IEEE Std 1003.1-2008, 2016 Edition

Copyright © 2001-2016 The IEEE and The Open Group

stdint.h - integer types

#include <stdint.h>

^{[CX]}Some of the functionality described on this reference page extends the ISO C standard. Applications shall define the appropriate feature test macro (see XSHThe Compilation Environment) to enable the visibility of these symbols in this header.The

<stdint.h>header shall declare sets of integer types having specified widths, and shall define corresponding sets of macros. It shall also define macros that specify limits of integer types corresponding to types defined in other standard headers.

Note:- The "width" of an integer type is the number of bits used to store its value in a pure binary system; the actual type may use more bits than that (for example, a 28-bit type could be stored in 32 bits of actual storage). An
N-bit signed type has values in the range -2^{N-1}or 1-2^{N-1}to 2^{N-1}-1, while anN-bit unsigned type has values in the range 0 to 2^{N}-1.Types are defined in the following categories:

Integer types having certain exact widths

Integer types having at least certain specified widths

Fastest integer types having at least certain specified widths

Integer types wide enough to hold pointers to objects

Integer types having greatest width

(Some of these types may denote the same type.)

Corresponding macros specify limits of the declared types and construct suitable constants.

For each type described herein that the implementation provides, the

<stdint.h>header shall declare thattypedefname and define the associated macros. Conversely, for each type described herein that the implementation does not provide, the<stdint.h>header shall not declare thattypedefname, nor shall it define the associated macros. An implementation shall provide those types described as required, but need not provide any of the others (described as optional).## Integer Types

When

typedefnames differing only in the absence or presence of the initialuare defined, they shall denote corresponding signed and unsigned types as described in the ISO/IEC 9899:1999 standard, Section 6.2.5; an implementation providing one of these corresponding types shall also provide the other.In the following descriptions, the symbol

Nrepresents an unsigned decimal integer with no leading zeros (for example, 8 or 24, but not 04 or 048).

Exact-width integer types

The

typedefnameintN_tdesignates a signed integer type with widthN, no padding bits, and a two's-complement representation. Thus,int8_tdenotes a signed integer type with a width of exactly 8 bits.The

typedefnameuintN_tdesignates an unsigned integer type with widthN. Thus,uint24_tdenotes an unsigned integer type with a width of exactly 24 bits.

^{[CX]}The following types are required:

int8_t

int16_t

int32_t

uint8_t

uint16_t

uint32_t

If an implementation provides integer types with width 64 that meet these requirements, then the following types are required:

int64_tuint64_t

^{[CX]}In particular, this will be the case if any of the following are true:

The implementation supports the _POSIX_V7_ILP32_OFFBIG programming environment and the application is being built in the _POSIX_V7_ILP32_OFFBIG programming environment (see the Shell and Utilities volume of POSIX.1-2008,

c99, Programming Environments).The implementation supports the _POSIX_V7_LP64_OFF64 programming environment and the application is being built in the _POSIX_V7_LP64_OFF64 programming environment.

The implementation supports the _POSIX_V7_LPBIG_OFFBIG programming environment and the application is being built in the _POSIX_V7_LPBIG_OFFBIG programming environment.

All other types of this form are optional.

Minimum-width integer types

The

typedefnameint_leastN_tdesignates a signed integer type with a width of at leastN, such that no signed integer type with lesser size has at least the specified width. Thus,int_least32_tdenotes a signed integer type with a width of at least 32 bits.The

typedefnameuint_leastN_tdesignates an unsigned integer type with a width of at leastN, such that no unsigned integer type with lesser size has at least the specified width. Thus,uint_least16_tdenotes an unsigned integer type with a width of at least 16 bits.The following types are required:

int_least8_tint_least16_tint_least32_tint_least64_tuint_least8_tuint_least16_tuint_least32_tuint_least64_tAll other types of this form are optional.

Fastest minimum-width integer types

Each of the following types designates an integer type that is usually fastest to operate with among all integer types that have at least the specified width.

The designated type is not guaranteed to be fastest for all purposes; if the implementation has no clear grounds for choosing one type over another, it will simply pick some integer type satisfying the signedness and width requirements.

