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=-1.9 required=5.0 tests=BAYES_00
	autolearn=unavailable autolearn_force=no version=3.4.4
Path: 
 eternal-september.org!reader01.eternal-september.org!reader02.eternal-september.org!news.eternal-september.org!mx02.eternal-september.org!.POSTED!not-for-mail
From: Jeffrey Carter <spam.jrcarter.not@spam.not.acm.org>
Newsgroups: comp.lang.ada
Subject: Re: How to get nice with GNAT?
Date: Sat, 22 Nov 2014 16:24:12 -0700
Organization: Also freenews.netfront.net; news.tornevall.net;
 news.eternal-september.org
Message-ID: <m4r5uf$8f0$1@dont-email.me>
References: <slrnm6u97f.nrc.lithiumcat@nat.rebma.instinctive.eu>
 <f132e71b-8852-40e7-b3f1-77ab3bb2526e@googlegroups.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=windows-1252
Content-Transfer-Encoding: 7bit
Injection-Date: Sat, 22 Nov 2014 23:24:01 +0000 (UTC)
Injection-Info: mx02.eternal-september.org;
 posting-host="6bb4f0a3c21c874c69dbcaa30e818f24";
	logging-data="8672"; mail-complaints-to="abuse@eternal-september.org";
	posting-account="U2FsdGVkX18Fet06kcPZPQXfO+dQaTJ/oo2AbFwqT2k="
User-Agent: Mozilla/5.0 (X11; Linux x86_64;
 rv:31.0) Gecko/20100101 Thunderbird/31.2.0
In-Reply-To: <f132e71b-8852-40e7-b3f1-77ab3bb2526e@googlegroups.com>
Cancel-Lock: sha1:h6pvmRRsvvf36idLoN30PwRGcY0=
Xref: news.eternal-september.org comp.lang.ada:23651
Date: 2014-11-22T16:24:12-07:00
List-Id: <comp.lang.ada>

On 11/22/2014 03:44 PM, brbarkstrom@gmail.com wrote:
> 
> One possibility is to get in the habit of putting exception handling
> messages in every procedure interface, as in
> 
> procedure DoSomething(stuff;
>                       OK      :    out Boolean;
>                       Err_Msg :    out Bounded_String);
> 
> if DoSomething throws an exception, the calling program can detect
> that OK is false and receive a message identifying the cause.

This is terrible advice. Boolean is a by-copy type; if the procedure call raises
an exception, then no value will have been copied out to the actual parameter.
Bounded_String may also be passed by copy.

This only works if you never raise exceptions, in which case you might as well
use a primitive language without exceptions.

-- 
Jeff Carter
"C++ is vast and dangerous, a sort of Mordor of
programming languages."
Jason R. Fruit
120