简介

stdlib.h内容

stdlib.h用法

简介

stdlib 头文件即standard library标准库头文件

stdlib 头文件里包含了C、C++语言的最常用的系统函数

该文件包含了的C语言标准库函数的定义

stdlib.h里面定义了五种类型、一些宏和通用工具函数。 类型例如size_t、wchar_t、div_t、ldiv_t和lldiv_t； 宏例如EXIT_FAILURE、EXIT_SUCCESS、RAND_MAX和MB_CUR_MAX等等； 常用的函数如malloc()、calloc()、realloc()、free()、system()、atoi()、atol()、rand()、srand()、exit()等等。 具体的内容你自己可以打开编译器的include目录里面的stdlib.h头文件看看。

stdlib.h内容

/***

*stdlib.h - declarations/definitions for commonly used library functions

*

* Copyright (c) 1985-1997, Microsoft Corporation. All rights reserved.

*

*Purpose:

* This include file contains the function declarations for commonly

* used library functions which either don't fit somewhere else, or,

* cannot be declared in the normal place for other reasons.

* [ANSI]

*

* [Public]

*

****/

#if _MSC_VER > 1000

#pragma once

#endif

#ifndef _INC_STDLIB

#define _INC_STDLIB

#if !defined(_WIN32) && !defined(_MAC)

#error ERROR: Only Mac or Win32 targets supported!

#endif

#ifdef _MSC_VER

/*

* Currently, all MS C compilers for Win32 platforms default to 8 byte

* alignment.

*/

#pragma pack(push,8)

#endif /* _MSC_VER */

#ifdef __cplusplus

extern "C" {

#endif

/* Define _CRTIMP */

#ifndef _CRTIMP

#ifdef _DLL

#define _CRTIMP __declspec(dllimport)

#else /* ndef _DLL */

#define _CRTIMP

#endif /* _DLL */

#endif /* _CRTIMP */

/* Define __cdecl for non-Microsoft compilers */

#if ( !defined(_MSC_VER) && !defined(__cdecl) )

#define __cdecl

#endif

/* Define _CRTAPI1 (for compatibility with the NT SDK) */

#ifndef _CRTAPI1

#if _MSC_VER >= 800 && _M_IX86 >= 300

#define _CRTAPI1 __cdecl

#else

#define _CRTAPI1

#endif

#endif

#ifndef _SIZE_T_DEFINED

typedef unsigned int size_t;

#define _SIZE_T_DEFINED

#endif

#ifndef _WCHAR_T_DEFINED

typedef unsigned short wchar_t;

#define _WCHAR_T_DEFINED

#endif

/* Define NULL pointer value */

#ifndef NULL

#ifdef __cplusplus

#define NULL 0

#else

#define NULL ((void *)0)

#endif

#endif

/* Definition of the argument values for the exit() function */

#define EXIT_SUCCESS 0

#define EXIT_FAILURE 1

#ifndef _ONEXIT_T_DEFINED

typedef int (__cdecl * _onexit_t)(void);

#if !__STDC__

/* Non-ANSI name for compatibility */

#define onexit_t _onexit_t

#endif

#define _ONEXIT_T_DEFINED

#endif

/* Data structure definitions for div and ldiv runtimes. */

#ifndef _DIV_T_DEFINED

typedef struct _div_t {

int quot;

int rem;

} div_t;

typedef struct _ldiv_t {

long quot;

long rem;

} ldiv_t;

#define _DIV_T_DEFINED

#endif

/* Maximum value that can be returned by the rand function. */

#define RAND_MAX 0x7fff

/*

* Maximum number of bytes in multi-byte character in the current locale

* (also defined in ctype.h).

*/

#ifndef MB_CUR_MAX

#define MB_CUR_MAX __mb_cur_max

_CRTIMP extern int __mb_cur_max;

#endif /* MB_CUR_MAX */

/* Minimum and maximum macros */

#define __max(a,b) (((a) > (b)) ? (a) : (b))

#define __min(a,b) (((a) < (b)) ? (a) : (b))

/*

* Sizes for buffers used by the _makepath() and _splitpath() functions.

