Static variables in static method in base class and inheritance

Question

I have these C++ classes:

class Base
{
protected:
    static int method()
    {
        static int x = 0;
        return x++;
    }
};

class A : public Base         


        

Answer 1

There will only be one instance of x in the entire program. A nice work-around is to use the CRTP:

template 
class Base
{
protected:
    static int method()
    {
        static int x = 0;
        return x++;
    }
};

class A : public Base { };
class B : public Base { };

This will create a different Base, and therefore a distinct x, for each class that derives from it.

You may also need a "Baser" base to retain polymorphism, as Neil and Akanksh point out.