C语言深入回顾讲解结构体对齐

struct data1
{
    char a;//1B
    int b;//4B
};
void test01()
{
    printf("%d\n",sizeof(struct data1));//8B 为啥？
}

struct data
{
	char c;//1B
	int i;//4B
};
void test05()
{
	struct data d;
	//结构体的大小 >= 成员大小之和
	printf("%d\n",sizeof(struct data));//8
	printf("&d.c = %u\n",&d.c );
	printf("&d.i = %u\n",&d.i );
}

typedef struct
{
	int a;
	char b;
	short c;
	char d;
}DATA;
void test06()
{
	DATA d;
	printf("%d\n", sizeof(DATA));
	printf("%u\n", &d.a);
	printf("%u\n", &d.b);
	printf("%u\n", &d.c);
	printf("%u\n", &d.d);
}

struct data1
{
    char a;//1B
    int b;//4B
};

struct data2
{
    char a;
    short b;
    char c;
    int d;
};

struct data2
{
    char a;
    short b;
    short c;
    char d;
};

struct data2
{
    char a[7];
    short b;
    int c;
};

typedef struct
{
	short d;
	char e;
}DATA2;
typedef struct
{
	short a;
	int b;
	DATA2 c;
	char f;
}DATA;
void test08()
{
	DATA data;
	printf("%d\n",sizeof(DATA));
	printf("a:%u\n", &data.a);
	printf("b:%u\n", &data.b);
	printf("c中d：%u\n",&data.c.d);
	printf("c中e：%u\n",&data.c.e);
	printf("f:%u\n",&data.f);
}

typedef struct
{
	char a;
	int b;
	short c;
}DATA;
void test10()
{
	DATA data={'a',100, 20};
	char *p = &data;
	printf("c = %hd\n", data.c);
	//需求 借助p访问20
	printf("c = %hd\n", *(short *)(p+8));
}

struct A
{
    char b;
    short c;
};
struct B
{
    int a;
    struct A ob;//结构体成员的偏移量
    int d;
};

struct A
{
    short b;
    char c;
};
struct B
{
    int f;
    char a;
    struct A ob;//结构体成员的偏移量
    char d;
};

#include <stdio.h>
#include<stdio.h>
#pragma pack (4)
struct stu
{
    char a;
    short b;
    short c;
};
void test01()
{
    printf("%d\n",sizeof(struct stu));//6
}

struct stu1
{
    char a;
    int b;
    char c;
    int d;
};

#include <stdio.h>
#include<stdio.h>
struct stu1
{
    char a;
    int b;
    char c;
    int d;
};
#define  OFF_SET(TYPE, member) (int)&(((TYPE *)0)->member)
void test01()
{
    struct stu1 data;
    printf("偏移量:%d\n",   OFF_SET(struct stu1, b) );//8
}