void swap(int *xp, int *yp){
  int t0 = *xp;
  int t1 = *yp;
  *xp = t1;
  *yp = t0;
}

int doit(){
  int x = 123;
  int y = 456;
  swap(&x, &y);
  return x + y;
}

int main(){
  int z = doit();
  return 0;
}