Refer base class members from derived class

Question

class A {
    public:
        void fa() {
        }
    };

class B : public A{
public:
    void fb() {
    }
};

class C : public A, public B {
public:
    void fc() {
        //call A::fa(), not B::A::fa();
    }
};

How to call A::fa() from C::fc() function.

GCC warns withdirect base A inaccessible in C due to ambiguity, does this mean there is no direct way to refer base class members?

Answer 1

One option would be to create a stub class that you can use for casting to the right base class subobject:

struct A {
    void fa() { }
};

struct B : A {
    void fb() { }
};

// Use a stub class that we can cast through:
struct A_ : A { };

struct C : A_, B {
    void fc() {
        implicit_cast<A_&>(*this).fa();
    }
};

Where implicit_cast is defined as:

template <typename T> struct identity { typedef T type; }

template <typename T>
T implicit_cast(typename identity<T>::type& x) { return x; }