* note that the sizes include space for 0-terminator

*/

#ifndef _MAC

#define _MAX_PATH 260 /* max. length of full pathname */

#define _MAX_DRIVE 3 /* max. length of drive component */

#define _MAX_DIR 256 /* max. length of path component */

#define _MAX_FNAME 256 /* max. length of file name component */

#define _MAX_EXT 256 /* max. length of extension component */

#else /* def _MAC */

#define _MAX_PATH 256 /* max. length of full pathname */

#define _MAX_DIR 32 /* max. length of path component */

#define _MAX_FNAME 64 /* max. length of file name component */

#endif /* _MAC */

/*

* Argument values for _set_error_mode().

*/

#define _OUT_TO_DEFAULT 0

#define _OUT_TO_STDERR 1

#define _OUT_TO_MSGBOX 2

#define _REPORT_ERRMODE 3

/* External variable declarations */

#if (defined(_MT) || defined(_DLL)) && !defined(_MAC)

_CRTIMP int * __cdecl _errno(void);

_CRTIMP unsigned long * __cdecl __doserrno(void);

#define errno (*_errno())

#define _doserrno (*__doserrno())

#else /* ndef _MT && ndef _DLL */

_CRTIMP extern int errno; /* XENIX style error number */

_CRTIMP extern unsigned long _doserrno; /* OS system error value */

#endif /* _MT || _DLL */

#ifdef _MAC

_CRTIMP extern int _macerrno; /* OS system error value */

#endif

_CRTIMP extern char * _sys_errlist[]; /* perror error message table */

_CRTIMP extern int _sys_nerr; /* # of entries in sys_errlist table */

#if defined(_DLL) && defined(_M_IX86)

#define __argc (*__p___argc()) /* count of cmd line args */

#define __argv (*__p___argv()) /* pointer to table of cmd line args */

#define __wargv (*__p___wargv()) /* pointer to table of wide cmd line args */

#define _environ (*__p__environ()) /* pointer to environment table */

#ifdef _POSIX_

extern char ** environ; /* pointer to environment table */

#else

#ifndef _MAC

#define _wenviron (*__p__wenviron()) /* pointer to wide environment table */

#endif /* ndef _MAC */

#endif /* _POSIX_ */

#define _pgmptr (*__p__pgmptr()) /* points to the module (EXE) name */

#ifndef _MAC

#define _wpgmptr (*__p__wpgmptr()) /* points to the module (EXE) wide name */

#endif /* ndef _MAC */

_CRTIMP int * __cdecl __p___argc(void);

_CRTIMP char *** __cdecl __p___argv(void);

_CRTIMP wchar_t *** __cdecl __p___wargv(void);

_CRTIMP char *** __cdecl __p__environ(void);

_CRTIMP wchar_t *** __cdecl __p__wenviron(void);

_CRTIMP char ** __cdecl __p__pgmptr(void);

_CRTIMP wchar_t ** __cdecl __p__wpgmptr(void);

#else

_CRTIMP extern int __argc; /* count of cmd line args */

_CRTIMP extern char ** __argv; /* pointer to table of cmd line args */

#ifndef _MAC

_CRTIMP extern wchar_t ** __wargv; /* pointer to table of wide cmd line args */

#endif /* ndef _MAC */

#ifdef _POSIX_

extern char ** environ; /* pointer to environment table */

#else

_CRTIMP extern char ** _environ; /* pointer to environment table */

#ifndef _MAC

_CRTIMP extern wchar_t ** _wenviron; /* pointer to wide environment table */

#endif /* ndef _MAC */

#endif /* _POSIX_ */

_CRTIMP extern char * _pgmptr; /* points to the module (EXE) name */

#ifndef _MAC

_CRTIMP extern wchar_t * _wpgmptr; /* points to the module (EXE) wide name */

#endif /* ndef _MAC */

#endif

_CRTIMP extern int _fmode; /* default file translation mode */

_CRTIMP extern int _fileinfo; /* open file info mode (for spawn) */

/* Windows major/minor and O.S. version numbers */

_CRTIMP extern unsigned int _osver;

