order of destruction using virtual

Question

Can some one please help what the order of destruction is when I am using virtual functions. Does it start with the base class and then derived class?

Answer 1

First the derived, then the base. No difference wrt the non-virtual cases.

Additional note. When you have inheritance and virtual methods, you have to declare destructors as virtual, otherwise you can have undefined behavior at deletion.

Example, suppose Derived is derived from Base, and you allocate Derived with the following line:

Base *o = new Derived();
delete(o);

If this case occurs in your code, and Base has no virtual destructor, the resulting behavior is undefined. Typically, only the destructor of Base will be called. The destructor of Derived will not be called, because you are calling delete on a Base pointer. However, the program might crash instead. Once you are in the realm of undefined behavior, all bets are off and your running code is doomed. To prevent chaos the Base destructor must be virtual.