1<stdint.h>(0P) POSIX Programmer's Manual <stdint.h>(0P)
2
6 stdint.h - integer types
7
9 #include <stdint.h>
10
12 Some of the functionality described on this reference page extends the
13 ISO C standard. Applications shall define the appropriate feature test
14 macro (see the System Interfaces volume of IEEE Std 1003.1-2001, Sec‐
15 tion 2.2, The Compilation Environment) to enable the visibility of
16 these symbols in this header.
17 The <stdint.h> header shall declare sets of integer types having speci‐
19 fied widths, and shall define corresponding sets of macros. It shall
20 also define macros that specify limits of integer types corresponding
21 to types defined in other standard headers.
22 Note: The "width" of an integer type is the number of bits used to
24 store its value in a pure binary system; the actual type may use
25 more bits than that (for example, a 28-bit type could be stored
26 in 32 bits of actual storage). An N-bit signed type has values
27 in the range -2**N-1 or 1-2**N-1 to 2**N-1-1, while an N-bit
28 unsigned type has values in the range 0 to 2**N-1.
29 Types are defined in the following categories:
32 * Integer types having certain exact widths
34 * Integer types having at least certain specified widths
36 * Fastest integer types having at least certain specified widths
38 * Integer types wide enough to hold pointers to objects
40 * Integer types having greatest width
42 (Some of these types may denote the same type.)
44 Corresponding macros specify limits of the declared types and construct
46 suitable constants.
47 For each type described herein that the implementation provides, the
49 <stdint.h> header shall declare that typedef name and define the asso‐
50 ciated macros. Conversely, for each type described herein that the
51 implementation does not provide, the <stdint.h> header shall not
52 declare that typedef name, nor shall it define the associated macros.
53 An implementation shall provide those types described as required, but
54 need not provide any of the others (described as optional).
55 Integer Types
57 When typedef names differing only in the absence or presence of the
58 initial u are defined, they shall denote corresponding signed and
59 unsigned types as described in the ISO/IEC 9899:1999 standard, Section
60 6.2.5; an implementation providing one of these corresponding types
61 shall also provide the other.
62 In the following descriptions, the symbol N represents an unsigned dec‐
64 imal integer with no leading zeros (for example, 8 or 24, but not 04 or
65 048).
66 * Exact-width integer types
68 The typedef name int N _t designates a signed integer type with width
70 N, no padding bits, and a two's-complement representation. Thus, int8_t
71 denotes a signed integer type with a width of exactly 8 bits.
72 The typedef name uint N _t designates an unsigned integer type with
74 width N. Thus, uint24_t denotes an unsigned integer type with a width
75 of exactly 24 bits.
76 The following types are required:
78 int8_t
80 int16_t
81 int32_t
82 uint8_t
83 uint16_t
84 uint32_t
85 If an implementation provides integer types with width 64 that meet
87 these requirements, then the following types are required: int64_t
88 uint64_t
89 In particular, this will be the case if any of the following are true:
91 * The implementation supports the _POSIX_V6_ILP32_OFFBIG pro‐
93 gramming environment and the application is being built in
94 the _POSIX_V6_ILP32_OFFBIG programming environment (see the
95 Shell and Utilities volume of IEEE Std 1003.1-2001, c99, Pro‐
96 gramming Environments).
97 * The implementation supports the _POSIX_V6_LP64_OFF64 program‐
99 ming environment and the application is being built in the
100 _POSIX_V6_LP64_OFF64 programming environment.
101 * The implementation supports the _POSIX_V6_LPBIG_OFFBIG pro‐
103 gramming environment and the application is being built in
104 the _POSIX_V6_LPBIG_OFFBIG programming environment.
105 All other types of this form are optional.
107 * Minimum-width integer types
109 The typedef name int_least N _t designates a signed integer type with a
111 width of at least N, such that no signed integer type with lesser size
112 has at least the specified width. Thus, int_least32_t denotes a signed
113 integer type with a width of at least 32 bits.
114 The typedef name uint_least N _t designates an unsigned integer type
116 with a width of at least N, such that no unsigned integer type with
117 lesser size has at least the specified width. Thus, uint_least16_t
118 denotes an unsigned integer type with a width of at least 16 bits.
119 The following types are required: int_least8_t int_least16_t
121 int_least32_t int_least64_t uint_least8_t uint_least16_t uint_least32_t
122 uint_least64_t
123 All other types of this form are optional.
125 * Fastest minimum-width integer types
127 Each of the following types designates an integer type that is usually
129 fastest to operate with among all integer types that have at least the
130 specified width.
131 The designated type is not guaranteed to be fastest for all purposes;
133 if the implementation has no clear grounds for choosing one type over
134 another, it will simply pick some integer type satisfying the signed‐
135 ness and width requirements.
