字节对齐设置的两种方式

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <sys/time.h>
#include <signal.h>
#include <sys/types.h>

#pragma pack (1)
struct data
{
int i;
int j;
int k;
char c;
};
#pragma pack ()

#pragma pack (4)
struct data2
{
int i;
int j;
int k;
char c;
};
#pragma pack ()

struct data3
{
int i;
int j;
int k;
char c;
} __attribute__((aligned(4)));

struct data4
{
int i;
int j;
int k;
char c;
}__attribute__((packed));

int main()
{
struct data dat;
struct data2 dat2;
struct data3 dat3;
struct data4 dat4;
int datt = sizeof(dat);

printf("sizeof(dat) = %d\n", sizeof(dat));
printf("sizeof(dat2) = %d\n", sizeof(dat2));
printf("sizeof(dat3) = %d\n", sizeof(dat3));
printf("sizeof(dat4) = %d\n", sizeof(dat4));
return 0;
}