Override Private

[John Love-Jensen]

Hi Liguo,

A private virtual function allows a derived class to implement behavior that
is used by the base class.  See C++PL 24.3.2.1

The situation you are describe relies on a happenstance where cavalier
casting that relies on the serendipity that the signatures in the vptrtbl
will happen to be in the same offset for the derived class as in the base
class, and thus casting-with-the-big-hammer avoids the compiler catching the
breach of access.

Casting in such a fashion is a source of bugs.  Should be avoided.

Sincerely,
--Eljay