Re: Override Private

[Liguo Song <Liguo dot Song at vanderbilt dot edu>]

Hi, Eljay,

Thanks for the reply.

> 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
Thanks for the reference. It is good to go back to the C++ bible and refresh my 
memory. :)
But it is the fact that Base::fun() is public surprised me, which isn't covered 
by C++PL.


> 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.
This is my first suspect. So I tried to add some other member functions into 
Base class, but failed to disturb the coincidence. Also, this works on both GCC 
2.96 and MS C++ .NET, so I assume it is not compiler dependent.

> Casting in such a fashion is a source of bugs.  Should be avoided.
I strongly agree with you on this, and this is why I hoped the compiler would 
catch this in compile time and was suprised that it didn't.

Thanks again for the discussion.


Liguo