结构指针的分段错误

Question

I am new in C, and i wrote the following code

#include <stdlib.h>
#include<stdio.h>

typedef struct
{
    int name1;
}check1;
typedef struct
{
    int name2;
}check2;

int main()
{
    check1 *test1;
    check2 *test2;
    test1->name1=1;
    test2->name2=2;
    return 0;
}

When I am executing it, it is giving me an error:

$ gcc test1.c
$ ./a.out
Memory fault

In gdb:-

Program received signal SIGSEGV, Segmentation fault.
0x000000000040045e in main ()

What could be the reason???

Thanks.

Answer 1

You have declared two pointers, but you haven't allocated any memory for them to point to. The pointers are pointing to invalid memory.

Try this:

check1 *test1 = malloc(sizeof(*test1));
if (test1 == NULL)
    // report failure

check2 *test2 = malloc(sizeof(*test2));
if (test2 == NULL)
    // report failure

Answer 2

You can also declare variables on the stack and assign their addresses to pointers.

check checka;
check* pcheck = &checka;
printf("%i",pcheck->name1);