The

typedefnameint_fastN_tdesignates the fastest signed integer type with a width of at leastN. Thetypedefnameuint_fastN_tdesignates the fastest unsigned integer type with a width of at leastN.The following types are required:

int_fast8_tint_fast16_tint_fast32_tint_fast64_tuint_fast8_tuint_fast16_tuint_fast32_tuint_fast64_tAll other types of this form are optional.

Integer types capable of holding object pointers

The following type designates a signed integer type with the property that any valid pointer to

voidcan be converted to this type, then converted back to a pointer tovoid, and the result will compare equal to the original pointer:intptr_tThe following type designates an unsigned integer type with the property that any valid pointer to

voidcan be converted to this type, then converted back to a pointer tovoid, and the result will compare equal to the original pointer:uintptr_t

^{[XSI]}On XSI-conformant systems, theintptr_tanduintptr_ttypes are required; otherwise, they are optional.Greatest-width integer types

The following type designates a signed integer type capable of representing any value of any signed integer type:

intmax_tThe following type designates an unsigned integer type capable of representing any value of any unsigned integer type:

uintmax_tThese types are required.

Note:- Applications can test for optional types by using the corresponding limit macro from Limits of Specified-Width Integer Types.
## Limits of Specified-Width Integer Types

The following macros specify the minimum and maximum limits of the types declared in the

<stdint.h>header. Each macro name corresponds to a similar type name in Integer Types.Each instance of any defined macro shall be replaced by a constant expression suitable for use in

#ifpreprocessing directives, and this expression shall have the same type as would an expression that is an object of the corresponding type converted according to the integer promotions. Its implementation-defined value shall be equal to or greater in magnitude (absolute value) than the corresponding value given below, with the same sign, except where stated to be exactly the given value.

Limits of exact-width integer types

Minimum values of exact-width signed integer types:

- {INT
N_MIN}- Exactly -(2
^{N-1})Maximum values of exact-width signed integer types:

- {INT
N_MAX}- Exactly 2
^{ N-1}-1Maximum values of exact-width unsigned integer types:

- {UINT
N_MAX}- Exactly 2
^{N}-1Limits of minimum-width integer types

Minimum values of minimum-width signed integer types:

- {INT_LEAST
N_MIN}- -(2
^{N-1}-1)Maximum values of minimum-width signed integer types:

- {INT_LEAST
N_MAX}- 2
^{N-1}-1Maximum values of minimum-width unsigned integer types:

- {UINT_LEAST
N_MAX}- 2
^{N}-1Limits of fastest minimum-width integer types

Minimum values of fastest minimum-width signed integer types:

- {INT_FAST
N_MIN}- -(2
^{ N-1}-1)Maximum values of fastest minimum-width signed integer types:

- {INT_FAST
N_MAX}- 2
^{ N-1}-1Maximum values of fastest minimum-width unsigned integer types:

- {UINT_FAST
N_MAX}- 2
^{ N}-1Limits of integer types capable of holding object pointers

Minimum value of pointer-holding signed integer type:

- {INTPTR_MIN}
- -(2
^{ 15}-1)Maximum value of pointer-holding signed integer type:

- {INTPTR_MAX}
- 2
^{ 15}-1Maximum value of pointer-holding unsigned integer type:

- {UINTPTR_MAX}
- 2
^{ 16}-1Limits of greatest-width integer types

Minimum value of greatest-width signed integer type:

- {INTMAX_MIN}
- -(2
^{ 63}-1)Maximum value of greatest-width signed integer type:

- {INTMAX_MAX}
- 2
^{ 63}-1Maximum value of greatest-width unsigned integer type:

- {UINTMAX_MAX}
- 2
^{ 64}-1## Limits of Other Integer Types

The following macros specify the minimum and maximum limits of integer types corresponding to types defined in other standard headers.

Each instance of these macros shall be replaced by a constant expression suitable for use in

#ifpreprocessing directives, and this expression shall have the same type as would an expression that is an object of the corresponding type converted according to the integer promotions. Its implementation-defined value shall be equal to or greater in magnitude (absolute value) than the corresponding value given below, with the same sign.

