Explain the need for "Virtual Destructor" ?

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Sabari...

these are the following reasons to use virtual destructors:-

1. Without a virtual destructor, the proper destructor may not be
called:

struct B {~B();};
struct D : B {~D();};
B* b = new D;
delete b; // <--------- Will not call D::~D() !!!!!

2. Without a virtual destructor, operator delete(void*, size_t) may
not be called with the correct size.

struct B {~B(); operator delete(void*, size_t);};
struct D : B {~D();};
B* b = new D;
delete b; // <--------- Will call operator delete(void*, size_t) with
// the size of B not the size of D!!!

3. Without a virtual destructor, and when MI is used, operator
delete(void*) or operator delete (void*, size_t) may be called with
the wrong address.

struct B {~B();};
struct A {};
struct D : A, B {~D();};
B* b = new D;
delete b; // <--------- May not pass to operator delete the address
// that was returned by operator new!!!

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