CODEWITHSUNDEEP
c++
cdleace
cdleace

Reputation: 123

Calling a virtual function from a destructor of a derived class in c++

Here is a snippet of my c++ code

class A {
public:
    virtual void method() {
        cout << "A::method" << endl;
    }

    virtual ~A() {
        cout << "A::destructor" << endl;
    }

};

class B : public A {
public:
    virtual void method() {
        cout << "B::method" << endl;
    }

    virtual ~B() {
        cout << "B::destructor" << endl;
        method();
    }
};

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

    a->method();

    delete a;

    return 0;
}

I've learned that it's not preferable to call any virtual functions from constructors or destructors. In the destructor of the derived class B, I call the virtual function named, "method()".

Here is the output message.

B::method
B::destructor
B::method
A::destructor

It seems to me there is no problem at all. The virtual function knows its object type and printed "B::method()". Is this a kind of undefined behavior that should be avoided?

Upvotes: 2

Views: 797

Answers (1)

Bathsheba
Bathsheba

Reputation: 234685

Conceptually all the virtual functions in B are accessible in the destructor body, so your code is fine and well-defined as it is.

But your code is extremely brittle: it would be a different matter if there was a child class of B which had method overridden. In that case writing B::method(); in the destructor body of B would be sufficient.

Short answer: calling virtual methods in constructors and destructors is best avoided.

Upvotes: 2

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