字节对齐及求结构体成员变量偏移量

#include<cstdio>
#include<cstring>

#define OFFSET(TYPE, MEMBER, OFF)   \
    TYPE temp;      OFF = (unsigned long)(&(temp.MEMBER)) - (unsigned long)(&(temp));

struct Type_t
{
    char a;
    int b;
    double c;
};

int main()
{
    int offset = 0;
    Type_t type;

    offset = (unsigned long)(&(type.c)) - (unsigned long)((&type));
    printf("offset = %d\n", offset);

    int offset_1 = 0;
    OFFSET(Type_t, c, offset_1);
    printf("offset = %d\n", offset_1);

    return 0;
}