13.2 Redefinition of Virtual Functions

If you make a subclass of an existing class and override a virtual function, make sure that the overriding function has exactly the same signature as the overridden function. This includes any const modifiers!

This problem arises particularly when creating new RWCollectable classes. For example:

class MyObject : public RWCollectable {
public:
  bool isEqual();                            // No "const" !
};

The compiler will treat this definition of isEqual() as completely independent of the isEqual() in the base class RWCollectable, because it is missing a const modifier. Hence, if called through a pointer:

MyObject obj;
  RWCollectable* c = &obj;
  c->isEqual();   // RWCollectable::isEqual() will get called!

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