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From: rpk@rice-chex.ai.mit.edu (Robert Krajewski)
Newsgroups: comp.lang.c++
Subject: Re: Virtual functions used in constructor illegal ! ??
Summary: Phylogeny recapitulates ontogeny.
Keywords: virtual functions, constructor
Message-ID: <12044@life.ai.mit.edu>
Date: 26 Nov 90 22:54:09 GMT
References: <822@orthogo.UUCP> <39733@ucbvax.BERKELEY.EDU>
Sender: news@ai.mit.edu
Organization: MIT Artificial Intelligence Laboratory
Lines: 15

If the base class constructor could use a function designed to be used
with a derived class instance, that (derived) function might try to refer to
data members that weren't yet initialized.  In a sense, an object
``evolves'' as more and more specialied constructors are run.

The problem is that we would like the C++ constructor and destructor
mechanism to handle *all* the semantics of creating and destroying and
object, including tasks that must be invoked (using virtual functions)
on all members of base class from which other classes are expected to
be derived.  You can get around this calling separate functions for
initialization and deletion, but such a technique is awkward for
stack-allocated objects.
----
Robert P. Krajewski
Internet: rpk@ai.mit.edu ; Lotus: robert_krajewski.lotus@crd.dnet.lotus.com