Virtual destructors

vdtor.c++

#include <iostream>
#include <memory>

using std::cout;

class Base {
public:
    virtual ~Base() = default; // REQUIRED!
};

class Noisy {
public:
    Noisy() { cout << "Noisy\n"; }
    ~Noisy() { cout << "~Noisy\n"; }
};

class Derived : public Base {
    std::unique_ptr<Noisy> noisy;
public:
    Derived() : noisy(new Noisy()) { }
    //virtual ~Derived() = default; // not required
};

int main () {
    std::unique_ptr<Base> base { new Derived() };
}