#include <stdio.h>
    int main()
    {
        void *p;
        int a[4] = {1, 2, 3, 8};
        p = &a[3];
        int *ptr = &a[2];
        int n = p - ptr;
        printf("%d\n", n);
   }

In function 'main':
Line 8: error: invalid operands to binary -