void swap(int *p, int *q) {
    int temp;
    temp = *p; *p = *q; *q = temp;   // will change the actual values of a and b
}

void test(void) {
    int a = 5, b = 7;
    swap(&a, &b);
    printf("a = %d, b = %d\n", a, b);  // a and b will now be successfully swapped
}