_CRTIMP extern unsigned int _winver;

_CRTIMP extern unsigned int _winmajor;

_CRTIMP extern unsigned int _winminor;

/* function prototypes */

#if _MSC_VER >= 1200

_CRTIMP __declspec(noreturn) void __cdecl abort(void);

_CRTIMP __declspec(noreturn) void __cdecl exit(int);

#else

_CRTIMP void __cdecl abort(void);

_CRTIMP void __cdecl exit(int);

#endif

#if defined(_M_MRX000)

_CRTIMP int __cdecl abs(int);

#else

int __cdecl abs(int);

#endif

int __cdecl atexit(void (__cdecl *)(void));

_CRTIMP double __cdecl atof(const char *);

_CRTIMP int __cdecl atoi(const char *);

_CRTIMP long __cdecl atol(const char *);

#ifdef _M_M68K

_CRTIMP long double __cdecl _atold(const char *);

#endif

_CRTIMP void * __cdecl bsearch(const void *, const void *, size_t, size_t,

int (__cdecl *)(const void *, const void *));

_CRTIMP void * __cdecl calloc(size_t, size_t);

_CRTIMP div_t __cdecl div(int, int);

_CRTIMP void __cdecl free(void *);

_CRTIMP char * __cdecl getenv(const char *);

_CRTIMP char * __cdecl _itoa(int, char *, int);

#if _INTEGRAL_MAX_BITS >= 64

_CRTIMP char * __cdecl _i64toa(__int64, char *, int);

_CRTIMP char * __cdecl _ui64toa(unsigned __int64, char *, int);

_CRTIMP __int64 __cdecl _atoi64(const char *);

#endif

#if defined(_M_MRX000)

_CRTIMP long __cdecl labs(long);

#else

long __cdecl labs(long);

#endif

_CRTIMP ldiv_t __cdecl ldiv(long, long);

_CRTIMP char * __cdecl _ltoa(long, char *, int);

_CRTIMP void * __cdecl malloc(size_t);

_CRTIMP int __cdecl mblen(const char *, size_t);

_CRTIMP size_t __cdecl _mbstrlen(const char *s);

_CRTIMP int __cdecl mbtowc(wchar_t *, const char *, size_t);

_CRTIMP size_t __cdecl mbstowcs(wchar_t *, const char *, size_t);

_CRTIMP void __cdecl qsort(void *, size_t, size_t, int (__cdecl *)

(const void *, const void *));

_CRTIMP int __cdecl rand(void);

_CRTIMP void * __cdecl realloc(void *, size_t);

_CRTIMP int __cdecl _set_error_mode(int);

_CRTIMP void __cdecl srand(unsigned int);

_CRTIMP double __cdecl strtod(const char *, char **);

_CRTIMP long __cdecl strtol(const char *, char **, int);

#ifdef _M_M68K

_CRTIMP long double __cdecl _strtold(const char *, char **);

#endif

_CRTIMP unsigned long __cdecl strtoul(const char *, char **, int);

#ifndef _MAC

_CRTIMP int __cdecl system(const char *);

#endif

_CRTIMP char * __cdecl _ultoa(unsigned long, char *, int);

_CRTIMP int __cdecl wctomb(char *, wchar_t);

_CRTIMP size_t __cdecl wcstombs(char *, const wchar_t *, size_t);

#ifndef _MAC

#ifndef _WSTDLIB_DEFINED

/* wide function prototypes, also declared in wchar.h */

_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);

_CRTIMP double __cdecl wcstod(const wchar_t *, wchar_t **);

_CRTIMP long __cdecl wcstol(const wchar_t *, wchar_t **, int);

_CRTIMP unsigned long __cdecl wcstoul(const wchar_t *, wchar_t **, int);

