Re: function is virtual in derived class but not base class

I am have a fair understanding of how virtual functions work but I am
not able to fathom how this works:

class a {
public:
        void fn() {
                cout<<"a::fn\n";
        }

};

class b : public a {
public:
        virtual void fn() {
                cout<<"b::fn\n";
        }

};

int main() {
        a * p = new b();
        p->fn();
        return 0;

}

The output is "a::fn".
Now since object is of type "b" shouldn't the vtbl of b contain
b::fn() and that be invoked instead?

Can someone explain me how this works?

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