[014] Precautions for using destructor as virtual functions

1. When a destructor is a virtual function, the destructor of all its derived classes automatically become virtual functions (whether or not they are marked as virtual ).

2. when the destructor of the base class is a virtual function, if you call the destructor of the subclass, the program will first call the destructor of the derived class, then, call the destructor of the base class.

However, if the destructor of the base class is not a virtual function, only the destructor of the base class will be called.

Example:

Class base {virtual ~ Base () {};...}; Class Device: public base {~ Device () {};}; base * pb = new device; Delete Pb;

The program first calls the device destructor and then calls the base destructor.

If the virtual of the base is removed, only the destructor of the Base will be called.

● However, if the derived class type is used to point to the derived class, the device destructor will be called first, regardless of whether the base class has virtual or not, and then the base destructor will be called. Example:

Class base {~ Base () {};...}; Class Device: public base {~ Device () {};}; device * Pd = new device; Delete PD;

 

[014] Precautions for using destructor as virtual functions