
18285 <h5><a name="7.24.4.5.6" href="#7.24.4.5.6">7.24.4.5.6 The wcsstr function</a></h5>
18289 #include <a href="#7.24"><wchar.h></a>
18290 wchar_t *wcsstr(const wchar_t *s1, const wchar_t *s2);</pre>
18291 <h6>Description</h6>
18293 The wcsstr function locates the first occurrence in the wide string pointed to by s1 of
18294 the sequence of wide characters (excluding the terminating null wide character) in the
18295 wide string pointed to by s2.
18298 The wcsstr function returns a pointer to the located wide string, or a null pointer if the
18299 wide string is not found. If s2 points to a wide string with zero length, the function
18302 <h5><a name="7.24.4.5.7" href="#7.24.4.5.7">7.24.4.5.7 The wcstok function</a></h5>
18306 #include <a href="#7.24"><wchar.h></a>
18307 wchar_t *wcstok(wchar_t * restrict s1,
18308 const wchar_t * restrict s2,
18309 wchar_t ** restrict ptr);</pre>
18310 <h6>Description</h6>
18312 A sequence of calls to the wcstok function breaks the wide string pointed to by s1 into
18313 a sequence of tokens, each of which is delimited by a wide character from the wide string
18314 pointed to by s2. The third argument points to a caller-provided wchar_t pointer into
18315 which the wcstok function stores information necessary for it to continue scanning the
18318 The first call in a sequence has a non-null first argument and stores an initial value in the
18319 object pointed to by ptr. Subsequent calls in the sequence have a null first argument and
18320 the object pointed to by ptr is required to have the value stored by the previous call in
18321 the sequence, which is then updated. The separator wide string pointed to by s2 may be
18322 different from call to call.
18324 The first call in the sequence searches the wide string pointed to by s1 for the first wide
18325 character that is not contained in the current separator wide string pointed to by s2. If no
18326 such wide character is found, then there are no tokens in the wide string pointed to by s1
18327 and the wcstok function returns a null pointer. If such a wide character is found, it is
18328 the start of the first token.
18330 The wcstok function then searches from there for a wide character that is contained in
18331 the current separator wide string. If no such wide character is found, the current token
18333 extends to the end of the wide string pointed to by s1, and subsequent searches in the
18334 same wide string for a token return a null pointer. If such a wide character is found, it is
18335 overwritten by a null wide character, which terminates the current token.
18337 In all cases, the wcstok function stores sufficient information in the pointer pointed to
18338 by ptr so that subsequent calls, with a null pointer for s1 and the unmodified pointer
18339 value for ptr, shall start searching just past the element overwritten by a null wide
18340 character (if any).
18343 The wcstok function returns a pointer to the first wide character of a token, or a null
18344 pointer if there is no token.
18348 #include <a href="#7.24"><wchar.h></a>
18349 static wchar_t str1[] = L"?a???b,,,#c";
18350 static wchar_t str2[] = L"\t \t";
18351 wchar_t *t, *ptr1, *ptr2;
18352 t = wcstok(str1, L"?", &ptr1); // t points to the token L"a"
18353 t = wcstok(NULL, L",", &ptr1); // t points to the token L"??b"
18354 t = wcstok(str2, L" \t", &ptr2); // t is a null pointer
18355 t = wcstok(NULL, L"#,", &ptr1); // t points to the token L"c"
18356 t = wcstok(NULL, L"?", &ptr1); // t is a null pointer</pre>
18359 <h5><a name="7.24.4.5.8" href="#7.24.4.5.8">7.24.4.5.8 The wmemchr function</a></h5>
18363 #include <a href="#7.24"><wchar.h></a>
18364 wchar_t *wmemchr(const wchar_t *s, wchar_t c,
18366 <h6>Description</h6>
18368 The wmemchr function locates the first occurrence of c in the initial n wide characters of
18369 the object pointed to by s.
18372 The wmemchr function returns a pointer to the located wide character, or a null pointer if
18373 the wide character does not occur in the object.
18376 <h5><a name="7.24.4.6" href="#7.24.4.6">7.24.4.6 Miscellaneous functions</a></h5>
18378 <h5><a name="7.24.4.6.1" href="#7.24.4.6.1">7.24.4.6.1 The wcslen function</a></h5>
18382 #include <a href="#7.24"><wchar.h></a>
18383 size_t wcslen(const wchar_t *s);</pre>
18384 <h6>Description</h6>
18386 The wcslen function computes the length of the wide string pointed to by s.
18389 The wcslen function returns the number of wide characters that precede the terminating
18390 null wide character.
18392 <h5><a name="7.24.4.6.2" href="#7.24.4.6.2">7.24.4.6.2 The wmemset function</a></h5>
18396 #include <a href="#7.24"><wchar.h></a>
18397 wchar_t *wmemset(wchar_t *s, wchar_t c, size_t n);</pre>
18398 <h6>Description</h6>
18400 The wmemset function copies the value of c into each of the first n wide characters of
18401 the object pointed to by s.
18404 The wmemset function returns the value of s.
18406 <h4><a name="7.24.5" href="#7.24.5">7.24.5 Wide character time conversion functions</a></h4>
18408 <h5><a name="7.24.5.1" href="#7.24.5.1">7.24.5.1 The wcsftime function</a></h5>
18412 #include <a href="#7.23"><time.h></a>
18413 #include <a href="#7.24"><wchar.h></a>
18414 size_t wcsftime(wchar_t * restrict s,
18416 const wchar_t * restrict format,
18417 const struct tm * restrict timeptr);</pre>
18418 <h6>Description</h6>
18420 The wcsftime function is equivalent to the strftime function, except that:
18422 <li> The argument s points to the initial element of an array of wide characters into which
18423 the generated output is to be placed.
18425 <li> The argument maxsize indicates the limiting number of wide characters.
18426 <li> The argument format is a wide string and the conversion specifiers are replaced by
18427 corresponding sequences of wide characters.
18428 <li> The return value indicates the number of wide characters.
18432 If the total number of resulting wide characters including the terminating null wide
18433 character is not more than maxsize, the wcsftime function returns the number of
18434 wide characters placed into the array pointed to by s not including the terminating null
18435 wide character. Otherwise, zero is returned and the contents of the array are
18438 <h4><a name="7.24.6" href="#7.24.6">7.24.6 Extended multibyte/wide character conversion utilities</a></h4>
18440 The header <a href="#7.24"><wchar.h></a> declares an extended set of functions useful for conversion
18441 between multibyte characters and wide characters.
18443 Most of the following functions -- those that are listed as ''restartable'', <a href="#7.24.6.3">7.24.6.3</a> and
18444 <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
18445 to describe the current conversion state from a particular multibyte character sequence to
18446 a wide character sequence (or the reverse) under the rules of a particular setting for the
18447 LC_CTYPE category of the current locale.
18449 The initial conversion state corresponds, for a conversion in either direction, to the
18450 beginning of a new multibyte character in the initial shift state. A zero-valued
18451 mbstate_t object is (at least) one way to describe an initial conversion state. A zero-
18452 valued mbstate_t object can be used to initiate conversion involving any multibyte
18453 character sequence, in any LC_CTYPE category setting. If an mbstate_t object has
18454 been altered by any of the functions described in this subclause, and is then used with a
18455 different multibyte character sequence, or in the other conversion direction, or with a
18456 different LC_CTYPE category setting than on earlier function calls, the behavior is
18457 undefined.<sup><a href="#note299"><b>299)</b></a></sup>
18459 On entry, each function takes the described conversion state (either internal or pointed to
18460 by an argument) as current. The conversion state described by the pointed-to object is
18461 altered as needed to track the shift state, and the position within a multibyte character, for
18462 the associated multibyte character sequence.
18470 <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
18471 mbsrtowcs functions as long as they are used to step sequentially through the same multibyte
18475 <h5><a name="7.24.6.1" href="#7.24.6.1">7.24.6.1 Single-byte/wide character conversion functions</a></h5>
18477 <h5><a name="7.24.6.1.1" href="#7.24.6.1.1">7.24.6.1.1 The btowc function</a></h5>
18481 #include <a href="#7.19"><stdio.h></a>
18482 #include <a href="#7.24"><wchar.h></a>
18483 wint_t btowc(int c);</pre>
18484 <h6>Description</h6>
18486 The btowc function determines whether c constitutes a valid single-byte character in the
18487 initial shift state.
18490 The btowc function returns WEOF if c has the value EOF or if (unsigned char)c
18491 does not constitute a valid single-byte character in the initial shift state. Otherwise, it
18492 returns the wide character representation of that character.
18494 <h5><a name="7.24.6.1.2" href="#7.24.6.1.2">7.24.6.1.2 The wctob function</a></h5>
18498 #include <a href="#7.19"><stdio.h></a>
18499 #include <a href="#7.24"><wchar.h></a>
18500 int wctob(wint_t c);</pre>
18501 <h6>Description</h6>
18503 The wctob function determines whether c corresponds to a member of the extended
18504 character set whose multibyte character representation is a single byte when in the initial
18508 The wctob function returns EOF if c does not correspond to a multibyte character with
18509 length one in the initial shift state. Otherwise, it returns the single-byte representation of
18510 that character as an unsigned char converted to an int.
18512 <h5><a name="7.24.6.2" href="#7.24.6.2">7.24.6.2 Conversion state functions</a></h5>
18514 <h5><a name="7.24.6.2.1" href="#7.24.6.2.1">7.24.6.2.1 The mbsinit function</a></h5>
18518 #include <a href="#7.24"><wchar.h></a>
18519 int mbsinit(const mbstate_t *ps);</pre>
18520 <h6>Description</h6>
18522 If ps is not a null pointer, the mbsinit function determines whether the pointed-to
18523 mbstate_t object describes an initial conversion state.
18527 The mbsinit function returns nonzero if ps is a null pointer or if the pointed-to object
18528 describes an initial conversion state; otherwise, it returns zero.
18530 <h5><a name="7.24.6.3" href="#7.24.6.3">7.24.6.3 Restartable multibyte/wide character conversion functions</a></h5>
18532 These functions differ from the corresponding multibyte character functions of <a href="#7.20.7">7.20.7</a>
18533 (mblen, mbtowc, and wctomb) in that they have an extra parameter, ps, of type
18534 pointer to mbstate_t that points to an object that can completely describe the current
18535 conversion state of the associated multibyte character sequence. If ps is a null pointer,
18536 each function uses its own internal mbstate_t object instead, which is initialized at
18537 program startup to the initial conversion state. The implementation behaves as if no
18538 library function calls these functions with a null pointer for ps.
18540 Also unlike their corresponding functions, the return value does not represent whether the
18541 encoding is state-dependent.
18543 <h5><a name="7.24.6.3.1" href="#7.24.6.3.1">7.24.6.3.1 The mbrlen function</a></h5>
18547 #include <a href="#7.24"><wchar.h></a>
18548 size_t mbrlen(const char * restrict s,
18550 mbstate_t * restrict ps);</pre>
18551 <h6>Description</h6>
18553 The mbrlen function is equivalent to the call:
18555 mbrtowc(NULL, s, n, ps != NULL ? ps : &internal)</pre>
18556 where internal is the mbstate_t object for the mbrlen function, except that the
18557 expression designated by ps is evaluated only once.
18560 The mbrlen function returns a value between zero and n, inclusive, (size_t)(-2),
18562 <p><b> Forward references</b>: the mbrtowc function (<a href="#7.24.6.3.2">7.24.6.3.2</a>).
18565 <h5><a name="7.24.6.3.2" href="#7.24.6.3.2">7.24.6.3.2 The mbrtowc function</a></h5>
18569 #include <a href="#7.24"><wchar.h></a>
18570 size_t mbrtowc(wchar_t * restrict pwc,
18571 const char * restrict s,
18573 mbstate_t * restrict ps);</pre>
18574 <h6>Description</h6>
18576 If s is a null pointer, the mbrtowc function is equivalent to the call:
18578 mbrtowc(NULL, "", 1, ps)</pre>
18579 In this case, the values of the parameters pwc and n are ignored.
18581 If s is not a null pointer, the mbrtowc function inspects at most n bytes beginning with
18582 the byte pointed to by s to determine the number of bytes needed to complete the next
18583 multibyte character (including any shift sequences). If the function determines that the
18584 next multibyte character is complete and valid, it determines the value of the
18585 corresponding wide character and then, if pwc is not a null pointer, stores that value in
18586 the object pointed to by pwc. If the corresponding wide character is the null wide
18587 character, the resulting state described is the initial conversion state.
18590 The mbrtowc function returns the first of the following that applies (given the current
18592 0 if the next n or fewer bytes complete the multibyte character that
18594 corresponds to the null wide character (which is the value stored).</pre>
18595 between 1 and n inclusive if the next n or fewer bytes complete a valid multibyte
18597 character (which is the value stored); the value returned is the number
18598 of bytes that complete the multibyte character.</pre>
18599 (size_t)(-2) if the next n bytes contribute to an incomplete (but potentially valid)
18601 multibyte character, and all n bytes have been processed (no value is
18602 stored).<sup><a href="#note300"><b>300)</b></a></sup></pre>
18603 (size_t)(-1) if an encoding error occurs, in which case the next n or fewer bytes
18605 do not contribute to a complete and valid multibyte character (no
18606 value is stored); the value of the macro EILSEQ is stored in errno,
18607 and the conversion state is unspecified.</pre>
18612 <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
18613 sequence of redundant shift sequences (for implementations with state-dependent encodings).
18616 <h5><a name="7.24.6.3.3" href="#7.24.6.3.3">7.24.6.3.3 The wcrtomb function</a></h5>
18620 #include <a href="#7.24"><wchar.h></a>
18621 size_t wcrtomb(char * restrict s,
18623 mbstate_t * restrict ps);</pre>
18624 <h6>Description</h6>
18626 If s is a null pointer, the wcrtomb function is equivalent to the call
18628 wcrtomb(buf, L'\0', ps)</pre>
18629 where buf is an internal buffer.
18631 If s is not a null pointer, the wcrtomb function determines the number of bytes needed
18632 to represent the multibyte character that corresponds to the wide character given by wc
18633 (including any shift sequences), and stores the multibyte character representation in the
18634 array whose first element is pointed to by s. At most MB_CUR_MAX bytes are stored. If
18635 wc is a null wide character, a null byte is stored, preceded by any shift sequence needed
18636 to restore the initial shift state; the resulting state described is the initial conversion state.
18639 The wcrtomb function returns the number of bytes stored in the array object (including
18640 any shift sequences). When wc is not a valid wide character, an encoding error occurs:
18641 the function stores the value of the macro EILSEQ in errno and returns
18642 (size_t)(-1); the conversion state is unspecified.
18644 <h5><a name="7.24.6.4" href="#7.24.6.4">7.24.6.4 Restartable multibyte/wide string conversion functions</a></h5>
18646 These functions differ from the corresponding multibyte string functions of <a href="#7.20.8">7.20.8</a>
18647 (mbstowcs and wcstombs) in that they have an extra parameter, ps, of type pointer to
18648 mbstate_t that points to an object that can completely describe the current conversion
18649 state of the associated multibyte character sequence. If ps is a null pointer, each function
18650 uses its own internal mbstate_t object instead, which is initialized at program startup
18651 to the initial conversion state. The implementation behaves as if no library function calls
18652 these functions with a null pointer for ps.
18654 Also unlike their corresponding functions, the conversion source parameter, src, has a
18655 pointer-to-pointer type. When the function is storing the results of conversions (that is,
18656 when dst is not a null pointer), the pointer object pointed to by this parameter is updated
18657 to reflect the amount of the source processed by that invocation.
18660 <h5><a name="7.24.6.4.1" href="#7.24.6.4.1">7.24.6.4.1 The mbsrtowcs function</a></h5>
18664 #include <a href="#7.24"><wchar.h></a>
18665 size_t mbsrtowcs(wchar_t * restrict dst,
18666 const char ** restrict src,
18668 mbstate_t * restrict ps);</pre>
18669 <h6>Description</h6>
18671 The mbsrtowcs function converts a sequence of multibyte characters that begins in the
18672 conversion state described by the object pointed to by ps, from the array indirectly
18673 pointed to by src into a sequence of corresponding wide characters. If dst is not a null
18674 pointer, the converted characters are stored into the array pointed to by dst. Conversion
18675 continues up to and including a terminating null character, which is also stored.
18676 Conversion stops earlier in two cases: when a sequence of bytes is encountered that does
18677 not form a valid multibyte character, or (if dst is not a null pointer) when len wide
18678 characters have been stored into the array pointed to by dst.<sup><a href="#note301"><b>301)</b></a></sup> Each conversion takes
18679 place as if by a call to the mbrtowc function.
18681 If dst is not a null pointer, the pointer object pointed to by src is assigned either a null
18682 pointer (if conversion stopped due to reaching a terminating null character) or the address
18683 just past the last multibyte character converted (if any). If conversion stopped due to
18684 reaching a terminating null character and if dst is not a null pointer, the resulting state
18685 described is the initial conversion state.
18688 If the input conversion encounters a sequence of bytes that do not form a valid multibyte
18689 character, an encoding error occurs: the mbsrtowcs function stores the value of the
18690 macro EILSEQ in errno and returns (size_t)(-1); the conversion state is
18691 unspecified. Otherwise, it returns the number of multibyte characters successfully
18692 converted, not including the terminating null character (if any).
18700 <p><small><a name="note301" href="#note301">301)</a> Thus, the value of len is ignored if dst is a null pointer.
18703 <h5><a name="7.24.6.4.2" href="#7.24.6.4.2">7.24.6.4.2 The wcsrtombs function</a></h5>
18707 #include <a href="#7.24"><wchar.h></a>
18708 size_t wcsrtombs(char * restrict dst,
18709 const wchar_t ** restrict src,
18711 mbstate_t * restrict ps);</pre>
18712 <h6>Description</h6>
18714 The wcsrtombs function converts a sequence of wide characters from the array
18715 indirectly pointed to by src into a sequence of corresponding multibyte characters that
18716 begins in the conversion state described by the object pointed to by ps. If dst is not a
18717 null pointer, the converted characters are then stored into the array pointed to by dst.
18718 Conversion continues up to and including a terminating null wide character, which is also
18719 stored. Conversion stops earlier in two cases: when a wide character is reached that does
18720 not correspond to a valid multibyte character, or (if dst is not a null pointer) when the
18721 next multibyte character would exceed the limit of len total bytes to be stored into the
18722 array pointed to by dst. Each conversion takes place as if by a call to the wcrtomb
18723 function.<sup><a href="#note302"><b>302)</b></a></sup>
18725 If dst is not a null pointer, the pointer object pointed to by src is assigned either a null
18726 pointer (if conversion stopped due to reaching a terminating null wide character) or the
18727 address just past the last wide character converted (if any). If conversion stopped due to
18728 reaching a terminating null wide character, the resulting state described is the initial
18732 If conversion stops because a wide character is reached that does not correspond to a
18733 valid multibyte character, an encoding error occurs: the wcsrtombs function stores the
18734 value of the macro EILSEQ in errno and returns (size_t)(-1); the conversion
18735 state is unspecified. Otherwise, it returns the number of bytes in the resulting multibyte
18736 character sequence, not including the terminating null character (if any).
18744 <p><small><a name="note302" href="#note302">302)</a> If conversion stops because a terminating null wide character has been reached, the bytes stored
18745 include those necessary to reach the initial shift state immediately before the null byte.
18748 <h3><a name="7.25" href="#7.25">7.25 Wide character classification and mapping utilities <wctype.h></a></h3>
18750 <h4><a name="7.25.1" href="#7.25.1">7.25.1 Introduction</a></h4>
18752 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>
18754 The types declared are
18757 described in <a href="#7.24.1">7.24.1</a>;
18760 which is a scalar type that can hold values which represent locale-specific character
18764 which is a scalar type that can hold values which represent locale-specific character
18767 The macro defined is WEOF (described in <a href="#7.24.1">7.24.1</a>).
18769 The functions declared are grouped as follows:
18771 <li> Functions that provide wide character classification;
18772 <li> Extensible functions that provide wide character classification;
18773 <li> Functions that provide wide character case mapping;
18774 <li> Extensible functions that provide wide character mapping.
18777 For all functions described in this subclause that accept an argument of type wint_t, the
18778 value shall be representable as a wchar_t or shall equal the value of the macro WEOF. If
18779 this argument has any other value, the behavior is undefined.
18781 The behavior of these functions is affected by the LC_CTYPE category of the current
18790 <p><small><a name="note303" href="#note303">303)</a> See ''future library directions'' (<a href="#7.26.13">7.26.13</a>).
18793 <h4><a name="7.25.2" href="#7.25.2">7.25.2 Wide character classification utilities</a></h4>
18795 The header <a href="#7.25"><wctype.h></a> declares several functions useful for classifying wide
18798 The term printing wide character refers to a member of a locale-specific set of wide
18799 characters, each of which occupies at least one printing position on a display device. The
18800 term control wide character refers to a member of a locale-specific set of wide characters
18801 that are not printing wide characters.
18803 <h5><a name="7.25.2.1" href="#7.25.2.1">7.25.2.1 Wide character classification functions</a></h5>
18805 The functions in this subclause return nonzero (true) if and only if the value of the
18806 argument wc conforms to that in the description of the function.
18808 Each of the following functions returns true for each wide character that corresponds (as
18809 if by a call to the wctob function) to a single-byte character for which the corresponding
18810 character classification function from <a href="#7.4.1">7.4.1</a> returns true, except that the iswgraph and
18811 iswpunct functions may differ with respect to wide characters other than L' ' that are
18812 both printing and white-space wide characters.<sup><a href="#note304"><b>304)</b></a></sup>
18813 <p><b> Forward references</b>: the wctob function (<a href="#7.24.6.1.2">7.24.6.1.2</a>).
18816 <p><small><a name="note304" href="#note304">304)</a> For example, if the expression isalpha(wctob(wc)) evaluates to true, then the call
18817 iswalpha(wc) also returns true. But, if the expression isgraph(wctob(wc)) evaluates to true
18818 (which cannot occur for wc == L' ' of course), then either iswgraph(wc) or iswprint(wc)
18819 && iswspace(wc) is true, but not both.
18822 <h5><a name="7.25.2.1.1" href="#7.25.2.1.1">7.25.2.1.1 The iswalnum function</a></h5>
18826 #include <a href="#7.25"><wctype.h></a>
18827 int iswalnum(wint_t wc);</pre>
18828 <h6>Description</h6>
18830 The iswalnum function tests for any wide character for which iswalpha or
18833 <h5><a name="7.25.2.1.2" href="#7.25.2.1.2">7.25.2.1.2 The iswalpha function</a></h5>
18837 #include <a href="#7.25"><wctype.h></a>
18838 int iswalpha(wint_t wc);</pre>
18839 <h6>Description</h6>
18841 The iswalpha function tests for any wide character for which iswupper or
18842 iswlower is true, or any wide character that is one of a locale-specific set of alphabetic
18845 wide characters for which none of iswcntrl, iswdigit, iswpunct, or iswspace
18846 is true.<sup><a href="#note305"><b>305)</b></a></sup>
18849 <p><small><a name="note305" href="#note305">305)</a> The functions iswlower and iswupper test true or false separately for each of these additional
18850 wide characters; all four combinations are possible.
18853 <h5><a name="7.25.2.1.3" href="#7.25.2.1.3">7.25.2.1.3 The iswblank function</a></h5>
18857 #include <a href="#7.25"><wctype.h></a>
18858 int iswblank(wint_t wc);</pre>
18859 <h6>Description</h6>
18861 The iswblank function tests for any wide character that is a standard blank wide
18862 character or is one of a locale-specific set of wide characters for which iswspace is true
18863 and that is used to separate words within a line of text. The standard blank wide
18864 characters are the following: space (L' '), and horizontal tab (L'\t'). In the "C"
18865 locale, iswblank returns true only for the standard blank characters.
18867 <h5><a name="7.25.2.1.4" href="#7.25.2.1.4">7.25.2.1.4 The iswcntrl function</a></h5>
18871 #include <a href="#7.25"><wctype.h></a>
18872 int iswcntrl(wint_t wc);</pre>
18873 <h6>Description</h6>
18875 The iswcntrl function tests for any control wide character.
18877 <h5><a name="7.25.2.1.5" href="#7.25.2.1.5">7.25.2.1.5 The iswdigit function</a></h5>
18881 #include <a href="#7.25"><wctype.h></a>
18882 int iswdigit(wint_t wc);</pre>
18883 <h6>Description</h6>
18885 The iswdigit function tests for any wide character that corresponds to a decimal-digit
18886 character (as defined in <a href="#5.2.1">5.2.1</a>).
18888 <h5><a name="7.25.2.1.6" href="#7.25.2.1.6">7.25.2.1.6 The iswgraph function</a></h5>
18892 #include <a href="#7.25"><wctype.h></a>
18893 int iswgraph(wint_t wc);</pre>
18899 <h6>Description</h6>
18901 The iswgraph function tests for any wide character for which iswprint is true and
18902 iswspace is false.<sup><a href="#note306"><b>306)</b></a></sup>
18905 <p><small><a name="note306" href="#note306">306)</a> Note that the behavior of the iswgraph and iswpunct functions may differ from their
18906 corresponding functions in <a href="#7.4.1">7.4.1</a> with respect to printing, white-space, single-byte execution
18907 characters other than ' '.
18910 <h5><a name="7.25.2.1.7" href="#7.25.2.1.7">7.25.2.1.7 The iswlower function</a></h5>
18914 #include <a href="#7.25"><wctype.h></a>
18915 int iswlower(wint_t wc);</pre>
18916 <h6>Description</h6>
18918 The iswlower function tests for any wide character that corresponds to a lowercase
18919 letter or is one of a locale-specific set of wide characters for which none of iswcntrl,
18920 iswdigit, iswpunct, or iswspace is true.
18922 <h5><a name="7.25.2.1.8" href="#7.25.2.1.8">7.25.2.1.8 The iswprint function</a></h5>
18926 #include <a href="#7.25"><wctype.h></a>
18927 int iswprint(wint_t wc);</pre>
18928 <h6>Description</h6>
18930 The iswprint function tests for any printing wide character.
18932 <h5><a name="7.25.2.1.9" href="#7.25.2.1.9">7.25.2.1.9 The iswpunct function</a></h5>
18936 #include <a href="#7.25"><wctype.h></a>
18937 int iswpunct(wint_t wc);</pre>
18938 <h6>Description</h6>
18940 The iswpunct function tests for any printing wide character that is one of a locale-
18941 specific set of punctuation wide characters for which neither iswspace nor iswalnum
18944 <h5><a name="7.25.2.1.10" href="#7.25.2.1.10">7.25.2.1.10 The iswspace function</a></h5>
18948 #include <a href="#7.25"><wctype.h></a>
18949 int iswspace(wint_t wc);</pre>
18954 <h6>Description</h6>
18956 The iswspace function tests for any wide character that corresponds to a locale-specific
18957 set of white-space wide characters for which none of iswalnum, iswgraph, or
18960 <h5><a name="7.25.2.1.11" href="#7.25.2.1.11">7.25.2.1.11 The iswupper function</a></h5>
18964 #include <a href="#7.25"><wctype.h></a>
18965 int iswupper(wint_t wc);</pre>
18966 <h6>Description</h6>
18968 The iswupper function tests for any wide character that corresponds to an uppercase
18969 letter or is one of a locale-specific set of wide characters for which none of iswcntrl,
18970 iswdigit, iswpunct, or iswspace is true.
18972 <h5><a name="7.25.2.1.12" href="#7.25.2.1.12">7.25.2.1.12 The iswxdigit function</a></h5>
18976 #include <a href="#7.25"><wctype.h></a>
18977 int iswxdigit(wint_t wc);</pre>
18978 <h6>Description</h6>
18980 The iswxdigit function tests for any wide character that corresponds to a
18981 hexadecimal-digit character (as defined in <a href="#6.4.4.1">6.4.4.1</a>).
18983 <h5><a name="7.25.2.2" href="#7.25.2.2">7.25.2.2 Extensible wide character classification functions</a></h5>
18985 The functions wctype and iswctype provide extensible wide character classification
18986 as well as testing equivalent to that performed by the functions described in the previous
18987 subclause (<a href="#7.25.2.1">7.25.2.1</a>).
18989 <h5><a name="7.25.2.2.1" href="#7.25.2.2.1">7.25.2.2.1 The iswctype function</a></h5>
18993 #include <a href="#7.25"><wctype.h></a>
18994 int iswctype(wint_t wc, wctype_t desc);</pre>
18995 <h6>Description</h6>
18997 The iswctype function determines whether the wide character wc has the property
18998 described by desc. The current setting of the LC_CTYPE category shall be the same as
18999 during the call to wctype that returned the value desc.
19001 Each of the following expressions has a truth-value equivalent to the call to the wide
19002 character classification function (<a href="#7.25.2.1">7.25.2.1</a>) in the comment that follows the expression:
19005 iswctype(wc, wctype("alnum")) // iswalnum(wc)
19006 iswctype(wc, wctype("alpha")) // iswalpha(wc)
19007 iswctype(wc, wctype("blank")) // iswblank(wc)
19008 iswctype(wc, wctype("cntrl")) // iswcntrl(wc)
19009 iswctype(wc, wctype("digit")) // iswdigit(wc)
19010 iswctype(wc, wctype("graph")) // iswgraph(wc)
19011 iswctype(wc, wctype("lower")) // iswlower(wc)
19012 iswctype(wc, wctype("print")) // iswprint(wc)
19013 iswctype(wc, wctype("punct")) // iswpunct(wc)
19014 iswctype(wc, wctype("space")) // iswspace(wc)
19015 iswctype(wc, wctype("upper")) // iswupper(wc)
19016 iswctype(wc, wctype("xdigit")) // iswxdigit(wc)</pre>
19019 The iswctype function returns nonzero (true) if and only if the value of the wide
19020 character wc has the property described by desc.
19021 <p><b> Forward references</b>: the wctype function (<a href="#7.25.2.2.2">7.25.2.2.2</a>).
19023 <h5><a name="7.25.2.2.2" href="#7.25.2.2.2">7.25.2.2.2 The wctype function</a></h5>
19027 #include <a href="#7.25"><wctype.h></a>
19028 wctype_t wctype(const char *property);</pre>
19029 <h6>Description</h6>
19031 The wctype function constructs a value with type wctype_t that describes a class of
19032 wide characters identified by the string argument property.
19034 The strings listed in the description of the iswctype function shall be valid in all
19035 locales as property arguments to the wctype function.
19038 If property identifies a valid class of wide characters according to the LC_CTYPE
19039 category of the current locale, the wctype function returns a nonzero value that is valid
19040 as the second argument to the iswctype function; otherwise, it returns zero. *
19043 <h4><a name="7.25.3" href="#7.25.3">7.25.3 Wide character case mapping utilities</a></h4>
19045 The header <a href="#7.25"><wctype.h></a> declares several functions useful for mapping wide characters.
19047 <h5><a name="7.25.3.1" href="#7.25.3.1">7.25.3.1 Wide character case mapping functions</a></h5>
19049 <h5><a name="7.25.3.1.1" href="#7.25.3.1.1">7.25.3.1.1 The towlower function</a></h5>
19053 #include <a href="#7.25"><wctype.h></a>
19054 wint_t towlower(wint_t wc);</pre>
19055 <h6>Description</h6>
19057 The towlower function converts an uppercase letter to a corresponding lowercase letter.
19060 If the argument is a wide character for which iswupper is true and there are one or
19061 more corresponding wide characters, as specified by the current locale, for which
19062 iswlower is true, the towlower function returns one of the corresponding wide
19063 characters (always the same one for any given locale); otherwise, the argument is
19064 returned unchanged.
19066 <h5><a name="7.25.3.1.2" href="#7.25.3.1.2">7.25.3.1.2 The towupper function</a></h5>
19070 #include <a href="#7.25"><wctype.h></a>
19071 wint_t towupper(wint_t wc);</pre>
19072 <h6>Description</h6>
19074 The towupper function converts a lowercase letter to a corresponding uppercase letter.
19077 If the argument is a wide character for which iswlower is true and there are one or
19078 more corresponding wide characters, as specified by the current locale, for which
19079 iswupper is true, the towupper function returns one of the corresponding wide
19080 characters (always the same one for any given locale); otherwise, the argument is
19081 returned unchanged.
19083 <h5><a name="7.25.3.2" href="#7.25.3.2">7.25.3.2 Extensible wide character case mapping functions</a></h5>
19085 The functions wctrans and towctrans provide extensible wide character mapping as
19086 well as case mapping equivalent to that performed by the functions described in the
19087 previous subclause (<a href="#7.25.3.1">7.25.3.1</a>).
19090 <h5><a name="7.25.3.2.1" href="#7.25.3.2.1">7.25.3.2.1 The towctrans function</a></h5>
19094 #include <a href="#7.25"><wctype.h></a>
19095 wint_t towctrans(wint_t wc, wctrans_t desc);</pre>
19096 <h6>Description</h6>
19098 The towctrans function maps the wide character wc using the mapping described by
19099 desc. The current setting of the LC_CTYPE category shall be the same as during the call
19100 to wctrans that returned the value desc.
19102 Each of the following expressions behaves the same as the call to the wide character case
19103 mapping function (<a href="#7.25.3.1">7.25.3.1</a>) in the comment that follows the expression:
19105 towctrans(wc, wctrans("tolower")) // towlower(wc)
19106 towctrans(wc, wctrans("toupper")) // towupper(wc)</pre>
19109 The towctrans function returns the mapped value of wc using the mapping described
19112 <h5><a name="7.25.3.2.2" href="#7.25.3.2.2">7.25.3.2.2 The wctrans function</a></h5>
19116 #include <a href="#7.25"><wctype.h></a>
19117 wctrans_t wctrans(const char *property);</pre>
19118 <h6>Description</h6>
19120 The wctrans function constructs a value with type wctrans_t that describes a
19121 mapping between wide characters identified by the string argument property.
19123 The strings listed in the description of the towctrans function shall be valid in all
19124 locales as property arguments to the wctrans function.
19127 If property identifies a valid mapping of wide characters according to the LC_CTYPE
19128 category of the current locale, the wctrans function returns a nonzero value that is valid
19129 as the second argument to the towctrans function; otherwise, it returns zero.
19132 <h3><a name="7.26" href="#7.26">7.26 Future library directions</a></h3>
19134 The following names are grouped under individual headers for convenience. All external
19135 names described below are reserved no matter what headers are included by the program.
19137 <h4><a name="7.26.1" href="#7.26.1">7.26.1 Complex arithmetic <complex.h></a></h4>
19142 cerfc clog10 clgamma
19143 cexp2 clog1p ctgamma</pre>
19144 and the same names suffixed with f or l may be added to the declarations in the
19145 <a href="#7.3"><complex.h></a> header.
19147 <h4><a name="7.26.2" href="#7.26.2">7.26.2 Character handling <ctype.h></a></h4>
19149 Function names that begin with either is or to, and a lowercase letter may be added to
19150 the declarations in the <a href="#7.4"><ctype.h></a> header.
19152 <h4><a name="7.26.3" href="#7.26.3">7.26.3 Errors <errno.h></a></h4>
19154 Macros that begin with E and a digit or E and an uppercase letter may be added to the
19155 declarations in the <a href="#7.5"><errno.h></a> header.
19157 <h4><a name="7.26.4" href="#7.26.4">7.26.4 Format conversion of integer types <inttypes.h></a></h4>
19159 Macro names beginning with PRI or SCN followed by any lowercase letter or X may be
19160 added to the macros defined in the <a href="#7.8"><inttypes.h></a> header.
19162 <h4><a name="7.26.5" href="#7.26.5">7.26.5 Localization <locale.h></a></h4>
19164 Macros that begin with LC_ and an uppercase letter may be added to the definitions in
19165 the <a href="#7.11"><locale.h></a> header.
19167 <h4><a name="7.26.6" href="#7.26.6">7.26.6 Signal handling <signal.h></a></h4>
19169 Macros that begin with either SIG and an uppercase letter or SIG_ and an uppercase
19170 letter may be added to the definitions in the <a href="#7.14"><signal.h></a> header.
19172 <h4><a name="7.26.7" href="#7.26.7">7.26.7 Boolean type and values <stdbool.h></a></h4>
19174 The ability to undefine and perhaps then redefine the macros bool, true, and false is
19175 an obsolescent feature.
19177 <h4><a name="7.26.8" href="#7.26.8">7.26.8 Integer types <stdint.h></a></h4>
19179 Typedef names beginning with int or uint and ending with _t may be added to the
19180 types defined in the <a href="#7.18"><stdint.h></a> header. Macro names beginning with INT or UINT
19181 and ending with _MAX, _MIN, or _C may be added to the macros defined in the
19182 <a href="#7.18"><stdint.h></a> header.
19185 <h4><a name="7.26.9" href="#7.26.9">7.26.9 Input/output <stdio.h></a></h4>
19187 Lowercase letters may be added to the conversion specifiers and length modifiers in
19188 fprintf and fscanf. Other characters may be used in extensions.
19190 The gets function is obsolescent, and is deprecated.
19192 The use of ungetc on a binary stream where the file position indicator is zero prior to
19193 the call is an obsolescent feature.
19195 <h4><a name="7.26.10" href="#7.26.10">7.26.10 General utilities <stdlib.h></a></h4>
19197 Function names that begin with str and a lowercase letter may be added to the
19198 declarations in the <a href="#7.20"><stdlib.h></a> header.
19200 <h4><a name="7.26.11" href="#7.26.11">7.26.11 String handling <string.h></a></h4>
19202 Function names that begin with str, mem, or wcs and a lowercase letter may be added
19203 to the declarations in the <a href="#7.21"><string.h></a> header.
19205 <h4><a name="7.26.12" href="#7.26.12">7.26.12 Extended multibyte and wide character utilities <wchar.h></a></h4>
19207 Function names that begin with wcs and a lowercase letter may be added to the
19208 declarations in the <a href="#7.24"><wchar.h></a> header.
19210 Lowercase letters may be added to the conversion specifiers and length modifiers in
19211 fwprintf and fwscanf. Other characters may be used in extensions.
19213 <h4><a name="7.26.13" href="#7.26.13">7.26.13 Wide character classification and mapping utilities</a></h4>
19214 <a href="#7.25"><wctype.h></a>
19216 Function names that begin with is or to and a lowercase letter may be added to the
19217 declarations in the <a href="#7.25"><wctype.h></a> header.
