All C inbuilt functions which are declared in stdlib.h header file are given below. The source code for stdlib.h header file is also given below for your reference.
……
List of inbuilt C functions in stdlib.h file:
| S.no |
Function
|
Description
|
| 1 | malloc() | This function is used to allocate space in memory during the execution of the program. |
| 2 | calloc() | This function is also like malloc () function. But calloc () initializes the allocated memory to zero. But, malloc() doesn’t |
| 3 | realloc() | This function modifies the allocated memory size by malloc () and calloc () functions to new size |
| 4 | free() | This function frees the allocated memory by malloc (), calloc (), realloc () functions and returns the memory to the system. |
| 5 | abs() | This function returns the absolute value of an integer . The absolute value of a number is always positive. Only integer values are supported in C. |
| 6 | div() | This function performs division operation |
| 7 | abort() | It terminates the C program |
| 8 | exit() | This function terminates the program and does not return any value |
| 9 | system() | This function is used to execute commands outside the C program. |
| 10 | atoi() | Converts string to int |
| 11 | atol() | Converts string to long |
| 12 | atof() | Converts string to float |
| 13 | strtod() | Converts string to double |
| 14 | strtol() | Converts string to long |
| 15 | getenv() | This function gets the current value of the environment variable |
| 16 | setenv() | This function sets the value for environment variable |
| 17 | putenv() | This function modifies the value for environment variable |
| 18 | perror() | This function displays most recent error that happened during library function call. |
| 19 | rand() | This function returns the random integer numbers |
| 20 | delay() | This function Suspends the execution of the program for particular time |
Source code for stdlib.h header file:
Please find the source code for stdlib.h header file below. This code is taken from DevC++ compiler files for your reference.
/*
* stdlib.h
* This file has no copyright assigned and is placed in the Public Domain.
* This file is a part of the mingw-runtime package.
* No warranty is given; refer to the file DISCLAIMER within the package.
*
* Definitions for common types, variables, and functions.
*
*/
#ifndef _STDLIB_H_
#define _STDLIB_H_
/* All the headers include this file. */
#include <_mingw.h>
#define __need_size_t
#define __need_wchar_t
#define __need_NULL
#ifndef RC_INVOKED
#include <stddef.h>
#endif /* RC_INVOKED */
/*
* RAND_MAX is the maximum value that may be returned by rand.
* The minimum is zero.
*/
#define RAND_MAX 0x7FFF
/*
* These values may be used as exit status codes.
*/
#define EXIT_SUCCESS 0
#define EXIT_FAILURE 1
/*
* Definitions for path name functions.
* NOTE: All of these values have simply been chosen to be conservatively high.
* Remember that with long file names we can no longer depend on
* extensions being short.
*/
#ifndef __STRICT_ANSI__
#ifndef MAX_PATH
#define MAX_PATH (260)
#endif
#define _MAX_PATH MAX_PATH
#define _MAX_DRIVE (3)
#define _MAX_DIR 256
#define _MAX_FNAME 256
#define _MAX_EXT 256
#endif /* Not __STRICT_ANSI__ */
#ifndef RC_INVOKED
#ifdef __cplusplus
extern "C" {
#endif
#if !defined (__STRICT_ANSI__)
/*
* This seems like a convenient place to declare these variables, which
* give programs using WinMain (or main for that matter) access to main-ish
* argc and argv. environ is a pointer to a table of environment variables.
* NOTE: Strings in _argv and environ are ANSI strings.
*/
extern int _argc;
extern char** _argv;
/* imports from runtime dll of the above variables */
#ifdef __MSVCRT__
extern int* __cdecl __p___argc(void);
extern char*** __cdecl __p___argv(void);
extern wchar_t*** __cdecl __p___wargv(void);
#define __argc (*__p___argc())
#define __argv (*__p___argv())
#define __wargv (*__p___wargv())
#else /* !MSVCRT */
#ifndef __DECLSPEC_SUPPORTED
extern int* _imp____argc_dll;
extern char*** _imp____argv_dll;
#define __argc (*_imp____argc_dll)
#define __argv (*_imp____argv_dll)
#else /* __DECLSPEC_SUPPORTED */
__MINGW_IMPORT int __argc_dll;
__MINGW_IMPORT char** __argv_dll;
#define __argc __argc_dll
#define __argv __argv_dll
#endif /* __DECLSPEC_SUPPORTED */
#endif /* __MSVCRT */
#endif /* __STRICT_ANSI__ */
/*
* Also defined in ctype.h.
