Question

I saw this question on SO and wondered where this kind of code can actually be used in the real time example.

struct a
{
    static struct a b;
};


int main()
{
    a::b;

    return 0;
}

Also what is the significance of a::b;
Thanks for your inputs.

Answer 1

Such code can be used in implementation of the Singleton pattern. Here, one instance of type a is declared; if other instances are somehow forbidden, it is the singleton. In practice, however, i recall, they usually use less confusing syntax.

And, as for a::b, it does nothing useful. It just shows the name of the instance. A more useful example would be this:

struct a
{
    static struct a b;
    int data;
};

a a::b = {9};

int main()
{
    int stuff = a::b.data;
    printf("%d\n", stuff);

    return 0;
}