136 The typedef name int_fast N _t designates the fastest signed integer
138 type with a width of at least N. The typedef name uint_fast N _t desig‐
139 nates the fastest unsigned integer type with a width of at least N.
140 The following types are required: int_fast8_t int_fast16_t int_fast32_t
142 int_fast64_t uint_fast8_t uint_fast16_t uint_fast32_t uint_fast64_t
143 All other types of this form are optional.
145 * Integer types capable of holding object pointers
147 The following type designates a signed integer type with the property
149 that any valid pointer to void can be converted to this type, then con‐
150 verted back to a pointer to void, and the result will compare equal to
151 the original pointer: intptr_t
152 The following type designates an unsigned integer type with the prop‐
154 erty that any valid pointer to void can be converted to this type, then
155 converted back to a pointer to void, and the result will compare equal
156 to the original pointer: uintptr_t
157 On XSI-conformant systems, the intptr_t and uintptr_t types are
159 required; otherwise, they are optional.
160 * Greatest-width integer types
162 The following type designates a signed integer type capable of repre‐
164 senting any value of any signed integer type: intmax_t
165 The following type designates an unsigned integer type capable of rep‐
167 resenting any value of any unsigned integer type: uintmax_t
168 These types are required.
170 Note: Applications can test for optional types by using the corre‐
172 sponding limit macro from Limits of Specified-Width Integer
173 Types .
174 Limits of Specified-Width Integer Types
177 The following macros specify the minimum and maximum limits of the
178 types declared in the <stdint.h> header. Each macro name corresponds to
179 a similar type name in Integer Types .
180 Each instance of any defined macro shall be replaced by a constant
182 expression suitable for use in #if preprocessing directives, and this
183 expression shall have the same type as would an expression that is an
184 object of the corresponding type converted according to the integer
185 promotions. Its implementation-defined value shall be equal to or
186 greater in magnitude (absolute value) than the corresponding value
187 given below, with the same sign, except where stated to be exactly the
188 given value.
189 * Limits of exact-width integer types
191 * Minimum values of exact-width signed integer types:
193 {INTN_MIN}
195 Exactly -(2 **N-1)
196 * Maximum values of exact-width signed integer types:
199 {INTN_MAX}
201 Exactly 2**N-1 -1
202 * Maximum values of exact-width unsigned integer types:
205 {UINTN_MAX}
207 Exactly 2 **N -1
208 * Limits of minimum-width integer types
211 * Minimum values of minimum-width signed integer types:
213 {INT_LEASTN_MIN}
215 -(2 ** N-1 -1)
216 * Maximum values of minimum-width signed integer types:
219 {INT_LEASTN_MAX}
221 2 ** N-1 -1
222 * Maximum values of minimum-width unsigned integer types:
225 {UINT_LEASTN_MAX}
227 2 ** N -1
228 * Limits of fastest minimum-width integer types
231 * Minimum values of fastest minimum-width signed integer types:
233 {INT_FASTN_MIN}
235 -(2 ** N-1 -1)
236 * Maximum values of fastest minimum-width signed integer types:
239 {INT_FASTN_MAX}
241 2 ** N-1 -1
242 * Maximum values of fastest minimum-width unsigned integer types:
245 {UINT_FASTN_MAX}
247 2 ** N -1
248 * Limits of integer types capable of holding object pointers
251 * Minimum value of pointer-holding signed integer type:
253 {INTPTR_MIN}
255 -(2 ** 15 -1)
256 * Maximum value of pointer-holding signed integer type:
259 {INTPTR_MAX}
261 2 ** 15 -1
262 * Maximum value of pointer-holding unsigned integer type:
265 {UINTPTR_MAX}
267 2 ** 16 -1
268 * Limits of greatest-width integer types
271 * Minimum value of greatest-width signed integer type:
273 {INTMAX_MIN}
275 -(2 ** 63 -1)
276 * Maximum value of greatest-width signed integer type:
279 {INTMAX_MAX}
281 2 ** 63 -1
282 * Maximum value of greatest-width unsigned integer type:
285 {UINTMAX_MAX}
287 2 ** 64 -1
288 Limits of Other Integer Types
291 The following macros specify the minimum and maximum limits of integer
292 types corresponding to types defined in other standard headers.
293 Each instance of these macros shall be replaced by a constant expres‐
295 sion suitable for use in #if preprocessing directives, and this expres‐
296 sion shall have the same type as would an expression that is an object
297 of the corresponding type converted according to the integer promo‐
298 tions. Its implementation-defined value shall be equal to or greater in
299 magnitude (absolute value) than the corresponding value given below,
300 with the same sign.
