Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!bywater!arnor!watson!blinn.watson.ibm.com!mittle
From: mittle@blinn.watson.ibm.com (Josh Mittleman)
Newsgroups: comp.lang.c++
Subject: Re: polymorphism on base objects?
Keywords: C++, polymorphism, references, base objects, bug
Message-ID: <1991May16.160803.22193@watson.ibm.com>
Date: 16 May 91 16:08:03 GMT
References: <dpg.674226630@extro>
Sender: @watson.ibm.com
Distribution: comp
Organization: IBM T. J. Watson Research
Lines: 19

I agree that your results are confusing, and I think that they are simply
wrong.  I compiled your code with the ATT v2.1 compiler, and I did not
reproduce your results.  My output was what you expected in the first
place: 

test_a(b) : Class name: Base
test_a(d1) : Class name: D1
test_a(bb) : Class name: Base
test_b(b) : Class name: Base
test_b(d1) : Class name: Base
test_b(bb) : Class name: Base

It is certainly incorrect to get polymorphism through a base class object,
as opposed to through a base class pointer or reference.  A Base is a Base,
and cannot be anything but a Base.

===========================================================================
Josh Mittleman (mittle@watson.ibm.com or joshua@paul.rutgers.edu)
J2-C28 T.J. Watson Research Center, PO Box 704, Yorktown Heights, NY  10598