测试环境:
c
#include<stdio.h>
int main(){
//1字节对齐
struct XXX{
unsigned char ch;
unsigned int in;
unsigned short si;
}__attribute__((packed));
struct XXX xxx;
printf("%zd\n",sizeof(xxx));//7
#pragma pack(1)
struct YYY{
unsigned char ch;
unsigned int in;
unsigned short si;
};
struct YYY yyy;
printf("%zd\n",sizeof(yyy));
#pragma pack()
//不进行对齐限制,编译器决定
//默认对齐方式是采用当前最长的变量的长度作为对齐方式
struct ZZZ{
unsigned char ch;
unsigned int in;
unsigned short si;
};
struct ZZZ zzz;
printf("%zd\n",sizeof(zzz));//12
return 0;
}