default override of virtual destructor

Question

Everyone knows that the desructor of base class usually has to be virtual. But what is about the destructor of derived class? In C++11 we have keyword \"override\" and ability t

Answer 1

The CPP Reference says that override makes sure that the function is virtual and that it indeed overrides a virtual function. So the override keyword would make sure that the destructor is virtual.

If you specify override but not = default, then you will get a linker error.

You do not need to do anything. Leaving the Child dtor undefined works just fine:

#include 

struct Notify {
    ~Notify() { std::cout << "dtor" << std::endl; }
};

struct Parent {
    std::string a;
    virtual ~Parent() {}
};

struct Child : public Parent {
    std::string b;
    Notify n;
};

int main(int argc, char **argv) {
    Parent *p = new Child();
    delete p;
}

That will output dtor. If you remove the virtual at Parent::~Parent, though, it will not output anything because that is undefined behavior, as pointed out in the comments.

Good style would be to not mention Child::~Child at all. If you cannot trust that the base class declared it virtual, then your suggestion with override and = default will work; I would hope that there are better ways to ensure that instead of littering your code with those destructor declarations.