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!.POSTED!not-for-mail
From: Simon Wright <simon@pushface.org>
Newsgroups: comp.lang.ada
Subject: Re: GNAT bug with assertions
Date: Fri, 10 Aug 2018 17:16:13 +0100
Organization: A noiseless patient Spider
Message-ID: <lyd0uqyz76.fsf@pushface.org>
References: <a9ceb787-b964-4c53-91de-02bee039f6e5@googlegroups.com>
	<87y3dejlq9.fsf@adaheads.home>
Mime-Version: 1.0
Content-Type: text/plain
Injection-Info: reader02.eternal-september.org;
 posting-host="bc4d137d7dfc00b04ac666a40b6ff046";
	logging-data="5720"; mail-complaints-to="abuse@eternal-september.org";
	posting-account="U2FsdGVkX19qv3WN0TFHpcs2ZaeZn+at7Q9Pkva7gb8="
User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/25.3 (darwin)
Cancel-Lock: sha1:jdrx4p3DPs+DugnCRFCNGUX4kBs=
	sha1:lXghxkFavUtpRM03q45IG3tYb3g=
Xref: reader02.eternal-september.org comp.lang.ada:54128
Date: 2018-08-10T17:16:13+01:00
List-Id: <comp.lang.ada>

Jacob Sparre Andersen <jacob@jacob-sparre.dk> writes:

> AdaMagica wrote:
>
>> I would have expected that predicates are also checked on return
>> values as they are checked on parameters.  In the following test, no
>> exception is raised on call of funcction Wrong although it returns a
>> value not fulfilling the predicate.
>>
>> Is this a GNAT bug or my wrong expectation?
>
> It seems that your expectations are slightly off.

Or perhaps you, Jacob, have a later release of the compiler which has
this bug fixed?

> Contracts are only checked if the assertion policy is set to "Check".
> You can do that, either by configuring your compiler to have the
> assertion policy set to "Check", or by explicitly inserting:
>
>    pragma Assertion_Policy (Check);
>
> at the beginning of the units, which should have this assertion policy.

Or, in the case of GNAT, by giving -gnata: see
http://docs.adacore.com/gnat_ugn-docs/html/gnat_ugn/gnat_ugn/building_executable_programs_with_gnat.html#debugging-and-assertion-control

If Cristoph hadn't been using -gnata, the first check would have failed.

IMO this is a bug in GNAT, present in CE2018 and FSF GCC 8 (and maybe
earlier, didn't check).