// Base has no default constructor
class Base {
 public:
  Base(int y) : y(y) { }
  int y;
};

// Compiler error when you try to instantiate a D1, as D1’s
// synthesized default constructor needs to invoke Base's default
// constructor.
class Der1 : public Base {
 public:
  int z;
};

// Works.
class Der2 : public Base {
 public:
  Der2(int y, int z) : Base(y), z(z) { }
  int z;
};

int main(int argc, char **argv) {
  Base b(1);   // OK
  Der2 d2(1, 2);  // OK
  // Der1 d1;     // compiler error
  return 0;
}