Can realloc fail in this case ?

int *a = NULL;

a = calloc(100, sizeof(*a));
printf("1.ptr: %d \n", a);

a = realloc(a, 50 * sizeof(*a));
printf("2.ptr: %d \n", a);

if(a == NULL){
    printf("Is it possible?");
}

return (0);

}

The output in my case is:

1.ptr: 4072560
2.ptr: 4072560

So 'a' points to the same adress. So should i enforce realloc check ?

Later edit:

• Using MinGW compiler under Windows XP.
• Is the behaviour similar with gcc on Linux ?

Later edit 2: Is it OK to check this way ?

int *a = NULL, *b = NULL;

a = calloc(100, sizeof(*a));
b = realloc(a, 50 * sizeof(*a));

if(b == NULL){
    return a;
}
a = b;
return a;