C/C++ offsetof

最新推荐文章于 2025-05-29 22:40:00 发布

Gordennizaicunzai

最新推荐文章于 2025-05-29 22:40:00 发布

阅读量739

点赞数

CC 4.0 BY-SA版权

分类专栏： C C++

本文链接：https://blog.youkuaiyun.com/Gordennizaicunzai/article/details/80960159

C++ 同时被 2 个专栏收录

41 篇文章

订阅专栏

29 篇文章

订阅专栏

offsetof宏用于获取结构体成员相对于结构体起始位置的字节偏移量。它返回一个size_t类型的值，表示指定成员在类型structName中的偏移。参数包括父结构体的名称和要获取偏移量的成员名。offsetof不适用于位字段，且不是一个函数，不能用C语言的原型来描述。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

offsetof

Retrieves the offset of a member from the beginning of its parent structure.返回结构成员相对于结构开头的字节偏移量。

size_t offsetof( structName, memberName );

Routine	Required Header	Compatibility
offsetof	<stddef.h>	ANSI, Win 95, Win NT

For additional compatibility information, see Compatibility in the Introduction.

Libraries

LIBC.LIB	Single thread static library, retail version
LIBCMT.LIB	Multithread static library, retail version
MSVCRT.LIB	Import library for MSVCRT.DLL, retail version

Return Value

offsetof returns the offset in bytes of the specified member from the beginning of its parent data structure. It is undefined for bit fields.该宏返回类型为 size_t 的值，表示 type 中成员的偏移量。

Parameters

structName

Name of the parent data structure

memberName

Name of the member in the parent data structure for which to determine the offset

Remarks

The offsetof macro returns the offset in bytes of memberName from the beginning of the structure specified by structName. You can specify types with the struct keyword.

Note offsetof is not a function and cannot be described using a C prototype.

e.g:

#include "stdafx.h"
#include "stddef.h"
#include "Afx.h"


typedef struct STUDENT_INFO
{
	CString csName;
	unsigned int wID;
	int iarrScore[3];	
	unsigned int wRanking;
}STUDENT;

int main()
{
    printf("STUDENT 结构中的 csName 偏移 %d 字节。\n",offsetof(STUDENT,csName));
    printf("STUDENT 结构中的 wID 偏移 %d 字节。\n",offsetof(STUDENT,wID));
    printf("STUDENT 结构中的 iarrScore 偏移 %d 字节。\n",offsetof(STUDENT,iarrScore));
	printf("STUDENT 结构中的 wRanking 偏移 %d 字节。\n",offsetof(STUDENT,wRanking));

	return true;
}