C语言（五）结构体对齐访问

版权声明：本文为博主原创文章，未经博主允许不得转载。 https://blog.csdn.net/qq_40818798/article/details/86688479

#include <stdio.h>

#define N 8 //1 2 4 8 ...
#pragma pack(N)  //N字节对齐开始
struct st1
{
	int a;		//N=1 4;   N=2 4;   N=4 4;   N=8 4
	char b;		//N=1 1;   N=2 2;   N=4 2;   N=8 2
	short c;	        //N=1 2;   N=2 2;   N=4 2;   N=8 2
}s1;			//N=1 7;   N=2 8;   N=4 8;   N=8 8
struct st2
{
	char a;		//N=1 1;   N=2 2;   N=4 4;    N=8 4
	int b;		//N=1 4;   N=2 4;   N=4 4;    N=8 4
	short c;	        //N=1 2;   N=2 2;   N=4 4;    N=8 4
}s2;			//N=1 7;   N=2 8;   N=4 12;   N=8 12
struct st3
{
	int a;			//N=1 4;    N=2 4;    N=4 4;   N=8 4
	struct st1 s;	        //N=1 7;    N=2 8;    N=4 8;   N=8 12
	double b;		//N=1 8;    N=2 8;    N=4 8;   N=8 8
	int c;			//N=1 4;    N=2 4;    N=4 4;   N=8 8
}s3;				//N=1 23;   N=2 24;   N=4 24;  N=8 32
struct st4
{
	char sex;		//N=1 1;    N=2 2;    N=4 4;   N=8 4
	int length;		//N=1 4;    N=2 4;    N=4 4;   N=8 4
	char name[10];	        //N=1 10;   N=2 10;   N=4 12;   N=8 12
}s4;				//N=1 15;   N=2 16;   N=4 20;   N=8 20
#pragma pack()	//N字节对齐结束

int main()
{
	printf("%d字节对齐\n", N);
	printf("sizeof(st1):%d\n", sizeof(struct st1));
	printf("&a:%p     &b:%p     &c:%p\n", &s1.a, &s1.b, &s1.c);

	printf("sizeof(st2):%d\n", sizeof(struct st2));
	printf("&a:%p     &b:%p     &c:%p\n", &s2.a, &s2.b, &s2.c);

	printf("sizeof(st3):%d\n", sizeof(struct st3));
	printf("&a:%p     &s:%p     &b:%p     &c:%p\n", &s3.a, &s3.s, &s3.b, &s3.c);

	printf("sizeof(st4):%d\n", sizeof(struct st4));
	printf("&sex:%p   &length:%p   &name:%p\n", &s4.sex, &s4.length, &s4.name);
	return 0;
}