301 * Limits of ptrdiff_t:
303 {PTRDIFF_MIN}
305 -65535
306 {PTRDIFF_MAX}
308 +65535
309 * Limits of sig_atomic_t:
312 {SIG_ATOMIC_MIN}
314 See below.
315 {SIG_ATOMIC_MAX}
317 See below.
318 * Limit of size_t:
321 {SIZE_MAX}
323 65535
324 * Limits of wchar_t:
327 {WCHAR_MIN}
329 See below.
330 {WCHAR_MAX}
332 See below.
333 * Limits of wint_t:
336 {WINT_MIN}
338 See below.
339 {WINT_MAX}
341 See below.
342 If sig_atomic_t (see the <signal.h> header) is defined as a signed
345 integer type, the value of {SIG_ATOMIC_MIN} shall be no greater than
346 -127 and the value of {SIG_ATOMIC_MAX} shall be no less than 127; oth‐
347 erwise, sig_atomic_t shall be defined as an unsigned integer type, and
348 the value of {SIG_ATOMIC_MIN} shall be 0 and the value of
349 {SIG_ATOMIC_MAX} shall be no less than 255.
350 If wchar_t (see the <stddef.h> header) is defined as a signed integer
352 type, the value of {WCHAR_MIN} shall be no greater than -127 and the
353 value of {WCHAR_MAX} shall be no less than 127; otherwise, wchar_t
354 shall be defined as an unsigned integer type, and the value of
355 {WCHAR_MIN} shall be 0 and the value of {WCHAR_MAX} shall be no less
356 than 255.
357 If wint_t (see the <wchar.h> header) is defined as a signed integer
359 type, the value of {WINT_MIN} shall be no greater than -32767 and the
360 value of {WINT_MAX} shall be no less than 32767; otherwise, wint_t
361 shall be defined as an unsigned integer type, and the value of
362 {WINT_MIN} shall be 0 and the value of {WINT_MAX} shall be no less than
363 65535.
364 Macros for Integer Constant Expressions
366 The following macros expand to integer constant expressions suitable
367 for initializing objects that have integer types corresponding to types
368 defined in the <stdint.h> header. Each macro name corresponds to a sim‐
369 ilar type name listed under Minimum-width integer types and Greatest-
370 width integer types.
371 Each invocation of one of these macros shall expand to an integer con‐
373 stant expression suitable for use in #if preprocessing directives. The
374 type of the expression shall have the same type as would an expression
375 that is an object of the corresponding type converted according to the
376 integer promotions. The value of the expression shall be that of the
377 argument.
378 The argument in any instance of these macros shall be a decimal, octal,
380 or hexadecimal constant with a value that does not exceed the limits
381 for the corresponding type.
382 * Macros for minimum-width integer constant expressions
384 The macro INTN_C( value) shall expand to an integer constant expression
386 corresponding to the type int_least N _t. The macro UINTN_C( value)
387 shall expand to an integer constant expression corresponding to the
388 type uint_least N _t. For example, if uint_least64_t is a name for the
389 type unsigned long long, then UINT64_C(0x123) might expand to the inte‐
390 ger constant 0x123ULL.
391 * Macros for greatest-width integer constant expressions
393 The following macro expands to an integer constant expression having
395 the value specified by its argument and the type intmax_t: INT‐
396 MAX_C(value)
397 The following macro expands to an integer constant expression having
399 the value specified by its argument and the type uintmax_t: UINT‐
400 MAX_C(value)
401 The following sections are informative.
403
405 None.
406
408 The <stdint.h> header is a subset of the <inttypes.h> header more suit‐
409 able for use in freestanding environments, which might not support the
410 formatted I/O functions. In some environments, if the formatted conver‐
411 sion support is not wanted, using this header instead of the <int‐
412 types.h> header avoids defining such a large number of macros.
413 As a consequence of adding int8_t, the following are true:
415 * A byte is exactly 8 bits.
417 * {CHAR_BIT} has the value 8, {SCHAR_MAX} has the value 127,
419 {SCHAR_MIN} has the value -127 or -128, and {UCHAR_MAX} has the
420 value 255.
421
423 typedef names beginning with int or uint and ending with _t may be
424 added to the types defined in the <stdint.h> header. Macro names begin‐
425 ning with INT or UINT and ending with _MAX, _MIN, or _C may be added to
426 the macros defined in the <stdint.h> header.
427
429 <inttypes.h>, <signal.h>, <stddef.h>, <wchar.h>
430
432 Portions of this text are reprinted and reproduced in electronic form
433 from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
434 -- Portable Operating System Interface (POSIX), The Open Group Base
435 Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
436 Electrical and Electronics Engineers, Inc and The Open Group. In the
437 event of any discrepancy between this version and the original IEEE and
438 The Open Group Standard, the original IEEE and The Open Group Standard
439 is the referee document. The original Standard can be obtained online
440 at http://www.opengroup.org/unix/online.html .
441IEEE/The Open Group 2003 <stdint.h>(0P)