19220 <h2><a name="A" href="#A">Annex A</a></h2>
19224 Language syntax summary</pre>
19225 NOTE The notation is described in <a href="#6.1">6.1</a>.
19228 <h3><a name="A.1" href="#A.1">A.1 Lexical grammar</a></h3>
19230 <h4><a name="A.1.1" href="#A.1.1">A.1.1 Lexical elements</a></h4>
19231 (<a href="#6.4">6.4</a>) token:
19238 (<a href="#6.4">6.4</a>) preprocessing-token:
19246 each non-white-space character that cannot be one of the above</pre>
19248 <h4><a name="A.1.2" href="#A.1.2">A.1.2 Keywords</a></h4>
19249 (<a href="#6.4.1">6.4.1</a>) keyword: one of
19252 auto enum restrict unsigned
19253 break extern return void
19254 case float short volatile
19255 char for signed while
19256 const goto sizeof _Bool
19257 continue if static _Complex
19258 default inline struct _Imaginary
19260 double long typedef
19261 else register union</pre>
19263 <h4><a name="A.1.3" href="#A.1.3">A.1.3 Identifiers</a></h4>
19264 (<a href="#6.4.2.1">6.4.2.1</a>) identifier:
19266 identifier-nondigit
19267 identifier identifier-nondigit
19268 identifier digit</pre>
19269 (<a href="#6.4.2.1">6.4.2.1</a>) identifier-nondigit:
19272 universal-character-name
19273 other implementation-defined characters</pre>
19274 (<a href="#6.4.2.1">6.4.2.1</a>) nondigit: one of
19276 _ a b c d e f g h i j k l m
19277 n o p q r s t u v w x y z
19278 A B C D E F G H I J K L M
19279 N O P Q R S T U V W X Y Z</pre>
19280 (<a href="#6.4.2.1">6.4.2.1</a>) digit: one of
19282 0 1 2 3 4 5 6 7 8 9</pre>
19284 <h4><a name="A.1.4" href="#A.1.4">A.1.4 Universal character names</a></h4>
19285 (<a href="#6.4.3">6.4.3</a>) universal-character-name:
19288 \U hex-quad hex-quad</pre>
19289 (<a href="#6.4.3">6.4.3</a>) hex-quad:
19291 hexadecimal-digit hexadecimal-digit
19292 hexadecimal-digit hexadecimal-digit</pre>
19294 <h4><a name="A.1.5" href="#A.1.5">A.1.5 Constants</a></h4>
19295 (<a href="#6.4.4">6.4.4</a>) constant:
19299 enumeration-constant
19300 character-constant</pre>
19301 (<a href="#6.4.4.1">6.4.4.1</a>) integer-constant:
19303 decimal-constant integer-suffixopt
19304 octal-constant integer-suffixopt
19305 hexadecimal-constant integer-suffixopt</pre>
19306 (<a href="#6.4.4.1">6.4.4.1</a>) decimal-constant:
19310 decimal-constant digit</pre>
19311 (<a href="#6.4.4.1">6.4.4.1</a>) octal-constant:
19314 octal-constant octal-digit</pre>
19315 (<a href="#6.4.4.1">6.4.4.1</a>) hexadecimal-constant:
19317 hexadecimal-prefix hexadecimal-digit
19318 hexadecimal-constant hexadecimal-digit</pre>
19319 (<a href="#6.4.4.1">6.4.4.1</a>) hexadecimal-prefix: one of
19322 (<a href="#6.4.4.1">6.4.4.1</a>) nonzero-digit: one of
19324 1 2 3 4 5 6 7 8 9</pre>
19325 (<a href="#6.4.4.1">6.4.4.1</a>) octal-digit: one of
19327 0 1 2 3 4 5 6 7</pre>
19328 (<a href="#6.4.4.1">6.4.4.1</a>) hexadecimal-digit: one of
19330 0 1 2 3 4 5 6 7 8 9
19333 (<a href="#6.4.4.1">6.4.4.1</a>) integer-suffix:
19335 unsigned-suffix long-suffixopt
19336 unsigned-suffix long-long-suffix
19337 long-suffix unsigned-suffixopt
19338 long-long-suffix unsigned-suffixopt</pre>
19339 (<a href="#6.4.4.1">6.4.4.1</a>) unsigned-suffix: one of
19342 (<a href="#6.4.4.1">6.4.4.1</a>) long-suffix: one of
19345 (<a href="#6.4.4.1">6.4.4.1</a>) long-long-suffix: one of
19348 (<a href="#6.4.4.2">6.4.4.2</a>) floating-constant:
19350 decimal-floating-constant
19351 hexadecimal-floating-constant</pre>
19352 (<a href="#6.4.4.2">6.4.4.2</a>) decimal-floating-constant:
19355 fractional-constant exponent-partopt floating-suffixopt
19356 digit-sequence exponent-part floating-suffixopt</pre>
19357 (<a href="#6.4.4.2">6.4.4.2</a>) hexadecimal-floating-constant:
19359 hexadecimal-prefix hexadecimal-fractional-constant
19360 binary-exponent-part floating-suffixopt
19361 hexadecimal-prefix hexadecimal-digit-sequence
19362 binary-exponent-part floating-suffixopt</pre>
19363 (<a href="#6.4.4.2">6.4.4.2</a>) fractional-constant:
19365 digit-sequenceopt . digit-sequence
19366 digit-sequence .</pre>
19367 (<a href="#6.4.4.2">6.4.4.2</a>) exponent-part:
19369 e signopt digit-sequence
19370 E signopt digit-sequence</pre>
19371 (<a href="#6.4.4.2">6.4.4.2</a>) sign: one of
19374 (<a href="#6.4.4.2">6.4.4.2</a>) digit-sequence:
19377 digit-sequence digit</pre>
19378 (<a href="#6.4.4.2">6.4.4.2</a>) hexadecimal-fractional-constant:
19380 hexadecimal-digit-sequenceopt .
19381 hexadecimal-digit-sequence
19382 hexadecimal-digit-sequence .</pre>
19383 (<a href="#6.4.4.2">6.4.4.2</a>) binary-exponent-part:
19385 p signopt digit-sequence
19386 P signopt digit-sequence</pre>
19387 (<a href="#6.4.4.2">6.4.4.2</a>) hexadecimal-digit-sequence:
19390 hexadecimal-digit-sequence hexadecimal-digit</pre>
19391 (<a href="#6.4.4.2">6.4.4.2</a>) floating-suffix: one of
19394 (<a href="#6.4.4.3">6.4.4.3</a>) enumeration-constant:
19397 (<a href="#6.4.4.4">6.4.4.4</a>) character-constant:
19400 ' c-char-sequence '
19401 L' c-char-sequence '</pre>
19402 (<a href="#6.4.4.4">6.4.4.4</a>) c-char-sequence:
19405 c-char-sequence c-char</pre>
19406 (<a href="#6.4.4.4">6.4.4.4</a>) c-char:
19408 any member of the source character set except
19409 the single-quote ', backslash \, or new-line character
19410 escape-sequence</pre>
19411 (<a href="#6.4.4.4">6.4.4.4</a>) escape-sequence:
19413 simple-escape-sequence
19414 octal-escape-sequence
19415 hexadecimal-escape-sequence
19416 universal-character-name</pre>
19417 (<a href="#6.4.4.4">6.4.4.4</a>) simple-escape-sequence: one of
19420 \a \b \f \n \r \t \v</pre>
19421 (<a href="#6.4.4.4">6.4.4.4</a>) octal-escape-sequence:
19424 \ octal-digit octal-digit
19425 \ octal-digit octal-digit octal-digit</pre>
19426 (<a href="#6.4.4.4">6.4.4.4</a>) hexadecimal-escape-sequence:
19428 \x hexadecimal-digit
19429 hexadecimal-escape-sequence hexadecimal-digit</pre>
19431 <h4><a name="A.1.6" href="#A.1.6">A.1.6 String literals</a></h4>
19432 (<a href="#6.4.5">6.4.5</a>) string-literal:
19434 " s-char-sequenceopt "
19435 L" s-char-sequenceopt "</pre>
19436 (<a href="#6.4.5">6.4.5</a>) s-char-sequence:
19439 s-char-sequence s-char</pre>
19440 (<a href="#6.4.5">6.4.5</a>) s-char:
19443 any member of the source character set except
19444 the double-quote ", backslash \, or new-line character
19445 escape-sequence</pre>
19447 <h4><a name="A.1.7" href="#A.1.7">A.1.7 Punctuators</a></h4>
19448 (<a href="#6.4.6">6.4.6</a>) punctuator: one of
19450 [ ] ( ) { } . ->
19451 ++ -- & * + - ~ !
19452 / % << >> < > <= >= == != ^ | && ||
19454 = *= /= %= += -= <<= >>= &= ^= |=
19456 <: :> <% %> %: %:%:</pre>
19458 <h4><a name="A.1.8" href="#A.1.8">A.1.8 Header names</a></h4>
19459 (<a href="#6.4.7">6.4.7</a>) header-name:
19461 < h-char-sequence >
19462 " q-char-sequence "</pre>
19463 (<a href="#6.4.7">6.4.7</a>) h-char-sequence:
19466 h-char-sequence h-char</pre>
19467 (<a href="#6.4.7">6.4.7</a>) h-char:
19469 any member of the source character set except
19470 the new-line character and ></pre>
19471 (<a href="#6.4.7">6.4.7</a>) q-char-sequence:
19474 q-char-sequence q-char</pre>
19475 (<a href="#6.4.7">6.4.7</a>) q-char:
19477 any member of the source character set except
19478 the new-line character and "</pre>
19480 <h4><a name="A.1.9" href="#A.1.9">A.1.9 Preprocessing numbers</a></h4>
19481 (<a href="#6.4.8">6.4.8</a>) pp-number:
19487 pp-number identifier-nondigit
19494 <h3><a name="A.2" href="#A.2">A.2 Phrase structure grammar</a></h3>
19496 <h4><a name="A.2.1" href="#A.2.1">A.2.1 Expressions</a></h4>
19497 (<a href="#6.5.1">6.5.1</a>) primary-expression:
19502 ( expression )</pre>
19503 (<a href="#6.5.2">6.5.2</a>) postfix-expression:
19506 postfix-expression [ expression ]
19507 postfix-expression ( argument-expression-listopt )
19508 postfix-expression . identifier
19509 postfix-expression -> identifier
19510 postfix-expression ++
19511 postfix-expression --
19512 ( type-name ) { initializer-list }
19513 ( type-name ) { initializer-list , }</pre>
19514 (<a href="#6.5.2">6.5.2</a>) argument-expression-list:
19516 assignment-expression
19517 argument-expression-list , assignment-expression</pre>
19518 (<a href="#6.5.3">6.5.3</a>) unary-expression:
19521 ++ unary-expression
19522 -- unary-expression
19523 unary-operator cast-expression
19524 sizeof unary-expression
19525 sizeof ( type-name )</pre>
19526 (<a href="#6.5.3">6.5.3</a>) unary-operator: one of
19528 & * + - ~ !</pre>
19529 (<a href="#6.5.4">6.5.4</a>) cast-expression:
19532 ( type-name ) cast-expression</pre>
19533 (<a href="#6.5.5">6.5.5</a>) multiplicative-expression:
19537 multiplicative-expression * cast-expression
19538 multiplicative-expression / cast-expression
19539 multiplicative-expression % cast-expression</pre>
19540 (<a href="#6.5.6">6.5.6</a>) additive-expression:
19542 multiplicative-expression
19543 additive-expression + multiplicative-expression
19544 additive-expression - multiplicative-expression</pre>
19545 (<a href="#6.5.7">6.5.7</a>) shift-expression:
19547 additive-expression
19548 shift-expression << additive-expression
19549 shift-expression >> additive-expression</pre>
19550 (<a href="#6.5.8">6.5.8</a>) relational-expression:
19553 relational-expression < shift-expression
19554 relational-expression > shift-expression
19555 relational-expression <= shift-expression
19556 relational-expression >= shift-expression</pre>
19557 (<a href="#6.5.9">6.5.9</a>) equality-expression:
19559 relational-expression
19560 equality-expression == relational-expression
19561 equality-expression != relational-expression</pre>
19562 (<a href="#6.5.10">6.5.10</a>) AND-expression:
19564 equality-expression
19565 AND-expression & equality-expression</pre>
19566 (<a href="#6.5.11">6.5.11</a>) exclusive-OR-expression:
19569 exclusive-OR-expression ^ AND-expression</pre>
19570 (<a href="#6.5.12">6.5.12</a>) inclusive-OR-expression:
19572 exclusive-OR-expression
19573 inclusive-OR-expression | exclusive-OR-expression</pre>
19574 (<a href="#6.5.13">6.5.13</a>) logical-AND-expression:
19576 inclusive-OR-expression
19577 logical-AND-expression && inclusive-OR-expression</pre>
19578 (<a href="#6.5.14">6.5.14</a>) logical-OR-expression:
19580 logical-AND-expression
19581 logical-OR-expression || logical-AND-expression</pre>
19582 (<a href="#6.5.15">6.5.15</a>) conditional-expression:
19585 logical-OR-expression
19586 logical-OR-expression ? expression : conditional-expression</pre>
19587 (<a href="#6.5.16">6.5.16</a>) assignment-expression:
19589 conditional-expression
19590 unary-expression assignment-operator assignment-expression</pre>
19591 (<a href="#6.5.16">6.5.16</a>) assignment-operator: one of
19593 = *= /= %= += -= <<= >>= &= ^= |=</pre>
19594 (<a href="#6.5.17">6.5.17</a>) expression:
19596 assignment-expression
19597 expression , assignment-expression</pre>
19598 (<a href="#6.6">6.6</a>) constant-expression:
19600 conditional-expression</pre>
19602 <h4><a name="A.2.2" href="#A.2.2">A.2.2 Declarations</a></h4>
19603 (<a href="#6.7">6.7</a>) declaration:
19605 declaration-specifiers init-declarator-listopt ;</pre>
19606 (<a href="#6.7">6.7</a>) declaration-specifiers:
19608 storage-class-specifier declaration-specifiersopt
19609 type-specifier declaration-specifiersopt
19610 type-qualifier declaration-specifiersopt
19611 function-specifier declaration-specifiersopt</pre>
19612 (<a href="#6.7">6.7</a>) init-declarator-list:
19615 init-declarator-list , init-declarator</pre>
19616 (<a href="#6.7">6.7</a>) init-declarator:
19619 declarator = initializer</pre>
19620 (<a href="#6.7.1">6.7.1</a>) storage-class-specifier:
19628 (<a href="#6.7.2">6.7.2</a>) type-specifier:
19641 struct-or-union-specifier *
19644 (<a href="#6.7.2.1">6.7.2.1</a>) struct-or-union-specifier:
19646 struct-or-union identifieropt { struct-declaration-list }
19647 struct-or-union identifier</pre>
19648 (<a href="#6.7.2.1">6.7.2.1</a>) struct-or-union:
19652 (<a href="#6.7.2.1">6.7.2.1</a>) struct-declaration-list:
19655 struct-declaration-list struct-declaration</pre>
19656 (<a href="#6.7.2.1">6.7.2.1</a>) struct-declaration:
19658 specifier-qualifier-list struct-declarator-list ;</pre>
19659 (<a href="#6.7.2.1">6.7.2.1</a>) specifier-qualifier-list:
19661 type-specifier specifier-qualifier-listopt
19662 type-qualifier specifier-qualifier-listopt</pre>
19663 (<a href="#6.7.2.1">6.7.2.1</a>) struct-declarator-list:
19666 struct-declarator-list , struct-declarator</pre>
19667 (<a href="#6.7.2.1">6.7.2.1</a>) struct-declarator:
19671 declaratoropt : constant-expression</pre>
19672 (<a href="#6.7.2.2">6.7.2.2</a>) enum-specifier:
19674 enum identifieropt { enumerator-list }
19675 enum identifieropt { enumerator-list , }
19676 enum identifier</pre>
19677 (<a href="#6.7.2.2">6.7.2.2</a>) enumerator-list:
19680 enumerator-list , enumerator</pre>
19681 (<a href="#6.7.2.2">6.7.2.2</a>) enumerator:
19683 enumeration-constant
19684 enumeration-constant = constant-expression</pre>
19685 (<a href="#6.7.3">6.7.3</a>) type-qualifier:
19690 (<a href="#6.7.4">6.7.4</a>) function-specifier:
19693 (<a href="#6.7.5">6.7.5</a>) declarator:
19695 pointeropt direct-declarator</pre>
19696 (<a href="#6.7.5">6.7.5</a>) direct-declarator:
19700 direct-declarator [ type-qualifier-listopt assignment-expressionopt ]
19701 direct-declarator [ static type-qualifier-listopt assignment-expression ]
19702 direct-declarator [ type-qualifier-list static assignment-expression ]
19703 direct-declarator [ type-qualifier-listopt * ]
19704 direct-declarator ( parameter-type-list )
19705 direct-declarator ( identifier-listopt )</pre>
19706 (<a href="#6.7.5">6.7.5</a>) pointer:
19708 * type-qualifier-listopt
19709 * type-qualifier-listopt pointer</pre>
19710 (<a href="#6.7.5">6.7.5</a>) type-qualifier-list:
19713 type-qualifier-list type-qualifier</pre>
19714 (<a href="#6.7.5">6.7.5</a>) parameter-type-list:
19718 parameter-list , ...</pre>
19719 (<a href="#6.7.5">6.7.5</a>) parameter-list:
19721 parameter-declaration
19722 parameter-list , parameter-declaration</pre>
19723 (<a href="#6.7.5">6.7.5</a>) parameter-declaration:
19725 declaration-specifiers declarator
19726 declaration-specifiers abstract-declaratoropt</pre>
19727 (<a href="#6.7.5">6.7.5</a>) identifier-list:
19730 identifier-list , identifier</pre>
19731 (<a href="#6.7.6">6.7.6</a>) type-name:
19733 specifier-qualifier-list abstract-declaratoropt</pre>
19734 (<a href="#6.7.6">6.7.6</a>) abstract-declarator:
19737 pointeropt direct-abstract-declarator</pre>
19738 (<a href="#6.7.6">6.7.6</a>) direct-abstract-declarator:
19740 ( abstract-declarator )
19741 direct-abstract-declaratoropt [ type-qualifier-listopt
19742 assignment-expressionopt ]
19743 direct-abstract-declaratoropt [ static type-qualifier-listopt
19744 assignment-expression ]
19745 direct-abstract-declaratoropt [ type-qualifier-list static
19746 assignment-expression ]
19747 direct-abstract-declaratoropt [ * ]
19748 direct-abstract-declaratoropt ( parameter-type-listopt )</pre>
19749 (<a href="#6.7.7">6.7.7</a>) typedef-name:
19752 (<a href="#6.7.8">6.7.8</a>) initializer:
19754 assignment-expression
19755 { initializer-list }
19756 { initializer-list , }</pre>
19757 (<a href="#6.7.8">6.7.8</a>) initializer-list:
19759 designationopt initializer
19760 initializer-list , designationopt initializer</pre>
19761 (<a href="#6.7.8">6.7.8</a>) designation:
19764 designator-list =</pre>
19765 (<a href="#6.7.8">6.7.8</a>) designator-list:
19768 designator-list designator</pre>
19769 (<a href="#6.7.8">6.7.8</a>) designator:
19771 [ constant-expression ]
19774 <h4><a name="A.2.3" href="#A.2.3">A.2.3 Statements</a></h4>
19775 (<a href="#6.8">6.8</a>) statement:
19779 expression-statement
19780 selection-statement
19781 iteration-statement
19782 jump-statement</pre>
19783 (<a href="#6.8.1">6.8.1</a>) labeled-statement:
19785 identifier : statement
19786 case constant-expression : statement
19787 default : statement</pre>
19788 (<a href="#6.8.2">6.8.2</a>) compound-statement:
19790 { block-item-listopt }</pre>
19791 (<a href="#6.8.2">6.8.2</a>) block-item-list:
19794 block-item-list block-item</pre>
19795 (<a href="#6.8.2">6.8.2</a>) block-item:
19799 (<a href="#6.8.3">6.8.3</a>) expression-statement:
19801 expressionopt ;</pre>
19802 (<a href="#6.8.4">6.8.4</a>) selection-statement:
19805 if ( expression ) statement
19806 if ( expression ) statement else statement
19807 switch ( expression ) statement</pre>
19808 (<a href="#6.8.5">6.8.5</a>) iteration-statement:
19810 while ( expression ) statement
19811 do statement while ( expression ) ;
19812 for ( expressionopt ; expressionopt ; expressionopt ) statement
19813 for ( declaration expressionopt ; expressionopt ) statement</pre>
19814 (<a href="#6.8.6">6.8.6</a>) jump-statement:
19819 return expressionopt ;</pre>
19821 <h4><a name="A.2.4" href="#A.2.4">A.2.4 External definitions</a></h4>
19822 (<a href="#6.9">6.9</a>) translation-unit:
19824 external-declaration
19825 translation-unit external-declaration</pre>
19826 (<a href="#6.9">6.9</a>) external-declaration:
19828 function-definition
19830 (<a href="#6.9.1">6.9.1</a>) function-definition:
19832 declaration-specifiers declarator declaration-listopt compound-statement</pre>
19833 (<a href="#6.9.1">6.9.1</a>) declaration-list:
19836 declaration-list declaration</pre>
19838 <h3><a name="A.3" href="#A.3">A.3 Preprocessing directives</a></h3>
19839 (<a href="#6.10">6.10</a>) preprocessing-file:
19842 (<a href="#6.10">6.10</a>) group:
19845 group group-part</pre>
19846 (<a href="#6.10">6.10</a>) group-part:
19851 # non-directive</pre>
19852 (<a href="#6.10">6.10</a>) if-section:
19855 if-group elif-groupsopt else-groupopt endif-line</pre>
19856 (<a href="#6.10">6.10</a>) if-group:
19858 # if constant-expression new-line groupopt
19859 # ifdef identifier new-line groupopt
19860 # ifndef identifier new-line groupopt</pre>
19861 (<a href="#6.10">6.10</a>) elif-groups:
19864 elif-groups elif-group</pre>
19865 (<a href="#6.10">6.10</a>) elif-group:
19867 # elif constant-expression new-line groupopt</pre>
19868 (<a href="#6.10">6.10</a>) else-group:
19870 # else new-line groupopt</pre>
19871 (<a href="#6.10">6.10</a>) endif-line:
19873 # endif new-line</pre>
19874 (<a href="#6.10">6.10</a>) control-line:
19876 # include pp-tokens new-line
19877 # define identifier replacement-list new-line
19878 # define identifier lparen identifier-listopt )
19879 replacement-list new-line
19880 # define identifier lparen ... ) replacement-list new-line
19881 # define identifier lparen identifier-list , ... )
19882 replacement-list new-line
19883 # undef identifier new-line
19884 # line pp-tokens new-line
19885 # error pp-tokensopt new-line
19886 # pragma pp-tokensopt new-line
19888 (<a href="#6.10">6.10</a>) text-line:
19890 pp-tokensopt new-line</pre>
19891 (<a href="#6.10">6.10</a>) non-directive:
19893 pp-tokens new-line</pre>
19894 (<a href="#6.10">6.10</a>) lparen:
19896 a ( character not immediately preceded by white-space</pre>
19897 (<a href="#6.10">6.10</a>) replacement-list:
19901 (<a href="#6.10">6.10</a>) pp-tokens:
19903 preprocessing-token
19904 pp-tokens preprocessing-token</pre>
19905 (<a href="#6.10">6.10</a>) new-line:
19908 the new-line character</pre>
19910 <h2><a name="B" href="#B">Annex B</a></h2>
19913 Library summary</pre>
19915 <h3><a name="B.1" href="#B.1">B.1 Diagnostics <assert.h></a></h3>
19918 void assert(scalar expression);</pre>
19920 <h3><a name="B.2" href="#B.2">B.2 Complex <complex.h></a></h3>
19924 complex imaginary I
19925 _Complex_I _Imaginary_I
19926 #pragma STDC CX_LIMITED_RANGE on-off-switch
19927 double complex cacos(double complex z);
19928 float complex cacosf(float complex z);
19929 long double complex cacosl(long double complex z);
19930 double complex casin(double complex z);
19931 float complex casinf(float complex z);
19932 long double complex casinl(long double complex z);
19933 double complex catan(double complex z);
19934 float complex catanf(float complex z);
19935 long double complex catanl(long double complex z);
19936 double complex ccos(double complex z);
19937 float complex ccosf(float complex z);
19938 long double complex ccosl(long double complex z);
19939 double complex csin(double complex z);
19940 float complex csinf(float complex z);
19941 long double complex csinl(long double complex z);
19942 double complex ctan(double complex z);
19943 float complex ctanf(float complex z);
19944 long double complex ctanl(long double complex z);
19945 double complex cacosh(double complex z);
19946 float complex cacoshf(float complex z);
19947 long double complex cacoshl(long double complex z);
19948 double complex casinh(double complex z);
19949 float complex casinhf(float complex z);
19950 long double complex casinhl(long double complex z);
19951 double complex catanh(double complex z);
19952 float complex catanhf(float complex z);
19953 long double complex catanhl(long double complex z);
19954 double complex ccosh(double complex z);
19955 float complex ccoshf(float complex z);
19956 long double complex ccoshl(long double complex z);
19957 double complex csinh(double complex z);
19958 float complex csinhf(float complex z);
19959 long double complex csinhl(long double complex z);
19960 double complex ctanh(double complex z);
19961 float complex ctanhf(float complex z);
19962 long double complex ctanhl(long double complex z);
19963 double complex cexp(double complex z);
19964 float complex cexpf(float complex z);
19965 long double complex cexpl(long double complex z);
19966 double complex clog(double complex z);
19967 float complex clogf(float complex z);
19968 long double complex clogl(long double complex z);
19969 double cabs(double complex z);
19970 float cabsf(float complex z);
19971 long double cabsl(long double complex z);
19972 double complex cpow(double complex x, double complex y);
19973 float complex cpowf(float complex x, float complex y);
19974 long double complex cpowl(long double complex x,
19975 long double complex y);
19976 double complex csqrt(double complex z);
19977 float complex csqrtf(float complex z);
19978 long double complex csqrtl(long double complex z);
19979 double carg(double complex z);
19980 float cargf(float complex z);
19981 long double cargl(long double complex z);
19982 double cimag(double complex z);
19983 float cimagf(float complex z);
19984 long double cimagl(long double complex z);
19985 double complex conj(double complex z);
19986 float complex conjf(float complex z);
19987 long double complex conjl(long double complex z);
19988 double complex cproj(double complex z);
19989 float complex cprojf(float complex z);
19990 long double complex cprojl(long double complex z);
19991 double creal(double complex z);
19992 float crealf(float complex z);
19993 long double creall(long double complex z);</pre>
19995 <h3><a name="B.3" href="#B.3">B.3 Character handling <ctype.h></a></h3>
19997 int isalnum(int c);
19998 int isalpha(int c);
19999 int isblank(int c);
20000 int iscntrl(int c);
20001 int isdigit(int c);
20002 int isgraph(int c);
20003 int islower(int c);
20004 int isprint(int c);
20005 int ispunct(int c);
20006 int isspace(int c);
20007 int isupper(int c);
20008 int isxdigit(int c);
20009 int tolower(int c);
20010 int toupper(int c);</pre>
20012 <h3><a name="B.4" href="#B.4">B.4 Errors <errno.h></a></h3>
20014 EDOM EILSEQ ERANGE errno</pre>
20016 <h3><a name="B.5" href="#B.5">B.5 Floating-point environment <fenv.h></a></h3>
20019 fenv_t FE_OVERFLOW FE_TOWARDZERO
20020 fexcept_t FE_UNDERFLOW FE_UPWARD
20021 FE_DIVBYZERO FE_ALL_EXCEPT FE_DFL_ENV
20022 FE_INEXACT FE_DOWNWARD
20023 FE_INVALID FE_TONEAREST
20024 #pragma STDC FENV_ACCESS on-off-switch
20025 int feclearexcept(int excepts);
20026 int fegetexceptflag(fexcept_t *flagp, int excepts);
20027 int feraiseexcept(int excepts);
20028 int fesetexceptflag(const fexcept_t *flagp,
20030 int fetestexcept(int excepts);
20031 int fegetround(void);
20032 int fesetround(int round);
20033 int fegetenv(fenv_t *envp);
20034 int feholdexcept(fenv_t *envp);
20035 int fesetenv(const fenv_t *envp);
20036 int feupdateenv(const fenv_t *envp);</pre>
20038 <h3><a name="B.6" href="#B.6">B.6 Characteristics of floating types <float.h></a></h3>
20040 FLT_ROUNDS DBL_MIN_EXP FLT_MAX
20041 FLT_EVAL_METHOD LDBL_MIN_EXP DBL_MAX
20042 FLT_RADIX FLT_MIN_10_EXP LDBL_MAX
20043 FLT_MANT_DIG DBL_MIN_10_EXP FLT_EPSILON
20044 DBL_MANT_DIG LDBL_MIN_10_EXP DBL_EPSILON
20045 LDBL_MANT_DIG FLT_MAX_EXP LDBL_EPSILON
20046 DECIMAL_DIG DBL_MAX_EXP FLT_MIN
20047 FLT_DIG LDBL_MAX_EXP DBL_MIN
20048 DBL_DIG FLT_MAX_10_EXP LDBL_MIN
20049 LDBL_DIG DBL_MAX_10_EXP
20050 FLT_MIN_EXP LDBL_MAX_10_EXP</pre>
20052 <h3><a name="B.7" href="#B.7">B.7 Format conversion of integer types <inttypes.h></a></h3>
20056 PRIdN PRIdLEASTN PRIdFASTN PRIdMAX PRIdPTR
20057 PRIiN PRIiLEASTN PRIiFASTN PRIiMAX PRIiPTR
20058 PRIoN PRIoLEASTN PRIoFASTN PRIoMAX PRIoPTR
20059 PRIuN PRIuLEASTN PRIuFASTN PRIuMAX PRIuPTR
20060 PRIxN PRIxLEASTN PRIxFASTN PRIxMAX PRIxPTR
20061 PRIXN PRIXLEASTN PRIXFASTN PRIXMAX PRIXPTR
20062 SCNdN SCNdLEASTN SCNdFASTN SCNdMAX SCNdPTR
20063 SCNiN SCNiLEASTN SCNiFASTN SCNiMAX SCNiPTR
20064 SCNoN SCNoLEASTN SCNoFASTN SCNoMAX SCNoPTR
20065 SCNuN SCNuLEASTN SCNuFASTN SCNuMAX SCNuPTR
20066 SCNxN SCNxLEASTN SCNxFASTN SCNxMAX SCNxPTR
20067 intmax_t imaxabs(intmax_t j);
20068 imaxdiv_t imaxdiv(intmax_t numer, intmax_t denom);
20069 intmax_t strtoimax(const char * restrict nptr,
20070 char ** restrict endptr, int base);
20071 uintmax_t strtoumax(const char * restrict nptr,
20072 char ** restrict endptr, int base);
20073 intmax_t wcstoimax(const wchar_t * restrict nptr,
20074 wchar_t ** restrict endptr, int base);
20075 uintmax_t wcstoumax(const wchar_t * restrict nptr,
20076 wchar_t ** restrict endptr, int base);</pre>
20078 <h3><a name="B.8" href="#B.8">B.8 Alternative spellings <iso646.h></a></h3>
20080 and bitor not_eq xor
20081 and_eq compl or xor_eq
20082 bitand not or_eq</pre>
20084 <h3><a name="B.9" href="#B.9">B.9 Sizes of integer types <limits.h></a></h3>
20086 CHAR_BIT CHAR_MAX INT_MIN ULONG_MAX
20087 SCHAR_MIN MB_LEN_MAX INT_MAX LLONG_MIN
20088 SCHAR_MAX SHRT_MIN UINT_MAX LLONG_MAX
20089 UCHAR_MAX SHRT_MAX LONG_MIN ULLONG_MAX
20090 CHAR_MIN USHRT_MAX LONG_MAX</pre>
20092 <h3><a name="B.10" href="#B.10">B.10 Localization <locale.h></a></h3>
20094 struct lconv LC_ALL LC_CTYPE LC_NUMERIC
20095 NULL LC_COLLATE LC_MONETARY LC_TIME
20096 char *setlocale(int category, const char *locale);
20097 struct lconv *localeconv(void);</pre>
20099 <h3><a name="B.11" href="#B.11">B.11 Mathematics <math.h></a></h3>
20106 float_t FP_INFINITE FP_FAST_FMAL
20107 double_t FP_NAN FP_ILOGB0
20108 HUGE_VAL FP_NORMAL FP_ILOGBNAN
20109 HUGE_VALF FP_SUBNORMAL MATH_ERRNO
20110 HUGE_VALL FP_ZERO MATH_ERREXCEPT
20111 INFINITY FP_FAST_FMA math_errhandling
20113 #pragma STDC FP_CONTRACT on-off-switch
20114 int fpclassify(real-floating x);
20115 int isfinite(real-floating x);
20116 int isinf(real-floating x);
20117 int isnan(real-floating x);
20118 int isnormal(real-floating x);
20119 int signbit(real-floating x);
20120 double acos(double x);
20121 float acosf(float x);
20122 long double acosl(long double x);
20123 double asin(double x);
20124 float asinf(float x);
20125 long double asinl(long double x);
20126 double atan(double x);
20127 float atanf(float x);
20128 long double atanl(long double x);
20129 double atan2(double y, double x);
20130 float atan2f(float y, float x);
20131 long double atan2l(long double y, long double x);
20132 double cos(double x);
20133 float cosf(float x);
20134 long double cosl(long double x);
20135 double sin(double x);
20136 float sinf(float x);
20137 long double sinl(long double x);
20138 double tan(double x);
20139 float tanf(float x);
20140 long double tanl(long double x);
20141 double acosh(double x);
20142 float acoshf(float x);
20143 long double acoshl(long double x);
20144 double asinh(double x);
20145 float asinhf(float x);
20146 long double asinhl(long double x);
20147 double atanh(double x);
20148 float atanhf(float x);
20149 long double atanhl(long double x);
20150 double cosh(double x);
20151 float coshf(float x);
20152 long double coshl(long double x);
20153 double sinh(double x);
20154 float sinhf(float x);
20155 long double sinhl(long double x);
20156 double tanh(double x);
20157 float tanhf(float x);
20158 long double tanhl(long double x);
20159 double exp(double x);
20160 float expf(float x);
20161 long double expl(long double x);
20162 double exp2(double x);
20163 float exp2f(float x);
20164 long double exp2l(long double x);
20165 double expm1(double x);
20166 float expm1f(float x);
20167 long double expm1l(long double x);
20168 double frexp(double value, int *exp);
20169 float frexpf(float value, int *exp);
20170 long double frexpl(long double value, int *exp);
20171 int ilogb(double x);
20172 int ilogbf(float x);
20173 int ilogbl(long double x);
20174 double ldexp(double x, int exp);
20175 float ldexpf(float x, int exp);
20176 long double ldexpl(long double x, int exp);
20177 double log(double x);
20178 float logf(float x);
20179 long double logl(long double x);
20180 double log10(double x);
20181 float log10f(float x);
20182 long double log10l(long double x);
20183 double log1p(double x);
20184 float log1pf(float x);
20185 long double log1pl(long double x);
20186 double log2(double x);
20187 float log2f(float x);
20188 long double log2l(long double x);
20189 double logb(double x);
20190 float logbf(float x);
20191 long double logbl(long double x);
20192 double modf(double value, double *iptr);
20193 float modff(float value, float *iptr);
20194 long double modfl(long double value, long double *iptr);
20195 double scalbn(double x, int n);
20196 float scalbnf(float x, int n);
20197 long double scalbnl(long double x, int n);
20198 double scalbln(double x, long int n);
20199 float scalblnf(float x, long int n);
20200 long double scalblnl(long double x, long int n);
20201 double cbrt(double x);
20202 float cbrtf(float x);
20203 long double cbrtl(long double x);
20204 double fabs(double x);
20205 float fabsf(float x);
20206 long double fabsl(long double x);
20207 double hypot(double x, double y);
20208 float hypotf(float x, float y);
20209 long double hypotl(long double x, long double y);
20210 double pow(double x, double y);
20211 float powf(float x, float y);
20212 long double powl(long double x, long double y);
20213 double sqrt(double x);
20214 float sqrtf(float x);
20215 long double sqrtl(long double x);
20216 double erf(double x);
20217 float erff(float x);
20218 long double erfl(long double x);
20219 double erfc(double x);
20220 float erfcf(float x);
20221 long double erfcl(long double x);
20222 double lgamma(double x);
20223 float lgammaf(float x);
20224 long double lgammal(long double x);
20225 double tgamma(double x);
20226 float tgammaf(float x);
20227 long double tgammal(long double x);
20228 double ceil(double x);
20229 float ceilf(float x);
20230 long double ceill(long double x);
20231 double floor(double x);
20232 float floorf(float x);
20233 long double floorl(long double x);
20234 double nearbyint(double x);
20235 float nearbyintf(float x);
20236 long double nearbyintl(long double x);
20237 double rint(double x);
20238 float rintf(float x);
20239 long double rintl(long double x);
20240 long int lrint(double x);
20241 long int lrintf(float x);
20242 long int lrintl(long double x);
20243 long long int llrint(double x);
20244 long long int llrintf(float x);
20245 long long int llrintl(long double x);
20246 double round(double x);
20247 float roundf(float x);
20248 long double roundl(long double x);
20249 long int lround(double x);
20250 long int lroundf(float x);
20251 long int lroundl(long double x);
20252 long long int llround(double x);
20253 long long int llroundf(float x);
20254 long long int llroundl(long double x);
20255 double trunc(double x);
20256 float truncf(float x);
20257 long double truncl(long double x);
20258 double fmod(double x, double y);
20259 float fmodf(float x, float y);
20260 long double fmodl(long double x, long double y);
20261 double remainder(double x, double y);
20262 float remainderf(float x, float y);
20263 long double remainderl(long double x, long double y);
20264 double remquo(double x, double y, int *quo);
20265 float remquof(float x, float y, int *quo);
20266 long double remquol(long double x, long double y,
20268 double copysign(double x, double y);
20269 float copysignf(float x, float y);
20270 long double copysignl(long double x, long double y);
20271 double nan(const char *tagp);
20272 float nanf(const char *tagp);
20273 long double nanl(const char *tagp);
20274 double nextafter(double x, double y);
20275 float nextafterf(float x, float y);
20276 long double nextafterl(long double x, long double y);
20277 double nexttoward(double x, long double y);
20278 float nexttowardf(float x, long double y);
20279 long double nexttowardl(long double x, long double y);
20280 double fdim(double x, double y);
20281 float fdimf(float x, float y);
20282 long double fdiml(long double x, long double y);
20283 double fmax(double x, double y);
20284 float fmaxf(float x, float y);
20285 long double fmaxl(long double x, long double y);
20286 double fmin(double x, double y);
20287 float fminf(float x, float y);
20288 long double fminl(long double x, long double y);
20289 double fma(double x, double y, double z);
20290 float fmaf(float x, float y, float z);
20291 long double fmal(long double x, long double y,
20293 int isgreater(real-floating x, real-floating y);
20294 int isgreaterequal(real-floating x, real-floating y);
20295 int isless(real-floating x, real-floating y);
20296 int islessequal(real-floating x, real-floating y);
20297 int islessgreater(real-floating x, real-floating y);
20298 int isunordered(real-floating x, real-floating y);</pre>
20300 <h3><a name="B.12" href="#B.12">B.12 Nonlocal jumps <setjmp.h></a></h3>
20303 int setjmp(jmp_buf env);
