C编程-结构

Question

#include<stdio.h>

struct s {  
  char *a1;
  int a;
};

int main(){
struct   s p={"asdv",11};
struct   s p1=p;

p1.a1="vshaj";
printf("%d %s",p.a,p.a1);
}

In above program Does p1.a1 and p.a1 point to same memory address?

Answer 1

1) Struct p1 is a copy of p

2) HOWEVER - since a1 is a pointer, the copied pointers both point to the same memory. Until you reassign p1.a1 to the address of "vshaj".

3) Don't ever, ever do anything like this in real code ;)

Answer 2

Yes, they do, until you reassign p1.a1 , then of course they don't. You could just print them out to prove it.

Example code:

#include <stdio.h>

struct s
{
    char *a1;
    int a;
};

int main(void)
{
    struct s p = { "asdv", 11 };
    struct s p1 = p;

    printf("They're the same: %p %p\n", p.a1, p1.a1);

    p1.a1 = "vshaj";
    printf("%d %s\n",p.a,p.a1);

    printf("They're different: %p %p\n", p.a1, p1.a1);

    return 0;
}

Example run:

$ make example
cc     example.c   -o example
$ ./example 
They're the same: 0x10e258f2a 0x10e258f2a
11 asdv
They're different: 0x10e258f2a 0x10e258f48