Covariant return types, const-ness, and incomplete classes

Question

This code compiles successfully under g++ 6.1 but gives an error with clang 3.8:

class C;

class Base {
public:
  virtual const C *getC();
};

class Derived : pu         


        

Answer 1

I also find nothing wrong with your code. It compiles with the head version of clang and all compilers I tried, except clang 3.8 and earlier.

Live demo

The relevant standard text:

10.3 note 8:

If the class type in the covariant return type of D::f differs from that of B::f, the class type in the return type of D::f shall be complete at the point of declaration of D::f or shall be the class type D.

The class type of the covariant methods must be the same or complete, but as I understand it const/volatile differences are still considered the same class type, making your example legal.