calling virtual function through pointer to const base class

Question

In the below program, the function 'f' in the base class A is hidden for the objects of derived class B. But when I call function f through const A *d which is pointing object of B, function f from the base class is getting invoked. If I remove const specifier for the pointer (i.e. A *d) function 'f' from derived class is called. My query how the constness is making a difference here ? Thanks for any help.

#include <iostream>

class A
{
public:
    virtual void f(int n) { std::cout << "A::f\n"; }
    virtual ~A() { }

    void f(int n) const { std::cout << "A::f const\n"; }
};

class B
    : public A
{
public:
    void f(int n) { std::cout << "B::f\n"; }

    void f(int n) const { std::cout << "B::f const\n"; }
};

int main()
{
    const A a;
    B b;
    A &c = b;
    const A *d = &b;

    c.f(1);
    d->f(1);


    return 0;
}

Output (with const A *d): B::f A::f const

Output (with A* d) B::f B::f

Answer 1

The signature of the function to be called is determined on call site based on the static type of the pointer. The correct overrider of this signature is then chosen at runtime.

In other words, if you have this:

const A *d;
d->f(1);

then the f is searched for in const A. So it finds the non-virtual void f(int) const.

However, if you have this:

A *e;
e->f(1);

then the f is searched for in non-const A. So it finds virtual void f(int), which is then (at runtime) delegated to the final overrider void B::f(int).

EDIT

This follows from the rules on member function selection. When accessing through a const path (pointer or reference), only const member functions are applicable. When accessing through a non-const path, non-const functions are considered. Only if there is none is the pointer (or reference) implicitly converted to a pointer (or-reference) to const and then the const member functions are considered.