Does it mean we will be able to do that to block inheritance?

class Final {};
class FinalClass : virtual private Final {};  // Can't derive from

Nicolas Fleury wrote:
> Hi,
>
> I've found the following C++ Standard Core Language Closed Issue:
> http://www.comeaucomputing.com/iso/cwg_closed.html#7
>
> I don't like at all the idea of not being able to derive from a class
> with a private virtual base class.  It's a pattern we commonly use where
> I work, particularly with an Observer class.  The virtual private
> inheritance allows us to store only one observer (and its lists of
> observed objects) for one object.
>
> I may not understand the issue well; maybe someone could explain me why
> it would be bad.
>
> I was also surprised to see this issue closed (note: I know nothing
> about how the Committee process), considering the recent huge thread
> about blocking inheritance and the fact that I don't remember reading
> anything about this.
>
> By the way, g++ 3.2 accepts the test case provide in the link in
> addition to the other compilers mentioned.
>
> Regards,
>
> Nicolas

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I guess I made the mistake of not asking directly any question in my post...

Does it mean that in future C++ we will be able to block inheritance by
doing something like the following code?

class Final {};
class MyFinalClass : private virtual Final, ...

If yes, what's the difference with a not-virtual private base class?

Thanks for insight.

Nicolas Fleury

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Hi,

I've found the following C++ Standard Core Language Closed Issue:
http://www.comeaucomputing.com/iso/cwg_closed.html#7

I don't like at all the idea of not being able to derive from a class
with a private virtual base class.  It's a pattern we commonly use where
I work, particularly with an Observer class.  The virtual private
inheritance allows us to store only one observer (and its lists of
observed objects) for one object.

I may not understand the issue well; maybe someone could explain me why
it would be bad.

I was also surprised to see this issue closed (note: I know nothing
about how the Committee process), considering the recent huge thread
about blocking inheritance and the fact that I don't remember reading
anything about this.

By the way, g++ 3.2 accepts the test case provide in the link in
addition to the other compilers mentioned.

Regards,

Nicolas

---
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[ your news-reader.  If that fails, use mailto:std-c++@ncar.ucar.edu    ]
[              --- Please see the FAQ before posting. ---               ]
[ FAQ: http://www.jamesd.demon.co.uk/csc/faq.html                       ]