Limits of

ptrdiff_t:

- {PTRDIFF_MIN}
- -65535
- {PTRDIFF_MAX}
- +65535
Limits of

sig_atomic_t:

- {SIG_ATOMIC_MIN}
- See below.
- {SIG_ATOMIC_MAX}
- See below.
Limit of

size_t:

- {SIZE_MAX}
- 65535
Limits of

wchar_t:

- {WCHAR_MIN}
- See below.
- {WCHAR_MAX}
- See below.
Limits of

wint_t:

- {WINT_MIN}
- See below.
- {WINT_MAX}
- See below.
If

sig_atomic_t(see the<signal.h>header) is defined as a signed integer type, the value of {SIG_ATOMIC_MIN} shall be no greater than -127 and the value of {SIG_ATOMIC_MAX} shall be no less than 127; otherwise,sig_atomic_tshall be defined as an unsigned integer type, and the value of {SIG_ATOMIC_MIN} shall be 0 and the value of {SIG_ATOMIC_MAX} shall be no less than 255.If

wchar_t(see the<stddef.h>header) is defined as a signed integer type, the value of {WCHAR_MIN} shall be no greater than -127 and the value of {WCHAR_MAX} shall be no less than 127; otherwise,wchar_tshall be defined as an unsigned integer type, and the value of {WCHAR_MIN} shall be 0 and the value of {WCHAR_MAX} shall be no less than 255.If

wint_t(see the<wchar.h>header) is defined as a signed integer type, the value of {WINT_MIN} shall be no greater than -32767 and the value of {WINT_MAX} shall be no less than 32767; otherwise,wint_tshall be defined as an unsigned integer type, and the value of {WINT_MIN} shall be 0 and the value of {WINT_MAX} shall be no less than 65535.## Macros for Integer Constant Expressions

The following macros expand to integer constant expressions suitable for initializing objects that have integer types corresponding to types defined in the

<stdint.h>header. Each macro name corresponds to a similar type name listed underMinimum-width integer typesandGreatest-width integer types.Each invocation of one of these macros shall expand to an integer constant expression suitable for use in

#ifpreprocessing directives. The type of the expression shall have the same type as would an expression that is an object of the corresponding type converted according to the integer promotions. The value of the expression shall be that of the argument.The argument in any instance of these macros shall be an unsuffixed integer constant with a value that does not exceed the limits for the corresponding type.

Macros for minimum-width integer constant expressions

The macro

INTN_C(value) shall expand to an integer constant expression corresponding to the typeint_leastN_t. The macroUINTN_C(value) shall expand to an integer constant expression corresponding to the typeuint_leastN_t. For example, ifuint_least64_tis a name for the typeunsigned long long, thenUINT64_C(0x123) might expand to the integer constant 0x123ULL.Macros for greatest-width integer constant expressions

The following macro expands to an integer constant expression having the value specified by its argument and the type

intmax_t: INTMAX_C(value)The following macro expands to an integer constant expression having the value specified by its argument and the type

uintmax_t: UINTMAX_C(value)

None.

The

<stdint.h>header is a subset of the<inttypes.h>header more suitable for use in freestanding environments, which might not support the formatted I/O functions. In some environments, if the formatted conversion support is not wanted, using this header instead of the<inttypes.h>header avoids defining such a large number of macros.

As a consequence of adding

int8_t, the following are true:

A byte is exactly 8 bits.

{CHAR_BIT} has the value 8, {SCHAR_MAX} has the value 127, {SCHAR_MIN} has the value -128, and {UCHAR_MAX} has the value 255.

(The POSIX standard explicitly requires 8-bit char and two's-complement arithmetic.)

typedefnames beginning withintoruintand ending with _t may be added to the types defined in the<stdint.h>header. Macro names beginning with INT or UINT and ending with _MAX, _MIN, or _C may be added to the macros defined in the<stdint.h>header.

First released in Issue 6. Included for alignment with the ISO/IEC 9899:1999 standard.

ISO/IEC 9899:1999 standard, Technical Corrigendum 1 is applied.

ISO/IEC 9899:1999 standard, Technical Corrigendum 3 #40 is applied.

SD5-XBD-ERN-67 is applied.

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