STRUCT_OFFSET( s, m )宏

参考：https://www.cnblogs.com/sggggr/p/15028904.html

define STRUCT_OFFSET(struct_object,e) (unsigned long)&(((struct_object*)0)->e)

如上宏的意义，获取结构体S中元素M,相对于首元素的偏移量。

#include <stdio.h>
#define STRUCT_OFFSET(s,m)   ( (int)(&((s*)0)->m)) /* 定义获取结构成员相对偏移地址的宏 */
 
struct man
{
	char name[63];
	int year;
	char son_name[59];
	char son_year;
};
int main()
{ 
    printf("name offset：%d\n",STRUCT_OFFSET( struct man, name ));
    printf("year offset：%d\n",STRUCT_OFFSET( struct man, year ));
	printf("son_name offset：%d\n",STRUCT_OFFSET( struct man, son_name ));
	printf("son_year offset：%d\n",STRUCT_OFFSET( struct man, son_year ));
    return 0;
}

程序结果：

name offset：0
year offset：64
son_name offset：68
son_year offset：127