_CRTIMP wchar_t * __cdecl _wgetenv(const wchar_t *);

_CRTIMP int __cdecl _wsystem(const wchar_t *);

_CRTIMP int __cdecl _wtoi(const wchar_t *);

_CRTIMP long __cdecl _wtol(const wchar_t *);

#if _INTEGRAL_MAX_BITS >= 64

_CRTIMP wchar_t * __cdecl _i64tow(__int64, wchar_t *, int);

_CRTIMP wchar_t * __cdecl _ui64tow(unsigned __int64, wchar_t *, int);

_CRTIMP __int64 __cdecl _wtoi64(const wchar_t *);

#endif

#define _WSTDLIB_DEFINED

#endif

#endif /* ndef _MAC */

#ifndef _POSIX_

_CRTIMP char * __cdecl _ecvt(double, int, int *, int *);

#if _MSC_VER >= 1200

_CRTIMP __declspec(noreturn) void __cdecl _exit(int);

#else

_CRTIMP void __cdecl _exit(int);

#endif

_CRTIMP char * __cdecl _fcvt(double, int, int *, int *);

_CRTIMP char * __cdecl _fullpath(char *, const char *, size_t);

_CRTIMP char * __cdecl _gcvt(double, int, char *);

unsigned long __cdecl _lrotl(unsigned long, int);

unsigned long __cdecl _lrotr(unsigned long, int);

#ifndef _MAC

_CRTIMP void __cdecl _makepath(char *, const char *, const char *, const char *,

const char *);

#endif

_onexit_t __cdecl _onexit(_onexit_t);

_CRTIMP void __cdecl perror(const char *);

_CRTIMP int __cdecl _putenv(const char *);

unsigned int __cdecl _rotl(unsigned int, int);

unsigned int __cdecl _rotr(unsigned int, int);

_CRTIMP void __cdecl _searchenv(const char *, const char *, char *);

#ifndef _MAC

_CRTIMP void __cdecl _splitpath(const char *, char *, char *, char *, char *);

#endif

_CRTIMP void __cdecl _swab(char *, char *, int);

#ifndef _MAC

#ifndef _WSTDLIBP_DEFINED

/* wide function prototypes, also declared in wchar.h */

_CRTIMP wchar_t * __cdecl _wfullpath(wchar_t *, const wchar_t *, size_t);

_CRTIMP void __cdecl _wmakepath(wchar_t *, const wchar_t *, const wchar_t *, const wchar_t *,

const wchar_t *);

_CRTIMP void __cdecl _wperror(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 _wsplitpath(const wchar_t *, wchar_t *, wchar_t *, wchar_t *, wchar_t *);

#define _WSTDLIBP_DEFINED

#endif

#endif /* ndef _MAC */

/* --------- The following functions are OBSOLETE --------- */

/* The Win32 API SetErrorMode, Beep and Sleep should be used instead. */

#ifndef _MAC

_CRTIMP void __cdecl _seterrormode(int);

_CRTIMP void __cdecl _beep(unsigned, unsigned);

_CRTIMP void __cdecl _sleep(unsigned long);

#endif /* ndef _MAC */

/* --------- The preceding functions are OBSOLETE --------- */

#endif /* _POSIX_ */

#if !__STDC__

/* --------- The declarations below should not be in stdlib.h --------- */

/* --------- and will be removed in a future release. Include --------- */

/* --------- ctype.h to obtain these declarations. --------- */

#ifndef tolower /* tolower has been undefined - use function */

_CRTIMP int __cdecl tolower(int);

#endif /* tolower */

#ifndef toupper /* toupper has been undefined - use function */

_CRTIMP int __cdecl toupper(int);

#endif /* toupper */

/* --------- The declarations above will be removed. --------- */

#endif

#if !__STDC__

#ifndef _POSIX_

/* Non-ANSI names for compatibility */

#ifndef __cplusplus

#define max(a,b) (((a) > (b)) ? (a) : (b))

