Virtual functions are never called in constructor and destructor.

Take a look at the following code and ask whether print calls the base class or the version of the derived class?

The answer is the base class...
Maybe everyone will be surprised. Isn't print a virtual function? Why not call the version of the derived class? First, when defining an object of A derived classThe execution of base class constructor is earlier than that of derived class.Constructor,Therefore, when the base class constructor calls this function, the member of the derived class has not yet been initialized (Note: The real virtual function table has not been fully initialized at this time ).If the function of the derived class is called at this time (the uninitialized member may be used), it will be troublesome. Therefore, C ++ prohibits you from doing so ..
In fact,During the base class construction of the derived class object, the object type is Bass class rather than derived class.Therefore, virtual function calls must be the base class version ..

The same principle applies to destructor.

As you know, the sequence of calling the Destructor is the opposite of that of the constructor when the object of the derived class is destructed:

The destructor of a derived class is prior to the destructor of the base class.

Therefore, in the process of calling the base destructor, the compiler regards it as a base class object ..