With virtual destructors, do I need to explicitly declare a virtual destructor for each subclass?

Question

I've got a scenario where I'm writing somewhat deep object oriented code, with multiple layers of abstract base classes, and I'm wondering if I have to explicitly declare a destructor for each one.

Will the compiler generate a default one that's already virtual, or will I have to tell it to?

Answer 1

The default destructor is not virtual. If you declare the destructor of your base class as virtual, the destructors of the subclasses will be overrides, and thus also be virtual even without explicitly declaring them to be.

The GNU GCC compiler even gives a warning if you have a class hierarchy and your base class does not declare the destructor to be virtual because you most likely want it to be.