*/
#ifndef MB_CUR_MAX
#ifdef __DECLSPEC_SUPPORTED
# ifdef __MSVCRT__
# define MB_CUR_MAX __mb_cur_max
__MINGW_IMPORT int __mb_cur_max;
# else /* not __MSVCRT */
# define MB_CUR_MAX __mb_cur_max_dll
__MINGW_IMPORT int __mb_cur_max_dll;
# endif /* not __MSVCRT */
#else /* ! __DECLSPEC_SUPPORTED */
# ifdef __MSVCRT__
extern int* _imp____mbcur_max;
# define MB_CUR_MAX (*_imp____mb_cur_max)
# else /* not __MSVCRT */
extern int* _imp____mbcur_max_dll;
# define MB_CUR_MAX (*_imp____mb_cur_max_dll)
# endif /* not __MSVCRT */
#endif /* __DECLSPEC_SUPPORTED */
#endif /* MB_CUR_MAX */
/*
* MS likes to declare errno in stdlib.h as well.
*/
#ifdef _UWIN
#undef errno
extern int errno;
#else
_CRTIMP int* __cdecl _errno(void);
#define errno (*_errno())
#endif
_CRTIMP int* __cdecl __doserrno(void);
#define _doserrno (*__doserrno())
#if !defined (__STRICT_ANSI__)
/*
* Use environ from the DLL, not as a global.
*/
#ifdef __MSVCRT__
extern _CRTIMP char *** __cdecl __p__environ(void);
extern _CRTIMP wchar_t *** __cdecl __p__wenviron(void);
# define _environ (*__p__environ())
# define _wenviron (*__p__wenviron())
#else /* ! __MSVCRT__ */
# ifndef __DECLSPEC_SUPPORTED
extern char *** _imp___environ_dll;
# define _environ (*_imp___environ_dll)
# else /* __DECLSPEC_SUPPORTED */
__MINGW_IMPORT char ** _environ_dll;
# define _environ _environ_dll
# endif /* __DECLSPEC_SUPPORTED */
#endif /* ! __MSVCRT__ */
#define environ _environ
#ifdef __MSVCRT__
/* One of the MSVCRTxx libraries */
#ifndef __DECLSPEC_SUPPORTED
extern int* _imp___sys_nerr;
# define sys_nerr (*_imp___sys_nerr)
#else /* __DECLSPEC_SUPPORTED */
__MINGW_IMPORT int _sys_nerr;
# ifndef _UWIN
# define sys_nerr _sys_nerr
# endif /* _UWIN */
#endif /* __DECLSPEC_SUPPORTED */
#else /* ! __MSVCRT__ */
/* CRTDLL run time library */
#ifndef __DECLSPEC_SUPPORTED
extern int* _imp___sys_nerr_dll;
# define sys_nerr (*_imp___sys_nerr_dll)
#else /* __DECLSPEC_SUPPORTED */
__MINGW_IMPORT int _sys_nerr_dll;
# define sys_nerr _sys_nerr_dll
#endif /* __DECLSPEC_SUPPORTED */
#endif /* ! __MSVCRT__ */
#ifndef __DECLSPEC_SUPPORTED
extern char*** _imp__sys_errlist;
#define sys_errlist (*_imp___sys_errlist)
#else /* __DECLSPEC_SUPPORTED */
__MINGW_IMPORT char* _sys_errlist[];
#ifndef _UWIN
#define sys_errlist _sys_errlist
#endif /* _UWIN */
#endif /* __DECLSPEC_SUPPORTED */
/*
* OS version and such constants.
