stdlib.h — Standard library functions

The stdlib.h header file contains declarations for the following functions:

abort()

abs()^[1,3]

aligned_alloc()

alloca()^[1]

atexit()

atof()

atoi()

atol()

bsearch()

calloc()

cds()^[1]

clearenv()

cs()^[1]

csid()

div()^[3]

exit()

fetch()^[2]

fetchep()^[2]

free()

getenv()

labs()

ldiv()

llabs()

lldiv()

__librel()

malloc()

mblen()

mbstowcs()

mbtowc()

__moservices()

qsort()

rand()

realloc()

release()^[2]

rpmatch()

setenv()

srand()

strtod()

strtol()

strtoll()

strtoul()

strtoull()

system()

unatexit()

wcsid()

wcstombs()

wctomb()

strtod32()^[4]

strtod64()^[4]

strtod128()^[4]

_UNIX03_SOURCE

unsetenv()

posix_memalign()

[1] Built-in function.

[2] Not supported under C++ applications.

[3] Special Behavior for C++: For C++ applications, the functions abs() and div() are also overloaded for the type long.

[4] The __STDC_WANT_DEC_FP__ feature test macro is required to expose decimal floating-point functionality.

Two type definitions are added to stdlib.h for the Compare and Swap functions cs() and cds(). The structures defined are __cs_t and __cds_t.

The type size_t is declared in the header file. It is used for the type of the value returned by sizeof. The type wchar_t is declared and used for a wide character constant. For more information on the types size_t and wchar_t, see stddef.h — typedef statements.

The stdlib.h declares div_t and ldiv_t, which define the structure types that are returned by div() and ldiv().

The stdlib.h file also contains definitions for the following macros:

NULL: The NULL pointer constant (also defined in stddef.h).
EXIT_SUCCESS: Used by the atexit() function.
EXIT_FAILURE: Used by the atexit() function.
RAND_MAX: Expands to an integer representing the largest number that the RAND function can return.
MB_CUR_MAX: Expands to an integer representing the maximum number of bytes in a multibyte character. This value is dependent on the current locale.
If MB_CUR_MAX is set to 1, multibyte functions will behave as if all multibyte characters are one byte long; wide-character functions are not supported and full DBCS support is not provided. If MB_CUR_MAX is 4, all DBCS support provided by the library is enabled.