20304 void longjmp(jmp_buf env, int val);</pre>
20306 <h3><a name="B.13" href="#B.13">B.13 Signal handling <signal.h></a></h3>
20308 sig_atomic_t SIG_IGN SIGILL SIGTERM
20309 SIG_DFL SIGABRT SIGINT
20310 SIG_ERR SIGFPE SIGSEGV
20311 void (*signal(int sig, void (*func)(int)))(int);
20312 int raise(int sig);</pre>
20314 <h3><a name="B.14" href="#B.14">B.14 Variable arguments <stdarg.h></a></h3>
20317 type va_arg(va_list ap, type);
20318 void va_copy(va_list dest, va_list src);
20319 void va_end(va_list ap);
20320 void va_start(va_list ap, parmN);</pre>
20322 <h3><a name="B.15" href="#B.15">B.15 Boolean type and values <stdbool.h></a></h3>
20328 __bool_true_false_are_defined</pre>
20330 <h3><a name="B.16" href="#B.16">B.16 Common definitions <stddef.h></a></h3>
20332 ptrdiff_t size_t wchar_t NULL
20333 offsetof(type, member-designator)</pre>
20335 <h3><a name="B.17" href="#B.17">B.17 Integer types <stdint.h></a></h3>
20337 intN_t INT_LEASTN_MIN PTRDIFF_MAX
20338 uintN_t INT_LEASTN_MAX SIG_ATOMIC_MIN
20339 int_leastN_t UINT_LEASTN_MAX SIG_ATOMIC_MAX
20340 uint_leastN_t INT_FASTN_MIN SIZE_MAX
20341 int_fastN_t INT_FASTN_MAX WCHAR_MIN
20342 uint_fastN_t UINT_FASTN_MAX WCHAR_MAX
20343 intptr_t INTPTR_MIN WINT_MIN
20344 uintptr_t INTPTR_MAX WINT_MAX
20345 intmax_t UINTPTR_MAX INTN_C(value)
20346 uintmax_t INTMAX_MIN UINTN_C(value)
20347 INTN_MIN INTMAX_MAX INTMAX_C(value)
20348 INTN_MAX UINTMAX_MAX UINTMAX_C(value)
20349 UINTN_MAX PTRDIFF_MIN</pre>
20351 <h3><a name="B.18" href="#B.18">B.18 Input/output <stdio.h></a></h3>
20355 size_t _IOLBF FILENAME_MAX TMP_MAX
20356 FILE _IONBF L_tmpnam stderr
20357 fpos_t BUFSIZ SEEK_CUR stdin
20358 NULL EOF SEEK_END stdout
20359 _IOFBF FOPEN_MAX SEEK_SET
20360 int remove(const char *filename);
20361 int rename(const char *old, const char *new);
20362 FILE *tmpfile(void);
20363 char *tmpnam(char *s);
20364 int fclose(FILE *stream);
20365 int fflush(FILE *stream);
20366 FILE *fopen(const char * restrict filename,
20367 const char * restrict mode);
20368 FILE *freopen(const char * restrict filename,
20369 const char * restrict mode,
20370 FILE * restrict stream);
20371 void setbuf(FILE * restrict stream,
20372 char * restrict buf);
20373 int setvbuf(FILE * restrict stream,
20374 char * restrict buf,
20375 int mode, size_t size);
20376 int fprintf(FILE * restrict stream,
20377 const char * restrict format, ...);
20378 int fscanf(FILE * restrict stream,
20379 const char * restrict format, ...);
20380 int printf(const char * restrict format, ...);
20381 int scanf(const char * restrict format, ...);
20382 int snprintf(char * restrict s, size_t n,
20383 const char * restrict format, ...);
20384 int sprintf(char * restrict s,
20385 const char * restrict format, ...);
20386 int sscanf(const char * restrict s,
20387 const char * restrict format, ...);
20388 int vfprintf(FILE * restrict stream,
20389 const char * restrict format, va_list arg);
20390 int vfscanf(FILE * restrict stream,
20391 const char * restrict format, va_list arg);
20392 int vprintf(const char * restrict format, va_list arg);
20393 int vscanf(const char * restrict format, va_list arg);
20394 int vsnprintf(char * restrict s, size_t n,
20395 const char * restrict format, va_list arg);
20396 int vsprintf(char * restrict s,
20397 const char * restrict format, va_list arg);
20398 int vsscanf(const char * restrict s,
20399 const char * restrict format, va_list arg);
20400 int fgetc(FILE *stream);
20401 char *fgets(char * restrict s, int n,
20402 FILE * restrict stream);
20403 int fputc(int c, FILE *stream);
20404 int fputs(const char * restrict s,
20405 FILE * restrict stream);
20406 int getc(FILE *stream);
20408 char *gets(char *s);
20409 int putc(int c, FILE *stream);
20410 int putchar(int c);
20411 int puts(const char *s);
20412 int ungetc(int c, FILE *stream);
20413 size_t fread(void * restrict ptr,
20414 size_t size, size_t nmemb,
20415 FILE * restrict stream);
20416 size_t fwrite(const void * restrict ptr,
20417 size_t size, size_t nmemb,
20418 FILE * restrict stream);
20419 int fgetpos(FILE * restrict stream,
20420 fpos_t * restrict pos);
20421 int fseek(FILE *stream, long int offset, int whence);
20422 int fsetpos(FILE *stream, const fpos_t *pos);
20423 long int ftell(FILE *stream);
20424 void rewind(FILE *stream);
20425 void clearerr(FILE *stream);
20426 int feof(FILE *stream);
20427 int ferror(FILE *stream);
20428 void perror(const char *s);</pre>
20430 <h3><a name="B.19" href="#B.19">B.19 General utilities <stdlib.h></a></h3>
20434 size_t ldiv_t EXIT_FAILURE MB_CUR_MAX
20435 wchar_t lldiv_t EXIT_SUCCESS
20436 div_t NULL RAND_MAX
20437 double atof(const char *nptr);
20438 int atoi(const char *nptr);
20439 long int atol(const char *nptr);
20440 long long int atoll(const char *nptr);
20441 double strtod(const char * restrict nptr,
20442 char ** restrict endptr);
20443 float strtof(const char * restrict nptr,
20444 char ** restrict endptr);
20445 long double strtold(const char * restrict nptr,
20446 char ** restrict endptr);
20447 long int strtol(const char * restrict nptr,
20448 char ** restrict endptr, int base);
20449 long long int strtoll(const char * restrict nptr,
20450 char ** restrict endptr, int base);
20451 unsigned long int strtoul(
20452 const char * restrict nptr,
20453 char ** restrict endptr, int base);
20454 unsigned long long int strtoull(
20455 const char * restrict nptr,
20456 char ** restrict endptr, int base);
20458 void srand(unsigned int seed);
20459 void *calloc(size_t nmemb, size_t size);
20460 void free(void *ptr);
20461 void *malloc(size_t size);
20462 void *realloc(void *ptr, size_t size);
20464 int atexit(void (*func)(void));
20465 void exit(int status);
20466 void _Exit(int status);
20467 char *getenv(const char *name);
20468 int system(const char *string);
20469 void *bsearch(const void *key, const void *base,
20470 size_t nmemb, size_t size,
20471 int (*compar)(const void *, const void *));
20472 void qsort(void *base, size_t nmemb, size_t size,
20473 int (*compar)(const void *, const void *));
20475 long int labs(long int j);
20476 long long int llabs(long long int j);
20477 div_t div(int numer, int denom);
20478 ldiv_t ldiv(long int numer, long int denom);
20479 lldiv_t lldiv(long long int numer,
20480 long long int denom);
20481 int mblen(const char *s, size_t n);
20482 int mbtowc(wchar_t * restrict pwc,
20483 const char * restrict s, size_t n);
20484 int wctomb(char *s, wchar_t wchar);
20485 size_t mbstowcs(wchar_t * restrict pwcs,
20486 const char * restrict s, size_t n);
20487 size_t wcstombs(char * restrict s,
20488 const wchar_t * restrict pwcs, size_t n);</pre>
20490 <h3><a name="B.20" href="#B.20">B.20 String handling <string.h></a></h3>
20495 void *memcpy(void * restrict s1,
20496 const void * restrict s2, size_t n);
20497 void *memmove(void *s1, const void *s2, size_t n);
20498 char *strcpy(char * restrict s1,
20499 const char * restrict s2);
20500 char *strncpy(char * restrict s1,
20501 const char * restrict s2, size_t n);
20502 char *strcat(char * restrict s1,
20503 const char * restrict s2);
20504 char *strncat(char * restrict s1,
20505 const char * restrict s2, size_t n);
20506 int memcmp(const void *s1, const void *s2, size_t n);
20507 int strcmp(const char *s1, const char *s2);
20508 int strcoll(const char *s1, const char *s2);
20509 int strncmp(const char *s1, const char *s2, size_t n);
20510 size_t strxfrm(char * restrict s1,
20511 const char * restrict s2, size_t n);
20512 void *memchr(const void *s, int c, size_t n);
20513 char *strchr(const char *s, int c);
20514 size_t strcspn(const char *s1, const char *s2);
20515 char *strpbrk(const char *s1, const char *s2);
20516 char *strrchr(const char *s, int c);
20517 size_t strspn(const char *s1, const char *s2);
20518 char *strstr(const char *s1, const char *s2);
20519 char *strtok(char * restrict s1,
20520 const char * restrict s2);
20521 void *memset(void *s, int c, size_t n);
20522 char *strerror(int errnum);
20523 size_t strlen(const char *s);</pre>
20525 <h3><a name="B.21" href="#B.21">B.21 Type-generic math <tgmath.h></a></h3>
20527 acos sqrt fmod nextafter
20528 asin fabs frexp nexttoward
20529 atan atan2 hypot remainder
20530 acosh cbrt ilogb remquo
20531 asinh ceil ldexp rint
20532 atanh copysign lgamma round
20533 cos erf llrint scalbn
20534 sin erfc llround scalbln
20535 tan exp2 log10 tgamma
20536 cosh expm1 log1p trunc
20537 sinh fdim log2 carg
20538 tanh floor logb cimag
20540 log fmax lround cproj
20541 pow fmin nearbyint creal</pre>
20543 <h3><a name="B.22" href="#B.22">B.22 Date and time <time.h></a></h3>
20547 CLOCKS_PER_SEC clock_t struct tm
20548 clock_t clock(void);
20549 double difftime(time_t time1, time_t time0);
20550 time_t mktime(struct tm *timeptr);
20551 time_t time(time_t *timer);
20552 char *asctime(const struct tm *timeptr);
20553 char *ctime(const time_t *timer);
20554 struct tm *gmtime(const time_t *timer);
20555 struct tm *localtime(const time_t *timer);
20556 size_t strftime(char * restrict s,
20558 const char * restrict format,
20559 const struct tm * restrict timeptr);</pre>
20561 <h3><a name="B.23" href="#B.23">B.23 Extended multibyte/wide character utilities <wchar.h></a></h3>
20565 wchar_t wint_t WCHAR_MAX
20566 size_t struct tm WCHAR_MIN
20567 mbstate_t NULL WEOF
20568 int fwprintf(FILE * restrict stream,
20569 const wchar_t * restrict format, ...);
20570 int fwscanf(FILE * restrict stream,
20571 const wchar_t * restrict format, ...);
20572 int swprintf(wchar_t * restrict s, size_t n,
20573 const wchar_t * restrict format, ...);
20574 int swscanf(const wchar_t * restrict s,
20575 const wchar_t * restrict format, ...);
20576 int vfwprintf(FILE * restrict stream,
20577 const wchar_t * restrict format, va_list arg);
20578 int vfwscanf(FILE * restrict stream,
20579 const wchar_t * restrict format, va_list arg);
20580 int vswprintf(wchar_t * restrict s, size_t n,
20581 const wchar_t * restrict format, va_list arg);
20582 int vswscanf(const wchar_t * restrict s,
20583 const wchar_t * restrict format, va_list arg);
20584 int vwprintf(const wchar_t * restrict format,
20586 int vwscanf(const wchar_t * restrict format,
20588 int wprintf(const wchar_t * restrict format, ...);
20589 int wscanf(const wchar_t * restrict format, ...);
20590 wint_t fgetwc(FILE *stream);
20591 wchar_t *fgetws(wchar_t * restrict s, int n,
20592 FILE * restrict stream);
20593 wint_t fputwc(wchar_t c, FILE *stream);
20594 int fputws(const wchar_t * restrict s,
20595 FILE * restrict stream);
20596 int fwide(FILE *stream, int mode);
20597 wint_t getwc(FILE *stream);
20598 wint_t getwchar(void);
20599 wint_t putwc(wchar_t c, FILE *stream);
20600 wint_t putwchar(wchar_t c);
20601 wint_t ungetwc(wint_t c, FILE *stream);
20602 double wcstod(const wchar_t * restrict nptr,
20603 wchar_t ** restrict endptr);
20604 float wcstof(const wchar_t * restrict nptr,
20605 wchar_t ** restrict endptr);
20606 long double wcstold(const wchar_t * restrict nptr,
20607 wchar_t ** restrict endptr);
20608 long int wcstol(const wchar_t * restrict nptr,
20609 wchar_t ** restrict endptr, int base);
20610 long long int wcstoll(const wchar_t * restrict nptr,
20611 wchar_t ** restrict endptr, int base);
20612 unsigned long int wcstoul(const wchar_t * restrict nptr,
20613 wchar_t ** restrict endptr, int base);
20614 unsigned long long int wcstoull(
20615 const wchar_t * restrict nptr,
20616 wchar_t ** restrict endptr, int base);
20617 wchar_t *wcscpy(wchar_t * restrict s1,
20618 const wchar_t * restrict s2);
20619 wchar_t *wcsncpy(wchar_t * restrict s1,
20620 const wchar_t * restrict s2, size_t n);
20621 wchar_t *wmemcpy(wchar_t * restrict s1,
20622 const wchar_t * restrict s2, size_t n);
20623 wchar_t *wmemmove(wchar_t *s1, const wchar_t *s2,
20625 wchar_t *wcscat(wchar_t * restrict s1,
20626 const wchar_t * restrict s2);
20627 wchar_t *wcsncat(wchar_t * restrict s1,
20628 const wchar_t * restrict s2, size_t n);
20629 int wcscmp(const wchar_t *s1, const wchar_t *s2);
20630 int wcscoll(const wchar_t *s1, const wchar_t *s2);
20631 int wcsncmp(const wchar_t *s1, const wchar_t *s2,
20633 size_t wcsxfrm(wchar_t * restrict s1,
20634 const wchar_t * restrict s2, size_t n);
20635 int wmemcmp(const wchar_t *s1, const wchar_t *s2,
20637 wchar_t *wcschr(const wchar_t *s, wchar_t c);
20638 size_t wcscspn(const wchar_t *s1, const wchar_t *s2);
20639 wchar_t *wcspbrk(const wchar_t *s1, const wchar_t *s2); *
20640 wchar_t *wcsrchr(const wchar_t *s, wchar_t c);
20641 size_t wcsspn(const wchar_t *s1, const wchar_t *s2);
20642 wchar_t *wcsstr(const wchar_t *s1, const wchar_t *s2);
20643 wchar_t *wcstok(wchar_t * restrict s1,
20644 const wchar_t * restrict s2,
20645 wchar_t ** restrict ptr);
20646 wchar_t *wmemchr(const wchar_t *s, wchar_t c, size_t n);
20647 size_t wcslen(const wchar_t *s);
20648 wchar_t *wmemset(wchar_t *s, wchar_t c, size_t n);
20649 size_t wcsftime(wchar_t * restrict s, size_t maxsize,
20650 const wchar_t * restrict format,
20651 const struct tm * restrict timeptr);
20652 wint_t btowc(int c);
20653 int wctob(wint_t c);
20654 int mbsinit(const mbstate_t *ps);
20655 size_t mbrlen(const char * restrict s, size_t n,
20656 mbstate_t * restrict ps);
20657 size_t mbrtowc(wchar_t * restrict pwc,
20658 const char * restrict s, size_t n,
20659 mbstate_t * restrict ps);
20660 size_t wcrtomb(char * restrict s, wchar_t wc,
20661 mbstate_t * restrict ps);
20662 size_t mbsrtowcs(wchar_t * restrict dst,
20663 const char ** restrict src, size_t len,
20664 mbstate_t * restrict ps);
20665 size_t wcsrtombs(char * restrict dst,
20666 const wchar_t ** restrict src, size_t len,
20667 mbstate_t * restrict ps);</pre>
20669 <h3><a name="B.24" href="#B.24">B.24 Wide character classification and mapping utilities <wctype.h></a></h3>
20673 wint_t wctrans_t wctype_t WEOF
20674 int iswalnum(wint_t wc);
20675 int iswalpha(wint_t wc);
20676 int iswblank(wint_t wc);
20677 int iswcntrl(wint_t wc);
20678 int iswdigit(wint_t wc);
20679 int iswgraph(wint_t wc);
20680 int iswlower(wint_t wc);
20681 int iswprint(wint_t wc);
20682 int iswpunct(wint_t wc);
20683 int iswspace(wint_t wc);
20684 int iswupper(wint_t wc);
20685 int iswxdigit(wint_t wc);
20686 int iswctype(wint_t wc, wctype_t desc);
20687 wctype_t wctype(const char *property);
20688 wint_t towlower(wint_t wc);
20689 wint_t towupper(wint_t wc);
20690 wint_t towctrans(wint_t wc, wctrans_t desc);
20691 wctrans_t wctrans(const char *property);</pre>
20693 <h2><a name="C" href="#C">Annex C</a></h2>
20697 Sequence points</pre>
20698 The following are the sequence points described in <a href="#5.1.2.3">5.1.2.3</a>:
20700 <li> The call to a function, after the arguments have been evaluated (<a href="#6.5.2.2">6.5.2.2</a>).
20701 <li> The end of the first operand of the following operators: logical AND && (<a href="#6.5.13">6.5.13</a>);
20702 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>).
20703 <li> The end of a full declarator: declarators (<a href="#6.7.5">6.7.5</a>);
20704 <li> The end of a full expression: an initializer (<a href="#6.7.8">6.7.8</a>); the expression in an expression
20705 statement (<a href="#6.8.3">6.8.3</a>); the controlling expression of a selection statement (if or switch)
20706 (<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
20707 expressions of a for statement (<a href="#6.8.5.3">6.8.5.3</a>); the expression in a return statement
20708 (<a href="#6.8.6.4">6.8.6.4</a>).
20709 <li> Immediately before a library function returns (<a href="#7.1.4">7.1.4</a>).
20710 <li> After the actions associated with each formatted input/output function conversion
20711 specifier (<a href="#7.19.6">7.19.6</a>, <a href="#7.24.2">7.24.2</a>).
20712 <li> Immediately before and immediately after each call to a comparison function, and
20713 also between any call to a comparison function and any movement of the objects
20714 passed as arguments to that call (<a href="#7.20.5">7.20.5</a>).
20718 <h2><a name="D" href="#D">Annex D</a></h2>
20722 Universal character names for identifiers</pre>
20723 This clause lists the hexadecimal code values that are valid in universal character names
20726 This table is reproduced unchanged from ISO/IEC TR 10176:1998, produced by ISO/IEC
20727 JTC 1/SC 22/WG 20, except for the omission of ranges that are part of the basic character
20729 Latin: 00AA, 00BA, 00C0-00D6, 00D8-00F6, 00F8-01F5, 01FA-0217,
20731 0250-02A8, 1E00-1E9B, 1EA0-1EF9, 207F</pre>
20732 Greek: 0386, 0388-038A, 038C, 038E-03A1, 03A3-03CE, 03D0-03D6,
20734 03DA, 03DC, 03DE, 03E0, 03E2-03F3, 1F00-1F15, 1F18-1F1D,
20735 1F20-1F45, 1F48-1F4D, 1F50-1F57, 1F59, 1F5B, 1F5D,
20736 1F5F-1F7D, 1F80-1FB4, 1FB6-1FBC, 1FC2-1FC4, 1FC6-1FCC,
20737 1FD0-1FD3, 1FD6-1FDB, 1FE0-1FEC, 1FF2-1FF4, 1FF6-1FFC</pre>
20738 Cyrillic: 0401-040C, 040E-044F, 0451-045C, 045E-0481, 0490-04C4,
20740 04C7-04C8, 04CB-04CC, 04D0-04EB, 04EE-04F5, 04F8-04F9</pre>
20741 Armenian: 0531-0556, 0561-0587
20742 Hebrew: 05B0-05B9, 05BB-05BD, 05BF, 05C1-05C2, 05D0-05EA,
20745 Arabic: 0621-063A, 0640-0652, 0670-06B7, 06BA-06BE, 06C0-06CE,
20747 06D0-06DC, 06E5-06E8, 06EA-06ED</pre>
20748 Devanagari: 0901-0903, 0905-0939, 093E-094D, 0950-0952, 0958-0963
20749 Bengali: 0981-0983, 0985-098C, 098F-0990, 0993-09A8, 09AA-09B0,
20751 09B2, 09B6-09B9, 09BE-09C4, 09C7-09C8, 09CB-09CD,
20752 09DC-09DD, 09DF-09E3, 09F0-09F1</pre>
20753 Gurmukhi: 0A02, 0A05-0A0A, 0A0F-0A10, 0A13-0A28, 0A2A-0A30,
20755 0A32-0A33, 0A35-0A36, 0A38-0A39, 0A3E-0A42, 0A47-0A48,
20756 0A4B-0A4D, 0A59-0A5C, 0A5E, 0A74</pre>
20757 Gujarati: 0A81-0A83, 0A85-0A8B, 0A8D, 0A8F-0A91, 0A93-0AA8,
20759 0AAA-0AB0, 0AB2-0AB3, 0AB5-0AB9, 0ABD-0AC5,
20760 0AC7-0AC9, 0ACB-0ACD, 0AD0, 0AE0</pre>
20761 Oriya: 0B01-0B03, 0B05-0B0C, 0B0F-0B10, 0B13-0B28, 0B2A-0B30,
20764 0B32-0B33, 0B36-0B39, 0B3E-0B43, 0B47-0B48, 0B4B-0B4D,
20765 0B5C-0B5D, 0B5F-0B61</pre>
20766 Tamil: 0B82-0B83, 0B85-0B8A, 0B8E-0B90, 0B92-0B95, 0B99-0B9A,
20768 0B9C, 0B9E-0B9F, 0BA3-0BA4, 0BA8-0BAA, 0BAE-0BB5,
20769 0BB7-0BB9, 0BBE-0BC2, 0BC6-0BC8, 0BCA-0BCD</pre>
20770 Telugu: 0C01-0C03, 0C05-0C0C, 0C0E-0C10, 0C12-0C28, 0C2A-0C33,
20772 0C35-0C39, 0C3E-0C44, 0C46-0C48, 0C4A-0C4D, 0C60-0C61</pre>
20773 Kannada: 0C82-0C83, 0C85-0C8C, 0C8E-0C90, 0C92-0CA8, 0CAA-0CB3,
20775 0CB5-0CB9, 0CBE-0CC4, 0CC6-0CC8, 0CCA-0CCD, 0CDE,
20777 Malayalam: 0D02-0D03, 0D05-0D0C, 0D0E-0D10, 0D12-0D28, 0D2A-0D39,
20779 0D3E-0D43, 0D46-0D48, 0D4A-0D4D, 0D60-0D61</pre>
20780 Thai: 0E01-0E3A, 0E40-0E5B
20781 Lao: 0E81-0E82, 0E84, 0E87-0E88, 0E8A, 0E8D, 0E94-0E97,
20783 0E99-0E9F, 0EA1-0EA3, 0EA5, 0EA7, 0EAA-0EAB,
20784 0EAD-0EAE, 0EB0-0EB9, 0EBB-0EBD, 0EC0-0EC4, 0EC6,
20785 0EC8-0ECD, 0EDC-0EDD</pre>
20786 Tibetan: 0F00, 0F18-0F19, 0F35, 0F37, 0F39, 0F3E-0F47, 0F49-0F69,
20788 0F71-0F84, 0F86-0F8B, 0F90-0F95, 0F97, 0F99-0FAD,
20789 0FB1-0FB7, 0FB9</pre>
20790 Georgian: 10A0-10C5, 10D0-10F6
20791 Hiragana: 3041-3093, 309B-309C
20792 Katakana: 30A1-30F6, 30FB-30FC
20793 Bopomofo: 3105-312C
20794 CJK Unified Ideographs: 4E00-9FA5
20796 Digits: 0660-0669, 06F0-06F9, 0966-096F, 09E6-09EF, 0A66-0A6F,
20798 0AE6-0AEF, 0B66-0B6F, 0BE7-0BEF, 0C66-0C6F, 0CE6-0CEF,
20799 0D66-0D6F, 0E50-0E59, 0ED0-0ED9, 0F20-0F33</pre>
20800 Special characters: 00B5, 00B7, 02B0-02B8, 02BB, 02BD-02C1, 02D0-02D1,
20803 02E0-02E4, 037A, 0559, 093D, 0B3D, 1FBE, 203F-2040, 2102,
20804 2107, 210A-2113, 2115, 2118-211D, 2124, 2126, 2128, 212A-2131,
20805 2133-2138, 2160-2182, 3005-3007, 3021-3029</pre>
20807 <h2><a name="E" href="#E">Annex E</a></h2>
20811 Implementation limits</pre>
20812 The contents of the header <a href="#7.10"><limits.h></a> are given below, in alphabetical order. The
20813 minimum magnitudes shown shall be replaced by implementation-defined magnitudes
20814 with the same sign. The values shall all be constant expressions suitable for use in #if
20815 preprocessing directives. The components are described further in <a href="#5.2.4.2.1">5.2.4.2.1</a>.
20819 #define CHAR_MAX UCHAR_MAX or SCHAR_MAX
20820 #define CHAR_MIN 0 or SCHAR_MIN
20821 #define INT_MAX +32767
20822 #define INT_MIN -32767
20823 #define LONG_MAX +2147483647
20824 #define LONG_MIN -2147483647
20825 #define LLONG_MAX +9223372036854775807
20826 #define LLONG_MIN -9223372036854775807
20827 #define MB_LEN_MAX 1
20828 #define SCHAR_MAX +127
20829 #define SCHAR_MIN -127
20830 #define SHRT_MAX +32767
20831 #define SHRT_MIN -32767
20832 #define UCHAR_MAX 255
20833 #define USHRT_MAX 65535
20834 #define UINT_MAX 65535
20835 #define ULONG_MAX 4294967295
20836 #define ULLONG_MAX 18446744073709551615</pre>
20837 The contents of the header <a href="#7.7"><float.h></a> are given below. All integer values, except
20838 FLT_ROUNDS, shall be constant expressions suitable for use in #if preprocessing
20839 directives; all floating values shall be constant expressions. The components are
20840 described further in <a href="#5.2.4.2.2">5.2.4.2.2</a>.
20842 The values given in the following list shall be replaced by implementation-defined
20846 #define FLT_EVAL_METHOD
20847 #define FLT_ROUNDS</pre>
20848 The values given in the following list shall be replaced by implementation-defined
20849 constant expressions that are greater or equal in magnitude (absolute value) to those
20850 shown, with the same sign:
20855 #define DBL_MANT_DIG
20856 #define DBL_MAX_10_EXP +37
20857 #define DBL_MAX_EXP
20858 #define DBL_MIN_10_EXP -37
20859 #define DBL_MIN_EXP
20860 #define DECIMAL_DIG 10
20862 #define FLT_MANT_DIG
20863 #define FLT_MAX_10_EXP +37
20864 #define FLT_MAX_EXP
20865 #define FLT_MIN_10_EXP -37
20866 #define FLT_MIN_EXP
20867 #define FLT_RADIX 2
20868 #define LDBL_DIG 10
20869 #define LDBL_MANT_DIG
20870 #define LDBL_MAX_10_EXP +37
20871 #define LDBL_MAX_EXP
20872 #define LDBL_MIN_10_EXP -37
20873 #define LDBL_MIN_EXP</pre>
20874 The values given in the following list shall be replaced by implementation-defined
20875 constant expressions with values that are greater than or equal to those shown:
20878 #define DBL_MAX 1E+37
20879 #define FLT_MAX 1E+37
20880 #define LDBL_MAX 1E+37</pre>
20881 The values given in the following list shall be replaced by implementation-defined
20882 constant expressions with (positive) values that are less than or equal to those shown:
20885 #define DBL_EPSILON 1E-9
20886 #define DBL_MIN 1E-37
20887 #define FLT_EPSILON 1E-5
20888 #define FLT_MIN 1E-37
20889 #define LDBL_EPSILON 1E-9
20890 #define LDBL_MIN 1E-37</pre>
20892 <h2><a name="F" href="#F">Annex F</a></h2>
20895 IEC 60559 floating-point arithmetic</pre>
20897 <h3><a name="F.1" href="#F.1">F.1 Introduction</a></h3>
20899 This annex specifies C language support for the IEC 60559 floating-point standard. The
20900 IEC 60559 floating-point standard is specifically Binary floating-point arithmetic for
20901 microprocessor systems, second edition (IEC 60559:1989), previously designated
20902 IEC 559:1989 and as IEEE Standard for Binary Floating-Point Arithmetic
20903 (ANSI/IEEE 754-1985). IEEE Standard for Radix-Independent Floating-Point
20904 Arithmetic (ANSI/IEEE 854-1987) generalizes the binary standard to remove
20905 dependencies on radix and word length. IEC 60559 generally refers to the floating-point
20906 standard, as in IEC 60559 operation, IEC 60559 format, etc. An implementation that
20907 defines __STDC_IEC_559__ shall conform to the specifications in this annex. Where
20908 a binding between the C language and IEC 60559 is indicated, the IEC 60559-specified
20909 behavior is adopted by reference, unless stated otherwise.
20911 <h3><a name="F.2" href="#F.2">F.2 Types</a></h3>
20913 The C floating types match the IEC 60559 formats as follows:
20915 <li> The float type matches the IEC 60559 single format.
20916 <li> The double type matches the IEC 60559 double format.
20917 <li> The long double type matches an IEC 60559 extended format,<sup><a href="#note307"><b>307)</b></a></sup> else a
20918 non-IEC 60559 extended format, else the IEC 60559 double format.
20920 Any non-IEC 60559 extended format used for the long double type shall have more
20921 precision than IEC 60559 double and at least the range of IEC 60559 double.<sup><a href="#note308"><b>308)</b></a></sup>
20922 Recommended practice
20924 The long double type should match an IEC 60559 extended format.
20932 <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
20933 and quadruple 128-bit IEC 60559 formats.
20935 <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
20939 <h4><a name="F.2.1" href="#F.2.1">F.2.1 Infinities, signed zeros, and NaNs</a></h4>
20941 This specification does not define the behavior of signaling NaNs.<sup><a href="#note309"><b>309)</b></a></sup> It generally uses
20942 the term NaN to denote quiet NaNs. The NAN and INFINITY macros and the nan
20943 functions in <a href="#7.12"><math.h></a> provide designations for IEC 60559 NaNs and infinities.
20946 <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
20947 sufficient for closure of the arithmetic.
20950 <h3><a name="F.3" href="#F.3">F.3 Operators and functions</a></h3>
20952 C operators and functions provide IEC 60559 required and recommended facilities as
20955 <li> The +, -, *, and / operators provide the IEC 60559 add, subtract, multiply, and
20957 <li> The sqrt functions in <a href="#7.12"><math.h></a> provide the IEC 60559 square root operation.
20958 <li> The remainder functions in <a href="#7.12"><math.h></a> provide the IEC 60559 remainder
20959 operation. The remquo functions in <a href="#7.12"><math.h></a> provide the same operation but
20960 with additional information.
20961 <li> The rint functions in <a href="#7.12"><math.h></a> provide the IEC 60559 operation that rounds a
20962 floating-point number to an integer value (in the same precision). The nearbyint
20963 functions in <a href="#7.12"><math.h></a> provide the nearbyinteger function recommended in the
20964 Appendix to ANSI/IEEE 854.
20965 <li> The conversions for floating types provide the IEC 60559 conversions between
20966 floating-point precisions.
20967 <li> The conversions from integer to floating types provide the IEC 60559 conversions
20968 from integer to floating point.
20969 <li> The conversions from floating to integer types provide IEC 60559-like conversions
20970 but always round toward zero.
20971 <li> The lrint and llrint functions in <a href="#7.12"><math.h></a> provide the IEC 60559
20972 conversions, which honor the directed rounding mode, from floating point to the
20973 long int and long long int integer formats. The lrint and llrint
20974 functions can be used to implement IEC 60559 conversions from floating to other
20976 <li> The translation time conversion of floating constants and the strtod, strtof,
20977 strtold, fprintf, fscanf, and related library functions in <a href="#7.20"><stdlib.h></a>,
20978 <a href="#7.19"><stdio.h></a>, and <a href="#7.24"><wchar.h></a> provide IEC 60559 binary-decimal conversions. The
20979 strtold function in <a href="#7.20"><stdlib.h></a> provides the conv function recommended in the
20980 Appendix to ANSI/IEEE 854.
20983 <li> The relational and equality operators provide IEC 60559 comparisons. IEC 60559
20984 identifies a need for additional comparison predicates to facilitate writing code that
20985 accounts for NaNs. The comparison macros (isgreater, isgreaterequal,
20986 isless, islessequal, islessgreater, and isunordered) in <a href="#7.12"><math.h></a>
20987 supplement the language operators to address this need. The islessgreater and
20988 isunordered macros provide respectively a quiet version of the <> predicate and
20989 the unordered predicate recommended in the Appendix to IEC 60559.
20990 <li> The feclearexcept, feraiseexcept, and fetestexcept functions in
20991 <a href="#7.6"><fenv.h></a> provide the facility to test and alter the IEC 60559 floating-point
20992 exception status flags. The fegetexceptflag and fesetexceptflag
20993 functions in <a href="#7.6"><fenv.h></a> provide the facility to save and restore all five status flags at
20994 one time. These functions are used in conjunction with the type fexcept_t and the
20995 floating-point exception macros (FE_INEXACT, FE_DIVBYZERO,
20996 FE_UNDERFLOW, FE_OVERFLOW, FE_INVALID) also in <a href="#7.6"><fenv.h></a>.
20997 <li> The fegetround and fesetround functions in <a href="#7.6"><fenv.h></a> provide the facility
20998 to select among the IEC 60559 directed rounding modes represented by the rounding
20999 direction macros in <a href="#7.6"><fenv.h></a> (FE_TONEAREST, FE_UPWARD, FE_DOWNWARD,
21000 FE_TOWARDZERO) and the values 0, 1, 2, and 3 of FLT_ROUNDS are the
21001 IEC 60559 directed rounding modes.
21002 <li> The fegetenv, feholdexcept, fesetenv, and feupdateenv functions in
21003 <a href="#7.6"><fenv.h></a> provide a facility to manage the floating-point environment, comprising
21004 the IEC 60559 status flags and control modes.
21005 <li> The copysign functions in <a href="#7.12"><math.h></a> provide the copysign function
21006 recommended in the Appendix to IEC 60559.
21007 <li> The unary minus (-) operator provides the minus (-) operation recommended in the
21008 Appendix to IEC 60559.
21009 <li> The scalbn and scalbln functions in <a href="#7.12"><math.h></a> provide the scalb function
21010 recommended in the Appendix to IEC 60559.
21011 <li> The logb functions in <a href="#7.12"><math.h></a> provide the logb function recommended in the
21012 Appendix to IEC 60559, but following the newer specifications in ANSI/IEEE 854.
21013 <li> The nextafter and nexttoward functions in <a href="#7.12"><math.h></a> provide the nextafter
21014 function recommended in the Appendix to IEC 60559 (but with a minor change to
21015 better handle signed zeros).
21016 <li> The isfinite macro in <a href="#7.12"><math.h></a> provides the finite function recommended in
21017 the Appendix to IEC 60559.
21018 <li> The isnan macro in <a href="#7.12"><math.h></a> provides the isnan function recommended in the
21019 Appendix to IEC 60559.
21021 <li> The signbit macro and the fpclassify macro in <a href="#7.12"><math.h></a>, used in
21022 conjunction with the number classification macros (FP_NAN, FP_INFINITE,
21023 FP_NORMAL, FP_SUBNORMAL, FP_ZERO), provide the facility of the class
21024 function recommended in the Appendix to IEC 60559 (except that the classification
21025 macros defined in <a href="#7.12.3">7.12.3</a> do not distinguish signaling from quiet NaNs).
21028 <h3><a name="F.4" href="#F.4">F.4 Floating to integer conversion</a></h3>
21030 If the floating value is infinite or NaN or if the integral part of the floating value exceeds
21031 the range of the integer type, then the ''invalid'' floating-point exception is raised and the
21032 resulting value is unspecified. Whether conversion of non-integer floating values whose
21033 integral part is within the range of the integer type raises the ''inexact'' floating-point
21034 exception is unspecified.<sup><a href="#note310"><b>310)</b></a></sup>
21037 <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
21038 conversions raise the ''inexact'' floating-point exception for non-integer in-range values. In those
21039 cases where it matters, library functions can be used to effect such conversions with or without raising
21040 the ''inexact'' floating-point exception. See rint, lrint, llrint, and nearbyint in
21041 <a href="#7.12"><math.h></a>.
21044 <h3><a name="F.5" href="#F.5">F.5 Binary-decimal conversion</a></h3>
21046 Conversion from the widest supported IEC 60559 format to decimal with
21047 DECIMAL_DIG digits and back is the identity function.<sup><a href="#note311"><b>311)</b></a></sup>
21049 Conversions involving IEC 60559 formats follow all pertinent recommended practice. In
21050 particular, conversion between any supported IEC 60559 format and decimal with
21051 DECIMAL_DIG or fewer significant digits is correctly rounded (honoring the current
21052 rounding mode), which assures that conversion from the widest supported IEC 60559
21053 format to decimal with DECIMAL_DIG digits and back is the identity function.
21055 Functions such as strtod that convert character sequences to floating types honor the
21056 rounding direction. Hence, if the rounding direction might be upward or downward, the
21057 implementation cannot convert a minus-signed sequence by negating the converted
21066 <p><small><a name="note311" href="#note311">311)</a> If the minimum-width IEC 60559 extended format (64 bits of precision) is supported,
21067 DECIMAL_DIG shall be at least 21. If IEC 60559 double (53 bits of precision) is the widest
21068 IEC 60559 format supported, then DECIMAL_DIG shall be at least 17. (By contrast, LDBL_DIG and
21069 DBL_DIG are 18 and 15, respectively, for these formats.)
21072 <h3><a name="F.6" href="#F.6">F.6 Contracted expressions</a></h3>
21074 A contracted expression treats infinities, NaNs, signed zeros, subnormals, and the
21075 rounding directions in a manner consistent with the basic arithmetic operations covered
21077 Recommended practice
21079 A contracted expression should raise floating-point exceptions in a manner generally
21080 consistent with the basic arithmetic operations. A contracted expression should deliver
21081 the same value as its uncontracted counterpart, else should be correctly rounded (once).
21083 <h3><a name="F.7" href="#F.7">F.7 Floating-point environment</a></h3>
21085 The floating-point environment defined in <a href="#7.6"><fenv.h></a> includes the IEC 60559 floating-
21086 point exception status flags and directed-rounding control modes. It includes also
21087 IEC 60559 dynamic rounding precision and trap enablement modes, if the
21088 implementation supports them.<sup><a href="#note312"><b>312)</b></a></sup>
21091 <p><small><a name="note312" href="#note312">312)</a> This specification does not require dynamic rounding precision nor trap enablement modes.