*/
#ifdef __MSVCRT__
/* msvcrtxx.dll */
extern _CRTIMP unsigned __cdecl int* __p__osver(void);
extern _CRTIMP unsigned __cdecl int* __p__winver(void);
extern _CRTIMP unsigned __cdecl int* __p__winmajor(void);
extern _CRTIMP unsigned __cdecl int* __p__winminor(void);
#ifndef __DECLSPEC_SUPPORTED
# define _osver (*__p__osver())
# define _winver (*__p__winver())
# define _winmajor (*__p__winmajor())
# define _winminor (*__p__winminor())
#else
__MINGW_IMPORT unsigned int _osver;
__MINGW_IMPORT unsigned int _winver;
__MINGW_IMPORT unsigned int _winmajor;
__MINGW_IMPORT unsigned int _winminor;
#endif /* __DECLSPEC_SUPPORTED */
#else
/* Not msvcrtxx.dll, thus crtdll.dll */
#ifndef __DECLSPEC_SUPPORTED
extern unsigned int* _imp___osver_dll;
extern unsigned int* _imp___winver_dll;
extern unsigned int* _imp___winmajor_dll;
extern unsigned int* _imp___winminor_dll;
#define _osver (*_imp___osver_dll)
#define _winver (*_imp___winver_dll)
#define _winmajor (*_imp___winmajor_dll)
#define _winminor (*_imp___winminor_dll)
#else /* __DECLSPEC_SUPPORTED */
__MINGW_IMPORT unsigned int _osver_dll;
__MINGW_IMPORT unsigned int _winver_dll;
__MINGW_IMPORT unsigned int _winmajor_dll;
__MINGW_IMPORT unsigned int _winminor_dll;
#define _osver _osver_dll
#define _winver _winver_dll
#define _winmajor _winmajor_dll
#define _winminor _winminor_dll
#endif /* __DECLSPEC_SUPPORTED */
#endif
#if defined __MSVCRT__
/* although the _pgmptr is exported as DATA,
* be safe and use the access function __p__pgmptr() to get it. */
_CRTIMP char** __cdecl __p__pgmptr(void);
#define _pgmptr (*__p__pgmptr())
_CRTIMP wchar_t** __cdecl __p__wpgmptr(void);
#define _wpgmptr (*__p__wpgmptr())
#else /* ! __MSVCRT__ */
# ifndef __DECLSPEC_SUPPORTED
extern char** __imp__pgmptr_dll;
# define _pgmptr (*_imp___pgmptr_dll)
# else /* __DECLSPEC_SUPPORTED */
__MINGW_IMPORT char* _pgmptr_dll;
# define _pgmptr _pgmptr_dll
# endif /* __DECLSPEC_SUPPORTED */
/* no wide version in CRTDLL */
#endif /* __MSVCRT__ */
/*
* This variable determines the default file mode.
* TODO: Which flags work?
*/
#if !defined (__DECLSPEC_SUPPORTED) || defined (__IN_MINGW_RUNTIME)
#ifdef __MSVCRT__
extern int* _imp___fmode;
#define _fmode (*_imp___fmode)
#else
/* CRTDLL */
extern int* _imp___fmode_dll;
#define _fmode (*_imp___fmode_dll)
#endif
#else /* __DECLSPEC_SUPPORTED */
#ifdef __MSVCRT__
__MINGW_IMPORT int _fmode;
#else /* ! __MSVCRT__ */
__MINGW_IMPORT int _fmode_dll;
#define _fmode _fmode_dll
#endif /* ! __MSVCRT__ */
#endif /* __DECLSPEC_SUPPORTED */
#endif /* Not __STRICT_ANSI__ */
_CRTIMP double __cdecl atof (const char*);
_CRTIMP int __cdecl atoi (const char*);
_CRTIMP long __cdecl atol (const char*);
#if !defined (__STRICT_ANSI__)
_CRTIMP int __cdecl _wtoi (const wchar_t *);
_CRTIMP long __cdecl _wtol (const wchar_t *);
#endif
_CRTIMP double __cdecl strtod (const char*, char**);
#if !defined __NO_ISOCEXT /* extern stub in static libmingwex.a */
__CRT_INLINE float __cdecl strtof (const char *nptr, char **endptr)
{ return (strtod (nptr, endptr));}
long double __cdecl strtold (const char * __restrict__, char ** __restrict__);
#endif /* __NO_ISOCEXT */
_CRTIMP long __cdecl strtol (const char*, char**, int);
_CRTIMP unsigned long __cdecl strtoul (const char*, char**, int);
#ifndef _WSTDLIB_DEFINED
/* also declared in wchar.h */
_CRTIMP double __cdecl wcstod (const wchar_t*, wchar_t**);
#if !defined __NO_ISOCEXT /* extern stub in static libmingwex.a */
