Answer Posted / chandra

Vitual destructor is used

(1) whenever the base class object pointer points to
derived class object,and is being created using new.
i.e class base - base class
in main - base bptr;
class derived - derived class
in main - bptr = new derived();

Then whenever we use "delete bptr" at runtime always the
memory of bptr is freed but not derived because here the
pointer is of type base and not of derived.

Note: The destructor that gets invoked is the one that
associated with the type of the object.

Simple rule of thumb: Make your destructor virtual if your
class has any virtual functions.

Example:
#include <iostream.h>
class Base
{
public:
Base(){ cout<<"Constructor: Base"<<endl;}
virtual ~Base(){ cout<<"Destructor : Base"<<endl;}
};
class Derived: public Base
{
//Doing a lot of jobs by extending the functionality
public:
Derived(){ cout<<"Constructor: Derived"<<endl;}
~Derived(){ cout<<"Destructor : Derived"<<endl;}
};
void main()
{
Base *Var = new Derived();
delete Var;
}

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