结构体，共用体，枚举所占内存大小

结构体要注意位补齐（有4位补齐和8位补齐，默认8位）

#include<stdio.h>
#pragma pack(push)
#pragma pack(4)
struct test
{    
    
    char a; //补3位
    long c;
    char d;
    char h;//补2位
    int b;
    char e;  //补3位或补7位  
    double f;
    char g;   //补3位或补7位
}s1;
#pragma pack(pop)

typedef struct{
    double a;
    char b;
}s2;

union test2
{    
    char a;
    short b;
}s3;

enum week{sun=7,mon=1,tue,wed,thu,fri,sta};
enum week weekday;

void main(void)
{
    printf("s1:%d 
",sizeof(s1));
    printf("s2:%d 
",sizeof(s2));
    printf("s3:%d 
",sizeof(s3));
    printf("week:%d 
",sizeof(weekday));
} 

以下是运行结果