In C++ Inheritance, Derived class destructor not called when pointer object to base class is pointed to derived class

Question

I am a newbie and I know this is a very basic concept and might be a duplicate too. Is it not true that once a constructor is called its corresponding destructor has to be called? [code run on Dev C++]

class Base
    {
     public:
            Base() { cout<<"Base Constructor\n";}
            int b;
     ~Base() {cout << "Base Destructor\n"; }
    };

class Derived:public Base
{
 public:
        Derived() { cout<<"Derived Constructor\n";}
        int a;
 ~Derived() { cout<< "Derived Destructor\n"; }
}; 
int main () {
Base* b = new Derived;    
//Derived *b = new Derived;
 delete b;
    getch();
    return 0;
}

GIVES OUTPUT

Base Constructor
Derived Constructor
Base Destructor

Answer 1

Your code has undefined behavior. The base class's destructor must be virtual for the following to have defined behavior.

Base* b = new Derived;    
delete b;

From the C++ standard:

5.3.5 Delete

3 In the first alternative (delete object), if the static type of the operand is different from its dynamic type, the static type shall be a base class of the operand’s dynamic type and the static type shall have a virtual destructor or the behavior is undefined.

So in your case, the static type is Base, and the dynamic type is Derived. So the Base's destructor should be:

virtual ~Base() {cout << "Base Destructor\n"; }