Question

The title is probably confusing.

Suppose we have the following set up;

class A
{
public:
    virtual void fn() = 0;
};

class B
{
public:
    virtual int fn() {};
};

class C: public A, public B
{
};

Is there any way to define A::fn in class C?

Answer 1

No. This is not possible. It will always conflict with either of the fn().

The syntax of fn() are different,

void fn();  // in A

and in B is,

int fn();  // in B

You have to make those syntax same in A and B to let C implement the fn(). Demo.