#include <stdio.h>

#define swap(T, x, y) \
    do { \
       T temp; \
       temp = x, x = y, y = temp; \
    } while (0) 

/* swap x and y */
int main()
{
    int x, y;
    x = -1, y = 1;
    printf("x = %d, y = %d\n", x, y);
    swap(int, x, y);
    printf("x = %d, y = %d\n", x, y);
    return 0;
}