#include <iostream>
using namespace std;
class c1 {};
class c2 : public c1 {};
class c3 : public c1 {};
class c4 : public c2, public c3 {};

int main () {
  c4 *x1 = new c4;
  c3 *x2 = x1;
  delete x2; // segmentation fault
}

class c3 : public c1 {
public:
    virtual ~c3() {}
};