Question

Possible Duplicate:
Pure virtual destructor in C++

class A{
    public:
        virtual ~A()=0;
};

class B:public A{
        int *i;
    public:
        ~B() {delete i;}
};

int main(){
    B* temp = new B;
}

I’m just trying to have B be an implementation of A. For some reason I cannot do this.

Answer 1

In C++ destructor can be pure virtual:

class A{
    public:
        virtual ~A()=0;
};

But in every case it needs to be implemented:

inline A::~A() {} 

Otherwise A is not usable class. I mean destruction of derived (S/B) is not possible. And possibility of destruction is needed in this line:

  B* temp = new B;

because in case of throwed exception – compiler will automatically destructs temp…