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NAME

       stdint.h — integer types

SYNOPSIS

       #include <stdint.h>

DESCRIPTION

       Some  of  the  functionality  described on this reference page extends the ISO C standard.
       Applications shall define the appropriate feature test macro (see  the  System  Interfaces
       volume of POSIX.1‐2008, Section 2.2, The 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 −2N−1 or 1−2N−1 to 2N−1−1, while an N-bit
                 unsigned type has values in the range 0 to 2N−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 that typedef name and define the associated  macros.  Conversely,  for  each
       type  described  herein  that  the  implementation does not provide, the <stdint.h> header
       shall not declare that typedef name,  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 typedef names differing only in the absence or presence of the initial u are 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 N represents an unsigned decimal integer with no
       leading zeros (for example, 8 or 24, but not 04 or 048).

        *  Exact-width integer types

           The typedef name intN_t designates a signed integer type  with  width  N,  no  padding
           bits,  and  a  two's-complement  representation. Thus, int8_t denotes a signed integer
           type with a width of exactly 8 bits.

           The typedef name uintN_t designates an unsigned integer  type  with  width  N.   Thus,
           uint24_t denotes an unsigned integer type with a width of exactly 24 bits.

           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_t uint64_t

           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  typedef  name  int_leastN_t  designates  a signed integer type with a width of at
           least N, such that no signed integer type with lesser size has at least the  specified
           width.  Thus,  int_least32_t denotes a signed integer type with a width of at least 32
           bits.

           The typedef name uint_leastN_t designates an unsigned integer type with a width of  at
           least  N,  such  that  no  unsigned  integer  type  with  lesser size has at least the
           specified width. Thus, uint_least16_t denotes an unsigned integer type with a width of
           at least 16 bits.

           The   following   types   are   required:   int_least8_t  int_least16_t  int_least32_t
           int_least64_t uint_least8_t uint_least16_t uint_least32_t uint_least64_t

           All 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  typedef  name int_fastN_t designates the fastest signed integer type with a width
           of at least N.  The typedef name uint_fastN_t designates the fastest unsigned  integer
           type with a width of at least N.

           The  following  types are required: int_fast8_t int_fast16_t int_fast32_t int_fast64_t
           uint_fast8_t uint_fast16_t uint_fast32_t uint_fast64_t

           All 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  void  can  be converted to this type, then converted back to a pointer to
           void, and the result will compare equal to the original pointer: intptr_t

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

           On XSI-conformant systems, the intptr_t and uintptr_t types 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_t

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

           These 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 #if preprocessing 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:

               {INTN_MIN}      Exactly −($2"^" N−1$)

           --  Maximum values of exact-width signed integer types:

               {INTN_MAX}      Exactly $2"^" N−1$ −1

           --  Maximum values of exact-width unsigned integer types:

               {UINTN_MAX}     Exactly $2"^" N$ −1

        *  Limits of minimum-width integer types

           --  Minimum values of minimum-width signed integer types:

               {INT_LEASTN_MIN}
                               −($2"^" N−1$ −1)

           --  Maximum values of minimum-width signed integer types:

               {INT_LEASTN_MAX}
                               $2"^" N−1$ −1

           --  Maximum values of minimum-width unsigned integer types:

               {UINT_LEASTN_MAX}
                               $2"^" N$ −1

        *  Limits of fastest minimum-width integer types

           --  Minimum values of fastest minimum-width signed integer types:

               {INT_FASTN_MIN} −($2"^" N−1$ −1)

           --  Maximum values of fastest minimum-width signed integer types:

               {INT_FASTN_MAX} $2"^" N−1$ −1

           --  Maximum values of fastest minimum-width unsigned integer types:

               {UINT_FASTN_MAX}
                               $2"^" N$ −1

        *  Limits 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}    $2"^" 15$ −1

           --  Maximum value of pointer-holding unsigned integer type:

               {UINTPTR_MAX}   $2"^" 16$ −1

        *  Limits 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}    $2"^" 63$ −1

           --  Maximum 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 #if preprocessing 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_t shall 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_t shall 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_t shall 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 under Minimum-width integer
       types and Greatest-width integer types.

       Each invocation of one of these macros shall expand  to  an  integer  constant  expression
       suitable  for  use  in #if preprocessing 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 type int_leastN_t.   The  macro  UINTN_C(value)  shall  expand  to  an  integer
           constant  expression  corresponding  to  the  type  uint_leastN_t.   For  example,  if
           uint_least64_t is a name for the type unsigned long long, then  UINT64_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)

       The following sections are informative.

APPLICATION USAGE

       None.

RATIONALE

       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.)

FUTURE DIRECTIONS

       typedef  names  beginning  with  int  or uint and 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.

SEE ALSO

       <inttypes.h>, <signal.h>, <stddef.h>, <wchar.h>

       The System Interfaces volume of POSIX.1‐2008, Section 2.2, The Compilation Environment

COPYRIGHT

       Portions  of  this  text  are  reprinted  and  reproduced in electronic form from IEEE Std
       1003.1, 2013 Edition, Standard for Information Technology  --  Portable  Operating  System
       Interface  (POSIX),  The Open Group Base Specifications Issue 7, Copyright (C) 2013 by the
       Institute of Electrical and Electronics Engineers, Inc  and  The  Open  Group.   (This  is
       POSIX.1-2008  with  the  2013  Technical  Corrigendum  1  applied.)  In  the  event of any
       discrepancy between this version and the original IEEE and The Open  Group  Standard,  the
       original  IEEE  and The Open Group Standard is the referee document. The original Standard
       can be obtained online at http://www.unix.org/online.html .

       Any typographical or formatting errors that appear in this page are most  likely  to  have
       been  introduced  during  the conversion of the source files to man page format. To report
       such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html .