linux c中局部变量/全局变量一瞥

来源：互联网发布：塔人网络接收奇迹世界编辑：程序博客网时间：2024/06/05 16:03

全局变量：

#include <stdio.h>
#if 1
#pragma pack (1)
char c = 0;
char e = 1;
struct a {} b, d;
#pragma pack ()
#endif
int main()
{
#if 0
#pragma pack (1)
char c = 0;
//char e = 1;
struct a {} b, d;
#pragma pack ()
#endif
struct a *ref_a = &b;
struct a *ref_b = &d;
printf("sizeof struct %d\n", sizeof(struct a));
printf("sizeof data %d\n", sizeof(b));
printf("address 1st %p\n", ref_a);
printf("address 2nd %p\n", ref_b);
printf("address none1 %p\n", &c);
// printf("adderss none2 %p\n", &e);
return 0;
}

===============================================================================================================================================

>>./a.out

sizeof struct 0
sizeof data 0
address 1st 0x80496ec
address 2nd 0x80496ec
address none1 0x80496e8

===============================================================================================================================================

局部变量：

#include <stdio.h>
#if 0
#pragma pack (1)
char c = 0;
char e = 1;
struct a {} b, d;
#pragma pack ()
#endif
int main()
{
#if 1
#pragma pack (1)
char c = 0;
//char e = 1;
struct a {} b, d;
#pragma pack ()
#endif
struct a *ref_a = &b;
struct a *ref_b = &d;
printf("sizeof struct %d\n", sizeof(struct a));
printf("sizeof data %d\n", sizeof(b));
printf("address 1st %p\n", ref_a);
printf("address 2nd %p\n", ref_b);
printf("address none1 %p\n", &c);
// printf("adderss none2 %p\n", &e);
return 0;
}

===============================================================================================================================================

./a.out

sizeof struct 0
sizeof data 0
address 1st 0xbf9591eb
address 2nd 0xbf9591eb
address none1 0xbf9591eb