__CRT_INLINE float __cdecl wcstof( const wchar_t *nptr, wchar_t **endptr)
{ return (wcstod(nptr, endptr)); }
long double __cdecl wcstold (const wchar_t * __restrict__, wchar_t ** __restrict__);
#endif /* __NO_ISOCEXT */
_CRTIMP long __cdecl wcstol (const wchar_t*, wchar_t**, int);
_CRTIMP unsigned long __cdecl wcstoul (const wchar_t*, wchar_t**, int);
#define _WSTDLIB_DEFINED
#endif
_CRTIMP size_t __cdecl wcstombs (char*, const wchar_t*, size_t);
_CRTIMP int __cdecl wctomb (char*, wchar_t);
_CRTIMP int __cdecl mblen (const char*, size_t);
_CRTIMP size_t __cdecl mbstowcs (wchar_t*, const char*, size_t);
_CRTIMP int __cdecl mbtowc (wchar_t*, const char*, size_t);
_CRTIMP int __cdecl rand (void);
_CRTIMP void __cdecl srand (unsigned int);
_CRTIMP void* __cdecl calloc (size_t, size_t) __MINGW_ATTRIB_MALLOC;
_CRTIMP void* __cdecl malloc (size_t) __MINGW_ATTRIB_MALLOC;
_CRTIMP void* __cdecl realloc (void*, size_t);
_CRTIMP void __cdecl free (void*);
_CRTIMP void __cdecl abort (void) __MINGW_ATTRIB_NORETURN;
_CRTIMP void __cdecl exit (int) __MINGW_ATTRIB_NORETURN;
/* Note: This is in startup code, not imported directly from dll */
int __cdecl atexit (void (*)(void));
_CRTIMP int __cdecl system (const char*);
_CRTIMP char* __cdecl getenv (const char*);
/* bsearch and qsort are also in non-ANSI header search.h */
_CRTIMP void* __cdecl bsearch (const void*, const void*, size_t, size_t,
int (*)(const void*, const void*));
_CRTIMP void __cdecl qsort (void*, size_t, size_t,
int (*)(const void*, const void*));
_CRTIMP int __cdecl abs (int) __MINGW_ATTRIB_CONST;
_CRTIMP long __cdecl labs (long) __MINGW_ATTRIB_CONST;
/*
* div_t and ldiv_t are structures used to return the results of div and
* ldiv.
*
* NOTE: div and ldiv appear not to work correctly unless
* -fno-pcc-struct-return is specified. This is included in the
* mingw32 specs file.
*/
typedef struct { int quot, rem; } div_t;
typedef struct { long quot, rem; } ldiv_t;
_CRTIMP div_t __cdecl div (int, int) __MINGW_ATTRIB_CONST;
_CRTIMP ldiv_t __cdecl ldiv (long, long) __MINGW_ATTRIB_CONST;
#if !defined (__STRICT_ANSI__)
/*
* NOTE: Officially the three following functions are obsolete. The Win32 API
* functions SetErrorMode, Beep and Sleep are their replacements.
*/
_CRTIMP void __cdecl _beep (unsigned int, unsigned int);
_CRTIMP void __cdecl _seterrormode (int);
_CRTIMP void __cdecl _sleep (unsigned long);
_CRTIMP void __cdecl _exit (int) __MINGW_ATTRIB_NORETURN;
/* _onexit is MS extension. Use atexit for portability. */
/* Note: This is in startup code, not imported directly from dll */
typedef int (* _onexit_t)(void);
_onexit_t __cdecl _onexit( _onexit_t );
_CRTIMP int __cdecl _putenv (const char*);
_CRTIMP void __cdecl _searchenv (const char*, const char*, char*);
_CRTIMP char* __cdecl _ecvt (double, int, int*, int*);
_CRTIMP char* __cdecl _fcvt (double, int, int*, int*);
_CRTIMP char* __cdecl _gcvt (double, int, char*);
_CRTIMP void __cdecl _makepath (char*, const char*, const char*, const char*, const char*);
_CRTIMP void __cdecl _splitpath (const char*, char*, char*, char*, char*);
_CRTIMP char* __cdecl _fullpath (char*, const char*, size_t);
_CRTIMP char* __cdecl _itoa (int, char*, int);
_CRTIMP char* __cdecl _ltoa (long, char*, int);
_CRTIMP char* __cdecl _ultoa(unsigned long, char*, int);
_CRTIMP wchar_t* __cdecl _itow (int, wchar_t*, int);
_CRTIMP wchar_t* __cdecl _ltow (long, wchar_t*, int);
_CRTIMP wchar_t* __cdecl _ultow (unsigned long, wchar_t*, int);
