Re: "virtual" not extended to derived classes by default?

From:
"Bo Persson" <bop@gmb.dk>
Newsgroups:
microsoft.public.vc.language
Date:
Tue, 30 Jan 2007 17:55:43 +0100
Message-ID:
<529bkaF1nkaobU1@mid.individual.net>
MrAsm wrote:

Hi,

I have defined a class to represent Stack errors (StackException).
I have derived it from std::exception.
Then, from StackException, two more classes are derived:
StackOverflowException and StackUnderflowException.

The std::exception has the virtual destructor.
I did not repeat the keyword "virtual" in my custom defined derived
classes, and I had a memory leak from DBGHEAP.C in Visual C++ 6.

If I repeat the "virtual" keyword in each class destructor,
everything goes fine.

So, I tought that, if a base class defines a virtual destructor,
then all derived classes will have a virtual destructor.


Yes.

But it seems that virtual declaration must be repeated for each
derived classes.


No.

My question is: is Visual C++ 6 out-of-standard in this particular
aspect, or is it a general C++ rule that "virtual" keyword must be
repeated in each derived class?


VC6 is generally out of standard in many regards, but hardly in this case.
You must have hit a very special case.

If you have any choice on what compiler to use, try one from this
millennium. :-)

Bo Persson

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