Why base class destructor (virtual) is called when a derived class object is deleted?

Question

A difference between a destructor (of course also the constructor) and other member functions is that, if a regular member function has a body at the derived class, only the

Answer 1

A base class destructor may be responsible for cleaning up resources that were allocated by the base class constructor.

If your base class has a default constructor (one that doesn't take parameters or has defaults for all its parameters) that constructor is automatically called upon construction of a derived instance.

If your base class has a constructor that requires parameters, you must call it manually in the initializer list of the derived class constructor.

Your base class destructor will always be automatically called upon deletion of the derived instance since destructors don't take parameters.

If you're using polymorphism and your derived instance is pointed to by a base class pointer, then the derived class destructor is only called if the base destructor is virtual.