stddef.h（通常#include<stdio.h>就包含了他）
C语言头文件。
作用：定义/声明了一些经常使用的常数，类型和变量
VC中stddef.h的内容：
/***
*stddef.h - definitions/declarations for common constants, types, variables
*
* Copyright (c) 1985-1997, Microsoft Corporation. All rights reserved.
*
*Purpose:
* This file contains definitions and declarations for some commonly
* used constants, types, and variables.
* [ANSI]
*
* [Public]
*
****/
#if _MSC_VER > 1000
#pragma once
#endif
#ifndef _INC_STDDEF
#define _INC_STDDEF
#if !defined(_WIN32) && !defined(_MAC)
#error ERROR: Only Mac or Win32 targets supported!
#endif
#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
/* Define NULL pointer value and the offset() macro */
#ifndef NULL
#ifdef __cplusplus
#define NULL 0
#else
#define NULL ((void *)0)
#endif
#endif
#define offsetof(s,m) (size_t)&(((s *)0)->m)
/* Declare reference to errno */
#if (defined(_MT) || defined(_DLL)) && !defined(_MAC)
_CRTIMP extern int * __cdecl _errno(void);
#define errno (*_errno())
#else /* ndef _MT && ndef _DLL */
_CRTIMP extern int errno;
#endif /* _MT || _DLL */
/* define the implementation dependent size types */
#ifndef _PTRDIFF_T_DEFINED
typedef int ptrdiff_t;
#define _PTRDIFF_T_DEFINED
#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
#ifdef _MT
_CRTIMP extern unsigned long __cdecl __threadid(void);
#define _threadid (__threadid())
_CRTIMP extern unsigned long __cdecl __threadhandle(void);
#endif
#ifdef __cplusplus
}
#endif
#endif /* _INC_STDDEF */
2011-05-20 11:39
