通过指向基类的指针删除没有新成员的派生类

Question

A common practice for deleting a derived class instance through a pointer to its base class is declaring a virtual destructor in the base class. But I am curious what happens in case the derived class adds no new members to the base class and the base class' destructor is non-virtual.

Imagine, the following design. The base class has a protected constructor, so it can't be created directly. The only purpose of the derived class here is to allow base class creation by some Factory class. The Factory instantiates the derived class and returns a pointer to the base class. Eventually, when the pointed instance gets deleted by a user, the destructor of the derived class won't be called, of course, but I'm not sure if it's necessary since the derived class adds no new data. I'd like to clear up what kind of problems (if any) are possible in this case.

class Base
{
public:
    ~Base() = default;

protected:
    Base(int x, int y): x(x), y(y) {}

private:
    int x, y;
};

class Factory
{
    // privately declared Derived class exposes protected constructor from the Base class
    class Derived : public Base
    {
    public:
        Derived(int x, int y) : Base(x, y) {}
        ~Derived() = default;
    };

public:

    Base* create(int x, int y)
    {
        return new Derived(x, y);
    }
};  // Factory


int main()
{
    Factory factory;
    Base *base = factory.create(3, 4);
    delete base;
}

Answer 1

But I am curious what happens in case the derived class adds no new members to the base class and the base class' destructor is non-virtual.

The behaviour of the program will be undefined regardless of the members of the derived class.