#ifdef __MSVCRT__
_CRTIMP __int64 __cdecl _atoi64(const char *);
_CRTIMP char* __cdecl _i64toa(__int64, char *, int);
_CRTIMP char* __cdecl _ui64toa(unsigned __int64, char *, int);
_CRTIMP __int64 __cdecl _wtoi64(const wchar_t *);
_CRTIMP wchar_t* __cdecl _i64tow(__int64, wchar_t *, int);
_CRTIMP wchar_t* __cdecl _ui64tow(unsigned __int64, wchar_t *, int);
_CRTIMP wchar_t* __cdecl _wgetenv(const wchar_t*);
_CRTIMP int __cdecl _wputenv(const wchar_t*);
_CRTIMP void __cdecl _wsearchenv(const wchar_t*, const wchar_t*, wchar_t*);
_CRTIMP void __cdecl _wmakepath(wchar_t*, const wchar_t*, const wchar_t*, const wchar_t*, const wchar_t*);
_CRTIMP void __cdecl _wsplitpath (const wchar_t*, wchar_t*, wchar_t*, wchar_t*, wchar_t*);
_CRTIMP wchar_t* __cdecl _wfullpath (wchar_t*, const wchar_t*, size_t);
_CRTIMP unsigned int __cdecl _rotl(unsigned int, int) __MINGW_ATTRIB_CONST;
_CRTIMP unsigned int __cdecl _rotr(unsigned int, int) __MINGW_ATTRIB_CONST;
_CRTIMP unsigned long __cdecl _lrotl(unsigned long, int) __MINGW_ATTRIB_CONST;
_CRTIMP unsigned long __cdecl _lrotr(unsigned long, int) __MINGW_ATTRIB_CONST;
#endif
#ifndef _NO_OLDNAMES
_CRTIMP int __cdecl putenv (const char*);
_CRTIMP void __cdecl searchenv (const char*, const char*, char*);
_CRTIMP char* __cdecl itoa (int, char*, int);
_CRTIMP char* __cdecl ltoa (long, char*, int);
#ifndef _UWIN
_CRTIMP char* __cdecl ecvt (double, int, int*, int*);
_CRTIMP char* __cdecl fcvt (double, int, int*, int*);
_CRTIMP char* __cdecl gcvt (double, int, char*);
#endif /* _UWIN */
#endif /* Not _NO_OLDNAMES */
#endif /* Not __STRICT_ANSI__ */
/* C99 names */
#if !defined __NO_ISOCEXT /* externs in static libmingwex.a */
/* C99 name for _exit */
void __cdecl _Exit(int) __MINGW_ATTRIB_NORETURN;
#ifndef __STRICT_ANSI__ /* inline using non-ansi functions */
__CRT_INLINE void __cdecl _Exit(int status)
{ _exit(status); }
#endif
typedef struct { long long quot, rem; } lldiv_t;
lldiv_t __cdecl lldiv (long long, long long) __MINGW_ATTRIB_CONST;
__CRT_INLINE long long __cdecl llabs(long long _j)
{return (_j >= 0 ? _j : -_j);}
long long __cdecl strtoll (const char* __restrict__, char** __restrict, int);
unsigned long long __cdecl strtoull (const char* __restrict__, char** __restrict__, int);
#if defined (__MSVCRT__) /* these are stubs for MS _i64 versions */
long long __cdecl atoll (const char *);
#if !defined (__STRICT_ANSI__)
long long __cdecl wtoll (const wchar_t *);
char* __cdecl lltoa (long long, char *, int);
char* __cdecl ulltoa (unsigned long long , char *, int);
wchar_t* __cdecl lltow (long long, wchar_t *, int);
wchar_t* __cdecl ulltow (unsigned long long, wchar_t *, int);
/* inline using non-ansi functions */
__CRT_INLINE long long __cdecl atoll (const char * _c)
{ return _atoi64 (_c); }
__CRT_INLINE char* __cdecl lltoa (long long _n, char * _c, int _i)
{ return _i64toa (_n, _c, _i); }
__CRT_INLINE char* __cdecl ulltoa (unsigned long long _n, char * _c, int _i)
{ return _ui64toa (_n, _c, _i); }
__CRT_INLINE long long __cdecl wtoll (const wchar_t * _w)
{ return _wtoi64 (_w); }
__CRT_INLINE wchar_t* __cdecl lltow (long long _n, wchar_t * _w, int _i)
{ return _i64tow (_n, _w, _i); }
__CRT_INLINE wchar_t* __cdecl ulltow (unsigned long long _n, wchar_t * _w, int _i)
{ return _ui64tow (_n, _w, _i); }
#endif /* (__STRICT_ANSI__) */
#endif /* __MSVCRT__ */
#endif /* !__NO_ISOCEXT */
#ifdef __cplusplus
}
#endif
#endif /* Not RC_INVOKED */
#endif /* Not _STDLIB_H_ */