#include <iostream>

class A{};
class B:public A{};
class C:public A{};
int main(void)
{
B *p = new B;
C *q = new C;
std::cout << (p == q) << std::endl;
return 0;
}

In function 'int main()':
Line 10: error: comparison between distinct pointer types 'B*' and 'C*' lacks a cast
compilation terminated due to -Wfatal-errors.