From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me
X-Spam-Level: 
X-Spam-Status: No, score=-1.3 required=5.0 tests=BAYES_00,MAILING_LIST_MULTI,
	REPLYTO_WITHOUT_TO_CC autolearn=no autolearn_force=no version=3.4.4
X-Google-Language: ENGLISH,ASCII-7-bit
X-Google-Thread: 103376,4c459ff0adb576bc
X-Google-Attributes: gid103376,public
X-Google-ArrivalTime: 2002-02-19 22:21:04 PST
Path: 
 archiver1.google.com!news1.google.com!sn-xit-02!supernews.com!news.tele.dk!small.news.tele.dk!213.56.195.71!fr.usenet-edu.net!usenet-edu.net!enst!enst.fr!not-for-mail
From: Christoph Grein <christoph.grein@eurocopter.com>
Newsgroups: comp.lang.ada
Subject: Re: Refactoring and Ada
Date: Wed, 20 Feb 2002 07:19:41 +0100 (MET)
Organization: ENST, France
Sender: comp.lang.ada-admin@ada.eu.org
Message-ID: <mailman.1014186062.20211.comp.lang.ada@ada.eu.org>
Reply-To: comp.lang.ada@ada.eu.org
NNTP-Posting-Host: marvin.enst.fr
Mime-Version: 1.0
Content-Type: TEXT/plain; charset=us-ascii
X-Trace: avanie.enst.fr 1014186062 67496 137.194.161.2 (20 Feb 2002 06:21:02
 GMT)
X-Complaints-To: usenet@enst.fr
NNTP-Posting-Date: Wed, 20 Feb 2002 06:21:02 +0000 (UTC)
Return-Path: <christoph.grein@eurocopter.com>
Content-MD5: yc6eC/TCAg4dF0WgaFz8Dw==
X-Mailer: dtmail 1.2.1 CDE Version 1.2.1 SunOS 5.6 sun4u sparc 
Errors-To: comp.lang.ada-admin@ada.eu.org
X-BeenThere: comp.lang.ada@ada.eu.org
X-Mailman-Version: 2.0.8
Precedence: bulk
X-Reply-To: Christoph Grein <christoph.grein@eurocopter.com>
List-Help: <mailto:comp.lang.ada-request@ada.eu.org?subject=help>
List-Post: <mailto:comp.lang.ada@ada.eu.org>
List-Subscribe: <http://ada.eu.org/mailman/listinfo/comp.lang.ada>,
	<mailto:comp.lang.ada-request@ada.eu.org?subject=subscribe>
List-Id: comp.lang.ada mail<->news gateway <comp.lang.ada.ada.eu.org>
List-Unsubscribe: <http://ada.eu.org/mailman/listinfo/comp.lang.ada>,
	<mailto:comp.lang.ada-request@ada.eu.org?subject=unsubscribe>
Errors-To: comp.lang.ada-admin@ada.eu.org
X-BeenThere: comp.lang.ada@ada.eu.org
Xref: archiver1.google.com comp.lang.ada:20160
Date: 2002-02-20T07:19:41+01:00

> > It turns out that 'Valid is not as useful as many of us thought it was. For
> > example,  the result of an erroneous result from unchecked conversion,
> > which we originally thought was harmless if we checked it ourselves
> > with 'Valid before using it is a problem.   Consider the following,
> > 
> >                type X is ... ;
> >                type Y is ... ;
> > 
> >                function Convert is new Ada.Unchecked_Conversion
> >                                          (Source => Y, Target => X);
> > 
> >                 X := Convert (Y);     -- suppose X is erroneous or not valid
> >                 if X'Valid then ...      -- We used to think this was OK.
> >                                                  -- Some compilers fail on 
this because of an
> > interpretation
> >                                                  -- of the ALRM rules.
> > 
> >  At present, one must wonder about the usefulness of 'Valid.
> 
> There is an AI with a binding interpretation that was included in the
> TC that says that at least for scalar types the above code is
> not errorious and must work as expected.
> 
> SO any compiler that fail on the above are non-compliant.

I've got  the AARM with COR.1:2000 in front of me. There are no changes in 13.9, 
13.9.1, 13.9.2.
Thus a compiler failing to handle the above correctly has always been buggy.

Note that 'Valid exists for scalar objects only.