Why the virtual destructor in derived class is empty?

Question

I see that in some codes, the virtual destructor in derived class is empty, then why we need it since it does nothing? Is it used to call the destructor in base class and without it, the destructor cannot be called? or it is just a notation to tell the code reader that this destructor is virtual which makes code much easier to read?

Answer 1

why we need it since it does nothing?

If the base class already has a virtual destructor, we don't have to define an empty one in the derived class. The only reason to put it there is to remind other readers of your code that there is a virtual destructor for the class.

Is it used to call the destructor in base class and without it, the destructor cannot be called?

An empty destructor does participate in destructor chaining in the same way as a non-empty or an inherited destructor does. As long as the base class has a virtual destructor, providing an empty override does not change the behavior.