C++ virtual override functions with same name

Question

I have something like that (simplified)

class A {   public:     virtual void Function () = 0; };  class B {   public:     virtual void Function () = 0; };  class Impl : public A , public B {   public:         ???? }; 

How can I implement the Function () for A and the Function() for B ? Visual C++ lets you only define the specific function inline (i.e. not in the cpp file), but I suppose it's an extension. GCC complains about this. Is there a standard C++ way to tell the compiler which function I want to override?

(visual c++ 2008)

class Impl : public A , public B {   public:      void A::Function () {  cout << "A::Function" << endl; }      void B::Function () {  cout << "B::Function" << endl; } }; 

Thank you!

Answer 1

You cannot use qualified names there. I you write void Function() { ... } you are overriding both functions. Herb Sutter shows how it can be solved.

Another option is to rename those functions, because apparently they do something different (otherwise i don't see the problem of overriding both with identical behavior).

Answer 2

I can suggest another way to resolve this issue. You can add wrapper Typed which changes Function signature by adding dummy parameter. Thus you can distinguish methods in your implementation.

class A { public:   virtual void Function() = 0;   virtual ~A() = default; };  class B { public:   virtual void Function() = 0;   virtual ~B() = default; };  template<typename T> class Typed : public T { public:   virtual void Function(T* dummy) = 0;   void Function() override {     Function(nullptr);   } };  class Impl : public Typed<A>, public Typed<B> { public:   void Function(A* dummy) override {     std::cerr << "implements A::Function()" << std::endl;   }   void Function(B* dummy) override {     std::cerr << "implements B::Function()" << std::endl;   } }; 

The benefit of such solution is that all implementation are placed in one class.