#define min(a,b) (((a) < (b)) ? (a) : (b))

#endif

#define sys_errlist _sys_errlist

#define sys_nerr _sys_nerr

#define environ _environ

_CRTIMP char * __cdecl ecvt(double, int, int *, int *);

_CRTIMP char * __cdecl fcvt(double, int, int *, int *);

_CRTIMP char * __cdecl gcvt(double, int, char *);

_CRTIMP char * __cdecl itoa(int, char *, int);

_CRTIMP char * __cdecl ltoa(long, char *, int);

onexit_t __cdecl onexit(onexit_t);

_CRTIMP int __cdecl putenv(const char *);

_CRTIMP void __cdecl swab(char *, char *, int);

_CRTIMP char * __cdecl ultoa(unsigned long, char *, int);

#endif /* _POSIX_ */

#endif /* __STDC__ */

#ifdef __cplusplus

}

#endif

#ifdef _MSC_VER

#pragma pack(pop)

#endif /* _MSC_VER */

#endif /* _INC_STDLIB */

stdlib.h用法

1函数名称: calloc

函数原型: void * calloc(unsigned n,unsigned size);

函数功能: 分配n个数据项的内存连续空间,每个数据项的大小为size

函数返回: 分配内存单元的起始地址,如果不成功,返回0

2函数名称: free

函数原型: void free(void* p);

函数功能: 释放p所指的内存区

函数返回:

参数说明: p-被释放的指针

3函数名称: malloc

函数原型: void * malloc(unsigned size);

函数功能: 分配size字节的存储区

函数返回: 所分配的内存区地址,如果内存不够,返回0

4函数名称: realloc

函数原型: void * realloc(void * p,unsigned size);

函数功能: 将p所指出的已分配内存区的大小改为size,size可以比原来分配的空间大或小

函数返回: 返回指向该内存区的指针.NULL-分配失败

5函数名称: rand

函数原型: int rand(void);

函数功能: 产生0到32767间的随机整数(0到0x7fff之间)

函数返回: 随机整数

6函数名称: abort

函数原型: void abort(void)

函数功能: 异常终止一个进程.

7函数名称: exit

函数原型: void exit(int state)

函数功能: 程序中止执行，返回调用过程

函数返回:

参数说明: state:0-正常中止，非0-非正常中止

8函数名称: getenv

函数原型: char* getenv(const char *name)

函数功能: 返回一个指向环境变量的指针

函数返回: 环境变量的定义

参数说明: name-环境字符串

9函数名称: putenv

函数原型: int putenv(const char *name)

函数功能: 将字符串name增加到DOS环境变量中

函数返回: 0:操作成功，-1:操作失败

参数说明: name-环境字符串

10函数名称: labs

函数原型: long labs(long num)

函数功能: 求长整型参数的绝对值

函数返回: 绝对值

11函数名称: atof

函数原型: double atof(char *str)

函数功能: 将字符串转换成一个双精度数值

函数返回: 转换后的数值

参数说明: str-待转换浮点型数的字符串

12函数名称: atoi

函数原型: int atoi(char *str)

函数功能: 将字符串转换成一个整数值

函数返回: 转换后的数值

参数说明: str-待转换为整型数的字符串

13函数名称: atol

函数原型: long atol(char *str)

函数功能: 将字符串转换成一个长整数

函数返回: 转换后的数值

参数说明: str-待转换为长整型的字符串

14函数名称: ecvt

函数原型: char *ecvt(double value,int ndigit,int *dec,int *sign)

函数功能: 将浮点数转换为字符串

函数返回: 转换后的字符串指针

参数说明: value-待转换底浮点数，ndigit-转换后的字符串长度

15函数名称: fcvt

函数原型: char *fcvt(double value,int ndigit,int *dec,int *sign)

函数功能: 将浮点数变成一个字符串

函数返回: 转换后字符串指针

参数说明: value-待转换底浮点数，ndigit-转换后底字符串长度