C++ Standard ISO/IEC 14882:2003(E)
The access rules (clause 11) for a virtual function are determined by its declaration and are not affected by the rules for a function that later overrides it.
当一个子类函数通过基类的指针调用时，访问权限取决于基类对该函数的声明。
The access rules (clause 11) for a virtual function are determined by its declaration and are not affected by the rules for a function that later overrides it.
当一个子类函数通过基类的指针调用时，访问权限取决于基类对该函数的声明。
