c++ - 根据 ISO 2003，内部类可以访问外部的私有(private)成员

Question

如 ISO C++ 2003 中所述

§11.8 Nested classes [class.access.nest]

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; the usual access rules (clause 11) shall be obeyed. The members of an enclosing class have no special access to members of a nested class; the usual access rules (clause 11) shall be obeyed.

[Example:

class E {
    int x;

    class B { };

    class I {
        B b; // error: E::B is private ERROR 1
        int y;
        void f(E* p, int i)
        {
            p->x = i; // error: E::x is private ERROR 2
        }
    };

    int g(I* p)
    {
        //return p->y; // error: I::y is private ERROR 3
    }
};

int main()
{}

—end example]

所以我认为 clang和 g++是错误的，因为他们成功地编译了这段代码。

还是我理解有误？

Answer 1

标准说“没有特殊访问权限”，但没有说“完全没有访问权限”。嵌套类与任何其他成员一样是外部类的成员。

C++03标准中没有明确说明，但C++11明确包含:

11.7 Nested classes [class.access.nest]

1 A nested class is a member and as such has the same access rights as any other member.