C++ inherit from multiple base classes with the same virtual function name

Question

I tried this code:

class A
{
    virtual void foo() = 0;
};

class B
{
    virtual void foo() = 0;
};

class C : public A, public B
{
    //virtual void A::f         


        

Answer 1

You can resolve this ambiguity with different function parameters.

In real-world code, such virtual functions do something, so they usually already have either:

1. different parameters in A and B, or
2. different return values in A and B that you can turn into [out] parameters for the sake of solving this inheritance problem; otherwise
3. you need to add some tag parameters, which the optimizer will throw away.

(In my own code I usually find myself in case (1), sometimes in (2), never so far in (3).)

Your example is case (3) and would look like this:

class A
{
public:
    struct tag_a { };
    virtual void foo(tag_a) = 0;
};

class B
{
public:
    struct tag_b { };
    virtual void foo(tag_b) = 0;
};

class C : public A, public B
{
    void foo(tag_a) override;
    void foo(tag_b) override;
};