caller.c

int swap_add(int *xp, int *yp){
	int x = *xp;
	int y = *yp;

	*xp = y;
	*yp = x;

	return x+y;
}

int caller(){
	int arg1 = 123;
	int arg2 = 456;
	int sum = swap_add(&arg1, &arg2);
	int diff = arg1 - arg2;

	return sum * diff;
}

int main(){
	caller();
	return 0;
}