Problem with inheritance

[rengaf]

Dear all,
could anybody tell me what is wrong with the attached code? It gives a Bus Error at run time.

I need to do:

  C *c = (C*)(new A());

because I have a function which returns a pointer to an object of class A and I want to use it as an object of class C. The code works if class C inherits directly from A.

Thank you very much for your help,

Francesco

#include "stdio.h"

class A {

public:
  A() {};
  virtual ~A() {};

};

class B : public A {

public:
  B() : A() {};
  virtual ~B() {};
 
  virtual void Hello() = 0;

};

class C : public B {

public:
  C() : B() {};
  ~C() {};

  void Hello();

};

void C::Hello() { printf("hello\n"); }

int main(){

  C *c = (C*)(new A());

  c->Hello();

}

[S G H]

You can't (And really shouldn't!) do that.

A does not derive from C.
Instead, you can do the opposite, because C derives from A.

The reason behind this, is because Hello is virtual in B, while it is not in its base class (A).