21094 <h4><a name="F.7.1" href="#F.7.1">F.7.1 Environment management</a></h4>
21096 IEC 60559 requires that floating-point operations implicitly raise floating-point exception
21097 status flags, and that rounding control modes can be set explicitly to affect result values of
21098 floating-point operations. When the state for the FENV_ACCESS pragma (defined in
21099 <a href="#7.6"><fenv.h></a>) is ''on'', these changes to the floating-point state are treated as side effects
21100 which respect sequence points.<sup><a href="#note313"><b>313)</b></a></sup>
21103 <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-
21104 point control modes will be the default ones and the floating-point status flags will not be tested,
21105 which allows certain optimizations (see <a href="#F.8">F.8</a>).
21108 <h4><a name="F.7.2" href="#F.7.2">F.7.2 Translation</a></h4>
21110 During translation the IEC 60559 default modes are in effect:
21112 <li> The rounding direction mode is rounding to nearest.
21113 <li> The rounding precision mode (if supported) is set so that results are not shortened.
21114 <li> Trapping or stopping (if supported) is disabled on all floating-point exceptions.
21116 Recommended practice
21118 The implementation should produce a diagnostic message for each translation-time
21124 floating-point exception, other than ''inexact'';<sup><a href="#note314"><b>314)</b></a></sup> the implementation should then
21125 proceed with the translation of the program.
21128 <p><small><a name="note314" href="#note314">314)</a> As floating constants are converted to appropriate internal representations at translation time, their
21129 conversion is subject to default rounding modes and raises no execution-time floating-point exceptions
21130 (even where the state of the FENV_ACCESS pragma is ''on''). Library functions, for example
21131 strtod, provide execution-time conversion of numeric strings.
21134 <h4><a name="F.7.3" href="#F.7.3">F.7.3 Execution</a></h4>
21136 At program startup the floating-point environment is initialized as prescribed by
21139 <li> All floating-point exception status flags are cleared.
21140 <li> The rounding direction mode is rounding to nearest.
21141 <li> The dynamic rounding precision mode (if supported) is set so that results are not
21143 <li> Trapping or stopping (if supported) is disabled on all floating-point exceptions.
21146 <h4><a name="F.7.4" href="#F.7.4">F.7.4 Constant expressions</a></h4>
21148 An arithmetic constant expression of floating type, other than one in an initializer for an
21149 object that has static storage duration, is evaluated (as if) during execution; thus, it is
21150 affected by any operative floating-point control modes and raises floating-point
21151 exceptions as required by IEC 60559 (provided the state for the FENV_ACCESS pragma
21152 is ''on'').<sup><a href="#note315"><b>315)</b></a></sup>
21157 #include <a href="#7.6"><fenv.h></a>
21158 #pragma STDC FENV_ACCESS ON
21161 float w[] = { 0.0/0.0 }; // raises an exception
21162 static float x = 0.0/0.0; // does not raise an exception
21163 float y = 0.0/0.0; // raises an exception
21164 double z = 0.0/0.0; // raises an exception
21167 For the static initialization, the division is done at translation time, raising no (execution-time) floating-
21168 point exceptions. On the other hand, for the three automatic initializations the invalid division occurs at
21176 <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
21177 are affected by rounding modes set at execution time, and expressions such as 0.0/0.0 and
21178 1.0/0.0 generate execution-time floating-point exceptions. The programmer can achieve the
21179 efficiency of translation-time evaluation through static initialization, such as
21182 const static double one_third = 1.0/3.0;</pre>
21185 <h4><a name="F.7.5" href="#F.7.5">F.7.5 Initialization</a></h4>
21187 All computation for automatic initialization is done (as if) at execution time; thus, it is
21188 affected by any operative modes and raises floating-point exceptions as required by
21189 IEC 60559 (provided the state for the FENV_ACCESS pragma is ''on''). All computation
21190 for initialization of objects that have static storage duration is done (as if) at translation
21196 #include <a href="#7.6"><fenv.h></a>
21197 #pragma STDC FENV_ACCESS ON
21200 float u[] = { 1.1e75 }; // raises exceptions
21201 static float v = 1.1e75; // does not raise exceptions
21202 float w = 1.1e75; // raises exceptions
21203 double x = 1.1e75; // may raise exceptions
21204 float y = 1.1e75f; // may raise exceptions
21205 long double z = 1.1e75; // does not raise exceptions
21208 The static initialization of v raises no (execution-time) floating-point exceptions because its computation is
21209 done at translation time. The automatic initialization of u and w require an execution-time conversion to
21210 float of the wider value 1.1e75, which raises floating-point exceptions. The automatic initializations
21211 of x and y entail execution-time conversion; however, in some expression evaluation methods, the
21212 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
21213 automatic initialization of z entails execution-time conversion, but not to a narrower format, so no floating-
21214 point exception is raised. Note that the conversions of the floating constants 1.1e75 and 1.1e75f to
21215 their internal representations occur at translation time in all cases.
21223 <p><small><a name="note316" href="#note316">316)</a> Use of float_t and double_t variables increases the likelihood of translation-time computation.
21224 For example, the automatic initialization
21227 double_t x = 1.1e75;</pre>
21228 could be done at translation time, regardless of the expression evaluation method.
21231 <h4><a name="F.7.6" href="#F.7.6">F.7.6 Changing the environment</a></h4>
21233 Operations defined in <a href="#6.5">6.5</a> and functions and macros defined for the standard libraries
21234 change floating-point status flags and control modes just as indicated by their
21235 specifications (including conformance to IEC 60559). They do not change flags or modes
21236 (so as to be detectable by the user) in any other cases.
21238 If the argument to the feraiseexcept function in <a href="#7.6"><fenv.h></a> represents IEC 60559
21239 valid coincident floating-point exceptions for atomic operations (namely ''overflow'' and
21240 ''inexact'', or ''underflow'' and ''inexact''), then ''overflow'' or ''underflow'' is raised
21241 before ''inexact''.
21243 <h3><a name="F.8" href="#F.8">F.8 Optimization</a></h3>
21245 This section identifies code transformations that might subvert IEC 60559-specified
21246 behavior, and others that do not.
21248 <h4><a name="F.8.1" href="#F.8.1">F.8.1 Global transformations</a></h4>
21250 Floating-point arithmetic operations and external function calls may entail side effects
21251 which optimization shall honor, at least where the state of the FENV_ACCESS pragma is
21252 ''on''. The flags and modes in the floating-point environment may be regarded as global
21253 variables; floating-point operations (+, *, etc.) implicitly read the modes and write the
21256 Concern about side effects may inhibit code motion and removal of seemingly useless
21257 code. For example, in
21259 #include <a href="#7.6"><fenv.h></a>
21260 #pragma STDC FENV_ACCESS ON
21264 for (i = 0; i < n; i++) x + 1;
21267 x + 1 might raise floating-point exceptions, so cannot be removed. And since the loop
21268 body might not execute (maybe 0 >= n), x + 1 cannot be moved out of the loop. (Of
21269 course these optimizations are valid if the implementation can rule out the nettlesome
21272 This specification does not require support for trap handlers that maintain information
21273 about the order or count of floating-point exceptions. Therefore, between function calls,
21274 floating-point exceptions need not be precise: the actual order and number of occurrences
21275 of floating-point exceptions (> 1) may vary from what the source code expresses. Thus,
21276 the preceding loop could be treated as
21279 if (0 < n) x + 1;</pre>
21281 <h4><a name="F.8.2" href="#F.8.2">F.8.2 Expression transformations</a></h4>
21283 x / 2 <-> x * 0.5 Although similar transformations involving inexact
21285 constants generally do not yield numerically equivalent
21286 expressions, if the constants are exact then such
21287 transformations can be made on IEC 60559 machines
21288 and others that round perfectly.</pre>
21289 1 * x and x / 1 -> x The expressions 1 * x, x / 1, and x are equivalent
21291 (on IEC 60559 machines, among others).<sup><a href="#note317"><b>317)</b></a></sup></pre>
21292 x / x -> 1.0 The expressions x / x and 1.0 are not equivalent if x
21294 can be zero, infinite, or NaN.</pre>
21295 x - y <-> x + (-y) The expressions x - y, x + (-y), and (-y) + x
21297 are equivalent (on IEC 60559 machines, among others).</pre>
21298 x - y <-> -(y - x) The expressions x - y and -(y - x) are not
21300 equivalent because 1 - 1 is +0 but -(1 - 1) is -0 (in the
21301 default rounding direction).<sup><a href="#note318"><b>318)</b></a></sup></pre>
21302 x - x -> 0.0 The expressions x - x and 0.0 are not equivalent if
21304 x is a NaN or infinite.</pre>
21305 0 * x -> 0.0 The expressions 0 * x and 0.0 are not equivalent if
21307 x is a NaN, infinite, or -0.</pre>
21308 x + 0->x The expressions x + 0 and x are not equivalent if x is
21310 -0, because (-0) + (+0) yields +0 (in the default
21311 rounding direction), not -0.</pre>
21312 x - 0->x (+0) - (+0) yields -0 when rounding is downward
21314 (toward -(inf)), but +0 otherwise, and (-0) - (+0) always
21315 yields -0; so, if the state of the FENV_ACCESS pragma
21316 is ''off'', promising default rounding, then the
21317 implementation can replace x - 0 by x, even if x</pre>
21322 might be zero.</pre>
21323 -x <-> 0 - x The expressions -x and 0 - x are not equivalent if x
21325 is +0, because -(+0) yields -0, but 0 - (+0) yields +0
21326 (unless rounding is downward).</pre>
21329 <p><small><a name="note317" href="#note317">317)</a> Strict support for signaling NaNs -- not required by this specification -- would invalidate these and
21330 other transformations that remove arithmetic operators.
21332 <p><small><a name="note318" href="#note318">318)</a> IEC 60559 prescribes a signed zero to preserve mathematical identities across certain discontinuities.
21336 1/(1/ (+-) (inf)) is (+-) (inf)</pre>
21340 conj(csqrt(z)) is csqrt(conj(z)),</pre>
21344 <h4><a name="F.8.3" href="#F.8.3">F.8.3 Relational operators</a></h4>
21346 x != x -> false The statement x != x is true if x is a NaN.
21347 x == x -> true The statement x == x is false if x is a NaN.
21348 x < y -> isless(x,y) (and similarly for <=, >, >=) Though numerically
21350 equal, these expressions are not equivalent because of
21351 side effects when x or y is a NaN and the state of the
21352 FENV_ACCESS pragma is ''on''. This transformation,
21353 which would be desirable if extra code were required to
21354 cause the ''invalid'' floating-point exception for
21355 unordered cases, could be performed provided the state
21356 of the FENV_ACCESS pragma is ''off''.</pre>
21357 The sense of relational operators shall be maintained. This includes handling unordered
21358 cases as expressed by the source code.
21362 // calls g and raises ''invalid'' if a and b are unordered
21367 is not equivalent to
21369 // calls f and raises ''invalid'' if a and b are unordered
21376 // calls f without raising ''invalid'' if a and b are unordered
21377 if (isgreaterequal(a,b))
21381 nor, unless the state of the FENV_ACCESS pragma is ''off'', to
21384 // calls g without raising ''invalid'' if a and b are unordered
21389 but is equivalent to
21397 <h4><a name="F.8.4" href="#F.8.4">F.8.4 Constant arithmetic</a></h4>
21399 The implementation shall honor floating-point exceptions raised by execution-time
21400 constant arithmetic wherever the state of the FENV_ACCESS pragma is ''on''. (See <a href="#F.7.4">F.7.4</a>
21401 and <a href="#F.7.5">F.7.5</a>.) An operation on constants that raises no floating-point exception can be
21402 folded during translation, except, if the state of the FENV_ACCESS pragma is ''on'', a
21403 further check is required to assure that changing the rounding direction to downward does
21404 not alter the sign of the result,<sup><a href="#note319"><b>319)</b></a></sup> and implementations that support dynamic rounding
21405 precision modes shall assure further that the result of the operation raises no floating-
21406 point exception when converted to the semantic type of the operation.
21409 <p><small><a name="note319" href="#note319">319)</a> 0 - 0 yields -0 instead of +0 just when the rounding direction is downward.
21412 <h3><a name="F.9" href="#F.9">F.9 Mathematics <math.h></a></h3>
21414 This subclause contains specifications of <a href="#7.12"><math.h></a> facilities that are particularly suited
21415 for IEC 60559 implementations.
21417 The Standard C macro HUGE_VAL and its float and long double analogs,
21418 HUGE_VALF and HUGE_VALL, expand to expressions whose values are positive
21421 Special cases for functions in <a href="#7.12"><math.h></a> are covered directly or indirectly by
21422 IEC 60559. The functions that IEC 60559 specifies directly are identified in <a href="#F.3">F.3</a>. The
21423 other functions in <a href="#7.12"><math.h></a> treat infinities, NaNs, signed zeros, subnormals, and
21424 (provided the state of the FENV_ACCESS pragma is ''on'') the floating-point status flags
21425 in a manner consistent with the basic arithmetic operations covered by IEC 60559.
21427 The expression math_errhandling & MATH_ERREXCEPT shall evaluate to a
21430 The ''invalid'' and ''divide-by-zero'' floating-point exceptions are raised as specified in
21431 subsequent subclauses of this annex.
21433 The ''overflow'' floating-point exception is raised whenever an infinity -- or, because of
21434 rounding direction, a maximal-magnitude finite number -- is returned in lieu of a value
21438 whose magnitude is too large.
21440 The ''underflow'' floating-point exception is raised whenever a result is tiny (essentially
21441 subnormal or zero) and suffers loss of accuracy.<sup><a href="#note320"><b>320)</b></a></sup>
21443 Whether or when library functions raise the ''inexact'' floating-point exception is
21444 unspecified, unless explicitly specified otherwise.
21446 Whether or when library functions raise an undeserved ''underflow'' floating-point
21447 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
21448 not raise spurious floating-point exceptions (detectable by the user), other than the
21449 ''inexact'' floating-point exception.
21451 Whether the functions honor the rounding direction mode is implementation-defined,
21452 unless explicitly specified otherwise.
21454 Functions with a NaN argument return a NaN result and raise no floating-point exception,
21455 except where stated otherwise.
21457 The specifications in the following subclauses append to the definitions in <a href="#7.12"><math.h></a>.
21458 For families of functions, the specifications apply to all of the functions even though only
21459 the principal function is shown. Unless otherwise specified, where the symbol ''(+-)''
21460 occurs in both an argument and the result, the result has the same sign as the argument.
21461 Recommended practice
21463 If a function with one or more NaN arguments returns a NaN result, the result should be
21464 the same as one of the NaN arguments (after possible type conversion), except perhaps
21468 <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
21469 when the floating-point exception is raised.
21471 <p><small><a name="note321" href="#note321">321)</a> It is intended that undeserved ''underflow'' and ''inexact'' floating-point exceptions are raised only if
21472 avoiding them would be too costly.
21475 <h4><a name="F.9.1" href="#F.9.1">F.9.1 Trigonometric functions</a></h4>
21477 <h5><a name="F.9.1.1" href="#F.9.1.1">F.9.1.1 The acos functions</a></h5>
21480 <li> acos(1) returns +0.
21481 <li> acos(x) returns a NaN and raises the ''invalid'' floating-point exception for
21490 <h5><a name="F.9.1.2" href="#F.9.1.2">F.9.1.2 The asin functions</a></h5>
21493 <li> asin((+-)0) returns (+-)0.
21494 <li> asin(x) returns a NaN and raises the ''invalid'' floating-point exception for
21498 <h5><a name="F.9.1.3" href="#F.9.1.3">F.9.1.3 The atan functions</a></h5>
21501 <li> atan((+-)0) returns (+-)0.
21502 <li> atan((+-)(inf)) returns (+-)pi /2.
21505 <h5><a name="F.9.1.4" href="#F.9.1.4">F.9.1.4 The atan2 functions</a></h5>
21508 <li> atan2((+-)0, -0) returns (+-)pi .<sup><a href="#note322"><b>322)</b></a></sup>
21509 <li> atan2((+-)0, +0) returns (+-)0.
21510 <li> atan2((+-)0, x) returns (+-)pi for x < 0.
21511 <li> atan2((+-)0, x) returns (+-)0 for x > 0.
21512 <li> atan2(y, (+-)0) returns -pi /2 for y < 0.
21513 <li> atan2(y, (+-)0) returns pi /2 for y > 0.
21514 <li> atan2((+-)y, -(inf)) returns (+-)pi for finite y > 0.
21515 <li> atan2((+-)y, +(inf)) returns (+-)0 for finite y > 0.
21516 <li> atan2((+-)(inf), x) returns (+-)pi /2 for finite x.
21517 <li> atan2((+-)(inf), -(inf)) returns (+-)3pi /4.
21518 <li> atan2((+-)(inf), +(inf)) returns (+-)pi /4.
21522 <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
21523 the ''divide-by-zero'' floating-point exception.
21526 <h5><a name="F.9.1.5" href="#F.9.1.5">F.9.1.5 The cos functions</a></h5>
21529 <li> cos((+-)0) returns 1.
21530 <li> cos((+-)(inf)) returns a NaN and raises the ''invalid'' floating-point exception.
21533 <h5><a name="F.9.1.6" href="#F.9.1.6">F.9.1.6 The sin functions</a></h5>
21536 <li> sin((+-)0) returns (+-)0.
21537 <li> sin((+-)(inf)) returns a NaN and raises the ''invalid'' floating-point exception.
21545 <h5><a name="F.9.1.7" href="#F.9.1.7">F.9.1.7 The tan functions</a></h5>
21548 <li> tan((+-)0) returns (+-)0.
21549 <li> tan((+-)(inf)) returns a NaN and raises the ''invalid'' floating-point exception.
21552 <h4><a name="F.9.2" href="#F.9.2">F.9.2 Hyperbolic functions</a></h4>
21554 <h5><a name="F.9.2.1" href="#F.9.2.1">F.9.2.1 The acosh functions</a></h5>
21557 <li> acosh(1) returns +0.
21558 <li> acosh(x) returns a NaN and raises the ''invalid'' floating-point exception for x < 1.
21559 <li> acosh(+(inf)) returns +(inf).
21562 <h5><a name="F.9.2.2" href="#F.9.2.2">F.9.2.2 The asinh functions</a></h5>
21565 <li> asinh((+-)0) returns (+-)0.
21566 <li> asinh((+-)(inf)) returns (+-)(inf).
21569 <h5><a name="F.9.2.3" href="#F.9.2.3">F.9.2.3 The atanh functions</a></h5>
21572 <li> atanh((+-)0) returns (+-)0.
21573 <li> atanh((+-)1) returns (+-)(inf) and raises the ''divide-by-zero'' floating-point exception.
21574 <li> atanh(x) returns a NaN and raises the ''invalid'' floating-point exception for
21578 <h5><a name="F.9.2.4" href="#F.9.2.4">F.9.2.4 The cosh functions</a></h5>
21581 <li> cosh((+-)0) returns 1.
21582 <li> cosh((+-)(inf)) returns +(inf).
21585 <h5><a name="F.9.2.5" href="#F.9.2.5">F.9.2.5 The sinh functions</a></h5>
21588 <li> sinh((+-)0) returns (+-)0.
21589 <li> sinh((+-)(inf)) returns (+-)(inf).
21592 <h5><a name="F.9.2.6" href="#F.9.2.6">F.9.2.6 The tanh functions</a></h5>
21595 <li> tanh((+-)0) returns (+-)0.
21596 <li> tanh((+-)(inf)) returns (+-)1.
21600 <h4><a name="F.9.3" href="#F.9.3">F.9.3 Exponential and logarithmic functions</a></h4>
21602 <h5><a name="F.9.3.1" href="#F.9.3.1">F.9.3.1 The exp functions</a></h5>
21605 <li> exp((+-)0) returns 1.
21606 <li> exp(-(inf)) returns +0.
21607 <li> exp(+(inf)) returns +(inf).
21610 <h5><a name="F.9.3.2" href="#F.9.3.2">F.9.3.2 The exp2 functions</a></h5>
21613 <li> exp2((+-)0) returns 1.
21614 <li> exp2(-(inf)) returns +0.
21615 <li> exp2(+(inf)) returns +(inf).
21618 <h5><a name="F.9.3.3" href="#F.9.3.3">F.9.3.3 The expm1 functions</a></h5>
21621 <li> expm1((+-)0) returns (+-)0.
21622 <li> expm1(-(inf)) returns -1.
21623 <li> expm1(+(inf)) returns +(inf).
21626 <h5><a name="F.9.3.4" href="#F.9.3.4">F.9.3.4 The frexp functions</a></h5>
21629 <li> frexp((+-)0, exp) returns (+-)0, and stores 0 in the object pointed to by exp.
21630 <li> frexp((+-)(inf), exp) returns (+-)(inf), and stores an unspecified value in the object
21632 <li> frexp(NaN, exp) stores an unspecified value in the object pointed to by exp
21633 (and returns a NaN).
21636 frexp raises no floating-point exceptions.
21638 On a binary system, the body of the frexp function might be
21641 *exp = (value == 0) ? 0 : (int)(1 + logb(value));
21642 return scalbn(value, -(*exp));
21645 <h5><a name="F.9.3.5" href="#F.9.3.5">F.9.3.5 The ilogb functions</a></h5>
21647 If the correct result is outside the range of the return type, the numeric result is
21648 unspecified and the ''invalid'' floating-point exception is raised.
21651 <h5><a name="F.9.3.6" href="#F.9.3.6">F.9.3.6 The ldexp functions</a></h5>
21653 On a binary system, ldexp(x, exp) is equivalent to scalbn(x, exp).
21655 <h5><a name="F.9.3.7" href="#F.9.3.7">F.9.3.7 The log functions</a></h5>
21658 <li> log((+-)0) returns -(inf) and raises the ''divide-by-zero'' floating-point exception.
21659 <li> log(1) returns +0.
21660 <li> log(x) returns a NaN and raises the ''invalid'' floating-point exception for x < 0.
21661 <li> log(+(inf)) returns +(inf).
21664 <h5><a name="F.9.3.8" href="#F.9.3.8">F.9.3.8 The log10 functions</a></h5>
21667 <li> log10((+-)0) returns -(inf) and raises the ''divide-by-zero'' floating-point exception.
21668 <li> log10(1) returns +0.
21669 <li> log10(x) returns a NaN and raises the ''invalid'' floating-point exception for x < 0.
21670 <li> log10(+(inf)) returns +(inf).
21673 <h5><a name="F.9.3.9" href="#F.9.3.9">F.9.3.9 The log1p functions</a></h5>
21676 <li> log1p((+-)0) returns (+-)0.
21677 <li> log1p(-1) returns -(inf) and raises the ''divide-by-zero'' floating-point exception.
21678 <li> log1p(x) returns a NaN and raises the ''invalid'' floating-point exception for
21680 <li> log1p(+(inf)) returns +(inf).
21683 <h5><a name="F.9.3.10" href="#F.9.3.10">F.9.3.10 The log2 functions</a></h5>
21686 <li> log2((+-)0) returns -(inf) and raises the ''divide-by-zero'' floating-point exception.
21687 <li> log2(1) returns +0.
21688 <li> log2(x) returns a NaN and raises the ''invalid'' floating-point exception for x < 0.
21689 <li> log2(+(inf)) returns +(inf).
21692 <h5><a name="F.9.3.11" href="#F.9.3.11">F.9.3.11 The logb functions</a></h5>
21695 <li> logb((+-)0) returns -(inf) and raises the ''divide-by-zero'' floating-point exception.
21696 <li> logb((+-)(inf)) returns +(inf).
21700 <h5><a name="F.9.3.12" href="#F.9.3.12">F.9.3.12 The modf functions</a></h5>
21703 <li> modf((+-)x, iptr) returns a result with the same sign as x.
21704 <li> modf((+-)(inf), iptr) returns (+-)0 and stores (+-)(inf) in the object pointed to by iptr.
21705 <li> modf(NaN, iptr) stores a NaN in the object pointed to by iptr (and returns a
21709 modf behaves as though implemented by
21711 #include <a href="#7.12"><math.h></a>
21712 #include <a href="#7.6"><fenv.h></a>
21713 #pragma STDC FENV_ACCESS ON
21714 double modf(double value, double *iptr)
21716 int save_round = fegetround();
21717 fesetround(FE_TOWARDZERO);
21718 *iptr = nearbyint(value);
21719 fesetround(save_round);
21721 isinf(value) ? 0.0 :
21722 value - (*iptr), value);
21725 <h5><a name="F.9.3.13" href="#F.9.3.13">F.9.3.13 The scalbn and scalbln functions</a></h5>
21728 <li> scalbn((+-)0, n) returns (+-)0.
21729 <li> scalbn(x, 0) returns x.
21730 <li> scalbn((+-)(inf), n) returns (+-)(inf).
21733 <h4><a name="F.9.4" href="#F.9.4">F.9.4 Power and absolute value functions</a></h4>
21735 <h5><a name="F.9.4.1" href="#F.9.4.1">F.9.4.1 The cbrt functions</a></h5>
21738 <li> cbrt((+-)0) returns (+-)0.
21739 <li> cbrt((+-)(inf)) returns (+-)(inf).
21742 <h5><a name="F.9.4.2" href="#F.9.4.2">F.9.4.2 The fabs functions</a></h5>
21745 <li> fabs((+-)0) returns +0.
21746 <li> fabs((+-)(inf)) returns +(inf).
21750 <h5><a name="F.9.4.3" href="#F.9.4.3">F.9.4.3 The hypot functions</a></h5>
21753 <li> hypot(x, y), hypot(y, x), and hypot(x, -y) are equivalent.
21754 <li> hypot(x, (+-)0) is equivalent to fabs(x).
21755 <li> hypot((+-)(inf), y) returns +(inf), even if y is a NaN.
21758 <h5><a name="F.9.4.4" href="#F.9.4.4">F.9.4.4 The pow functions</a></h5>
21761 <li> pow((+-)0, y) returns (+-)(inf) and raises the ''divide-by-zero'' floating-point exception
21762 for y an odd integer < 0.
21763 <li> pow((+-)0, y) returns +(inf) and raises the ''divide-by-zero'' floating-point exception
21764 for y < 0 and not an odd integer.
21765 <li> pow((+-)0, y) returns (+-)0 for y an odd integer > 0.
21766 <li> pow((+-)0, y) returns +0 for y > 0 and not an odd integer.
21767 <li> pow(-1, (+-)(inf)) returns 1.
21768 <li> pow(+1, y) returns 1 for any y, even a NaN.
21769 <li> pow(x, (+-)0) returns 1 for any x, even a NaN.
21770 <li> pow(x, y) returns a NaN and raises the ''invalid'' floating-point exception for
21771 finite x < 0 and finite non-integer y.
21772 <li> pow(x, -(inf)) returns +(inf) for | x | < 1.
21773 <li> pow(x, -(inf)) returns +0 for | x | > 1.
21774 <li> pow(x, +(inf)) returns +0 for | x | < 1.
21775 <li> pow(x, +(inf)) returns +(inf) for | x | > 1.
21776 <li> pow(-(inf), y) returns -0 for y an odd integer < 0.
21777 <li> pow(-(inf), y) returns +0 for y < 0 and not an odd integer.
21778 <li> pow(-(inf), y) returns -(inf) for y an odd integer > 0.
21779 <li> pow(-(inf), y) returns +(inf) for y > 0 and not an odd integer.
21780 <li> pow(+(inf), y) returns +0 for y < 0.
21781 <li> pow(+(inf), y) returns +(inf) for y > 0.
21785 <h5><a name="F.9.4.5" href="#F.9.4.5">F.9.4.5 The sqrt functions</a></h5>
21787 sqrt is fully specified as a basic arithmetic operation in IEC 60559.
21789 <h4><a name="F.9.5" href="#F.9.5">F.9.5 Error and gamma functions</a></h4>
21791 <h5><a name="F.9.5.1" href="#F.9.5.1">F.9.5.1 The erf functions</a></h5>
21794 <li> erf((+-)0) returns (+-)0.
21795 <li> erf((+-)(inf)) returns (+-)1.
21798 <h5><a name="F.9.5.2" href="#F.9.5.2">F.9.5.2 The erfc functions</a></h5>
21801 <li> erfc(-(inf)) returns 2.
21802 <li> erfc(+(inf)) returns +0.
21805 <h5><a name="F.9.5.3" href="#F.9.5.3">F.9.5.3 The lgamma functions</a></h5>
21808 <li> lgamma(1) returns +0.
21809 <li> lgamma(2) returns +0.
21810 <li> lgamma(x) returns +(inf) and raises the ''divide-by-zero'' floating-point exception for
21811 x a negative integer or zero.
21812 <li> lgamma(-(inf)) returns +(inf).
21813 <li> lgamma(+(inf)) returns +(inf).
21816 <h5><a name="F.9.5.4" href="#F.9.5.4">F.9.5.4 The tgamma functions</a></h5>
21819 <li> tgamma((+-)0) returns (+-)(inf) and raises the ''divide-by-zero'' floating-point exception.
21820 <li> tgamma(x) returns a NaN and raises the ''invalid'' floating-point exception for x a
21822 <li> tgamma(-(inf)) returns a NaN and raises the ''invalid'' floating-point exception.
21823 <li> tgamma(+(inf)) returns +(inf).
21826 <h4><a name="F.9.6" href="#F.9.6">F.9.6 Nearest integer functions</a></h4>
21828 <h5><a name="F.9.6.1" href="#F.9.6.1">F.9.6.1 The ceil functions</a></h5>
21831 <li> ceil((+-)0) returns (+-)0.
21832 <li> ceil((+-)(inf)) returns (+-)(inf).
21835 The double version of ceil behaves as though implemented by
21838 #include <a href="#7.12"><math.h></a>
21839 #include <a href="#7.6"><fenv.h></a>
21840 #pragma STDC FENV_ACCESS ON
21841 double ceil(double x)
21844 int save_round = fegetround();
21845 fesetround(FE_UPWARD);
21846 result = rint(x); // or nearbyint instead of rint
21847 fesetround(save_round);
21851 <h5><a name="F.9.6.2" href="#F.9.6.2">F.9.6.2 The floor functions</a></h5>
21854 <li> floor((+-)0) returns (+-)0.
21855 <li> floor((+-)(inf)) returns (+-)(inf).
21858 See the sample implementation for ceil in <a href="#F.9.6.1">F.9.6.1</a>.
21860 <h5><a name="F.9.6.3" href="#F.9.6.3">F.9.6.3 The nearbyint functions</a></h5>
21862 The nearbyint functions use IEC 60559 rounding according to the current rounding
21863 direction. They do not raise the ''inexact'' floating-point exception if the result differs in
21864 value from the argument.
21866 <li> nearbyint((+-)0) returns (+-)0 (for all rounding directions).
21867 <li> nearbyint((+-)(inf)) returns (+-)(inf) (for all rounding directions).
21870 <h5><a name="F.9.6.4" href="#F.9.6.4">F.9.6.4 The rint functions</a></h5>
21872 The rint functions differ from the nearbyint functions only in that they do raise the
21873 ''inexact'' floating-point exception if the result differs in value from the argument.
21875 <h5><a name="F.9.6.5" href="#F.9.6.5">F.9.6.5 The lrint and llrint functions</a></h5>
21877 The lrint and llrint functions provide floating-to-integer conversion as prescribed
21878 by IEC 60559. They round according to the current rounding direction. If the rounded
21879 value is outside the range of the return type, the numeric result is unspecified and the
21880 ''invalid'' floating-point exception is raised. When they raise no other floating-point
21881 exception and the result differs from the argument, they raise the ''inexact'' floating-point
21885 <h5><a name="F.9.6.6" href="#F.9.6.6">F.9.6.6 The round functions</a></h5>
21888 <li> round((+-)0) returns (+-)0.
21889 <li> round((+-)(inf)) returns (+-)(inf).
21892 The double version of round behaves as though implemented by
21894 #include <a href="#7.12"><math.h></a>
21895 #include <a href="#7.6"><fenv.h></a>
21896 #pragma STDC FENV_ACCESS ON
21897 double round(double x)
21901 feholdexcept(&save_env);
21903 if (fetestexcept(FE_INEXACT)) {
21904 fesetround(FE_TOWARDZERO);
21905 result = rint(copysign(0.5 + fabs(x), x));
21907 feupdateenv(&save_env);
21910 The round functions may, but are not required to, raise the ''inexact'' floating-point
21911 exception for non-integer numeric arguments, as this implementation does.
21913 <h5><a name="F.9.6.7" href="#F.9.6.7">F.9.6.7 The lround and llround functions</a></h5>
21915 The lround and llround functions differ from the lrint and llrint functions
21916 with the default rounding direction just in that the lround and llround functions
21917 round halfway cases away from zero and need not raise the ''inexact'' floating-point
21918 exception for non-integer arguments that round to within the range of the return type.
21920 <h5><a name="F.9.6.8" href="#F.9.6.8">F.9.6.8 The trunc functions</a></h5>
21922 The trunc functions use IEC 60559 rounding toward zero (regardless of the current
21923 rounding direction).
21925 <li> trunc((+-)0) returns (+-)0.
21926 <li> trunc((+-)(inf)) returns (+-)(inf).
21930 <h4><a name="F.9.7" href="#F.9.7">F.9.7 Remainder functions</a></h4>
21932 <h5><a name="F.9.7.1" href="#F.9.7.1">F.9.7.1 The fmod functions</a></h5>
21935 <li> fmod((+-)0, y) returns (+-)0 for y not zero.
21936 <li> fmod(x, y) returns a NaN and raises the ''invalid'' floating-point exception for x
21937 infinite or y zero.
21938 <li> fmod(x, (+-)(inf)) returns x for x not infinite.
21941 The double version of fmod behaves as though implemented by
21943 #include <a href="#7.12"><math.h></a>
21944 #include <a href="#7.6"><fenv.h></a>
21945 #pragma STDC FENV_ACCESS ON
21946 double fmod(double x, double y)
21949 result = remainder(fabs(x), (y = fabs(y)));
21950 if (signbit(result)) result += y;
21951 return copysign(result, x);
21954 <h5><a name="F.9.7.2" href="#F.9.7.2">F.9.7.2 The remainder functions</a></h5>
21956 The remainder functions are fully specified as a basic arithmetic operation in
21959 <h5><a name="F.9.7.3" href="#F.9.7.3">F.9.7.3 The remquo functions</a></h5>
21961 The remquo functions follow the specifications for the remainder functions. They
21962 have no further specifications special to IEC 60559 implementations.
21964 <h4><a name="F.9.8" href="#F.9.8">F.9.8 Manipulation functions</a></h4>
21966 <h5><a name="F.9.8.1" href="#F.9.8.1">F.9.8.1 The copysign functions</a></h5>
21968 copysign is specified in the Appendix to IEC 60559.
21970 <h5><a name="F.9.8.2" href="#F.9.8.2">F.9.8.2 The nan functions</a></h5>
21972 All IEC 60559 implementations support quiet NaNs, in all floating formats.
21975 <h5><a name="F.9.8.3" href="#F.9.8.3">F.9.8.3 The nextafter functions</a></h5>
21978 <li> nextafter(x, y) raises the ''overflow'' and ''inexact'' floating-point exceptions
21979 for x finite and the function value infinite.
21980 <li> nextafter(x, y) raises the ''underflow'' and ''inexact'' floating-point
21981 exceptions for the function value subnormal or zero and x != y.
21984 <h5><a name="F.9.8.4" href="#F.9.8.4">F.9.8.4 The nexttoward functions</a></h5>
21986 No additional requirements beyond those on nextafter.
21988 <h4><a name="F.9.9" href="#F.9.9">F.9.9 Maximum, minimum, and positive difference functions</a></h4>
21990 <h5><a name="F.9.9.1" href="#F.9.9.1">F.9.9.1 The fdim functions</a></h5>
21992 No additional requirements.
21994 <h5><a name="F.9.9.2" href="#F.9.9.2">F.9.9.2 The fmax functions</a></h5>
21996 If just one argument is a NaN, the fmax functions return the other argument (if both
21997 arguments are NaNs, the functions return a NaN).
21999 The body of the fmax function might be<sup><a href="#note323"><b>323)</b></a></sup>
22001 { return (isgreaterequal(x, y) ||
22002 isnan(y)) ? x : y; }</pre>
22005 <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
22006 return +0; however, implementation in software might be impractical.
22009 <h5><a name="F.9.9.3" href="#F.9.9.3">F.9.9.3 The fmin functions</a></h5>
22011 The fmin functions are analogous to the fmax functions (see <a href="#F.9.9.2">F.9.9.2</a>).
22013 <h4><a name="F.9.10" href="#F.9.10">F.9.10 Floating multiply-add</a></h4>
22015 <h5><a name="F.9.10.1" href="#F.9.10.1">F.9.10.1 The fma functions</a></h5>
22018 <li> fma(x, y, z) computes xy + z, correctly rounded once.
22019 <li> fma(x, y, z) returns a NaN and optionally raises the ''invalid'' floating-point
22020 exception if one of x and y is infinite, the other is zero, and z is a NaN.
22021 <li> fma(x, y, z) returns a NaN and raises the ''invalid'' floating-point exception if
22022 one of x and y is infinite, the other is zero, and z is not a NaN.
22023 <li> fma(x, y, z) returns a NaN and raises the ''invalid'' floating-point exception if x
22024 times y is an exact infinity and z is also an infinity but with the opposite sign.
22032 <h2><a name="G" href="#G">Annex G</a></h2>
22035 IEC 60559-compatible complex arithmetic</pre>
22037 <h3><a name="G.1" href="#G.1">G.1 Introduction</a></h3>
22039 This annex supplements <a href="#F">annex F</a> to specify complex arithmetic for compatibility with
22040 IEC 60559 real floating-point arithmetic. Although these specifications have been
22041 carefully designed, there is little existing practice to validate the design decisions.
22042 Therefore, these specifications are not normative, but should be viewed more as
22043 recommended practice. An implementation that defines
22044 __STDC_IEC_559_COMPLEX__ should conform to the specifications in this annex.
22046 <h3><a name="G.2" href="#G.2">G.2 Types</a></h3>
22048 There is a new keyword _Imaginary, which is used to specify imaginary types. It is
22049 used as a type specifier within declaration specifiers in the same way as _Complex is
22050 (thus, _Imaginary float is a valid type name).
22052 There are three imaginary types, designated as float _Imaginary, double
22053 _Imaginary, and long double _Imaginary. The imaginary types (along with
22054 the real floating and complex types) are floating types.
22056 For imaginary types, the corresponding real type is given by deleting the keyword
22057 _Imaginary from the type name.
22059 Each imaginary type has the same representation and alignment requirements as the
22060 corresponding real type. The value of an object of imaginary type is the value of the real
22061 representation times the imaginary unit.
22063 The imaginary type domain comprises the imaginary types.
22065 <h3><a name="G.3" href="#G.3">G.3 Conventions</a></h3>
22067 A complex or imaginary value with at least one infinite part is regarded as an infinity
22068 (even if its other part is a NaN). A complex or imaginary value is a finite number if each
22069 of its parts is a finite number (neither infinite nor NaN). A complex or imaginary value is
22070 a zero if each of its parts is a zero.
