Suppress delete-non-virtual-dtor warning when using a protected non-virtual destructor

Question

I have a pure abstract interface class, and a derived class which implements the interface.

struct Foo
{
    virtual void doStuff() = 0;
};

struct Bar : Foo         


        

Answer 1

The compiler is telling you that the problem is in Bar not in Foo. If you were to have another class that inherits from Bar say Baz:

struct Baz : public Bar
{
  void doStuff() override { }
};

This could lead to undefined behavior such as the case

int main()
{
    Bar* bar_ptr = new Baz();
    bar_ptr->do_stuff();
    delete bar_ptr; // uh-oh! this is bad!
}

because the destructor in Bar is not virtual. So the solution is to mark Bar as final as has been suggested, or make the destructor in Bar virtual (since it's public) or make it protected in accordance with Herb's suggestions.

Answer 2

Marking the class final remove the warning.

struct Bar final : Foo
{
    void doStuff() override { }
};

int main()
{
    Bar* f = new Bar;
    f->doStuff();
    delete f;
}

Demo