nested class access control in C++

Question

Can inner class access a private member variable of its enclosing class? There seems to be some contradictions on the internet and compiler. Compile (g++ on cygwin) allows it. But, some technical documents say that it is not allowed.

Answer 1

No special access is granted to to the outer class from the nested class.

Section 11.8-1 of the C++03 standard on Nested classes:

The members of a nested class have no special access to members of an enclosing class, nor to classes or functions that have granted friendship to an enclosing class;

class E {
    int x;
    class B { };
    class I {
        B b; // error: E::B is private
        int y;
        void f(E* p, int i)
        {
            p->x = i; // error: E::x is private
        }
    };
    int g(I* p)
    {
        return p->y; // error: I::y is private
    }
};