lifetime and virtuals

#include <iostream>

struct base {
    base()
    {
        std::cout << "base is under construction, derived unborn" << std::endl;
        f();
    }

    virtual ~base()
    {
        std::cout << "base dtor" << std::endl;
        f();
    }

    virtual void f()
    {
        std::cout << "base::f()" << std::endl;
    }
};

struct derived : base {
    derived()
    {
        std::cout << "derived is under construction" << std::endl;
    }

    virtual ~derived()
    {
        std::cout << "derived no longer exists" << std::endl;
    }

    virtual void f() override
    {
        std::cout << "derived::f()" << std::endl;
    }
};

void f()
{
    base* b = new derived;
    std::cout << "derived object X is alive" << std::endl;
    b->f();
    delete b;
}