22073 <h3><a name="G.4" href="#G.4">G.4 Conversions</a></h3>
22075 <h4><a name="G.4.1" href="#G.4.1">G.4.1 Imaginary types</a></h4>
22077 Conversions among imaginary types follow rules analogous to those for real floating
22080 <h4><a name="G.4.2" href="#G.4.2">G.4.2 Real and imaginary</a></h4>
22082 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
22083 result is a positive zero.
22085 When a value of real type is converted to an imaginary type, the result is a positive
22089 <p><small><a name="note324" href="#note324">324)</a> See <a href="#6.3.1.2">6.3.1.2</a>.
22092 <h4><a name="G.4.3" href="#G.4.3">G.4.3 Imaginary and complex</a></h4>
22094 When a value of imaginary type is converted to a complex type, the real part of the
22095 complex result value is a positive zero and the imaginary part of the complex result value
22096 is determined by the conversion rules for the corresponding real types.
22098 When a value of complex type is converted to an imaginary type, the real part of the
22099 complex value is discarded and the value of the imaginary part is converted according to
22100 the conversion rules for the corresponding real types.
22102 <h3><a name="G.5" href="#G.5">G.5 Binary operators</a></h3>
22104 The following subclauses supplement <a href="#6.5">6.5</a> in order to specify the type of the result for an
22105 operation with an imaginary operand.
22107 For most operand types, the value of the result of a binary operator with an imaginary or
22108 complex operand is completely determined, with reference to real arithmetic, by the usual
22109 mathematical formula. For some operand types, the usual mathematical formula is
22110 problematic because of its treatment of infinities and because of undue overflow or
22111 underflow; in these cases the result satisfies certain properties (specified in <a href="#G.5.1">G.5.1</a>), but is
22112 not completely determined.
22119 <h4><a name="G.5.1" href="#G.5.1">G.5.1 Multiplicative operators</a></h4>
22122 If one operand has real type and the other operand has imaginary type, then the result has
22123 imaginary type. If both operands have imaginary type, then the result has real type. (If
22124 either operand has complex type, then the result has complex type.)
22126 If the operands are not both complex, then the result and floating-point exception
22127 behavior of the * operator is defined by the usual mathematical formula:
22129 * u iv u + iv</pre>
22132 x xu i(xv) (xu) + i(xv)</pre>
22135 iy i(yu) -yv (-yv) + i(yu)</pre>
22139 x + iy (xu) + i(yu) (-yv) + i(xv)</pre>
22140 If the second operand is not complex, then the result and floating-point exception
22141 behavior of the / operator is defined by the usual mathematical formula:
22146 x x/u i(-x/v)</pre>
22149 iy i(y/u) y/v</pre>
22153 x + iy (x/u) + i(y/u) (y/v) + i(-x/v)</pre>
22154 The * and / operators satisfy the following infinity properties for all real, imaginary, and
22155 complex operands:<sup><a href="#note325"><b>325)</b></a></sup>
22157 <li> if one operand is an infinity and the other operand is a nonzero finite number or an
22158 infinity, then the result of the * operator is an infinity;
22159 <li> if the first operand is an infinity and the second operand is a finite number, then the
22160 result of the / operator is an infinity;
22161 <li> if the first operand is a finite number and the second operand is an infinity, then the
22162 result of the / operator is a zero;
22168 <li> if the first operand is a nonzero finite number or an infinity and the second operand is
22169 a zero, then the result of the / operator is an infinity.
22172 If both operands of the * operator are complex or if the second operand of the / operator
22173 is complex, the operator raises floating-point exceptions if appropriate for the calculation
22174 of the parts of the result, and may raise spurious floating-point exceptions.
22176 EXAMPLE 1 Multiplication of double _Complex operands could be implemented as follows. Note
22177 that the imaginary unit I has imaginary type (see <a href="#G.6">G.6</a>).
22181 #include <a href="#7.12"><math.h></a>
22182 #include <a href="#7.3"><complex.h></a>
22183 /* Multiply z * w ... */
22184 double complex _Cmultd(double complex z, double complex w)
22186 #pragma STDC FP_CONTRACT OFF
22187 double a, b, c, d, ac, bd, ad, bc, x, y;
22188 a = creal(z); b = cimag(z);
22189 c = creal(w); d = cimag(w);
22190 ac = a * c; bd = b * d;
22191 ad = a * d; bc = b * c;
22192 x = ac - bd; y = ad + bc;
22193 if (isnan(x) && isnan(y)) {
22194 /* Recover infinities that computed as NaN+iNaN ... */
22196 if ( isinf(a) || isinf(b) ) { // z is infinite
22197 /* "Box" the infinity and change NaNs in the other factor to 0 */
22198 a = copysign(isinf(a) ? 1.0 : 0.0, a);
22199 b = copysign(isinf(b) ? 1.0 : 0.0, b);
22200 if (isnan(c)) c = copysign(0.0, c);
22201 if (isnan(d)) d = copysign(0.0, d);
22204 if ( isinf(c) || isinf(d) ) { // w is infinite
22205 /* "Box" the infinity and change NaNs in the other factor to 0 */
22206 c = copysign(isinf(c) ? 1.0 : 0.0, c);
22207 d = copysign(isinf(d) ? 1.0 : 0.0, d);
22208 if (isnan(a)) a = copysign(0.0, a);
22209 if (isnan(b)) b = copysign(0.0, b);
22212 if (!recalc && (isinf(ac) || isinf(bd) ||
22213 isinf(ad) || isinf(bc))) {
22214 /* Recover infinities from overflow by changing NaNs to 0 ... */
22215 if (isnan(a)) a = copysign(0.0, a);
22216 if (isnan(b)) b = copysign(0.0, b);
22217 if (isnan(c)) c = copysign(0.0, c);
22218 if (isnan(d)) d = copysign(0.0, d);
22222 x = INFINITY * ( a * c - b * d );
22223 y = INFINITY * ( a * d + b * c );
22228 This implementation achieves the required treatment of infinities at the cost of only one isnan test in
22229 ordinary (finite) cases. It is less than ideal in that undue overflow and underflow may occur.
22232 EXAMPLE 2 Division of two double _Complex operands could be implemented as follows.
22236 #include <a href="#7.12"><math.h></a>
22237 #include <a href="#7.3"><complex.h></a>
22238 /* Divide z / w ... */
22239 double complex _Cdivd(double complex z, double complex w)
22241 #pragma STDC FP_CONTRACT OFF
22242 double a, b, c, d, logbw, denom, x, y;
22244 a = creal(z); b = cimag(z);
22245 c = creal(w); d = cimag(w);
22246 logbw = logb(fmax(fabs(c), fabs(d)));
22247 if (isfinite(logbw)) {
22248 ilogbw = (int)logbw;
22249 c = scalbn(c, -ilogbw); d = scalbn(d, -ilogbw);
22251 denom = c * c + d * d;
22252 x = scalbn((a * c + b * d) / denom, -ilogbw);
22253 y = scalbn((b * c - a * d) / denom, -ilogbw);
22254 /* Recover infinities and zeros that computed as NaN+iNaN; */
22255 /* the only cases are nonzero/zero, infinite/finite, and finite/infinite, ... */
22256 if (isnan(x) && isnan(y)) {
22257 if ((denom == 0.0) &&
22258 (!isnan(a) || !isnan(b))) {
22259 x = copysign(INFINITY, c) * a;
22260 y = copysign(INFINITY, c) * b;
22262 else if ((isinf(a) || isinf(b)) &&
22263 isfinite(c) && isfinite(d)) {
22264 a = copysign(isinf(a) ? 1.0 : 0.0, a);
22265 b = copysign(isinf(b) ? 1.0 : 0.0, b);
22266 x = INFINITY * ( a * c + b * d );
22267 y = INFINITY * ( b * c - a * d );
22269 else if (isinf(logbw) &&
22270 isfinite(a) && isfinite(b)) {
22271 c = copysign(isinf(c) ? 1.0 : 0.0, c);
22272 d = copysign(isinf(d) ? 1.0 : 0.0, d);
22273 x = 0.0 * ( a * c + b * d );
22274 y = 0.0 * ( b * c - a * d );
22279 Scaling the denominator alleviates the main overflow and underflow problem, which is more serious than
22280 for multiplication. In the spirit of the multiplication example above, this code does not defend against
22281 overflow and underflow in the calculation of the numerator. Scaling with the scalbn function, instead of
22282 with division, provides better roundoff characteristics.
22286 <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
22287 (at least where the state for CX_LIMITED_RANGE is ''off'').
22290 <h4><a name="G.5.2" href="#G.5.2">G.5.2 Additive operators</a></h4>
22293 If both operands have imaginary type, then the result has imaginary type. (If one operand
22294 has real type and the other operand has imaginary type, or if either operand has complex
22295 type, then the result has complex type.)
22297 In all cases the result and floating-point exception behavior of a + or - operator is defined
22298 by the usual mathematical formula:
22300 + or - u iv u + iv</pre>
22303 x x(+-)u x (+-) iv (x (+-) u) (+-) iv</pre>
22306 iy (+-)u + iy i(y (+-) v) (+-)u + i(y (+-) v)</pre>
22309 x + iy (x (+-) u) + iy x + i(y (+-) v) (x (+-) u) + i(y (+-) v)</pre>
22311 <h3><a name="G.6" href="#G.6">G.6 Complex arithmetic <complex.h></a></h3>
22319 are defined, respectively, as _Imaginary and a constant expression of type const
22320 float _Imaginary with the value of the imaginary unit. The macro
22323 is defined to be _Imaginary_I (not _Complex_I as stated in <a href="#7.3">7.3</a>). Notwithstanding
22324 the provisions of <a href="#7.1.3">7.1.3</a>, a program may undefine and then perhaps redefine the macro
22327 This subclause contains specifications for the <a href="#7.3"><complex.h></a> functions that are
22328 particularly suited to IEC 60559 implementations. For families of functions, the
22329 specifications apply to all of the functions even though only the principal function is
22331 shown. Unless otherwise specified, where the symbol ''(+-)'' occurs in both an argument
22332 and the result, the result has the same sign as the argument.
22334 The functions are continuous onto both sides of their branch cuts, taking into account the
22335 sign of zero. For example, csqrt(-2 (+-) i0) = (+-)i(sqrt)2. ???
22337 Since complex and imaginary values are composed of real values, each function may be
22338 regarded as computing real values from real values. Except as noted, the functions treat
22339 real infinities, NaNs, signed zeros, subnormals, and the floating-point exception flags in a
22340 manner consistent with the specifications for real functions in F.9.<sup><a href="#note326"><b>326)</b></a></sup>
22342 The functions cimag, conj, cproj, and creal are fully specified for all
22343 implementations, including IEC 60559 ones, in <a href="#7.3.9">7.3.9</a>. These functions raise no floating-
22346 Each of the functions cabs and carg is specified by a formula in terms of a real
22347 function (whose special cases are covered in <a href="#F">annex F</a>):
22350 cabs(x + iy) = hypot(x, y)
22351 carg(x + iy) = atan2(y, x)</pre>
22352 Each of the functions casin, catan, ccos, csin, and ctan is specified implicitly by
22353 a formula in terms of other complex functions (whose special cases are specified below):
22356 casin(z) = -i casinh(iz)
22357 catan(z) = -i catanh(iz)
22358 ccos(z) = ccosh(iz)
22359 csin(z) = -i csinh(iz)
22360 ctan(z) = -i ctanh(iz)</pre>
22361 For the other functions, the following subclauses specify behavior for special cases,
22362 including treatment of the ''invalid'' and ''divide-by-zero'' floating-point exceptions. For
22363 families of functions, the specifications apply to all of the functions even though only the
22364 principal function is shown. For a function f satisfying f (conj(z)) = conj( f (z)), the
22365 specifications for the upper half-plane imply the specifications for the lower half-plane; if
22366 the function f is also either even, f (-z) = f (z), or odd, f (-z) = - f (z), then the
22367 specifications for the first quadrant imply the specifications for the other three quadrants.
22369 In the following subclauses, cis(y) is defined as cos(y) + i sin(y).
22377 <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
22378 other part is a NaN.
22381 <h4><a name="G.6.1" href="#G.6.1">G.6.1 Trigonometric functions</a></h4>
22383 <h5><a name="G.6.1.1" href="#G.6.1.1">G.6.1.1 The cacos functions</a></h5>
22386 <li> cacos(conj(z)) = conj(cacos(z)).
22387 <li> cacos((+-)0 + i0) returns pi /2 - i0.
22388 <li> cacos((+-)0 + iNaN) returns pi /2 + iNaN.
22389 <li> cacos(x + i (inf)) returns pi /2 - i (inf), for finite x.
22390 <li> cacos(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22391 point exception, for nonzero finite x.
22392 <li> cacos(-(inf) + iy) returns pi - i (inf), for positive-signed finite y.
22393 <li> cacos(+(inf) + iy) returns +0 - i (inf), for positive-signed finite y.
22394 <li> cacos(-(inf) + i (inf)) returns 3pi /4 - i (inf).
22395 <li> cacos(+(inf) + i (inf)) returns pi /4 - i (inf).
22396 <li> cacos((+-)(inf) + iNaN) returns NaN (+-) i (inf) (where the sign of the imaginary part of the
22397 result is unspecified).
22398 <li> cacos(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22399 point exception, for finite y.
22400 <li> cacos(NaN + i (inf)) returns NaN - i (inf).
22401 <li> cacos(NaN + iNaN) returns NaN + iNaN.
22404 <h4><a name="G.6.2" href="#G.6.2">G.6.2 Hyperbolic functions</a></h4>
22406 <h5><a name="G.6.2.1" href="#G.6.2.1">G.6.2.1 The cacosh functions</a></h5>
22409 <li> cacosh(conj(z)) = conj(cacosh(z)).
22410 <li> cacosh((+-)0 + i0) returns +0 + ipi /2.
22411 <li> cacosh(x + i (inf)) returns +(inf) + ipi /2, for finite x.
22412 <li> cacosh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid''
22413 floating-point exception, for finite x.
22414 <li> cacosh(-(inf) + iy) returns +(inf) + ipi , for positive-signed finite y.
22415 <li> cacosh(+(inf) + iy) returns +(inf) + i0, for positive-signed finite y.
22416 <li> cacosh(-(inf) + i (inf)) returns +(inf) + i3pi /4.
22417 <li> cacosh(+(inf) + i (inf)) returns +(inf) + ipi /4.
22418 <li> cacosh((+-)(inf) + iNaN) returns +(inf) + iNaN.
22420 <li> cacosh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid''
22421 floating-point exception, for finite y.
22422 <li> cacosh(NaN + i (inf)) returns +(inf) + iNaN.
22423 <li> cacosh(NaN + iNaN) returns NaN + iNaN.
22426 <h5><a name="G.6.2.2" href="#G.6.2.2">G.6.2.2 The casinh functions</a></h5>
22429 <li> casinh(conj(z)) = conj(casinh(z)) and casinh is odd.
22430 <li> casinh(+0 + i0) returns 0 + i0.
22431 <li> casinh(x + i (inf)) returns +(inf) + ipi /2 for positive-signed finite x.
22432 <li> casinh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid''
22433 floating-point exception, for finite x.
22434 <li> casinh(+(inf) + iy) returns +(inf) + i0 for positive-signed finite y.
22435 <li> casinh(+(inf) + i (inf)) returns +(inf) + ipi /4.
22436 <li> casinh(+(inf) + iNaN) returns +(inf) + iNaN.
22437 <li> casinh(NaN + i0) returns NaN + i0.
22438 <li> casinh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid''
22439 floating-point exception, for finite nonzero y.
22440 <li> casinh(NaN + i (inf)) returns (+-)(inf) + iNaN (where the sign of the real part of the result
22442 <li> casinh(NaN + iNaN) returns NaN + iNaN.
22445 <h5><a name="G.6.2.3" href="#G.6.2.3">G.6.2.3 The catanh functions</a></h5>
22448 <li> catanh(conj(z)) = conj(catanh(z)) and catanh is odd.
22449 <li> catanh(+0 + i0) returns +0 + i0.
22450 <li> catanh(+0 + iNaN) returns +0 + iNaN.
22451 <li> catanh(+1 + i0) returns +(inf) + i0 and raises the ''divide-by-zero'' floating-point
22453 <li> catanh(x + i (inf)) returns +0 + ipi /2, for finite positive-signed x.
22454 <li> catanh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid''
22455 floating-point exception, for nonzero finite x.
22456 <li> catanh(+(inf) + iy) returns +0 + ipi /2, for finite positive-signed y.
22457 <li> catanh(+(inf) + i (inf)) returns +0 + ipi /2.
22458 <li> catanh(+(inf) + iNaN) returns +0 + iNaN.
22460 <li> catanh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid''
22461 floating-point exception, for finite y.
22462 <li> catanh(NaN + i (inf)) returns (+-)0 + ipi /2 (where the sign of the real part of the result is
22464 <li> catanh(NaN + iNaN) returns NaN + iNaN.
22467 <h5><a name="G.6.2.4" href="#G.6.2.4">G.6.2.4 The ccosh functions</a></h5>
22470 <li> ccosh(conj(z)) = conj(ccosh(z)) and ccosh is even.
22471 <li> ccosh(+0 + i0) returns 1 + i0.
22472 <li> ccosh(+0 + i (inf)) returns NaN (+-) i0 (where the sign of the imaginary part of the
22473 result is unspecified) and raises the ''invalid'' floating-point exception.
22474 <li> ccosh(+0 + iNaN) returns NaN (+-) i0 (where the sign of the imaginary part of the
22475 result is unspecified).
22476 <li> ccosh(x + i (inf)) returns NaN + iNaN and raises the ''invalid'' floating-point
22477 exception, for finite nonzero x.
22478 <li> ccosh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22479 point exception, for finite nonzero x.
22480 <li> ccosh(+(inf) + i0) returns +(inf) + i0.
22481 <li> ccosh(+(inf) + iy) returns +(inf) cis(y), for finite nonzero y.
22482 <li> ccosh(+(inf) + i (inf)) returns (+-)(inf) + iNaN (where the sign of the real part of the result is
22483 unspecified) and raises the ''invalid'' floating-point exception.
22484 <li> ccosh(+(inf) + iNaN) returns +(inf) + iNaN.
22485 <li> ccosh(NaN + i0) returns NaN (+-) i0 (where the sign of the imaginary part of the
22486 result is unspecified).
22487 <li> ccosh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22488 point exception, for all nonzero numbers y.
22489 <li> ccosh(NaN + iNaN) returns NaN + iNaN.
22492 <h5><a name="G.6.2.5" href="#G.6.2.5">G.6.2.5 The csinh functions</a></h5>
22495 <li> csinh(conj(z)) = conj(csinh(z)) and csinh is odd.
22496 <li> csinh(+0 + i0) returns +0 + i0.
22497 <li> csinh(+0 + i (inf)) returns (+-)0 + iNaN (where the sign of the real part of the result is
22498 unspecified) and raises the ''invalid'' floating-point exception.
22499 <li> csinh(+0 + iNaN) returns (+-)0 + iNaN (where the sign of the real part of the result is
22502 <li> csinh(x + i (inf)) returns NaN + iNaN and raises the ''invalid'' floating-point
22503 exception, for positive finite x.
22504 <li> csinh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22505 point exception, for finite nonzero x.
22506 <li> csinh(+(inf) + i0) returns +(inf) + i0.
22507 <li> csinh(+(inf) + iy) returns +(inf) cis(y), for positive finite y.
22508 <li> csinh(+(inf) + i (inf)) returns (+-)(inf) + iNaN (where the sign of the real part of the result is
22509 unspecified) and raises the ''invalid'' floating-point exception.
22510 <li> csinh(+(inf) + iNaN) returns (+-)(inf) + iNaN (where the sign of the real part of the result
22512 <li> csinh(NaN + i0) returns NaN + i0.
22513 <li> csinh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22514 point exception, for all nonzero numbers y.
22515 <li> csinh(NaN + iNaN) returns NaN + iNaN.
22518 <h5><a name="G.6.2.6" href="#G.6.2.6">G.6.2.6 The ctanh functions</a></h5>
22521 <li> ctanh(conj(z)) = conj(ctanh(z))and ctanh is odd.
22522 <li> ctanh(+0 + i0) returns +0 + i0.
22523 <li> ctanh(x + i (inf)) returns NaN + iNaN and raises the ''invalid'' floating-point
22524 exception, for finite x.
22525 <li> ctanh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22526 point exception, for finite x.
22527 <li> ctanh(+(inf) + iy) returns 1 + i0 sin(2y), for positive-signed finite y.
22528 <li> ctanh(+(inf) + i (inf)) returns 1 (+-) i0 (where the sign of the imaginary part of the result
22530 <li> ctanh(+(inf) + iNaN) returns 1 (+-) i0 (where the sign of the imaginary part of the
22531 result is unspecified).
22532 <li> ctanh(NaN + i0) returns NaN + i0.
22533 <li> ctanh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22534 point exception, for all nonzero numbers y.
22535 <li> ctanh(NaN + iNaN) returns NaN + iNaN.
22539 <h4><a name="G.6.3" href="#G.6.3">G.6.3 Exponential and logarithmic functions</a></h4>
22541 <h5><a name="G.6.3.1" href="#G.6.3.1">G.6.3.1 The cexp functions</a></h5>
22544 <li> cexp(conj(z)) = conj(cexp(z)).
22545 <li> cexp((+-)0 + i0) returns 1 + i0.
22546 <li> cexp(x + i (inf)) returns NaN + iNaN and raises the ''invalid'' floating-point
22547 exception, for finite x.
22548 <li> cexp(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22549 point exception, for finite x.
22550 <li> cexp(+(inf) + i0) returns +(inf) + i0.
22551 <li> cexp(-(inf) + iy) returns +0 cis(y), for finite y.
22552 <li> cexp(+(inf) + iy) returns +(inf) cis(y), for finite nonzero y.
22553 <li> cexp(-(inf) + i (inf)) returns (+-)0 (+-) i0 (where the signs of the real and imaginary parts of
22554 the result are unspecified).
22555 <li> cexp(+(inf) + i (inf)) returns (+-)(inf) + iNaN and raises the ''invalid'' floating-point
22556 exception (where the sign of the real part of the result is unspecified).
22557 <li> cexp(-(inf) + iNaN) returns (+-)0 (+-) i0 (where the signs of the real and imaginary parts
22558 of the result are unspecified).
22559 <li> cexp(+(inf) + iNaN) returns (+-)(inf) + iNaN (where the sign of the real part of the result
22561 <li> cexp(NaN + i0) returns NaN + i0.
22562 <li> cexp(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22563 point exception, for all nonzero numbers y.
22564 <li> cexp(NaN + iNaN) returns NaN + iNaN.
22567 <h5><a name="G.6.3.2" href="#G.6.3.2">G.6.3.2 The clog functions</a></h5>
22570 <li> clog(conj(z)) = conj(clog(z)).
22571 <li> clog(-0 + i0) returns -(inf) + ipi and raises the ''divide-by-zero'' floating-point
22573 <li> clog(+0 + i0) returns -(inf) + i0 and raises the ''divide-by-zero'' floating-point
22575 <li> clog(x + i (inf)) returns +(inf) + ipi /2, for finite x.
22576 <li> clog(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22577 point exception, for finite x.
22579 <li> clog(-(inf) + iy) returns +(inf) + ipi , for finite positive-signed y.
22580 <li> clog(+(inf) + iy) returns +(inf) + i0, for finite positive-signed y.
22581 <li> clog(-(inf) + i (inf)) returns +(inf) + i3pi /4.
22582 <li> clog(+(inf) + i (inf)) returns +(inf) + ipi /4.
22583 <li> clog((+-)(inf) + iNaN) returns +(inf) + iNaN.
22584 <li> clog(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22585 point exception, for finite y.
22586 <li> clog(NaN + i (inf)) returns +(inf) + iNaN.
22587 <li> clog(NaN + iNaN) returns NaN + iNaN.
22590 <h4><a name="G.6.4" href="#G.6.4">G.6.4 Power and absolute-value functions</a></h4>
22592 <h5><a name="G.6.4.1" href="#G.6.4.1">G.6.4.1 The cpow functions</a></h5>
22594 The cpow functions raise floating-point exceptions if appropriate for the calculation of
22595 the parts of the result, and may raise spurious exceptions.<sup><a href="#note327"><b>327)</b></a></sup>
22598 <p><small><a name="note327" href="#note327">327)</a> This allows cpow( z , c ) to be implemented as cexp(c clog( z )) without precluding
22599 implementations that treat special cases more carefully.
22602 <h5><a name="G.6.4.2" href="#G.6.4.2">G.6.4.2 The csqrt functions</a></h5>
22605 <li> csqrt(conj(z)) = conj(csqrt(z)).
22606 <li> csqrt((+-)0 + i0) returns +0 + i0.
22607 <li> csqrt(x + i (inf)) returns +(inf) + i (inf), for all x (including NaN).
22608 <li> csqrt(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22609 point exception, for finite x.
22610 <li> csqrt(-(inf) + iy) returns +0 + i (inf), for finite positive-signed y.
22611 <li> csqrt(+(inf) + iy) returns +(inf) + i0, for finite positive-signed y.
22612 <li> csqrt(-(inf) + iNaN) returns NaN (+-) i (inf) (where the sign of the imaginary part of the
22613 result is unspecified).
22614 <li> csqrt(+(inf) + iNaN) returns +(inf) + iNaN.
22615 <li> csqrt(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22616 point exception, for finite y.
22617 <li> csqrt(NaN + iNaN) returns NaN + iNaN.
22625 <h3><a name="G.7" href="#G.7">G.7 Type-generic math <tgmath.h></a></h3>
22627 Type-generic macros that accept complex arguments also accept imaginary arguments. If
22628 an argument is imaginary, the macro expands to an expression whose type is real,
22629 imaginary, or complex, as appropriate for the particular function: if the argument is
22630 imaginary, then the types of cos, cosh, fabs, carg, cimag, and creal are real; the
22631 types of sin, tan, sinh, tanh, asin, atan, asinh, and atanh are imaginary; and
22632 the types of the others are complex.
22634 Given an imaginary argument, each of the type-generic macros cos, sin, tan, cosh,
22635 sinh, tanh, asin, atan, asinh, atanh is specified by a formula in terms of real
22640 sin(iy) = i sinh(y)
22641 tan(iy) = i tanh(y)
22643 sinh(iy) = i sin(y)
22644 tanh(iy) = i tan(y)
22645 asin(iy) = i asinh(y)
22646 atan(iy) = i atanh(y)
22647 asinh(iy) = i asin(y)
22648 atanh(iy) = i atan(y)</pre>
22650 <h2><a name="H" href="#H">Annex H</a></h2>
22653 Language independent arithmetic</pre>
22655 <h3><a name="H.1" href="#H.1">H.1 Introduction</a></h3>
22657 This annex documents the extent to which the C language supports the ISO/IEC 10967-1
22658 standard for language-independent arithmetic (LIA-1). LIA-1 is more general than
22659 IEC 60559 (<a href="#F">annex F</a>) in that it covers integer and diverse floating-point arithmetics.
22661 <h3><a name="H.2" href="#H.2">H.2 Types</a></h3>
22663 The relevant C arithmetic types meet the requirements of LIA-1 types if an
22664 implementation adds notification of exceptional arithmetic operations and meets the 1
22665 unit in the last place (ULP) accuracy requirement (LIA-1 subclause <a href="#5.2.8">5.2.8</a>).
22667 <h4><a name="H.2.1" href="#H.2.1">H.2.1 Boolean type</a></h4>
22669 The LIA-1 data type Boolean is implemented by the C data type bool with values of
22670 true and false, all from <a href="#7.16"><stdbool.h></a>.
22672 <h4><a name="H.2.2" href="#H.2.2">H.2.2 Integer types</a></h4>
22674 The signed C integer types int, long int, long long int, and the corresponding
22675 unsigned types are compatible with LIA-1. If an implementation adds support for the
22676 LIA-1 exceptional values ''integer_overflow'' and ''undefined'', then those types are
22677 LIA-1 conformant types. C's unsigned integer types are ''modulo'' in the LIA-1 sense
22678 in that overflows or out-of-bounds results silently wrap. An implementation that defines
22679 signed integer types as also being modulo need not detect integer overflow, in which case,
22680 only integer divide-by-zero need be detected.
22682 The parameters for the integer data types can be accessed by the following:
22683 maxint INT_MAX, LONG_MAX, LLONG_MAX, UINT_MAX, ULONG_MAX,
22686 minint INT_MIN, LONG_MIN, LLONG_MIN
22688 The parameter ''bounded'' is always true, and is not provided. The parameter ''minint''
22689 is always 0 for the unsigned types, and is not provided for those types.
22692 <h5><a name="H.2.2.1" href="#H.2.2.1">H.2.2.1 Integer operations</a></h5>
22694 The integer operations on integer types are the following:
22701 absI abs(x), labs(x), llabs(x)
22708 where x and y are expressions of the same integer type.
22710 <h4><a name="H.2.3" href="#H.2.3">H.2.3 Floating-point types</a></h4>
22712 The C floating-point types float, double, and long double are compatible with
22713 LIA-1. If an implementation adds support for the LIA-1 exceptional values
22714 ''underflow'', ''floating_overflow'', and ''"undefined'', then those types are conformant
22715 with LIA-1. An implementation that uses IEC 60559 floating-point formats and
22716 operations (see <a href="#F">annex F</a>) along with IEC 60559 status flags and traps has LIA-1
22719 <h5><a name="H.2.3.1" href="#H.2.3.1">H.2.3.1 Floating-point parameters</a></h5>
22721 The parameters for a floating point data type can be accessed by the following:
22723 p FLT_MANT_DIG, DBL_MANT_DIG, LDBL_MANT_DIG
22724 emax FLT_MAX_EXP, DBL_MAX_EXP, LDBL_MAX_EXP
22725 emin FLT_MIN_EXP, DBL_MIN_EXP, LDBL_MIN_EXP
22727 The derived constants for the floating point types are accessed by the following:
22729 fmax FLT_MAX, DBL_MAX, LDBL_MAX
22730 fminN FLT_MIN, DBL_MIN, LDBL_MIN
22731 epsilon FLT_EPSILON, DBL_EPSILON, LDBL_EPSILON
22732 rnd_style FLT_ROUNDS
22734 <h5><a name="H.2.3.2" href="#H.2.3.2">H.2.3.2 Floating-point operations</a></h5>
22736 The floating-point operations on floating-point types are the following:
22742 absF fabsf(x), fabs(x), fabsl(x)
22743 exponentF 1.f+logbf(x), 1.0+logb(x), 1.L+logbl(x)
22744 scaleF scalbnf(x, n), scalbn(x, n), scalbnl(x, n),
22746 scalblnf(x, li), scalbln(x, li), scalblnl(x, li)</pre>
22747 intpartF modff(x, &y), modf(x, &y), modfl(x, &y)
22748 fractpartF modff(x, &y), modf(x, &y), modfl(x, &y)
22755 where x and y are expressions of the same floating point type, n is of type int, and li
22756 is of type long int.
22758 <h5><a name="H.2.3.3" href="#H.2.3.3">H.2.3.3 Rounding styles</a></h5>
22760 The C Standard requires all floating types to use the same radix and rounding style, so
22761 that only one identifier for each is provided to map to LIA-1.
22763 The FLT_ROUNDS parameter can be used to indicate the LIA-1 rounding styles:
22764 truncate FLT_ROUNDS == 0
22766 nearest FLT_ROUNDS == 1
22767 other FLT_ROUNDS != 0 && FLT_ROUNDS != 1
22768 provided that an implementation extends FLT_ROUNDS to cover the rounding style used
22769 in all relevant LIA-1 operations, not just addition as in C.
22771 <h4><a name="H.2.4" href="#H.2.4">H.2.4 Type conversions</a></h4>
22773 The LIA-1 type conversions are the following type casts:
22774 cvtI' -> I (int)i, (long int)i, (long long int)i,
22776 (unsigned int)i, (unsigned long int)i,
22777 (unsigned long long int)i</pre>
22778 cvtF -> I (int)x, (long int)x, (long long int)x,
22780 (unsigned int)x, (unsigned long int)x,
22781 (unsigned long long int)x</pre>
22782 cvtI -> F (float)i, (double)i, (long double)i
22783 cvtF' -> F (float)x, (double)x, (long double)x
22785 In the above conversions from floating to integer, the use of (cast)x can be replaced with
22786 (cast)round(x), (cast)rint(x), (cast)nearbyint(x), (cast)trunc(x),
22787 (cast)ceil(x), or (cast)floor(x). In addition, C's floating-point to integer
22788 conversion functions, lrint(), llrint(), lround(), and llround(), can be
22789 used. They all meet LIA-1's requirements on floating to integer rounding for in-range
22790 values. For out-of-range values, the conversions shall silently wrap for the modulo types.
22792 The fmod() function is useful for doing silent wrapping to unsigned integer types, e.g.,
22793 fmod( fabs(rint(x)), 65536.0 ) or (0.0 <= (y = fmod( rint(x),
22794 65536.0 )) ? y : 65536.0 + y) will compute an integer value in the range 0.0
22795 to 65535.0 which can then be cast to unsigned short int. But, the
22796 remainder() function is not useful for doing silent wrapping to signed integer types,
22797 e.g., remainder( rint(x), 65536.0 ) will compute an integer value in the
22798 range -32767.0 to +32768.0 which is not, in general, in the range of signed short
22801 C's conversions (casts) from floating-point to floating-point can meet LIA-1
22802 requirements if an implementation uses round-to-nearest (IEC 60559 default).
22804 C's conversions (casts) from integer to floating-point can meet LIA-1 requirements if an
22805 implementation uses round-to-nearest.
22808 <h3><a name="H.3" href="#H.3">H.3 Notification</a></h3>
22810 Notification is the process by which a user or program is informed that an exceptional
22811 arithmetic operation has occurred. C's operations are compatible with LIA-1 in that C
22812 allows an implementation to cause a notification to occur when any arithmetic operation
22813 returns an exceptional value as defined in LIA-1 clause 5.
22815 <h4><a name="H.3.1" href="#H.3.1">H.3.1 Notification alternatives</a></h4>
22817 LIA-1 requires at least the following two alternatives for handling of notifications:
22818 setting indicators or trap-and-terminate. LIA-1 allows a third alternative: trap-and-
22821 An implementation need only support a given notification alternative for the entire
22822 program. An implementation may support the ability to switch between notification
22823 alternatives during execution, but is not required to do so. An implementation can
22824 provide separate selection for each kind of notification, but this is not required.
22826 C allows an implementation to provide notification. C's SIGFPE (for traps) and
22827 FE_INVALID, FE_DIVBYZERO, FE_OVERFLOW, FE_UNDERFLOW (for indicators)
22828 can provide LIA-1 notification.
22830 C's signal handlers are compatible with LIA-1. Default handling of SIGFPE can
22831 provide trap-and-terminate behavior, except for those LIA-1 operations implemented by
22832 math library function calls. User-provided signal handlers for SIGFPE allow for trap-
22833 and-resume behavior with the same constraint.
22835 <h5><a name="H.3.1.1" href="#H.3.1.1">H.3.1.1 Indicators</a></h5>
22837 C's <a href="#7.6"><fenv.h></a> status flags are compatible with the LIA-1 indicators.
22839 The following mapping is for floating-point types:
22840 undefined FE_INVALID, FE_DIVBYZERO
22841 floating_overflow FE_OVERFLOW
22842 underflow FE_UNDERFLOW
22844 The floating-point indicator interrogation and manipulation operations are:
22845 set_indicators feraiseexcept(i)
22846 clear_indicators feclearexcept(i)
22847 test_indicators fetestexcept(i)
22848 current_indicators fetestexcept(FE_ALL_EXCEPT)
22849 where i is an expression of type int representing a subset of the LIA-1 indicators.
22851 C allows an implementation to provide the following LIA-1 required behavior: at
22852 program termination if any indicator is set the implementation shall send an unambiguous
22854 and ''hard to ignore'' message (see LIA-1 subclause <a href="#6.1.2">6.1.2</a>)
22856 LIA-1 does not make the distinction between floating-point and integer for ''undefined''.
22857 This documentation makes that distinction because <a href="#7.6"><fenv.h></a> covers only the floating-
22860 <h5><a name="H.3.1.2" href="#H.3.1.2">H.3.1.2 Traps</a></h5>
22862 C is compatible with LIA-1's trap requirements for arithmetic operations, but not for
22863 math library functions (which are not permitted to generate any externally visible
22864 exceptional conditions). An implementation can provide an alternative of notification
22865 through termination with a ''hard-to-ignore'' message (see LIA-1 subclause <a href="#6.1.3">6.1.3</a>).
22867 LIA-1 does not require that traps be precise.
22869 C does require that SIGFPE be the signal corresponding to arithmetic exceptions, if there
22870 is any signal raised for them.
22872 C supports signal handlers for SIGFPE and allows trapping of arithmetic exceptions.
22873 When arithmetic exceptions do trap, C's signal-handler mechanism allows trap-and-
22874 terminate (either default implementation behavior or user replacement for it) or trap-and-
22875 resume, at the programmer's option.
22878 <h2><a name="I" href="#I">Annex I</a></h2>
22882 Common warnings</pre>
22883 An implementation may generate warnings in many situations, none of which are
22884 specified as part of this International Standard. The following are a few of the more
22888 <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>).
22889 <li> A block with initialization of an object that has automatic storage duration is jumped
22890 into (<a href="#6.2.4">6.2.4</a>).
22891 <li> An implicit narrowing conversion is encountered, such as the assignment of a long
22892 int or a double to an int, or a pointer to void to a pointer to any type other than
22893 a character type (<a href="#6.3">6.3</a>).
22894 <li> A hexadecimal floating constant cannot be represented exactly in its evaluation format
22895 (<a href="#6.4.4.2">6.4.4.2</a>).
22896 <li> An integer character constant includes more than one character or a wide character
22897 constant includes more than one multibyte character (<a href="#6.4.4.4">6.4.4.4</a>).
22898 <li> The characters /* are found in a comment (<a href="#6.4.7">6.4.7</a>).
22899 <li> An ''unordered'' binary operator (not comma, &&, or ||) contains a side effect to an
22900 lvalue in one operand, and a side effect to, or an access to the value of, the identical
22901 lvalue in the other operand (<a href="#6.5">6.5</a>).
22902 <li> A function is called but no prototype has been supplied (<a href="#6.5.2.2">6.5.2.2</a>).
22903 <li> The arguments in a function call do not agree in number and type with those of the
22904 parameters in a function definition that is not a prototype (<a href="#6.5.2.2">6.5.2.2</a>).
22905 <li> An object is defined but not used (<a href="#6.7">6.7</a>).
22906 <li> A value is given to an object of an enumerated type other than by assignment of an
22907 enumeration constant that is a member of that type, or an enumeration object that has
22908 the same type, or the value of a function that returns the same enumerated type
22909 (<a href="#6.7.2.2">6.7.2.2</a>).
22910 <li> An aggregate has a partly bracketed initialization (<a href="#6.7.7">6.7.7</a>).
22911 <li> A statement cannot be reached (<a href="#6.8">6.8</a>).
22912 <li> A statement with no apparent effect is encountered (<a href="#6.8">6.8</a>).
