Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!fernwood!lia!jgro
From: jgro@lia (Jeremy Grodberg)
Newsgroups: comp.lang.c++
Subject: Re: multiple inheritance bug
Message-ID: <1991Feb11.213836.1840@lia>
Date: 11 Feb 91 21:38:36 GMT
References: <3553@island.COM> <9592@dog.ee.lbl.gov>
Reply-To: jgro@lia.com (Jeremy Grodberg)
Lines: 39

In article <9592@dog.ee.lbl.gov> beard@ux5.lbl.gov (Patrick C Beard) writes:
>In article <3553@island.COM> lars@island.COM (Lars Nyman) writes:
>#
>#I have a problem with multiple inheritance using virtual base classes, and
>#suspect it's a bug in the C++ compiler.
>
>Don't be so quick to call this a bug.  It's actually a feature.  C++ does
>not officially support the calling of virtual functions from a constructor.

You are wrong, Mr. Beard.  ARM 12.7 clearly says 
    
    Member functions may be called in constructors and destructors.  This
    implies that virtual functions may be called (directly or indirectly).
    The function called will be the one defined in the constructor's
    (or destructor's) own class or its bases, but *not* any
    function overriding it in a derived class. [...] The effect of calling
    a pure virtual function directly or indirectly for the object being
    constructed from a constructor, except using explicit qualification,
    is undefined.

So, Mr. Beard, you are totally wrong in saying C++ does not offically
support the calling of virtual functions from a constructor.

However, Mr. Nyman's example code did involve calling a pure virtual
function indirectly for the object being constructed from a constructor,
without explicit qualification, so he has no reason to claim his sample
code should work.  

Also, since Mr. Nyman didn't include the output of his sample code in his
posting, it is hard to know if the problem was the code not working as
it should, or Mr. Nyman not understanding what the code should do.
Another test, without the pure virtual function, is called for before
calling this a bug.



-- 
Jeremy Grodberg      "I don't feel witty today.  Don't bug me."
jgro@lia.com