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: How to tell whether program finalization can be suppressed
Date: Wed, 27 Dec 2017 15:49:53 +0000
Organization: A noiseless patient Spider
Message-ID: <lyk1x8dvby.fsf@pushface.org>
References: <lyzi729lh2.fsf@pushface.org>
Mime-Version: 1.0
Content-Type: text/plain
Injection-Info: reader02.eternal-september.org;
 posting-host="cec595888f8967b41b3a8a8d6edeae89";
	logging-data="20608"; mail-complaints-to="abuse@eternal-september.org";
	posting-account="U2FsdGVkX185qvDjdCHFVYH/2mkW56Mhy6Zxk/53P7k="
User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/25.3 (darwin)
Cancel-Lock: sha1:Tp/YO8oEQIO2eWvtKkoeFMdAfX0=
	sha1:oOGzPKihRitOFSMyazljxB98/eo=
Xref: reader02.eternal-september.org comp.lang.ada:49656
Date: 2017-12-27T15:49:53+00:00
List-Id: <comp.lang.ada>

Simon Wright <simon@pushface.org> writes:

> In Cortex GNAT RTS[1] (a Ravenscar RTS), I've wanted to support
> finalization (at present, I have the possibly GNAT-specific
> restriction No_Finalization).
>
> Unfortunately, as reported in PR66205[2], without No_Finalization and
> in the presence of other RTS-limiting features, gnatbind generates
> binding code which won't compile.
>
> I need to find a way of determining whether the RTS actually needs
> program-level finalization (that is, finalization called on program
> exit), because that's where the bad code is generated.
>
> Clearly, if the program never exits, there will be no need for
> program-level finalization.
>
> Amongst other things, I can test for specific restrictions, and I'm
> wondering whether No_Task_Termination would be appropriate for this?
> (I'm assuming that the environment task mustn't terminate, even if the
> main program exits; and in this RTS, exceptions can't be propagated).
>
> [1] https://github.com/simonjwright/cortex-gnat-rts
> [2] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66205

To close this thread, which has had many interesting and helpful
responses:

I proposed a patch based on these ideas, which worked for me but wasn't
acceptable for AdaCore; some automated tests failed (I don't know the
details. I guess a Ravenscar program in such a context is allowed to
terminate & finalize itself!).

The working fix turned out to be to tell the compiler that the "standard
library" (not quite sure what that is) is supported (which I don't think
it is): this is the only way to get current gnatbind to generate
compilable code when it sees finalization. Then, one needs additional
dummy variables which would control aspects of a full RTS (e.g. wide
character encoding, locking policy, task dispatching policy, to name but
a few).

Thaks for the help.