22913 <li> A constant expression is used as the controlling expression of a selection statement
22914 (<a href="#6.8.4">6.8.4</a>).
22916 <li> An incorrectly formed preprocessing group is encountered while skipping a
22917 preprocessing group (<a href="#6.10.1">6.10.1</a>).
22918 <li> An unrecognized #pragma directive is encountered (<a href="#6.10.6">6.10.6</a>).
22922 <h2><a name="J" href="#J">Annex J</a></h2>
22926 Portability issues</pre>
22927 This annex collects some information about portability that appears in this International
22930 <h3><a name="J.1" href="#J.1">J.1 Unspecified behavior</a></h3>
22932 The following are unspecified:
22934 <li> The manner and timing of static initialization (<a href="#5.1.2">5.1.2</a>).
22935 <li> The termination status returned to the hosted environment if the return type of main
22936 is not compatible with int (<a href="#5.1.2.2.3">5.1.2.2.3</a>).
22937 <li> The behavior of the display device if a printing character is written when the active
22938 position is at the final position of a line (<a href="#5.2.2">5.2.2</a>).
22939 <li> The behavior of the display device if a backspace character is written when the active
22940 position is at the initial position of a line (<a href="#5.2.2">5.2.2</a>).
22941 <li> The behavior of the display device if a horizontal tab character is written when the
22942 active position is at or past the last defined horizontal tabulation position (<a href="#5.2.2">5.2.2</a>).
22943 <li> The behavior of the display device if a vertical tab character is written when the active
22944 position is at or past the last defined vertical tabulation position (<a href="#5.2.2">5.2.2</a>).
22945 <li> How an extended source character that does not correspond to a universal character
22946 name counts toward the significant initial characters in an external identifier (<a href="#5.2.4.1">5.2.4.1</a>).
22947 <li> Many aspects of the representations of types (<a href="#6.2.6">6.2.6</a>).
22948 <li> The value of padding bytes when storing values in structures or unions (<a href="#6.2.6.1">6.2.6.1</a>).
22949 <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>).
22950 <li> The representation used when storing a value in an object that has more than one
22951 object representation for that value (<a href="#6.2.6.1">6.2.6.1</a>).
22952 <li> The values of any padding bits in integer representations (<a href="#6.2.6.2">6.2.6.2</a>).
22953 <li> Whether certain operators can generate negative zeros and whether a negative zero
22954 becomes a normal zero when stored in an object (<a href="#6.2.6.2">6.2.6.2</a>).
22955 <li> Whether two string literals result in distinct arrays (<a href="#6.4.5">6.4.5</a>).
22956 <li> The order in which subexpressions are evaluated and the order in which side effects
22957 take place, except as specified for the function-call (), &&, ||, ?:, and comma
22958 operators (<a href="#6.5">6.5</a>).
22960 <li> The order in which the function designator, arguments, and subexpressions within the
22961 arguments are evaluated in a function call (<a href="#6.5.2.2">6.5.2.2</a>).
22962 <li> The order of side effects among compound literal initialization list expressions
22963 (<a href="#6.5.2.5">6.5.2.5</a>).
22964 <li> The order in which the operands of an assignment operator are evaluated (<a href="#6.5.16">6.5.16</a>).
22965 <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>).
22966 <li> Whether a call to an inline function uses the inline definition or the external definition
22967 of the function (<a href="#6.7.4">6.7.4</a>).
22968 <li> Whether or not a size expression is evaluated when it is part of the operand of a
22969 sizeof operator and changing the value of the size expression would not affect the
22970 result of the operator (<a href="#6.7.5.2">6.7.5.2</a>).
22971 <li> The order in which any side effects occur among the initialization list expressions in
22972 an initializer (<a href="#6.7.8">6.7.8</a>).
22973 <li> The layout of storage for function parameters (<a href="#6.9.1">6.9.1</a>).
22974 <li> When a fully expanded macro replacement list contains a function-like macro name
22975 as its last preprocessing token and the next preprocessing token from the source file is
22976 a (, and the fully expanded replacement of that macro ends with the name of the first
22977 macro and the next preprocessing token from the source file is again a (, whether that
22978 is considered a nested replacement (<a href="#6.10.3">6.10.3</a>).
22979 <li> The order in which # and ## operations are evaluated during macro substitution
22980 (<a href="#6.10.3.2">6.10.3.2</a>, <a href="#6.10.3.3">6.10.3.3</a>).
22981 <li> Whether errno is a macro or an identifier with external linkage (<a href="#7.5">7.5</a>).
22982 <li> The state of the floating-point status flags when execution passes from a part of the
22983 program translated with FENV_ACCESS ''off'' to a part translated with
22984 FENV_ACCESS ''on'' (<a href="#7.6.1">7.6.1</a>).
22985 <li> The order in which feraiseexcept raises floating-point exceptions, except as
22986 stated in <a href="#F.7.6">F.7.6</a> (<a href="#7.6.2.3">7.6.2.3</a>).
22987 <li> Whether math_errhandling is a macro or an identifier with external linkage
22988 (<a href="#7.12">7.12</a>).
22989 <li> The results of the frexp functions when the specified value is not a floating-point
22990 number (<a href="#7.12.6.4">7.12.6.4</a>).
22991 <li> The numeric result of the ilogb functions when the correct value is outside the
22992 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>).
22993 <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>).
22995 <li> The value stored by the remquo functions in the object pointed to by quo when y is
22996 zero (<a href="#7.12.10.3">7.12.10.3</a>).
22997 <li> Whether setjmp is a macro or an identifier with external linkage (<a href="#7.13">7.13</a>).
22998 <li> Whether va_copy and va_end are macros or identifiers with external linkage
22999 (<a href="#7.15.1">7.15.1</a>).
23000 <li> The hexadecimal digit before the decimal point when a non-normalized floating-point
23001 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>).
23002 <li> The value of the file position indicator after a successful call to the ungetc function
23003 for a text stream, or the ungetwc function for any stream, until all pushed-back
23004 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>).
23005 <li> The details of the value stored by the fgetpos function (<a href="#7.19.9.1">7.19.9.1</a>).
23006 <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>).
23007 <li> Whether the strtod, strtof, strtold, wcstod, wcstof, and wcstold
23008 functions convert a minus-signed sequence to a negative number directly or by
23009 negating the value resulting from converting the corresponding unsigned sequence
23010 (<a href="#7.20.1.3">7.20.1.3</a>, <a href="#7.24.4.1.1">7.24.4.1.1</a>).
23011 <li> The order and contiguity of storage allocated by successive calls to the calloc,
23012 malloc, and realloc functions (<a href="#7.20.3">7.20.3</a>).
23013 <li> The amount of storage allocated by a successful call to the calloc, malloc, or
23014 realloc function when 0 bytes was requested (<a href="#7.20.3">7.20.3</a>).
23015 <li> Which of two elements that compare as equal is matched by the bsearch function
23016 (<a href="#7.20.5.1">7.20.5.1</a>).
23017 <li> The order of two elements that compare as equal in an array sorted by the qsort
23018 function (<a href="#7.20.5.2">7.20.5.2</a>).
23019 <li> The encoding of the calendar time returned by the time function (<a href="#7.23.2.4">7.23.2.4</a>).
23020 <li> The characters stored by the strftime or wcsftime function if any of the time
23021 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>).
23022 <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>,
23023 <a href="#7.24.6.4.2">7.24.6.4.2</a>,
23024 <li> The resulting value when the ''invalid'' floating-point exception is raised during
23025 IEC 60559 floating to integer conversion (<a href="#F.4">F.4</a>).
23026 <li> Whether conversion of non-integer IEC 60559 floating values to integer raises the
23027 ''inexact'' floating-point exception (<a href="#F.4">F.4</a>).
23029 <li> Whether or when library functions in <a href="#7.12"><math.h></a> raise the ''inexact'' floating-point
23030 exception in an IEC 60559 conformant implementation (<a href="#F.9">F.9</a>).
23031 <li> Whether or when library functions in <a href="#7.12"><math.h></a> raise an undeserved ''underflow''
23032 floating-point exception in an IEC 60559 conformant implementation (<a href="#F.9">F.9</a>).
23033 <li> The exponent value stored by frexp for a NaN or infinity (<a href="#F.9.3.4">F.9.3.4</a>).
23034 <li> The numeric result returned by the lrint, llrint, lround, and llround
23035 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>).
23036 <li> The sign of one part of the complex result of several math functions for certain
23037 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>,
23038 <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>).
23041 <h3><a name="J.2" href="#J.2">J.2 Undefined behavior</a></h3>
23043 The behavior is undefined in the following circumstances:
23045 <li> A ''shall'' or ''shall not'' requirement that appears outside of a constraint is violated
23047 <li> A nonempty source file does not end in a new-line character which is not immediately
23048 preceded by a backslash character or ends in a partial preprocessing token or
23049 comment (<a href="#5.1.1.2">5.1.1.2</a>).
23050 <li> Token concatenation produces a character sequence matching the syntax of a
23051 universal character name (<a href="#5.1.1.2">5.1.1.2</a>).
23052 <li> A program in a hosted environment does not define a function named main using one
23053 of the specified forms (<a href="#5.1.2.2.1">5.1.2.2.1</a>).
23054 <li> A character not in the basic source character set is encountered in a source file, except
23055 in an identifier, a character constant, a string literal, a header name, a comment, or a
23056 preprocessing token that is never converted to a token (<a href="#5.2.1">5.2.1</a>).
23057 <li> An identifier, comment, string literal, character constant, or header name contains an
23058 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>).
23059 <li> The same identifier has both internal and external linkage in the same translation unit
23060 (<a href="#6.2.2">6.2.2</a>).
23061 <li> An object is referred to outside of its lifetime (<a href="#6.2.4">6.2.4</a>).
23062 <li> The value of a pointer to an object whose lifetime has ended is used (<a href="#6.2.4">6.2.4</a>).
23063 <li> The value of an object with automatic storage duration is used while it is
23064 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>).
23065 <li> A trap representation is read by an lvalue expression that does not have character type
23066 (<a href="#6.2.6.1">6.2.6.1</a>).
23068 <li> A trap representation is produced by a side effect that modifies any part of the object
23069 using an lvalue expression that does not have character type (<a href="#6.2.6.1">6.2.6.1</a>).
23070 <li> The arguments to certain operators are such that could produce a negative zero result,
23071 but the implementation does not support negative zeros (<a href="#6.2.6.2">6.2.6.2</a>).
23072 <li> Two declarations of the same object or function specify types that are not compatible
23073 (<a href="#6.2.7">6.2.7</a>).
23074 <li> Conversion to or from an integer type produces a value outside the range that can be
23075 represented (<a href="#6.3.1.4">6.3.1.4</a>).
23076 <li> Demotion of one real floating type to another produces a value outside the range that
23077 can be represented (<a href="#6.3.1.5">6.3.1.5</a>).
23078 <li> An lvalue does not designate an object when evaluated (<a href="#6.3.2.1">6.3.2.1</a>).
23079 <li> A non-array lvalue with an incomplete type is used in a context that requires the value
23080 of the designated object (<a href="#6.3.2.1">6.3.2.1</a>).
23081 <li> An lvalue having array type is converted to a pointer to the initial element of the
23082 array, and the array object has register storage class (<a href="#6.3.2.1">6.3.2.1</a>).
23083 <li> An attempt is made to use the value of a void expression, or an implicit or explicit
23084 conversion (except to void) is applied to a void expression (<a href="#6.3.2.2">6.3.2.2</a>).
23085 <li> Conversion of a pointer to an integer type produces a value outside the range that can
23086 be represented (<a href="#6.3.2.3">6.3.2.3</a>).
23087 <li> Conversion between two pointer types produces a result that is incorrectly aligned
23088 (<a href="#6.3.2.3">6.3.2.3</a>).
23089 <li> A pointer is used to call a function whose type is not compatible with the pointed-to
23090 type (<a href="#6.3.2.3">6.3.2.3</a>).
23091 <li> An unmatched ' or " character is encountered on a logical source line during
23092 tokenization (<a href="#6.4">6.4</a>).
23093 <li> A reserved keyword token is used in translation phase 7 or 8 for some purpose other
23094 than as a keyword (<a href="#6.4.1">6.4.1</a>).
23095 <li> A universal character name in an identifier does not designate a character whose
23096 encoding falls into one of the specified ranges (<a href="#6.4.2.1">6.4.2.1</a>).
23097 <li> The initial character of an identifier is a universal character name designating a digit
23098 (<a href="#6.4.2.1">6.4.2.1</a>).
23099 <li> Two identifiers differ only in nonsignificant characters (<a href="#6.4.2.1">6.4.2.1</a>).
23100 <li> The identifier __func__ is explicitly declared (<a href="#6.4.2.2">6.4.2.2</a>).
23102 <li> The program attempts to modify a string literal (<a href="#6.4.5">6.4.5</a>).
23103 <li> The characters ', \, ", //, or /* occur in the sequence between the < and >
23104 delimiters, or the characters ', \, //, or /* occur in the sequence between the "
23105 delimiters, in a header name preprocessing token (<a href="#6.4.7">6.4.7</a>).
23106 <li> Between two sequence points, an object is modified more than once, or is modified
23107 and the prior value is read other than to determine the value to be stored (<a href="#6.5">6.5</a>).
23108 <li> An exceptional condition occurs during the evaluation of an expression (<a href="#6.5">6.5</a>).
23109 <li> An object has its stored value accessed other than by an lvalue of an allowable type
23110 (<a href="#6.5">6.5</a>).
23111 <li> An attempt is made to modify the result of a function call, a conditional operator, an
23112 assignment operator, or a comma operator, or to access it after the next sequence
23113 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>).
23114 <li> For a call to a function without a function prototype in scope, the number of
23115 arguments does not equal the number of parameters (<a href="#6.5.2.2">6.5.2.2</a>).
23116 <li> For call to a function without a function prototype in scope where the function is
23117 defined with a function prototype, either the prototype ends with an ellipsis or the
23118 types of the arguments after promotion are not compatible with the types of the
23119 parameters (<a href="#6.5.2.2">6.5.2.2</a>).
23120 <li> For a call to a function without a function prototype in scope where the function is not
23121 defined with a function prototype, the types of the arguments after promotion are not
23122 compatible with those of the parameters after promotion (with certain exceptions)
23123 (<a href="#6.5.2.2">6.5.2.2</a>).
23124 <li> A function is defined with a type that is not compatible with the type (of the
23125 expression) pointed to by the expression that denotes the called function (<a href="#6.5.2.2">6.5.2.2</a>).
23126 <li> The operand of the unary * operator has an invalid value (<a href="#6.5.3.2">6.5.3.2</a>).
23127 <li> A pointer is converted to other than an integer or pointer type (<a href="#6.5.4">6.5.4</a>).
23128 <li> The value of the second operand of the / or % operator is zero (<a href="#6.5.5">6.5.5</a>).
23129 <li> Addition or subtraction of a pointer into, or just beyond, an array object and an
23130 integer type produces a result that does not point into, or just beyond, the same array
23131 object (<a href="#6.5.6">6.5.6</a>).
23132 <li> Addition or subtraction of a pointer into, or just beyond, an array object and an
23133 integer type produces a result that points just beyond the array object and is used as
23134 the operand of a unary * operator that is evaluated (<a href="#6.5.6">6.5.6</a>).
23135 <li> Pointers that do not point into, or just beyond, the same array object are subtracted
23136 (<a href="#6.5.6">6.5.6</a>).
23138 <li> An array subscript is out of range, even if an object is apparently accessible with the
23139 given subscript (as in the lvalue expression a[1][7] given the declaration int
23140 a[4][5]) (<a href="#6.5.6">6.5.6</a>).
23141 <li> The result of subtracting two pointers is not representable in an object of type
23142 ptrdiff_t (<a href="#6.5.6">6.5.6</a>).
23143 <li> An expression is shifted by a negative number or by an amount greater than or equal
23144 to the width of the promoted expression (<a href="#6.5.7">6.5.7</a>).
23145 <li> An expression having signed promoted type is left-shifted and either the value of the
23146 expression is negative or the result of shifting would be not be representable in the
23147 promoted type (<a href="#6.5.7">6.5.7</a>).
23148 <li> Pointers that do not point to the same aggregate or union (nor just beyond the same
23149 array object) are compared using relational operators (<a href="#6.5.8">6.5.8</a>).
23150 <li> An object is assigned to an inexactly overlapping object or to an exactly overlapping
23151 object with incompatible type (<a href="#6.5.16.1">6.5.16.1</a>).
23152 <li> An expression that is required to be an integer constant expression does not have an
23153 integer type; has operands that are not integer constants, enumeration constants,
23154 character constants, sizeof expressions whose results are integer constants, or
23155 immediately-cast floating constants; or contains casts (outside operands to sizeof
23156 operators) other than conversions of arithmetic types to integer types (<a href="#6.6">6.6</a>).
23157 <li> A constant expression in an initializer is not, or does not evaluate to, one of the
23158 following: an arithmetic constant expression, a null pointer constant, an address
23159 constant, or an address constant for an object type plus or minus an integer constant
23160 expression (<a href="#6.6">6.6</a>).
23161 <li> An arithmetic constant expression does not have arithmetic type; has operands that
23162 are not integer constants, floating constants, enumeration constants, character
23163 constants, or sizeof expressions; or contains casts (outside operands to sizeof
23164 operators) other than conversions of arithmetic types to arithmetic types (<a href="#6.6">6.6</a>).
23165 <li> The value of an object is accessed by an array-subscript [], member-access . or ->,
23166 address &, or indirection * operator or a pointer cast in creating an address constant
23167 (<a href="#6.6">6.6</a>).
23168 <li> An identifier for an object is declared with no linkage and the type of the object is
23169 incomplete after its declarator, or after its init-declarator if it has an initializer (<a href="#6.7">6.7</a>).
23170 <li> A function is declared at block scope with an explicit storage-class specifier other
23171 than extern (<a href="#6.7.1">6.7.1</a>).
23172 <li> A structure or union is defined as containing no named members (<a href="#6.7.2.1">6.7.2.1</a>).
23174 <li> An attempt is made to access, or generate a pointer to just past, a flexible array
23175 member of a structure when the referenced object provides no elements for that array
23176 (<a href="#6.7.2.1">6.7.2.1</a>).
23177 <li> When the complete type is needed, an incomplete structure or union type is not
23178 completed in the same scope by another declaration of the tag that defines the content
23179 (<a href="#6.7.2.3">6.7.2.3</a>).
23180 <li> An attempt is made to modify an object defined with a const-qualified type through
23181 use of an lvalue with non-const-qualified type (<a href="#6.7.3">6.7.3</a>).
23182 <li> An attempt is made to refer to an object defined with a volatile-qualified type through
23183 use of an lvalue with non-volatile-qualified type (<a href="#6.7.3">6.7.3</a>).
23184 <li> The specification of a function type includes any type qualifiers (<a href="#6.7.3">6.7.3</a>).
23185 <li> Two qualified types that are required to be compatible do not have the identically
23186 qualified version of a compatible type (<a href="#6.7.3">6.7.3</a>).
23187 <li> An object which has been modified is accessed through a restrict-qualified pointer to
23188 a const-qualified type, or through a restrict-qualified pointer and another pointer that
23189 are not both based on the same object (<a href="#6.7.3.1">6.7.3.1</a>).
23190 <li> A restrict-qualified pointer is assigned a value based on another restricted pointer
23191 whose associated block neither began execution before the block associated with this
23192 pointer, nor ended before the assignment (<a href="#6.7.3.1">6.7.3.1</a>).
23193 <li> A function with external linkage is declared with an inline function specifier, but is
23194 not also defined in the same translation unit (<a href="#6.7.4">6.7.4</a>).
23195 <li> Two pointer types that are required to be compatible are not identically qualified, or
23196 are not pointers to compatible types (<a href="#6.7.5.1">6.7.5.1</a>).
23197 <li> The size expression in an array declaration is not a constant expression and evaluates
23198 at program execution time to a nonpositive value (<a href="#6.7.5.2">6.7.5.2</a>).
23199 <li> In a context requiring two array types to be compatible, they do not have compatible
23200 element types, or their size specifiers evaluate to unequal values (<a href="#6.7.5.2">6.7.5.2</a>).
23201 <li> A declaration of an array parameter includes the keyword static within the [ and
23202 ] and the corresponding argument does not provide access to the first element of an
23203 array with at least the specified number of elements (<a href="#6.7.5.3">6.7.5.3</a>).
23204 <li> A storage-class specifier or type qualifier modifies the keyword void as a function
23205 parameter type list (<a href="#6.7.5.3">6.7.5.3</a>).
23206 <li> In a context requiring two function types to be compatible, they do not have
23207 compatible return types, or their parameters disagree in use of the ellipsis terminator
23208 or the number and type of parameters (after default argument promotion, when there
23209 is no parameter type list or when one type is specified by a function definition with an
23211 identifier list) (<a href="#6.7.5.3">6.7.5.3</a>).
23212 <li> The value of an unnamed member of a structure or union is used (<a href="#6.7.8">6.7.8</a>).
23213 <li> The initializer for a scalar is neither a single expression nor a single expression
23214 enclosed in braces (<a href="#6.7.8">6.7.8</a>).
23215 <li> The initializer for a structure or union object that has automatic storage duration is
23216 neither an initializer list nor a single expression that has compatible structure or union
23217 type (<a href="#6.7.8">6.7.8</a>).
23218 <li> The initializer for an aggregate or union, other than an array initialized by a string
23219 literal, is not a brace-enclosed list of initializers for its elements or members (<a href="#6.7.8">6.7.8</a>).
23220 <li> An identifier with external linkage is used, but in the program there does not exist
23221 exactly one external definition for the identifier, or the identifier is not used and there
23222 exist multiple external definitions for the identifier (<a href="#6.9">6.9</a>).
23223 <li> A function definition includes an identifier list, but the types of the parameters are not
23224 declared in a following declaration list (<a href="#6.9.1">6.9.1</a>).
23225 <li> An adjusted parameter type in a function definition is not an object type (<a href="#6.9.1">6.9.1</a>).
23226 <li> A function that accepts a variable number of arguments is defined without a
23227 parameter type list that ends with the ellipsis notation (<a href="#6.9.1">6.9.1</a>).
23228 <li> The } that terminates a function is reached, and the value of the function call is used
23229 by the caller (<a href="#6.9.1">6.9.1</a>).
23230 <li> An identifier for an object with internal linkage and an incomplete type is declared
23231 with a tentative definition (<a href="#6.9.2">6.9.2</a>).
23232 <li> The token defined is generated during the expansion of a #if or #elif
23233 preprocessing directive, or the use of the defined unary operator does not match
23234 one of the two specified forms prior to macro replacement (<a href="#6.10.1">6.10.1</a>).
23235 <li> The #include preprocessing directive that results after expansion does not match
23236 one of the two header name forms (<a href="#6.10.2">6.10.2</a>).
23237 <li> The character sequence in an #include preprocessing directive does not start with a
23238 letter (<a href="#6.10.2">6.10.2</a>).
23239 <li> There are sequences of preprocessing tokens within the list of macro arguments that
23240 would otherwise act as preprocessing directives (<a href="#6.10.3">6.10.3</a>).
23241 <li> The result of the preprocessing operator # is not a valid character string literal
23242 (<a href="#6.10.3.2">6.10.3.2</a>).
23243 <li> The result of the preprocessing operator ## is not a valid preprocessing token
23244 (<a href="#6.10.3.3">6.10.3.3</a>).
23246 <li> The #line preprocessing directive that results after expansion does not match one of
23247 the two well-defined forms, or its digit sequence specifies zero or a number greater
23248 than 2147483647 (<a href="#6.10.4">6.10.4</a>).
23249 <li> A non-STDC #pragma preprocessing directive that is documented as causing
23250 translation failure or some other form of undefined behavior is encountered (<a href="#6.10.6">6.10.6</a>).
23251 <li> A #pragma STDC preprocessing directive does not match one of the well-defined
23252 forms (<a href="#6.10.6">6.10.6</a>).
23253 <li> The name of a predefined macro, or the identifier defined, is the subject of a
23254 #define or #undef preprocessing directive (<a href="#6.10.8">6.10.8</a>).
23255 <li> An attempt is made to copy an object to an overlapping object by use of a library
23256 function, other than as explicitly allowed (e.g., memmove) (clause 7).
23257 <li> A file with the same name as one of the standard headers, not provided as part of the
23258 implementation, is placed in any of the standard places that are searched for included
23259 source files (<a href="#7.1.2">7.1.2</a>).
23260 <li> A header is included within an external declaration or definition (<a href="#7.1.2">7.1.2</a>).
23261 <li> A function, object, type, or macro that is specified as being declared or defined by
23262 some standard header is used before any header that declares or defines it is included
23263 (<a href="#7.1.2">7.1.2</a>).
23264 <li> A standard header is included while a macro is defined with the same name as a
23265 keyword (<a href="#7.1.2">7.1.2</a>).
23266 <li> The program attempts to declare a library function itself, rather than via a standard
23267 header, but the declaration does not have external linkage (<a href="#7.1.2">7.1.2</a>).
23268 <li> The program declares or defines a reserved identifier, other than as allowed by <a href="#7.1.4">7.1.4</a>
23269 (<a href="#7.1.3">7.1.3</a>).
23270 <li> The program removes the definition of a macro whose name begins with an
23271 underscore and either an uppercase letter or another underscore (<a href="#7.1.3">7.1.3</a>).
23272 <li> An argument to a library function has an invalid value or a type not expected by a
23273 function with variable number of arguments (<a href="#7.1.4">7.1.4</a>).
23274 <li> The pointer passed to a library function array parameter does not have a value such
23275 that all address computations and object accesses are valid (<a href="#7.1.4">7.1.4</a>).
23276 <li> The macro definition of assert is suppressed in order to access an actual function
23277 (<a href="#7.2">7.2</a>).
23278 <li> The argument to the assert macro does not have a scalar type (<a href="#7.2">7.2</a>).
23279 <li> The CX_LIMITED_RANGE, FENV_ACCESS, or FP_CONTRACT pragma is used in
23280 any context other than outside all external declarations or preceding all explicit
23282 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>).
23283 <li> The value of an argument to a character handling function is neither equal to the value
23284 of EOF nor representable as an unsigned char (<a href="#7.4">7.4</a>).
23285 <li> A macro definition of errno is suppressed in order to access an actual object, or the
23286 program defines an identifier with the name errno (<a href="#7.5">7.5</a>).
23287 <li> Part of the program tests floating-point status flags, sets floating-point control modes,
23288 or runs under non-default mode settings, but was translated with the state for the
23289 FENV_ACCESS pragma ''off'' (<a href="#7.6.1">7.6.1</a>).
23290 <li> The exception-mask argument for one of the functions that provide access to the
23291 floating-point status flags has a nonzero value not obtained by bitwise OR of the
23292 floating-point exception macros (<a href="#7.6.2">7.6.2</a>).
23293 <li> The fesetexceptflag function is used to set floating-point status flags that were
23294 not specified in the call to the fegetexceptflag function that provided the value
23295 of the corresponding fexcept_t object (<a href="#7.6.2.4">7.6.2.4</a>).
23296 <li> The argument to fesetenv or feupdateenv is neither an object set by a call to
23297 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>).
23298 <li> The value of the result of an integer arithmetic or conversion function cannot be
23299 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>).
23300 <li> The program modifies the string pointed to by the value returned by the setlocale
23301 function (<a href="#7.11.1.1">7.11.1.1</a>).
23302 <li> The program modifies the structure pointed to by the value returned by the
23303 localeconv function (<a href="#7.11.2.1">7.11.2.1</a>).
23304 <li> A macro definition of math_errhandling is suppressed or the program defines
23305 an identifier with the name math_errhandling (<a href="#7.12">7.12</a>).
23306 <li> An argument to a floating-point classification or comparison macro is not of real
23307 floating type (<a href="#7.12.3">7.12.3</a>, <a href="#7.12.14">7.12.14</a>).
23308 <li> A macro definition of setjmp is suppressed in order to access an actual function, or
23309 the program defines an external identifier with the name setjmp (<a href="#7.13">7.13</a>).
23310 <li> An invocation of the setjmp macro occurs other than in an allowed context
23311 (<a href="#7.13.2.1">7.13.2.1</a>).
23312 <li> The longjmp function is invoked to restore a nonexistent environment (<a href="#7.13.2.1">7.13.2.1</a>).
23313 <li> After a longjmp, there is an attempt to access the value of an object of automatic
23314 storage class with non-volatile-qualified type, local to the function containing the
23315 invocation of the corresponding setjmp macro, that was changed between the
23316 setjmp invocation and longjmp call (<a href="#7.13.2.1">7.13.2.1</a>).
23318 <li> The program specifies an invalid pointer to a signal handler function (<a href="#7.14.1.1">7.14.1.1</a>).
23319 <li> A signal handler returns when the signal corresponded to a computational exception
23320 (<a href="#7.14.1.1">7.14.1.1</a>).
23321 <li> A signal occurs as the result of calling the abort or raise function, and the signal
23322 handler calls the raise function (<a href="#7.14.1.1">7.14.1.1</a>).
23323 <li> A signal occurs other than as the result of calling the abort or raise function, and
23324 the signal handler refers to an object with static storage duration other than by
23325 assigning a value to an object declared as volatile sig_atomic_t, or calls any
23326 function in the standard library other than the abort function, the _Exit function,
23327 or the signal function (for the same signal number) (<a href="#7.14.1.1">7.14.1.1</a>).
23328 <li> The value of errno is referred to after a signal occurred other than as the result of
23329 calling the abort or raise function and the corresponding signal handler obtained
23330 a SIG_ERR return from a call to the signal function (<a href="#7.14.1.1">7.14.1.1</a>).
23331 <li> A signal is generated by an asynchronous signal handler (<a href="#7.14.1.1">7.14.1.1</a>).
23332 <li> A function with a variable number of arguments attempts to access its varying
23333 arguments other than through a properly declared and initialized va_list object, or
23334 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>).
23335 <li> The macro va_arg is invoked using the parameter ap that was passed to a function
23336 that invoked the macro va_arg with the same parameter (<a href="#7.15">7.15</a>).
23337 <li> A macro definition of va_start, va_arg, va_copy, or va_end is suppressed in
23338 order to access an actual function, or the program defines an external identifier with
23339 the name va_copy or va_end (<a href="#7.15.1">7.15.1</a>).
23340 <li> The va_start or va_copy macro is invoked without a corresponding invocation
23341 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>,
23342 <a href="#7.15.1.4">7.15.1.4</a>).
23343 <li> The type parameter to the va_arg macro is not such that a pointer to an object of
23344 that type can be obtained simply by postfixing a * (<a href="#7.15.1.1">7.15.1.1</a>).
23345 <li> The va_arg macro is invoked when there is no actual next argument, or with a
23346 specified type that is not compatible with the promoted type of the actual next
23347 argument, with certain exceptions (<a href="#7.15.1.1">7.15.1.1</a>).
23348 <li> The va_copy or va_start macro is called to initialize a va_list that was
23349 previously initialized by either macro without an intervening invocation of the
23350 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>).
23351 <li> The parameter parmN of a va_start macro is declared with the register
23352 storage class, with a function or array type, or with a type that is not compatible with
23353 the type that results after application of the default argument promotions (<a href="#7.15.1.4">7.15.1.4</a>).
23355 <li> The member designator parameter of an offsetof macro is an invalid right
23356 operand of the . operator for the type parameter, or designates a bit-field (<a href="#7.17">7.17</a>).
23357 <li> The argument in an instance of one of the integer-constant macros is not a decimal,
23358 octal, or hexadecimal constant, or it has a value that exceeds the limits for the
23359 corresponding type (<a href="#7.18.4">7.18.4</a>).
23360 <li> A byte input/output function is applied to a wide-oriented stream, or a wide character
23361 input/output function is applied to a byte-oriented stream (<a href="#7.19.2">7.19.2</a>).
23362 <li> Use is made of any portion of a file beyond the most recent wide character written to
23363 a wide-oriented stream (<a href="#7.19.2">7.19.2</a>).
23364 <li> The value of a pointer to a FILE object is used after the associated file is closed
23365 (<a href="#7.19.3">7.19.3</a>).
23366 <li> The stream for the fflush function points to an input stream or to an update stream
23367 in which the most recent operation was input (<a href="#7.19.5.2">7.19.5.2</a>).
23368 <li> The string pointed to by the mode argument in a call to the fopen function does not
23369 exactly match one of the specified character sequences (<a href="#7.19.5.3">7.19.5.3</a>).
23370 <li> An output operation on an update stream is followed by an input operation without an
23371 intervening call to the fflush function or a file positioning function, or an input
23372 operation on an update stream is followed by an output operation with an intervening
23373 call to a file positioning function (<a href="#7.19.5.3">7.19.5.3</a>).
23374 <li> An attempt is made to use the contents of the array that was supplied in a call to the
23375 setvbuf function (<a href="#7.19.5.6">7.19.5.6</a>).
23376 <li> There are insufficient arguments for the format in a call to one of the formatted
23377 input/output functions, or an argument does not have an appropriate type (<a href="#7.19.6.1">7.19.6.1</a>,
23378 <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>).
23379 <li> The format in a call to one of the formatted input/output functions or to the
23380 strftime or wcsftime function is not a valid multibyte character sequence that
23381 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>,
23382 <a href="#7.24.5.1">7.24.5.1</a>).
23383 <li> In a call to one of the formatted output functions, a precision appears with a
23384 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>).
23385 <li> A conversion specification for a formatted output function uses an asterisk to denote
23386 an argument-supplied field width or precision, but the corresponding argument is not
23387 provided (<a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.24.2.1">7.24.2.1</a>).
23388 <li> A conversion specification for a formatted output function uses a # or 0 flag 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>).
23391 <li> A conversion specification for one of the formatted input/output functions uses a
23392 length modifier with a conversion specifier other than those described (<a href="#7.19.6.1">7.19.6.1</a>,
23393 <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>).
23394 <li> An s conversion specifier is encountered by one of the formatted output functions,
23395 and the argument is missing the null terminator (unless a precision is specified that
23396 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>).
23397 <li> An n conversion specification for one of the formatted input/output functions includes
23398 any flags, an assignment-suppressing character, a field width, or a precision (<a href="#7.19.6.1">7.19.6.1</a>,
23399 <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>).
23400 <li> A % conversion specifier is encountered by one of the formatted input/output
23401 functions, but the complete conversion specification is not exactly %% (<a href="#7.19.6.1">7.19.6.1</a>,
23402 <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>).
23403 <li> An invalid conversion specification is found in the format for one of the formatted
23404 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>,
23405 <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>).
23406 <li> The number of characters transmitted by a formatted output function is greater than
23407 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>).
23408 <li> The result of a conversion by one of the formatted input functions cannot be
23409 represented in the corresponding object, or the receiving object does not have an
23410 appropriate type (<a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.2">7.24.2.2</a>).
23411 <li> A c, s, or [ conversion specifier is encountered by one of the formatted input
23412 functions, and the array pointed to by the corresponding argument is not large enough
23413 to accept the input sequence (and a null terminator if the conversion specifier is s or
23414 [) (<a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.2">7.24.2.2</a>).
23415 <li> A c, s, or [ conversion specifier with an l qualifier is encountered by one of the
23416 formatted input functions, but the input is not a valid multibyte character sequence
23417 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>).
23418 <li> The input item for a %p conversion by one of the formatted input functions is not a
23419 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>).
23420 <li> The vfprintf, vfscanf, vprintf, vscanf, vsnprintf, vsprintf,
23421 vsscanf, vfwprintf, vfwscanf, vswprintf, vswscanf, vwprintf, or
23422 vwscanf function is called with an improperly initialized va_list argument, or
23423 the argument is used (other than in an invocation of va_end) after the function
23424 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>,
23425 <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>).
23426 <li> The contents of the array supplied in a call to the fgets, gets, or fgetws function
23427 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>).
23429 <li> The file position indicator for a binary stream is used after a call to the ungetc
23430 function where its value was zero before the call (<a href="#7.19.7.11">7.19.7.11</a>).
23431 <li> The file position indicator for a stream is used after an error occurred during a call to
23432 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>).
23433 <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>).
23434 <li> The fseek function is called for a text stream with a nonzero offset and either the
23435 offset was not returned by a previous successful call to the ftell function on a
23436 stream associated with the same file or whence is not SEEK_SET (<a href="#7.19.9.2">7.19.9.2</a>).
23437 <li> The fsetpos function is called to set a position that was not returned by a previous
23438 successful call to the fgetpos function on a stream associated with the same file
23439 (<a href="#7.19.9.3">7.19.9.3</a>).
23440 <li> A non-null pointer returned by a call to the calloc, malloc, or realloc function
23441 with a zero requested size is used to access an object (<a href="#7.20.3">7.20.3</a>).
23442 <li> The value of a pointer that refers to space deallocated by a call to the free or
23443 realloc function is used (<a href="#7.20.3">7.20.3</a>).
23444 <li> The pointer argument to the free or realloc function does not match a pointer
23445 earlier returned by calloc, malloc, or realloc, or the space has been
23446 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>).
23447 <li> The value of the object allocated by the malloc function is used (<a href="#7.20.3.3">7.20.3.3</a>).
23448 <li> The value of any bytes in a new object allocated by the realloc function beyond
23449 the size of the old object are used (<a href="#7.20.3.4">7.20.3.4</a>).
23450 <li> The program executes more than one call to the exit function (<a href="#7.20.4.3">7.20.4.3</a>).
23451 <li> During the call to a function registered with the atexit function, a call is made to
23452 the longjmp function that would terminate the call to the registered function
23453 (<a href="#7.20.4.3">7.20.4.3</a>).
23454 <li> The string set up by the getenv or strerror function is modified by the program
23455 (<a href="#7.20.4.5">7.20.4.5</a>, <a href="#7.21.6.2">7.21.6.2</a>).
23456 <li> A command is executed through the system function in a way that is documented as
23457 causing termination or some other form of undefined behavior (<a href="#7.20.4.6">7.20.4.6</a>).
23458 <li> A searching or sorting utility function is called with an invalid pointer argument, even
23459 if the number of elements is zero (<a href="#7.20.5">7.20.5</a>).
23460 <li> The comparison function called by a searching or sorting utility function alters the
23461 contents of the array being searched or sorted, or returns ordering values
23462 inconsistently (<a href="#7.20.5">7.20.5</a>).
23464 <li> The array being searched by the bsearch function does not have its elements in
23465 proper order (<a href="#7.20.5.1">7.20.5.1</a>).
23466 <li> The current conversion state is used by a multibyte/wide character conversion
23467 function after changing the LC_CTYPE category (<a href="#7.20.7">7.20.7</a>).
23468 <li> A string or wide string utility function is instructed to access an array beyond the end
23469 of an object (<a href="#7.21.1">7.21.1</a>, <a href="#7.24.4">7.24.4</a>).
23470 <li> A string or wide string utility function is called with an invalid pointer argument, even
23471 if the length is zero (<a href="#7.21.1">7.21.1</a>, <a href="#7.24.4">7.24.4</a>).
23472 <li> The contents of the destination array are used after a call to the strxfrm,
23473 strftime, wcsxfrm, or wcsftime function in which the specified length was
23474 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>,
23475 <a href="#7.24.5.1">7.24.5.1</a>).
