Question

I have a situation that looks like the following code:

#include <iostream>

class A
{
public:
    A() { std::cout << "A created!" << std::endl; }
    ~A() { std::cout << "A destroyed!" << std::endl; }

    virtual const char* Name() { return "A"; }
};

class B : public A
{
public:
    B() { std::cout << "B created!" << std::endl; }
    ~B() { std::cout << "B destroyed!" << std::endl; }

    const char* Name() { return "B"; }
};

int main()
{
    A* a = new B();

    std::cout << a->Name() << "\n";

    delete a;

    return 0;
}

I want B to be destroyed when A is destroyed too. Is this possible in its destructor or do I have to implement a virtual Destroy() method or something like that?

Answer 1

As a rule of thumb, if any of your methods are virtual, the destructor must also be virtual. If it isn’t, the declared type of a variable decides which destructor gets called, which is almost never what you want. 99.9% of all cases, you want the destructor from the runtime type.