23476 <li> The first argument in the very first call to the strtok or wcstok is a null pointer
23477 (<a href="#7.21.5.8">7.21.5.8</a>, <a href="#7.24.4.5.7">7.24.4.5.7</a>).
23478 <li> The type of an argument to a type-generic macro is not compatible with the type of
23479 the corresponding parameter of the selected function (<a href="#7.22">7.22</a>).
23480 <li> A complex argument is supplied for a generic parameter of a type-generic macro that
23481 has no corresponding complex function (<a href="#7.22">7.22</a>).
23482 <li> The argument corresponding to an s specifier without an l qualifier in a call to the
23483 fwprintf function does not point to a valid multibyte character sequence that
23484 begins in the initial shift state (<a href="#7.24.2.11">7.24.2.11</a>).
23485 <li> In a call to the wcstok function, the object pointed to by ptr does not have the
23486 value stored by the previous call for the same wide string (<a href="#7.24.4.5.7">7.24.4.5.7</a>).
23487 <li> An mbstate_t object is used inappropriately (<a href="#7.24.6">7.24.6</a>).
23488 <li> The value of an argument of type wint_t to a wide character classification or case
23489 mapping function is neither equal to the value of WEOF nor representable as a
23490 wchar_t (<a href="#7.25.1">7.25.1</a>).
23491 <li> The iswctype function is called using a different LC_CTYPE category from the
23492 one in effect for the call to the wctype function that returned the description
23493 (<a href="#7.25.2.2.1">7.25.2.2.1</a>).
23494 <li> The towctrans function is called using a different LC_CTYPE category from the
23495 one in effect for the call to the wctrans function that returned the description
23496 (<a href="#7.25.3.2.1">7.25.3.2.1</a>).
23500 <h3><a name="J.3" href="#J.3">J.3 Implementation-defined behavior</a></h3>
23502 A conforming implementation is required to document its choice of behavior in each of
23503 the areas listed in this subclause. The following are implementation-defined:
23505 <h4><a name="J.3.1" href="#J.3.1">J.3.1 Translation</a></h4>
23508 <li> How a diagnostic is identified (<a href="#3.10">3.10</a>, <a href="#5.1.1.3">5.1.1.3</a>).
23509 <li> Whether each nonempty sequence of white-space characters other than new-line is
23510 retained or replaced by one space character in translation phase 3 (<a href="#5.1.1.2">5.1.1.2</a>).
23513 <h4><a name="J.3.2" href="#J.3.2">J.3.2 Environment</a></h4>
23516 <li> The mapping between physical source file multibyte characters and the source
23517 character set in translation phase 1 (<a href="#5.1.1.2">5.1.1.2</a>).
23518 <li> The name and type of the function called at program startup in a freestanding
23519 environment (<a href="#5.1.2.1">5.1.2.1</a>).
23520 <li> The effect of program termination in a freestanding environment (<a href="#5.1.2.1">5.1.2.1</a>).
23521 <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>).
23522 <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>).
23523 <li> What constitutes an interactive device (<a href="#5.1.2.3">5.1.2.3</a>).
23524 <li> The set of signals, their semantics, and their default handling (<a href="#7.14">7.14</a>).
23525 <li> Signal values other than SIGFPE, SIGILL, and SIGSEGV that correspond to a
23526 computational exception (<a href="#7.14.1.1">7.14.1.1</a>).
23527 <li> Signals for which the equivalent of signal(sig, SIG_IGN); is executed at
23528 program startup (<a href="#7.14.1.1">7.14.1.1</a>).
23529 <li> The set of environment names and the method for altering the environment list used
23530 by the getenv function (<a href="#7.20.4.5">7.20.4.5</a>).
23531 <li> The manner of execution of the string by the system function (<a href="#7.20.4.6">7.20.4.6</a>).
23534 <h4><a name="J.3.3" href="#J.3.3">J.3.3 Identifiers</a></h4>
23537 <li> Which additional multibyte characters may appear in identifiers and their
23538 correspondence to universal character names (<a href="#6.4.2">6.4.2</a>).
23539 <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>).
23543 <h4><a name="J.3.4" href="#J.3.4">J.3.4 Characters</a></h4>
23546 <li> The number of bits in a byte (<a href="#3.6">3.6</a>).
23547 <li> The values of the members of the execution character set (<a href="#5.2.1">5.2.1</a>).
23548 <li> The unique value of the member of the execution character set produced for each of
23549 the standard alphabetic escape sequences (<a href="#5.2.2">5.2.2</a>).
23550 <li> The value of a char object into which has been stored any character other than a
23551 member of the basic execution character set (<a href="#6.2.5">6.2.5</a>).
23552 <li> Which of signed char or unsigned char has the same range, representation,
23553 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>).
23554 <li> The mapping of members of the source character set (in character constants and string
23555 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>).
23556 <li> The value of an integer character constant containing more than one character or
23557 containing a character or escape sequence that does not map to a single-byte
23558 execution character (<a href="#6.4.4.4">6.4.4.4</a>).
23559 <li> The value of a wide character constant containing more than one multibyte character,
23560 or containing a multibyte character or escape sequence not represented in the
23561 extended execution character set (<a href="#6.4.4.4">6.4.4.4</a>).
23562 <li> The current locale used to convert a wide character constant consisting of a single
23563 multibyte character that maps to a member of the extended execution character set
23564 into a corresponding wide character code (<a href="#6.4.4.4">6.4.4.4</a>).
23565 <li> The current locale used to convert a wide string literal into corresponding wide
23566 character codes (<a href="#6.4.5">6.4.5</a>).
23567 <li> The value of a string literal containing a multibyte character or escape sequence not
23568 represented in the execution character set (<a href="#6.4.5">6.4.5</a>).
23571 <h4><a name="J.3.5" href="#J.3.5">J.3.5 Integers</a></h4>
23574 <li> Any extended integer types that exist in the implementation (<a href="#6.2.5">6.2.5</a>).
23575 <li> Whether signed integer types are represented using sign and magnitude, two's
23576 complement, or ones' complement, and whether the extraordinary value is a trap
23577 representation or an ordinary value (<a href="#6.2.6.2">6.2.6.2</a>).
23578 <li> The rank of any extended integer type relative to another extended integer type with
23579 the same precision (<a href="#6.3.1.1">6.3.1.1</a>).
23580 <li> The result of, or the signal raised by, converting an integer to a signed integer type
23581 when the value cannot be represented in an object of that type (<a href="#6.3.1.3">6.3.1.3</a>).
23583 <li> The results of some bitwise operations on signed integers (<a href="#6.5">6.5</a>).
23586 <h4><a name="J.3.6" href="#J.3.6">J.3.6 Floating point</a></h4>
23589 <li> The accuracy of the floating-point operations and of the library functions in
23590 <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>).
23591 <li> The accuracy of the conversions between floating-point internal representations and
23592 string representations performed by the library functions in <a href="#7.19"><stdio.h></a>,
23593 <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>).
23594 <li> The rounding behaviors characterized by non-standard values of FLT_ROUNDS
23595 (<a href="#5.2.4.2.2">5.2.4.2.2</a>).
23596 <li> The evaluation methods characterized by non-standard negative values of
23597 FLT_EVAL_METHOD (<a href="#5.2.4.2.2">5.2.4.2.2</a>).
23598 <li> The direction of rounding when an integer is converted to a floating-point number that
23599 cannot exactly represent the original value (<a href="#6.3.1.4">6.3.1.4</a>).
23600 <li> The direction of rounding when a floating-point number is converted to a narrower
23601 floating-point number (<a href="#6.3.1.5">6.3.1.5</a>).
23602 <li> How the nearest representable value or the larger or smaller representable value
23603 immediately adjacent to the nearest representable value is chosen for certain floating
23604 constants (<a href="#6.4.4.2">6.4.4.2</a>).
23605 <li> Whether and how floating expressions are contracted when not disallowed by the
23606 FP_CONTRACT pragma (<a href="#6.5">6.5</a>).
23607 <li> The default state for the FENV_ACCESS pragma (<a href="#7.6.1">7.6.1</a>).
23608 <li> Additional floating-point exceptions, rounding modes, environments, and
23609 classifications, and their macro names (<a href="#7.6">7.6</a>, <a href="#7.12">7.12</a>).
23610 <li> The default state for the FP_CONTRACT pragma (<a href="#7.12.2">7.12.2</a>). *
23613 <h4><a name="J.3.7" href="#J.3.7">J.3.7 Arrays and pointers</a></h4>
23616 <li> The result of converting a pointer to an integer or vice versa (<a href="#6.3.2.3">6.3.2.3</a>).
23617 <li> The size of the result of subtracting two pointers to elements of the same array
23618 (<a href="#6.5.6">6.5.6</a>).
23622 <h4><a name="J.3.8" href="#J.3.8">J.3.8 Hints</a></h4>
23625 <li> The extent to which suggestions made by using the register storage-class
23626 specifier are effective (<a href="#6.7.1">6.7.1</a>).
23627 <li> The extent to which suggestions made by using the inline function specifier are
23628 effective (<a href="#6.7.4">6.7.4</a>).
23631 <h4><a name="J.3.9" href="#J.3.9">J.3.9 Structures, unions, enumerations, and bit-fields</a></h4>
23634 <li> Whether a ''plain'' int bit-field is treated as a signed int bit-field or as an
23635 unsigned int bit-field (<a href="#6.7.2">6.7.2</a>, <a href="#6.7.2.1">6.7.2.1</a>).
23636 <li> Allowable bit-field types other than _Bool, signed int, and unsigned int
23637 (<a href="#6.7.2.1">6.7.2.1</a>).
23638 <li> Whether a bit-field can straddle a storage-unit boundary (<a href="#6.7.2.1">6.7.2.1</a>).
23639 <li> The order of allocation of bit-fields within a unit (<a href="#6.7.2.1">6.7.2.1</a>).
23640 <li> The alignment of non-bit-field members of structures (<a href="#6.7.2.1">6.7.2.1</a>). This should present
23641 no problem unless binary data written by one implementation is read by another.
23642 <li> The integer type compatible with each enumerated type (<a href="#6.7.2.2">6.7.2.2</a>).
23645 <h4><a name="J.3.10" href="#J.3.10">J.3.10 Qualifiers</a></h4>
23648 <li> What constitutes an access to an object that has volatile-qualified type (<a href="#6.7.3">6.7.3</a>).
23651 <h4><a name="J.3.11" href="#J.3.11">J.3.11 Preprocessing directives</a></h4>
23654 <li> The locations within #pragma directives where header name preprocessing tokens
23655 are recognized (<a href="#6.4">6.4</a>, <a href="#6.4.7">6.4.7</a>).
23656 <li> How sequences in both forms of header names are mapped to headers or external
23657 source file names (<a href="#6.4.7">6.4.7</a>).
23658 <li> Whether the value of a character constant in a constant expression that controls
23659 conditional inclusion matches the value of the same character constant in the
23660 execution character set (<a href="#6.10.1">6.10.1</a>).
23661 <li> Whether the value of a single-character character constant in a constant expression
23662 that controls conditional inclusion may have a negative value (<a href="#6.10.1">6.10.1</a>).
23663 <li> The places that are searched for an included < > delimited header, and how the places
23664 are specified or the header is identified (<a href="#6.10.2">6.10.2</a>).
23665 <li> How the named source file is searched for in an included " " delimited header
23666 (<a href="#6.10.2">6.10.2</a>).
23667 <li> The method by which preprocessing tokens (possibly resulting from macro
23668 expansion) in a #include directive are combined into a header name (<a href="#6.10.2">6.10.2</a>).
23670 <li> The nesting limit for #include processing (<a href="#6.10.2">6.10.2</a>).
23671 <li> Whether the # operator inserts a \ character before the \ character that begins a
23672 universal character name in a character constant or string literal (<a href="#6.10.3.2">6.10.3.2</a>).
23673 <li> The behavior on each recognized non-STDC #pragma directive (<a href="#6.10.6">6.10.6</a>).
23674 <li> The definitions for __DATE__ and __TIME__ when respectively, the date and
23675 time of translation are not available (<a href="#6.10.8">6.10.8</a>).
23678 <h4><a name="J.3.12" href="#J.3.12">J.3.12 Library functions</a></h4>
23681 <li> Any library facilities available to a freestanding program, other than the minimal set
23682 required by clause 4 (<a href="#5.1.2.1">5.1.2.1</a>).
23683 <li> The format of the diagnostic printed by the assert macro (<a href="#7.2.1.1">7.2.1.1</a>).
23684 <li> The representation of the floating-point status flags stored by the
23685 fegetexceptflag function (<a href="#7.6.2.2">7.6.2.2</a>).
23686 <li> Whether the feraiseexcept function raises the ''inexact'' floating-point
23687 exception in addition to the ''overflow'' or ''underflow'' floating-point exception
23688 (<a href="#7.6.2.3">7.6.2.3</a>).
23689 <li> Strings other than "C" and "" that may be passed as the second argument to the
23690 setlocale function (<a href="#7.11.1.1">7.11.1.1</a>).
23691 <li> The types defined for float_t and double_t when the value of the
23692 FLT_EVAL_METHOD macro is less than 0 (<a href="#7.12">7.12</a>).
23693 <li> Domain errors for the mathematics functions, other than those required by this
23694 International Standard (<a href="#7.12.1">7.12.1</a>).
23695 <li> The values returned by the mathematics functions on domain errors (<a href="#7.12.1">7.12.1</a>).
23696 <li> The values returned by the mathematics functions on underflow range errors, whether
23697 errno is set to the value of the macro ERANGE when the integer expression
23698 math_errhandling & MATH_ERRNO is nonzero, and whether the ''underflow''
23699 floating-point exception is raised when the integer expression math_errhandling
23700 & MATH_ERREXCEPT is nonzero. (<a href="#7.12.1">7.12.1</a>).
23701 <li> Whether a domain error occurs or zero is returned when an fmod function has a
23702 second argument of zero (<a href="#7.12.10.1">7.12.10.1</a>).
23703 <li> Whether a domain error occurs or zero is returned when a remainder function has
23704 a second argument of zero (<a href="#7.12.10.2">7.12.10.2</a>).
23705 <li> The base-2 logarithm of the modulus used by the remquo functions in reducing the
23706 quotient (<a href="#7.12.10.3">7.12.10.3</a>).
23708 <li> Whether a domain error occurs or zero is returned when a remquo function has a
23709 second argument of zero (<a href="#7.12.10.3">7.12.10.3</a>).
23710 <li> Whether the equivalent of signal(sig, SIG_DFL); is executed prior to the call
23711 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>).
23712 <li> The null pointer constant to which the macro NULL expands (<a href="#7.17">7.17</a>).
23713 <li> Whether the last line of a text stream requires a terminating new-line character
23714 (<a href="#7.19.2">7.19.2</a>).
23715 <li> Whether space characters that are written out to a text stream immediately before a
23716 new-line character appear when read in (<a href="#7.19.2">7.19.2</a>).
23717 <li> The number of null characters that may be appended to data written to a binary
23718 stream (<a href="#7.19.2">7.19.2</a>).
23719 <li> Whether the file position indicator of an append-mode stream is initially positioned at
23720 the beginning or end of the file (<a href="#7.19.3">7.19.3</a>).
23721 <li> Whether a write on a text stream causes the associated file to be truncated beyond that
23722 point (<a href="#7.19.3">7.19.3</a>).
23723 <li> The characteristics of file buffering (<a href="#7.19.3">7.19.3</a>).
23724 <li> Whether a zero-length file actually exists (<a href="#7.19.3">7.19.3</a>).
23725 <li> The rules for composing valid file names (<a href="#7.19.3">7.19.3</a>).
23726 <li> Whether the same file can be simultaneously open multiple times (<a href="#7.19.3">7.19.3</a>).
23727 <li> The nature and choice of encodings used for multibyte characters in files (<a href="#7.19.3">7.19.3</a>).
23728 <li> The effect of the remove function on an open file (<a href="#7.19.4.1">7.19.4.1</a>).
23729 <li> The effect if a file with the new name exists prior to a call to the rename function
23730 (<a href="#7.19.4.2">7.19.4.2</a>).
23731 <li> Whether an open temporary file is removed upon abnormal program termination
23732 (<a href="#7.19.4.3">7.19.4.3</a>).
23733 <li> Which changes of mode are permitted (if any), and under what circumstances
23734 (<a href="#7.19.5.4">7.19.5.4</a>).
23735 <li> The style used to print an infinity or NaN, and the meaning of any n-char or n-wchar
23736 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>).
23737 <li> The output for %p conversion in the fprintf or fwprintf function (<a href="#7.19.6.1">7.19.6.1</a>,
23738 <a href="#7.24.2.1">7.24.2.1</a>).
23739 <li> The interpretation of a - character that is neither the first nor the last character, nor
23740 the second where a ^ character is the first, in the scanlist for %[ conversion in the
23741 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>).
23743 <li> The set of sequences matched by a %p conversion and the interpretation of the
23744 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>).
23745 <li> The value to which the macro errno is set by the fgetpos, fsetpos, or ftell
23746 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>).
23747 <li> The meaning of any n-char or n-wchar sequence in a string representing a NaN that is
23748 converted by the strtod, strtof, strtold, wcstod, wcstof, or wcstold
23749 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>).
23750 <li> Whether or not the strtod, strtof, strtold, wcstod, wcstof, or wcstold
23751 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>).
23752 <li> Whether the calloc, malloc, and realloc functions return a null pointer or a
23753 pointer to an allocated object when the size requested is zero (<a href="#7.20.3">7.20.3</a>).
23754 <li> Whether open streams with unwritten buffered data are flushed, open streams are
23755 closed, or temporary files are removed when the abort or _Exit function is called
23756 (<a href="#7.20.4.1">7.20.4.1</a>, <a href="#7.20.4.4">7.20.4.4</a>).
23757 <li> The termination status returned to the host environment by the abort, exit, or
23758 _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>).
23759 <li> The value returned by the system function when its argument is not a null pointer
23760 (<a href="#7.20.4.6">7.20.4.6</a>).
23761 <li> The local time zone and Daylight Saving Time (<a href="#7.23.1">7.23.1</a>).
23762 <li> The range and precision of times representable in clock_t and time_t (<a href="#7.23">7.23</a>).
23763 <li> The era for the clock function (<a href="#7.23.2.1">7.23.2.1</a>).
23764 <li> The replacement string for the %Z specifier to the strftime, and wcsftime
23765 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>).
23766 <li> Whether the functions in <a href="#7.12"><math.h></a> honor the rounding direction mode in an
23767 IEC 60559 conformant implementation, unless explicitly specified otherwise (<a href="#F.9">F.9</a>).
23770 <h4><a name="J.3.13" href="#J.3.13">J.3.13 Architecture</a></h4>
23773 <li> The values or expressions assigned to the macros specified in the headers
23774 <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>).
23775 <li> The number, order, and encoding of bytes in any object (when not explicitly specified
23776 in this International Standard) (<a href="#6.2.6.1">6.2.6.1</a>).
23777 <li> The value of the result of the sizeof operator (<a href="#6.5.3.4">6.5.3.4</a>).
23781 <h3><a name="J.4" href="#J.4">J.4 Locale-specific behavior</a></h3>
23783 The following characteristics of a hosted environment are locale-specific and are required
23784 to be documented by the implementation:
23786 <li> Additional members of the source and execution character sets beyond the basic
23787 character set (<a href="#5.2.1">5.2.1</a>).
23788 <li> The presence, meaning, and representation of additional multibyte characters in the
23789 execution character set beyond the basic character set (<a href="#5.2.1.2">5.2.1.2</a>).
23790 <li> The shift states used for the encoding of multibyte characters (<a href="#5.2.1.2">5.2.1.2</a>).
23791 <li> The direction of writing of successive printing characters (<a href="#5.2.2">5.2.2</a>).
23792 <li> The decimal-point character (<a href="#7.1.1">7.1.1</a>).
23793 <li> The set of printing characters (<a href="#7.4">7.4</a>, <a href="#7.25.2">7.25.2</a>).
23794 <li> The set of control characters (<a href="#7.4">7.4</a>, <a href="#7.25.2">7.25.2</a>).
23795 <li> The sets of characters tested for by the isalpha, isblank, islower, ispunct,
23796 isspace, isupper, iswalpha, iswblank, iswlower, iswpunct,
23797 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>,
23798 <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>).
23799 <li> The native environment (<a href="#7.11.1.1">7.11.1.1</a>).
23800 <li> Additional subject sequences accepted by the numeric conversion functions (<a href="#7.20.1">7.20.1</a>,
23801 <a href="#7.24.4.1">7.24.4.1</a>).
23802 <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>).
23803 <li> The contents of the error message strings set up by the strerror function
23804 (<a href="#7.21.6.2">7.21.6.2</a>).
23805 <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>).
23806 <li> Character mappings that are supported by the towctrans function (<a href="#7.25.1">7.25.1</a>).
23807 <li> Character classifications that are supported by the iswctype function (<a href="#7.25.1">7.25.1</a>).
23811 <h3><a name="J.5" href="#J.5">J.5 Common extensions</a></h3>
23813 The following extensions are widely used in many systems, but are not portable to all
23814 implementations. The inclusion of any extension that may cause a strictly conforming
23815 program to become invalid renders an implementation nonconforming. Examples of such
23816 extensions are new keywords, extra library functions declared in standard headers, or
23817 predefined macros with names that do not begin with an underscore.
23819 <h4><a name="J.5.1" href="#J.5.1">J.5.1 Environment arguments</a></h4>
23821 In a hosted environment, the main function receives a third argument, char *envp[],
23822 that points to a null-terminated array of pointers to char, each of which points to a string
23823 that provides information about the environment for this execution of the program
23824 (<a href="#5.1.2.2.1">5.1.2.2.1</a>).
23826 <h4><a name="J.5.2" href="#J.5.2">J.5.2 Specialized identifiers</a></h4>
23828 Characters other than the underscore _, letters, and digits, that are not part of the basic
23829 source character set (such as the dollar sign $, or characters in national character sets)
23830 may appear in an identifier (<a href="#6.4.2">6.4.2</a>).
23832 <h4><a name="J.5.3" href="#J.5.3">J.5.3 Lengths and cases of identifiers</a></h4>
23834 All characters in identifiers (with or without external linkage) are significant (<a href="#6.4.2">6.4.2</a>).
23836 <h4><a name="J.5.4" href="#J.5.4">J.5.4 Scopes of identifiers</a></h4>
23838 A function identifier, or the identifier of an object the declaration of which contains the
23839 keyword extern, has file scope (<a href="#6.2.1">6.2.1</a>).
23841 <h4><a name="J.5.5" href="#J.5.5">J.5.5 Writable string literals</a></h4>
23843 String literals are modifiable (in which case, identical string literals should denote distinct
23844 objects) (<a href="#6.4.5">6.4.5</a>).
23846 <h4><a name="J.5.6" href="#J.5.6">J.5.6 Other arithmetic types</a></h4>
23848 Additional arithmetic types, such as __int128 or double double, and their
23849 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
23850 more range or precision than long double, may be used for evaluating expressions of
23851 other floating types, and may be used to define float_t or double_t.
23854 <h4><a name="J.5.7" href="#J.5.7">J.5.7 Function pointer casts</a></h4>
23856 A pointer to an object or to void may be cast to a pointer to a function, allowing data to
23857 be invoked as a function (<a href="#6.5.4">6.5.4</a>).
23859 A pointer to a function may be cast to a pointer to an object or to void, allowing a
23860 function to be inspected or modified (for example, by a debugger) (<a href="#6.5.4">6.5.4</a>).
23862 <h4><a name="J.5.8" href="#J.5.8">J.5.8 Extended bit-field types</a></h4>
23864 A bit-field may be declared with a type other than _Bool, unsigned int, or
23865 signed int, with an appropriate maximum width (<a href="#6.7.2.1">6.7.2.1</a>).
23867 <h4><a name="J.5.9" href="#J.5.9">J.5.9 The fortran keyword</a></h4>
23869 The fortran function specifier may be used in a function declaration to indicate that
23870 calls suitable for FORTRAN should be generated, or that a different representation for the
23871 external name is to be generated (<a href="#6.7.4">6.7.4</a>).
23873 <h4><a name="J.5.10" href="#J.5.10">J.5.10 The asm keyword</a></h4>
23875 The asm keyword may be used to insert assembly language directly into the translator
23876 output (<a href="#6.8">6.8</a>). The most common implementation is via a statement of the form:
23878 asm ( character-string-literal );</pre>
23880 <h4><a name="J.5.11" href="#J.5.11">J.5.11 Multiple external definitions</a></h4>
23882 There may be more than one external definition for the identifier of an object, with or
23883 without the explicit use of the keyword extern; if the definitions disagree, or more than
23884 one is initialized, the behavior is undefined (<a href="#6.9.2">6.9.2</a>).
23886 <h4><a name="J.5.12" href="#J.5.12">J.5.12 Predefined macro names</a></h4>
23888 Macro names that do not begin with an underscore, describing the translation and
23889 execution environments, are defined by the implementation before translation begins
23890 (<a href="#6.10.8">6.10.8</a>).
23892 <h4><a name="J.5.13" href="#J.5.13">J.5.13 Floating-point status flags</a></h4>
23894 If any floating-point status flags are set on normal termination after all calls to functions
23895 registered by the atexit function have been made (see <a href="#7.20.4.3">7.20.4.3</a>), the implementation
23896 writes some diagnostics indicating the fact to the stderr stream, if it is still open,
23899 <h4><a name="J.5.14" href="#J.5.14">J.5.14 Extra arguments for signal handlers</a></h4>
23901 Handlers for specific signals are called with extra arguments in addition to the signal
23902 number (<a href="#7.14.1.1">7.14.1.1</a>).
23904 <h4><a name="J.5.15" href="#J.5.15">J.5.15 Additional stream types and file-opening modes</a></h4>
23906 Additional mappings from files to streams are supported (<a href="#7.19.2">7.19.2</a>).
23908 Additional file-opening modes may be specified by characters appended to the mode
23909 argument of the fopen function (<a href="#7.19.5.3">7.19.5.3</a>).
23911 <h4><a name="J.5.16" href="#J.5.16">J.5.16 Defined file position indicator</a></h4>
23913 The file position indicator is decremented by each successful call to the ungetc or
23914 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>,
23915 <a href="#7.24.3.10">7.24.3.10</a>).
23917 <h4><a name="J.5.17" href="#J.5.17">J.5.17 Math error reporting</a></h4>
23919 Functions declared in <a href="#7.3"><complex.h></a> and <a href="#7.12"><math.h></a> raise SIGFPE to report errors
23920 instead of, or in addition to, setting errno or raising floating-point exceptions (<a href="#7.3">7.3</a>,
23921 <a href="#7.12">7.12</a>).
23924 <h2><a name="Bibliography" href="#Bibliography">Bibliography</a></h2>
23926 <li> ''The C Reference Manual'' by Dennis M. Ritchie, a version of which was
23927 published in The C Programming Language by Brian W. Kernighan and Dennis
23928 M. Ritchie, Prentice-Hall, Inc., (1978). Copyright owned by AT&T.
23929 <li> 1984 /usr/group Standard by the /usr/group Standards Committee, Santa Clara,
23930 California, USA, November 1984.
23931 <li> ANSI X3/TR-1-82 (1982), American National Dictionary for Information
23932 Processing Systems, Information Processing Systems Technical Report.
23933 <li> ANSI/IEEE 754-1985, American National Standard for Binary Floating-Point
23935 <li> ANSI/IEEE 854-1988, American National Standard for Radix-Independent
23936 Floating-Point Arithmetic.
23937 <li> IEC 60559:1989, Binary floating-point arithmetic for microprocessor systems,
23938 second edition (previously designated IEC 559:1989).
23939 <li> ISO 31-11:1992, Quantities and units -- Part 11: Mathematical signs and
23940 symbols for use in the physical sciences and technology.
23941 <li> ISO/IEC 646:1991, Information technology -- ISO 7-bit coded character set for
23942 information interchange.
23943 <li> ISO/IEC 2382-1:1993, Information technology -- Vocabulary -- Part 1:
23945 <li> ISO 4217:1995, Codes for the representation of currencies and funds.
23946 <li> ISO 8601:1988, Data elements and interchange formats -- Information
23947 interchange -- Representation of dates and times.
23948 <li> ISO/IEC 9899:1990, Programming languages -- C.
23949 <li> ISO/IEC 9899/COR1:1994, Technical Corrigendum 1.
23950 <li> ISO/IEC 9899/COR2:1996, Technical Corrigendum 2.
23951 <li> ISO/IEC 9899/AMD1:1995, Amendment 1 to ISO/IEC 9899:1990 C Integrity.
23952 <li> ISO/IEC 9945-2:1993, Information technology -- Portable Operating System
23953 Interface (POSIX) -- Part 2: Shell and Utilities.
23954 <li> ISO/IEC TR 10176:1998, Information technology -- Guidelines for the
23955 preparation of programming language standards.
23956 <li> ISO/IEC 10646-1:1993, Information technology -- Universal Multiple-Octet
23957 Coded Character Set (UCS) -- Part 1: Architecture and Basic Multilingual Plane.
23959 <li> ISO/IEC 10646-1/COR1:1996, Technical Corrigendum 1 to
23960 ISO/IEC 10646-1:1993.
23961 <li> ISO/IEC 10646-1/COR2:1998, Technical Corrigendum 2 to
23962 ISO/IEC 10646-1:1993.
23963 <li> ISO/IEC 10646-1/AMD1:1996, Amendment 1 to ISO/IEC 10646-1:1993
23964 Transformation Format for 16 planes of group 00 (UTF-16).
23965 <li> ISO/IEC 10646-1/AMD2:1996, Amendment 2 to ISO/IEC 10646-1:1993 UCS
23966 Transformation Format 8 (UTF-8).
23967 <li> ISO/IEC 10646-1/AMD3:1996, Amendment 3 to ISO/IEC 10646-1:1993.
23968 <li> ISO/IEC 10646-1/AMD4:1996, Amendment 4 to ISO/IEC 10646-1:1993.
23969 <li> ISO/IEC 10646-1/AMD5:1998, Amendment 5 to ISO/IEC 10646-1:1993 Hangul
23971 <li> ISO/IEC 10646-1/AMD6:1997, Amendment 6 to ISO/IEC 10646-1:1993 Tibetan.
23972 <li> ISO/IEC 10646-1/AMD7:1997, Amendment 7 to ISO/IEC 10646-1:1993 33
23973 additional characters.
23974 <li> ISO/IEC 10646-1/AMD8:1997, Amendment 8 to ISO/IEC 10646-1:1993.
23975 <li> ISO/IEC 10646-1/AMD9:1997, Amendment 9 to ISO/IEC 10646-1:1993
23976 Identifiers for characters.
23977 <li> ISO/IEC 10646-1/AMD10:1998, Amendment 10 to ISO/IEC 10646-1:1993
23979 <li> ISO/IEC 10646-1/AMD11:1998, Amendment 11 to ISO/IEC 10646-1:1993
23980 Unified Canadian Aboriginal Syllabics.
23981 <li> ISO/IEC 10646-1/AMD12:1998, Amendment 12 to ISO/IEC 10646-1:1993
23983 <li> ISO/IEC 10967-1:1994, Information technology -- Language independent
23984 arithmetic -- Part 1: Integer and floating point arithmetic.
23989 <h2><a name="Index" href="#Index">Index</a></h2>
23991 ??? 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>,
23992 <a href="#6.7.2.3">6.7.2.3</a>, <a href="#6.7.8">6.7.8</a>
23993 ??? 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>
23994 ! (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>
23995 != (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>
23996 # 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>
23997 # 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>
23998 # punctuator, <a href="#6.10">6.10</a> -> (structure/union pointer operator), <a href="#6.5.2.3">6.5.2.3</a>
23999 ## 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>,
24000 #define preprocessing directive, <a href="#6.10.3">6.10.3</a> <a href="#6.5.2.3">6.5.2.3</a>
24001 #elif preprocessing directive, <a href="#6.10.1">6.10.1</a> . punctuator, <a href="#6.7.8">6.7.8</a>
24002 #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>
24003 #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>
24004 #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>
24005 #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>
24006 <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>
24007 #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>
24008 #ifndef preprocessing directive, <a href="#6.10.1">6.10.1</a> :> (alternative spelling of ]), <a href="#6.4.6">6.4.6</a>
24009 #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>,
24010 <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>
24011 #line preprocessing directive, <a href="#6.10.4">6.10.4</a> < (less-than operator), <a href="#6.5.8">6.5.8</a>
24012 #pragma preprocessing directive, <a href="#6.10.6">6.10.6</a> <% (alternative spelling of {), <a href="#6.4.6">6.4.6</a>
24013 #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>
24014 <a href="#7.1.4">7.1.4</a> << (left-shift operator), <a href="#6.5.7">6.5.7</a>
24015 % (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>
24016 %: (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>
24017 %:%: (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>
24018 %= (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>,
24019 %> (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>
24020 & (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>
24021 & (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>
24022 && (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>,
24023 &= (bitwise AND assignment operator), <a href="#6.5.16.2">6.5.16.2</a> <a href="#H">H</a>
24024 ' ' (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>,
24025 <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>
24026 ( ) (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>
24027 ( ) (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>
24028 ( ) (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>
24029 ( ){ } (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>
24030 * (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>,
24031 * (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>
24032 * (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>
24033 *= (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>
24034 + (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>
24035 <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>
24036 + (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>,
24037 ++ (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>
24038 ++ (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>,
24039 += (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>
24040 , (comma operator), <a href="#6.5.17">6.5.17</a>
24042 <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>
24043 <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>
24044 <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>
24045 <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>
24046 <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>
24047 <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>
24048 <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>
24049 <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>
24050 = (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>
24051 = (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>
24052 == (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>
24053 > (greater-than operator), <a href="#6.5.8">6.5.8</a> __STDC_IEC_559_COMPLEX__ macro,
24054 >= (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>
24055 >> (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>
24056 >>= (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>,
24057 ? : (conditional operator), <a href="#6.5.15">6.5.15</a> <a href="#7.18.3">7.18.3</a>
24058 ?? (trigraph sequences), <a href="#5.2.1.1">5.2.1.1</a> __STDC_MB_MIGHT_NEQ_WC__ macro,
24059 [ ] (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>
24060 [ ] (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>
24061 \ (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>
24062 \ (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>
24063 \" (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>
24064 <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>
24065 \\ (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>
24066 \' (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>
24067 \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>
24068 padding of binary stream, <a href="#7.19.2">7.19.2</a> _Imaginary keyword, <a href="#G.2">G.2</a>
24069 \? (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>
24070 \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>
24071 \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>
24072 \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>
24073 <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>
24074 \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>
24075 <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>,
24076 \octal digits (octal-character escape sequence), <a href="#6.8.2">6.8.2</a>
24077 <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>
24078 \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>
24079 <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),
24080 \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>
24081 <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>
24082 \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>
24083 \u (universal character names), <a href="#6.4.3">6.4.3</a>
24084 \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>,
24085 <a href="#7.4.1.10">7.4.1.10</a> <a href="#7.20.4.1">7.20.4.1</a>
24086 \x hexadecimal digits (hexadecimal-character abs function, <a href="#7.20.6.1">7.20.6.1</a>
24087 escape sequence), <a href="#6.4.4.4">6.4.4.4</a> absolute-value functions
24088 ^ (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>
24089 ^= (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>
24090 <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>
24091 __bool_true_false_are_defined abstract declarator, <a href="#6.7.6">6.7.6</a>
24092 macro, <a href="#7.16">7.16</a> abstract machine, <a href="#5.1.2.3">5.1.2.3</a>
24094 access, <a href="#3.1">3.1</a>, <a href="#6.7.3">6.7.3</a> array
24095 accuracy, see floating-point accuracy argument, <a href="#6.9.1">6.9.1</a>
24096 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>
24097 acos type-generic macro, <a href="#7.22">7.22</a> initialization, <a href="#6.7.8">6.7.8</a>
24098 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>
24099 acosh type-generic macro, <a href="#7.22">7.22</a> parameter, <a href="#6.9.1">6.9.1</a>
24100 active position, <a href="#5.2.2">5.2.2</a> storage order, <a href="#6.5.2.1">6.5.2.1</a>
24101 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>
24102 actual parameter (deprecated), <a href="#3.3">3.3</a> subscripting, <a href="#6.5.2.1">6.5.2.1</a>
24103 addition assignment operator (+=), <a href="#6.5.16.2">6.5.16.2</a> type, <a href="#6.2.5">6.2.5</a>
24104 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>
24105 <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>
24106 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>
24107 address constant, <a href="#6.6">6.6</a> as-if rule, <a href="#5.1.2.3">5.1.2.3</a>
24108 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>
24109 aggregate initialization, <a href="#6.7.8">6.7.8</a> asctime function, <a href="#7.23.3.1">7.23.3.1</a>
24110 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>
24111 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>
24112 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>
24113 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>
24114 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>
24115 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>
24116 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>
24117 and macro, <a href="#7.9">7.9</a> assignment
24118 AND operators compound, <a href="#6.5.16.2">6.5.16.2</a>
24119 bitwise (&), <a href="#6.5.10">6.5.10</a> conversion, <a href="#6.5.16.1">6.5.16.1</a>
24120 bitwise assignment (&=), <a href="#6.5.16.2">6.5.16.2</a> expression, <a href="#6.5.16">6.5.16</a>
24121 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>
24122 and_eq macro, <a href="#7.9">7.9</a> simple, <a href="#6.5.16.1">6.5.16.1</a>
24123 ANSI/IEEE 754, <a href="#F.1">F.1</a> associativity of operators, <a href="#6.5">6.5</a>
24124 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>
24125 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>
24126 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>
24127 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>
24128 default promotions, <a href="#6.5.2.2">6.5.2.2</a> atan2 type-generic macro, <a href="#7.22">7.22</a>
24129 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>
24130 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>
24131 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>,
24132 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>
24133 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>
24134 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>
24135 conversions atol function, <a href="#7.20.1">7.20.1</a>, <a href="#7.20.1.2">7.20.1.2</a>
24136 arithmetic operators atoll function, <a href="#7.20.1">7.20.1</a>, <a href="#7.20.1.2">7.20.1.2</a>
24137 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>
24138 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>
24139 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>
24140 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>
24141 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>
24142 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>
24143 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>
24144 arithmetic, pointer, <a href="#6.5.6">6.5.6</a> basic types, <a href="#6.2.5">6.2.5</a>
24146 behavior, <a href="#3.4">3.4</a> call by value, <a href="#6.5.2.2">6.5.2.2</a>
24147 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>,
24148 <a href="#7.19.9.4">7.19.9.4</a> <a href="#7.20.3.4">7.20.3.4</a>
24149 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>
24150 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>
24151 low order, <a href="#3.6">3.6</a> carriage-return escape sequence (\r), <a href="#5.2.2">5.2.2</a>,
24152 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>
24153 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>
24154 bitor macro, <a href="#7.9">7.9</a> case mapping functions
24155 bitwise operators, <a href="#6.5">6.5</a> character, <a href="#7.4.2">7.4.2</a>
24156 AND, <a href="#6.5.10">6.5.10</a> wide character, <a href="#7.25.3.1">7.25.3.1</a>
24157 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>
24158 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>
24159 exclusive OR, <a href="#6.5.11">6.5.11</a> type-generic macro for, <a href="#7.22">7.22</a>
24160 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>
24161 inclusive OR, <a href="#6.5.12">6.5.12</a> type-generic macro for, <a href="#7.22">7.22</a>
24162 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>
24163 shift, <a href="#6.5.7">6.5.7</a> cast operator (( )), <a href="#6.5.4">6.5.4</a>
24164 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>
24165 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>
24166 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>
24167 block structure, <a href="#6.2.1">6.2.1</a> type-generic macro for, <a href="#7.22">7.22</a>
24168 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>
24169 bool macro, <a href="#7.16">7.16</a> cbrt type-generic macro, <a href="#7.22">7.22</a>
24170 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>
24171 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>
24172 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>
24173 <a href="#6.8.2">6.8.2</a> type-generic macro for, <a href="#7.22">7.22</a>
24174 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>
24175 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>
24176 branch cuts, <a href="#7.3.3">7.3.3</a> cerf function, <a href="#7.26.1">7.26.1</a>
24177 break statement, <a href="#6.8.6.3">6.8.6.3</a> cerfc function, <a href="#7.26.1">7.26.1</a>
24178 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>
24179 <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>
24180 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>
24181 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>
24182 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>
24183 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>,
24184 byte input/output functions, <a href="#7.19.1">7.19.1</a> <a href="#6.3.1.8">6.3.1.8</a>
24185 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>
24186 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>
24187 <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>
24188 <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>
24189 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>
24190 type-generic macro for, <a href="#7.22">7.22</a> character case mapping functions, <a href="#7.4.2">7.4.2</a>
24191 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>
24192 type-generic macro for, <a href="#7.22">7.22</a> extensible, <a href="#7.25.3.2">7.25.3.2</a>
24193 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>
24194 type-generic macro for, <a href="#7.22">7.22</a> wide character, <a href="#7.25.2.1">7.25.2.1</a>
24195 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>
24196 <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>
24198 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>,
24199 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>
24200 character input/output functions, <a href="#7.19.7">7.19.7</a> compliance, see conformance
24201 wide character, <a href="#7.24.3">7.24.3</a> components of time, <a href="#7.23.1">7.23.1</a>
24202 character sets, <a href="#5.2.1">5.2.1</a> composite type, <a href="#6.2.7">6.2.7</a>
24203 character string literal, see string literal compound assignment, <a href="#6.5.16.2">6.5.16.2</a>
24204 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>
24205 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>
24206 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>
24207 cimag type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a> concatenation functions
24208 cis function, <a href="#G.6">G.6</a> string, <a href="#7.21.3">7.21.3</a>
24209 classification functions wide string, <a href="#7.24.4.3">7.24.4.3</a>
24210 character, <a href="#7.4.1">7.4.1</a> concatenation, preprocessing, see preprocessing
24211 floating-point, <a href="#7.12.3">7.12.3</a> concatenation
24212 wide character, <a href="#7.25.2.1">7.25.2.1</a> conceptual models, <a href="#5.1">5.1</a>
24213 extensible, <a href="#7.25.2.2">7.25.2.2</a> conditional inclusion, <a href="#6.10.1">6.10.1</a>
24214 clearerr function, <a href="#7.19.10.1">7.19.10.1</a> conditional operator (? :), <a href="#6.5.15">6.5.15</a>
24215 clgamma function, <a href="#7.26.1">7.26.1</a> conformance, <a href="#4">4</a>
24216 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>
24217 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>
24218 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>
24219 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>
24220 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>
24221 clog10 function, <a href="#7.26.1">7.26.1</a> constants, <a href="#6.4.4">6.4.4</a>
24222 clog1p function, <a href="#7.26.1">7.26.1</a> as primary expression, <a href="#6.5.1">6.5.1</a>
24223 clog2 function, <a href="#7.26.1">7.26.1</a> character, <a href="#6.4.4.4">6.4.4.4</a>
24224 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>
24225 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>
24226 comma operator (,), <a href="#6.5.17">6.5.17</a> hexadecimal, <a href="#6.4.4.1">6.4.4.1</a>
24227 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>
24228 <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>
24229 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>
24230 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>
24231 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>
24232 common extensions, <a href="#J.5">J.5</a> continue statement, <a href="#6.8.6.2">6.8.6.2</a>
24233 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>
24234 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>
24235 common warnings, <a href="#I">I</a> control wide character, <a href="#7.25.2">7.25.2</a>
24236 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>
24237 string, <a href="#7.21.4">7.21.4</a> arithmetic operands, <a href="#6.3.1">6.3.1</a>
24238 wide string, <a href="#7.24.4.4">7.24.4.4</a> array argument, <a href="#6.9.1">6.9.1</a> *
24239 comparison macros, <a href="#7.12.14">7.12.14</a> array parameter, <a href="#6.9.1">6.9.1</a>
24240 comparison, pointer, <a href="#6.5.8">6.5.8</a> arrays, <a href="#6.3.2.1">6.3.2.1</a>
24241 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>
24242 compl macro, <a href="#7.9">7.9</a> boolean, characters, and integers, <a href="#6.3.1.1">6.3.1.1</a>
24243 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>
24244 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>
24245 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>
24246 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>
24247 complex type domain, <a href="#6.2.5">6.2.5</a> function, <a href="#6.3.2.1">6.3.2.1</a>
24248 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>
24250 function designators, <a href="#6.3.2.1">6.3.2.1</a> type-generic macro for, <a href="#7.22">7.22</a>
24251 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>
24252 imaginary, <a href="#G.4.1">G.4.1</a> type-generic macro for, <a href="#7.22">7.22</a>
24253 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>
24254 implicit, <a href="#6.3">6.3</a> type-generic macro for, <a href="#7.22">7.22</a>
24255 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>
24256 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>
24257 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>
24258 real and imaginary, <a href="#G.4.2">G.4.2</a> type-generic macro for, <a href="#7.22">7.22</a>
24259 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>
24260 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>
24261 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>
24262 usual arithmetic, see usual arithmetic current object, <a href="#6.7.8">6.7.8</a>
24263 conversions CX_LIMITED_RANGE pragma, <a href="#6.10.6">6.10.6</a>, <a href="#7.3.4">7.3.4</a>
24264 void type, <a href="#6.3.2.2">6.3.2.2</a>
24265 conversion functions data stream, see streams
24266 multibyte/wide character, <a href="#7.20.7">7.20.7</a> date and time header, <a href="#7.23">7.23</a>
24267 extended, <a href="#7.24.6">7.24.6</a> Daylight Saving Time, <a href="#7.23.1">7.23.1</a>
24268 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>
24269 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>
24270 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>
24271 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>
24272 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>
24273 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>
24274 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>
24275 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>
24276 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>
24277 <a href="#7.24.2.2">7.24.2.2</a> decimal constant, <a href="#6.4.4.1">6.4.4.1</a>
24278 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>
24279 <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>
24280 <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>,
24281 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>
24282 copying functions declaration specifiers, <a href="#6.7">6.7</a>
24283 string, <a href="#7.21.2">7.21.2</a> declarations, <a href="#6.7">6.7</a>
24284 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>
24285 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>
24286 <a href="#F.9.8.1">F.9.8.1</a> structure/union, <a href="#6.7.2.1">6.7.2.1</a>
24287 copysign type-generic macro, <a href="#7.22">7.22</a> typedef, <a href="#6.7.7">6.7.7</a>
24288 correctly rounded result, <a href="#3.9">3.9</a> declarator, <a href="#6.7.5">6.7.5</a>
24289 corresponding real type, <a href="#6.2.5">6.2.5</a> abstract, <a href="#6.7.6">6.7.6</a>
24290 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>
24291 cos type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a> decrement operators, see arithmetic operators,
24292 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
24293 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>
24294 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>
24295 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>
24296 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>
24297 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>
24298 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>
24299 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>
24300 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>
24302 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>,
24303 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>,
24304 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>,
24305 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>
24306 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
24307 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>
24308 diagnostics header, <a href="#7.2">7.2</a> endif preprocessing directive, <a href="#6.10.1">6.10.1</a>
24309 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>
24310 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>
24311 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>
24312 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>
24313 display device, <a href="#5.2.2">5.2.2</a> enumeration content, <a href="#6.7.2.3">6.7.2.3</a>
24314 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>
24315 div_t type, <a href="#7.20">7.20</a> enumeration specifiers, <a href="#6.7.2.2">6.7.2.2</a>
24316 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>
24317 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>
24318 do statement, <a href="#6.8.5.2">6.8.5.2</a> environment, <a href="#5">5</a>
24319 documentation of implementation, <a href="#4">4</a> environment functions, <a href="#7.20.4">7.20.4</a>
24320 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>
24321 <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>
24322 <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>,
24323 <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>,
24324 <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>
24325 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>,
24326 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>,
24327 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>,
24328 <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>,
24329 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>,
24330 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>,
24331 <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>
24332 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>
24333 <a href="#6.3.1.8">6.3.1.8</a> equal-to operator, see equality operator
24334 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>
24335 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>
24336 <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>,
24337 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
24339 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>
24340 effective type, <a href="#6.5">6.5</a> erf type-generic macro, <a href="#7.22">7.22</a>
24341 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>
24342 <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>
24343 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>,
24344 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>,
24345 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>,
24346 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>,
24347 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>
24348 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>
24349 empty statement, <a href="#6.8.3">6.8.3</a> error
24350 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
24351 <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
24352 end-of-file, <a href="#7.24.1">7.24.1</a> range, see range error
24354 error conditions, <a href="#7.12.1">7.12.1</a> extended characters, <a href="#5.2.1">5.2.1</a>
24355 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>,
24356 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>
24357 <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
24358 <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>
24359 <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,
24360 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>
24361 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,
24362 escape character (\), <a href="#6.4.4.4">6.4.4.4</a> <a href="#7.25.2.2">7.25.2.2</a>
24363 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>
24364 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>
24365 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>
24366 evaluation order, <a href="#6.5">6.5</a> external linkage, <a href="#6.2.2">6.2.2</a>
24367 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>
24368 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>
24369 <a href="#6.8.6.4">6.8.6.4</a>
24370 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>
24371 exclusive OR operators fabs type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a>
24372 bitwise (^), <a href="#6.5.11">6.5.11</a> false macro, <a href="#7.16">7.16</a>
24373 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>
24374 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>
24375 execution character set, <a href="#5.2.1">5.2.1</a> fdim type-generic macro, <a href="#7.22">7.22</a>
24376 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>
24377 environmental limits FE_DFL_ENV macro, <a href="#7.6">7.6</a>
24378 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>
24379 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>
24380 <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>
24381 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>
24382 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>
24383 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>
24384 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>
24385 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>
24386 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>
24387 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>
24388 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>
24389 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>
24390 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>
24391 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>,
24392 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>
24393 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>
24394 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>,
24395 assignment, <a href="#6.5.16">6.5.16</a> <a href="#F.9">F.9</a>
24396 cast, <a href="#6.5.4">6.5.4</a> fenv_t type, <a href="#7.6">7.6</a>
24397 constant, <a href="#6.6">6.6</a> feof function, <a href="#7.19.10.2">7.19.10.2</a>
24398 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>
24399 order of evaluation, <a href="#6.5">6.5</a> ferror function, <a href="#7.19.10.3">7.19.10.3</a>
24400 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>
24401 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>
24402 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>
24403 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>
24404 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>
24406 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>
24407 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>
24408 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>
24409 <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>
24410 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>
24411 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>,
24412 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>
24413 <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>
24414 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>
24415 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>
24416 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>
24417 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>
24418 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>
24419 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>
24420 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>,
24421 <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>
24422 <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>
24423 <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>
24424 <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>
24425 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>
24426 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>
24427 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>
24428 FILENAME_MAX macro, <a href="#7.19.1">7.19.1</a> fmin type-generic macro, <a href="#7.22">7.22</a>
24429 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>
24430 floating-point status, see floating-point status fmod type-generic macro, <a href="#7.22">7.22</a>
24431 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>
24432 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>
24433 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>
24434 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>
24435 <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>,
24436 float _Imaginary type, <a href="#G.2">G.2</a> <a href="#7.4.1.10">7.4.1.10</a>
24437 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>
24438 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>
24439 <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>
24440 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>
24441 <a href="#7.24.4.1.1">7.24.4.1.1</a> fortran keyword, <a href="#J.5.9">J.5.9</a>
24442 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>
24443 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
24444 floating suffix, f or <a href="#F">F</a>, <a href="#6.4.4.2">6.4.4.2</a> also contracted expression
24445 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>
24446 <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>
24447 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>
24448 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>
24449 <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>
24450 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>
24451 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>
24452 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>
24453 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>
24454 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>
24455 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>
24456 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>
24458 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>
24459 <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>
24460 <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>
24461 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>,
24462 <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>,
24463 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>
24464 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>
24465 <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>,
24466 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>
24467 fread function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.8.1">7.19.8.1</a>
24468 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>
24469 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>
24470 <a href="#5.1.2.1">5.1.2.1</a> wide string, <a href="#7.24.4">7.24.4</a>
24471 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>
24472 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>
24473 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>
24474 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>
24475 <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>
24476 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>
24477 <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>
24478 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>
24479 <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>
24480 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>
24481 full declarator, <a href="#6.7.5">6.7.5</a> graphic characters, <a href="#5.2.1">5.2.1</a>
24482 full expression, <a href="#6.8">6.8</a> greater-than operator (>), <a href="#6.5.8">6.5.8</a>
24483 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>
24485 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
24486 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>
24487 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>
24488 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>
24489 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>
24490 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
24491 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>
24492 image, <a href="#5.2.3">5.2.3</a> high-order bit, <a href="#3.6">3.6</a>
24493 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>
24494 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>
24495 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>,
24496 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>
24497 <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>
24498 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>,
24499 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>
24500 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>,
24501 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>
24502 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>,
24503 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>
24504 function specifiers, <a href="#6.7.4">6.7.4</a> hyperbolic functions
24505 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>
24506 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>
24507 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>
24508 future directions hypot type-generic macro, <a href="#7.22">7.22</a>
24510 <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>
24511 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>
24512 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>,
24513 maximum length, <a href="#6.4.2.1">6.4.2.1</a> <a href="#F.7.5">F.7.5</a>
24514 name spaces, <a href="#6.2.3">6.2.3</a> in blocks, <a href="#6.8">6.8</a>
24515 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>
24516 scope, <a href="#6.2.1">6.2.1</a> permitted form, <a href="#6.6">6.6</a>
24517 type, <a href="#6.2.5">6.2.5</a> string literal, <a href="#6.3.2.1">6.3.2.1</a>
24518 identifier list, <a href="#6.7.5">6.7.5</a> inline, <a href="#6.7.4">6.7.4</a>
24519 identifier nondigit, <a href="#6.4.2.1">6.4.2.1</a> inner scope, <a href="#6.2.1">6.2.1</a>
24520 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>
24521 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
24522 <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>
24523 IEEE 754, <a href="#F.1">F.1</a> direct, <a href="#7.19.8">7.19.8</a>
24524 IEEE 854, <a href="#F.1">F.1</a> formatted, <a href="#7.19.6">7.19.6</a>
24525 IEEE floating-point arithmetic standard, see wide character, <a href="#7.24.2">7.24.2</a>
24526 IEC 60559, ANSI/IEEE 754, wide character, <a href="#7.24.3">7.24.3</a>
24527 ANSI/IEEE 854 formatted, <a href="#7.24.2">7.24.2</a>
24528 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>
24529 <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>
24530 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>
24531 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>,
24532 ifndef preprocessing directive, <a href="#6.10.1">6.10.1</a> <a href="#6.3.1.8">6.3.1.8</a>
24533 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>
24534 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>
24535 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>
24536 imaginary numbers, <a href="#G">G</a> INT_LEASTN_MAX macros, <a href="#7.18.2.2">7.18.2.2</a>
24537 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>
24538 imaginary types, <a href="#G">G</a> int_leastN_t types, <a href="#7.18.1.2">7.18.1.2</a>
24539 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>
24540 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>
24541 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>,
24542 implementation, <a href="#3.12">3.12</a> <a href="#7.20.6">7.20.6</a>
24543 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>
24544 <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>
24545 limits integer constant expression, <a href="#6.6">6.6</a>
24546 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>
24547 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>,
24548 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>,
24549 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>
24550 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>
24551 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>,
24552 bitwise (|), <a href="#6.5.12">6.5.12</a> <a href="#F.3">F.3</a>, <a href="#F.4">F.4</a>
24553 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>
24554 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>
24555 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>
24556 increment and decrement internal linkage, <a href="#6.2.2">6.2.2</a>
24557 indeterminate value, <a href="#3.17.2">3.17.2</a> internal name, <a href="#6.4.2.1">6.4.2.1</a>
24558 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>
24559 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>
24560 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>
24562 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>,
24563 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>
24564 <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>
24565 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>,
24566 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>
24567 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>
24568 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>,
24569 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>
24570 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>,
24571 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>
24572 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>,
24573 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>
24574 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>,
24575 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>
24576 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>,
24577 <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>,
24578 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>
24579 <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>,
24580 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>,
24581 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>,
24582 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>
24583 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>,
24584 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>
24585 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>
24586 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>
24587 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>
24588 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>
24589 <a href="#7.4.2.2">7.4.2.2</a>
24590 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>
24591 isnormal macro, <a href="#7.12.3.5">7.12.3.5</a> jump statements, <a href="#6.8.6">6.8.6</a>
24592 ISO 31-11, <a href="#2">2</a>, <a href="#3">3</a>
24593 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>
24594 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>
24595 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>
24596 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>
24597 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>
24598 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>
24599 ISO/IEC 9945-2, <a href="#7.11">7.11</a> labs function, <a href="#7.20.6.1">7.20.6.1</a>
24600 ISO/IEC TR 10176, <a href="#D">D</a> language, <a href="#6">6</a>
24601 iso646.h header, <a href="#4">4</a>, <a href="#7.9">7.9</a> future directions, <a href="#6.11">6.11</a>
24602 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>
24603 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>
24604 <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>
24605 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>,
24606 <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>
24607 <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>,
24608 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>,
24609 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>
24610 <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>
24611 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>
24612 <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>
24614 lconv structure type, <a href="#7.11">7.11</a> llabs function, <a href="#7.20.6.1">7.20.6.1</a>
24615 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>
24616 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>
24617 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>,
24618 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>
24619 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>,
24620 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>
24621 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>
24622 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>
24623 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>
24624 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>
24625 ldexp type-generic macro, <a href="#7.22">7.22</a> local time, <a href="#7.23.1">7.23.1</a>
24626 ldiv function, <a href="#7.20.6.2">7.20.6.2</a> locale, <a href="#3.4.2">3.4.2</a>
24627 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>
24628 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>
24629 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>
24630 left-shift operator (<<), <a href="#6.5.7">6.5.7</a> localization, <a href="#7.11">7.11</a>
24631 length localtime function, <a href="#7.23.3.4">7.23.3.4</a>
24632 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>
24633 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>
24634 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>
24635 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>
24636 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>
24637 <a href="#7.24.6.3.1">7.24.6.3.1</a> log1p type-generic macro, <a href="#7.22">7.22</a>
24638 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>
24639 <a href="#7.24.2.2">7.24.2.2</a> log2 type-generic macro, <a href="#7.22">7.22</a>
24640 less-than operator (<), <a href="#6.5.8">6.5.8</a> logarithmic functions
24641 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>
24642 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>
24643 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>
24644 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>
24645 lgamma type-generic macro, <a href="#7.22">7.22</a> logical operators
24646 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>
24647 future directions, <a href="#7.26">7.26</a> negation (!), <a href="#6.5.3.3">6.5.3.3</a>
24648 summary, <a href="#B">B</a> OR (||), <a href="#6.5.14">6.5.14</a>
24649 terms, <a href="#7.1.1">7.1.1</a> logical source lines, <a href="#5.1.1.2">5.1.1.2</a>
24650 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>
24651 lifetime, <a href="#6.2.4">6.2.4</a> long double _Complex type conversion,
24652 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>
24653 environmental, see environmental limits long double _Imaginary type, <a href="#G.2">G.2</a>
24654 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>
24655 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>,
24656 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>
24657 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>,
24658 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>
24659 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>,
24660 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>
24661 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>,
24662 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>
24663 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>
24664 <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>,
24666 <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>
24667 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>
24668 <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>,
24669 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>,
24670 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>
24671 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>
24672 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>,
24673 loop body, <a href="#6.8.5">6.8.5</a> <a href="#7.24.6.3">7.24.6.3</a>
24674 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>
24675 lowercase letter, <a href="#5.2.1">5.2.1</a> member alignment, <a href="#6.7.2.1">6.7.2.1</a>
24676 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>
24677 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>
24678 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>
24679 lround type-generic macro, <a href="#7.22">7.22</a> memmove function, <a href="#7.21.2.2">7.21.2.2</a>
24680 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>
24681 memset function, <a href="#7.21.6.1">7.21.6.1</a>
24682 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>
24683 macro definition minus operator, unary, <a href="#6.5.3.3">6.5.3.3</a>
24684 library function, <a href="#7.1.4">7.1.4</a> miscellaneous functions
24685 macro invocation, <a href="#6.10.3">6.10.3</a> string, <a href="#7.21.6">7.21.6</a>
24686 macro name, <a href="#6.10.3">6.10.3</a> wide string, <a href="#7.24.4.6">7.24.4.6</a>
24687 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>
24688 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>
24689 redefinition, <a href="#6.10.3">6.10.3</a> modifiable lvalue, <a href="#6.3.2.1">6.3.2.1</a>
24690 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>
24691 macro parameter, <a href="#6.10.3">6.10.3</a> modulus, complex, <a href="#7.3.8.1">7.3.8.1</a>
24692 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>
24693 macro replacement, <a href="#6.10.3">6.10.3</a> multibyte conversion functions
24694 magnitude, complex, <a href="#7.3.8.1">7.3.8.1</a> wide character, <a href="#7.20.7">7.20.7</a>
24695 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>
24696 <a href="#7.19.3">7.19.3</a> restartable, <a href="#7.24.6.3">7.24.6.3</a>
24697 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>
24698 <a href="#7.20.3.4">7.20.3.4</a> restartable, <a href="#7.24.6.4">7.24.6.4</a>
24699 manipulation functions multibyte string, <a href="#7.1.1">7.1.1</a>
24700 complex, <a href="#7.3.9">7.3.9</a> multibyte/wide character conversion functions,
24701 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>
24702 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>
24703 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>
24704 <a href="#J.5.17">J.5.17</a> multibyte/wide string conversion functions, <a href="#7.20.8">7.20.8</a>
24705 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>
24706 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>
24707 MATH_ERRNO macro, <a href="#7.12">7.12</a> multiplication assignment operator (*=), <a href="#6.5.16.2">6.5.16.2</a>
24708 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>
24709 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>
24710 <a href="#7.20.7.3">7.20.7.3</a>, <a href="#7.24.6.3.3">7.24.6.3.3</a>
24711 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>
24712 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>
24713 mbrlen function, <a href="#7.24.6.3.1">7.24.6.3.1</a> name
24714 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>
24715 <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>
24716 <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>
24718 label, <a href="#6.2.3">6.2.3</a> octal-character escape sequence (\octal digits),
24719 structure/union member, <a href="#6.2.3">6.2.3</a> <a href="#6.4.4.4">6.4.4.4</a>
24720 name spaces, <a href="#6.2.3">6.2.3</a> offsetof macro, <a href="#7.17">7.17</a>
24721 named label, <a href="#6.8.1">6.8.1</a> on-off switch, <a href="#6.10.6">6.10.6</a>
24722 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>
24723 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>
24724 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>
24725 NDEBUG macro, <a href="#7.2">7.2</a> operations on files, <a href="#7.19.4">7.19.4</a>
24726 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>
24727 <a href="#F.9.6.3">F.9.6.3</a> operators, <a href="#6.5">6.5</a>
24728 nearbyint type-generic macro, <a href="#7.22">7.22</a> assignment, <a href="#6.5.16">6.5.16</a>
24729 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>
24730 negation operator (!), <a href="#6.5.3.3">6.5.3.3</a> equality, <a href="#6.5.9">6.5.9</a>
24731 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>
24732 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>
24733 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>
24734 <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>
24735 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>
24736 <a href="#F.9.8.3">F.9.8.3</a> shift, <a href="#6.5.7">6.5.7</a>
24737 nextafter type-generic macro, <a href="#7.22">7.22</a> unary, <a href="#6.5.3">6.5.3</a>
24738 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>
24739 nexttoward type-generic macro, <a href="#7.22">7.22</a> or macro, <a href="#7.9">7.9</a>
24740 no linkage, <a href="#6.2.2">6.2.2</a> OR operators
24741 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>
24742 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>
24743 nonlocal jumps header, <a href="#7.13">7.13</a> bitwise inclusive (|), <a href="#6.5.12">6.5.12</a>
24744 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>
24745 not macro, <a href="#7.9">7.9</a> logical (||), <a href="#6.5.14">6.5.14</a>
24746 not-equal-to operator, see inequality operator or_eq macro, <a href="#7.9">7.9</a>
24747 not_eq macro, <a href="#7.9">7.9</a> order of allocated storage, <a href="#7.20.3">7.20.3</a>
24748 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>
24749 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>
24750 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>
24751 <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>
24752 null pointer, <a href="#6.3.2.3">6.3.2.3</a>
24753 null pointer constant, <a href="#6.3.2.3">6.3.2.3</a> padding
24754 null preprocessing directive, <a href="#6.10.7">6.10.7</a> binary stream, <a href="#7.19.2">7.19.2</a>
24755 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>
24756 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>
24757 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>
24758 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>
24759 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>
24760 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>
24761 macro, <a href="#6.10.3">6.10.3</a>
24762 object, <a href="#3.14">3.14</a> main function, <a href="#5.1.2.2.1">5.1.2.2.1</a>
24763 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>
24764 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>
24765 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>
24766 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>
24767 octal constant, <a href="#6.4.4.1">6.4.4.1</a> parse state, <a href="#7.19.2">7.19.2</a>
24768 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>
24770 perror function, <a href="#7.19.10.4">7.19.10.4</a> PRIcPTR macros, <a href="#7.8.1">7.8.1</a>
24771 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>
24772 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>
24773 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>
24774 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>
24775 pointer arithmetic, <a href="#6.5.6">6.5.6</a> program diagnostics, <a href="#7.2.1">7.2.1</a>
24776 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>
24777 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>
24778 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>
24779 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>
24780 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>
24781 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>
24782 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>
24783 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>,
24784 position indicator, file, see file position indicator <a href="#5.1.2.3">5.1.2.3</a>
24785 positive difference, <a href="#7.12.12.1">7.12.12.1</a> program, conforming, <a href="#4">4</a>
24786 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>
24787 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
24788 postfix expressions, <a href="#6.5.2">6.5.2</a> default argument, <a href="#6.5.2.2">6.5.2.2</a>
24789 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>
24790 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
24791 pow type-generic macro, <a href="#7.22">7.22</a> pseudo-random sequence functions, <a href="#7.20.2">7.20.2</a>
24792 power functions PTRDIFF_MAX macro, <a href="#7.18.3">7.18.3</a>
24793 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>
24794 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>,
24795 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>
24796 pragma operator, <a href="#6.10.9">6.10.9</a> punctuators, <a href="#6.4.6">6.4.6</a>
24797 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>
24798 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>
24799 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>
24800 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>
24801 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>
24802 predefined macro names, <a href="#6.10.8">6.10.8</a>, <a href="#6.11.9">6.11.9</a>
24803 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>
24804 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>
24805 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>
24806 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>
24807 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>
24808 preprocessing numbers, <a href="#6.4">6.4</a>, <a href="#6.4.8">6.4.8</a>
24809 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>
24810 #, <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>
24811 ##, <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>
24812 _Pragma, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.10.9">6.10.9</a> range
24813 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>
24814 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>,
24815 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>,
24816 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>,
24817 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>,
24818 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>,
24819 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>,
24820 PRIcN macros, <a href="#7.8.1">7.8.1</a> <a href="#7.12.13.1">7.12.13.1</a>
24822 rank, see integer conversion rank same scope, <a href="#6.2.1">6.2.1</a>
24823 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>
24824 <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>
24825 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>
24826 real type domain, <a href="#6.2.5">6.2.5</a> scalbln type-generic macro, <a href="#7.22">7.22</a>
24827 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>
24828 real-floating, <a href="#7.12.3">7.12.3</a> scalbn type-generic macro, <a href="#7.22">7.22</a>
24829 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>
24830 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>
24831 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>
24832 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>
24833 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>
24834 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>
24835 library functions, <a href="#7.1.4">7.1.4</a> SCNcLEASTN macros, <a href="#7.8.1">7.8.1</a>
24836 referenced type, <a href="#6.2.5">6.2.5</a> SCNcMAX macros, <a href="#7.8.1">7.8.1</a>
24837 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>
24838 relational expressions, <a href="#6.5.8">6.5.8</a> SCNcPTR macros, <a href="#7.8.1">7.8.1</a>
24839 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>
24840 remainder assignment operator (%=), <a href="#6.5.16.2">6.5.16.2</a> search functions
24841 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>
24842 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>
24843 <a href="#F.9.7.2">F.9.7.2</a> wide string, <a href="#7.24.4.5">7.24.4.5</a>
24844 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>
24845 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>
24846 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>
24847 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>
24848 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>
24849 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>,
24850 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>
24851 pointer, <a href="#6.2.5">6.2.5</a> separate compilation, <a href="#5.1.1.1">5.1.1.1</a>
24852 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>
24853 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>,
24854 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>
24855 functions, <a href="#7.24.6.3">7.24.6.3</a> sequencing of statements, <a href="#6.8">6.8</a>
24856 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>
24857 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>
24858 restore calling environment function, <a href="#7.13.2">7.13.2</a> setjmp.h header, <a href="#7.13">7.13</a>
24859 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>
24860 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>,
24861 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>
24862 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>
24863 <a href="#7.24.3.10">7.24.3.10</a> shift expressions, <a href="#6.5.7">6.5.7</a>
24864 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>
24865 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>
24866 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>
24867 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>,
24868 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>
24869 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>,
24870 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>
24871 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>
24872 SHRT_MIN macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>
24874 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>
24875 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>
24876 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>,
24877 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>
24878 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>
24879 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>
24880 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>
24881 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>
24882 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>
24883 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>
24884 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>
24885 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>
24886 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>,
24887 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>
24888 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>
24889 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>
24890 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>
24891 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>,
24892 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>
24893 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>
24894 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>
24895 <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>
24896 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>
24897 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>,
24898 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>
24899 <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>
24900 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>
24901 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>
24902 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>
24903 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>,
24904 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>
24905 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>,
24906 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>
24907 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>
24908 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>
24909 <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>
24910 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>
24911 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>
24912 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>,
24913 sinh type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a> <a href="#F">F</a>
24914 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>
24915 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>
24916 <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>
24917 <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>
24918 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>
24919 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>
24920 sorting utility functions, <a href="#7.20.5">7.20.5</a> statements, <a href="#6.8">6.8</a>
24921 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>
24922 source file, <a href="#5.1.1.1">5.1.1.1</a> compound, <a href="#6.8.2">6.8.2</a>
24923 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>
24924 source file inclusion, <a href="#6.10.2">6.10.2</a> do, <a href="#6.8.5.2">6.8.5.2</a>
24926 else, <a href="#6.8.4.1">6.8.4.1</a> strictly conforming program, <a href="#4">4</a>
24927 expression, <a href="#6.8.3">6.8.3</a> string, <a href="#7.1.1">7.1.1</a>
24928 for, <a href="#6.8.5.3">6.8.5.3</a> comparison functions, <a href="#7.21.4">7.21.4</a>
24929 goto, <a href="#6.8.6.1">6.8.6.1</a> concatenation functions, <a href="#7.21.3">7.21.3</a>
24930 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>
24931 iteration, <a href="#6.8.5">6.8.5</a> copying functions, <a href="#7.21.2">7.21.2</a>
24932 jump, <a href="#6.8.6">6.8.6</a> library function conventions, <a href="#7.21.1">7.21.1</a>
24933 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>
24934 null, <a href="#6.8.3">6.8.3</a> miscellaneous functions, <a href="#7.21.6">7.21.6</a>
24935 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>
24936 selection, <a href="#6.8.4">6.8.4</a> search functions, <a href="#7.21.5">7.21.5</a>
24937 sequencing, <a href="#6.8">6.8</a> string handling header, <a href="#7.21">7.21</a>
24938 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>
24939 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>
24940 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>
24941 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>
24942 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>
24943 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>
24944 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>
24945 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>
24946 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>
24947 <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>
24948 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>,
24949 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>
24950 <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>
24951 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>
24952 <a href="#7.26.8">7.26.8</a> strtok function, <a href="#7.21.5.8">7.21.5.8</a>
24953 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>,
24954 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>
24955 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>
24956 <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>
24957 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>,
24958 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>
24959 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>
24960 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>
24961 strchr function, <a href="#7.21.5.2">7.21.5.2</a> struct hack, see flexible array member
24962 strcmp function, <a href="#7.21.4">7.21.4</a>, <a href="#7.21.4.2">7.21.4.2</a> structure
24963 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>
24964 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>
24965 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>
24966 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>
24967 fully buffered, <a href="#7.19.3">7.19.3</a> member alignment, <a href="#6.7.2.1">6.7.2.1</a>
24968 line buffered, <a href="#7.19.3">7.19.3</a> member name space, <a href="#6.2.3">6.2.3</a>
24969 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>
24970 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>
24971 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>
24972 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>
24973 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>
24974 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>
24975 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>
24976 <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>
24978 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>
24979 suffix toupper function, <a href="#7.4.2.2">7.4.2.2</a>
24980 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>
24981 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>
24982 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>
24983 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>
24984 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>
24985 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>
24986 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>
24987 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>,
24988 symbols, <a href="#3">3</a> <a href="#6.5.2.3">6.5.2.3</a>
24989 syntactic categories, <a href="#6.1">6.1</a> trigonometric functions
24990 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>
24991 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>
24992 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>
24993 system function, <a href="#7.20.4.6">7.20.4.6</a> true macro, <a href="#7.16">7.16</a>
24994 trunc functions, <a href="#7.12.9.8">7.12.9.8</a>, <a href="#F.9.6.8">F.9.6.8</a>
24995 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>
24996 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>
24997 tag name space, <a href="#6.2.3">6.2.3</a> truncation toward zero, <a href="#6.5.5">6.5.5</a>
24998 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>
24999 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>
25000 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>
25001 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>
25002 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>
25003 tentative definition, <a href="#6.9.2">6.9.2</a> type names, <a href="#6.7.6">6.7.6</a>
25004 terms, <a href="#3">3</a> type punning, <a href="#6.5.2.3">6.5.2.3</a>
25005 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>
25006 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>
25007 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>
25008 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>
25009 time typedef storage-class specifier, <a href="#6.7.1">6.7.1</a>, <a href="#6.7.7">6.7.7</a>
25010 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>
25011 <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>
25012 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>
25013 <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>
25014 components, <a href="#7.23.1">7.23.1</a> composite, <a href="#6.2.7">6.2.7</a>
25015 conversion functions, <a href="#7.23.3">7.23.3</a> const qualified, <a href="#6.7.3">6.7.3</a>
25016 wide character, <a href="#7.24.5">7.24.5</a> conversions, <a href="#6.3">6.3</a>
25017 local, <a href="#7.23.1">7.23.1</a> imaginary, <a href="#G">G</a>
25018 manipulation functions, <a href="#7.23.2">7.23.2</a> restrict qualified, <a href="#6.7.3">6.7.3</a>
25019 time function, <a href="#7.23.2.4">7.23.2.4</a> volatile qualified, <a href="#6.7.3">6.7.3</a>
25020 time.h header, <a href="#7.23">7.23</a>
25021 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>
25022 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>
25023 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>
25024 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>
25025 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>
25026 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>
25027 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>
25028 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>
25030 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>
25031 <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>,
25032 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>
25033 UINTN_MAX macros, <a href="#7.18.2.1">7.18.2.1</a> utilities, general, <a href="#7.20">7.20</a>
25034 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>
25035 UINTPTR_MAX macro, <a href="#7.18.2.4">7.18.2.4</a>
25036 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>,
25037 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>,
25038 <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>,
25039 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>,
25040 <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>
25041 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>,
25042 unary expression, <a href="#6.5.3">6.5.3</a> <a href="#7.15.1.3">7.15.1.3</a>
25043 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>,
25044 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>,
25045 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>,
25046 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>,
25047 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>
25048 <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>
25049 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>,
25050 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>,
25051 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>,
25052 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>,
25053 <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>
25054 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>
25055 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>
25056 union variable arguments, <a href="#6.10.3">6.10.3</a>, <a href="#7.15">7.15</a>
25057 arrow operator (->), <a href="#6.5.2.3">6.5.2.3</a> variable arguments header, <a href="#7.15">7.15</a>
25058 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>
25059 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>
25060 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>
25061 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>,
25062 member name space, <a href="#6.2.3">6.2.3</a> <a href="#7.4.1.10">7.4.1.10</a>
25063 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>
25064 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>
25065 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>
25066 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>
25067 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>
25068 universal character name, <a href="#6.4.3">6.4.3</a> VLA, see variable length array
25069 unqualified type, <a href="#6.2.5">6.2.5</a> void expression, <a href="#6.3.2.2">6.3.2.2</a>
25070 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>
25071 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>
25072 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>
25073 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>
25074 <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>
25075 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>
25076 <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>
25077 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>
25078 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>
25079 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>
25080 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>
25082 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>
25083 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>
25084 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>,
25085 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>,
25086 <a href="#7.24.6.1.1">7.24.6.1.1</a>, <a href="#7.25.1">7.25.1</a>
25087 warnings, <a href="#I">I</a> while statement, <a href="#6.8.5.1">6.8.5.1</a>
25088 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>,
25089 <a href="#F">F</a> <a href="#7.25.2.1.10">7.25.2.1.10</a>
25090 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>
25091 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>
25092 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>
25093 <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>
25094 <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>
25095 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>
25096 <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>
25097 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>
25098 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>
25099 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>
25100 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>
25101 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>
25102 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>
25103 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>
25104 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>
25105 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>
25106 wcsncmp function, <a href="#7.24.4.4.3">7.24.4.4.3</a> wide string literal, see string literal
25107 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>
25108 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>,
25109 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>
25110 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>
25111 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>
25112 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>
25113 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>
25114 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>
25115 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>,
25116 wcstoimax function, <a href="#7.8.2.4">7.8.2.4</a> <a href="#7.25.1">7.25.1</a>
25117 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>
25118 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>
25119 <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>
25120 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>
25121 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>
25122 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>
25123 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>,
25124 <a href="#7.24.4.1.2">7.24.4.1.2</a> <a href="#7.24.3.10">7.24.3.10</a>
25125 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>
25126 wcstoumax function, <a href="#7.8.2.4">7.8.2.4</a> xor macro, <a href="#7.9">7.9</a>
25127 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>
25128 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>
25129 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>
25130 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>
25131 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>
25132 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>