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From: Simon Wright <simon@pushface.org>
Newsgroups: comp.lang.ada
Subject: Re: Strange bug in GNAT
Date: Wed, 02 Jul 2014 21:12:06 +0100
Organization: A noiseless patient Spider
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Date: 2014-07-02T21:12:06+01:00
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Natasha Kerensikova <lithiumcat@instinctive.eu> writes:

> After a lot of experimentation, I found the following workaround, which
> is committed:
>
>          when others =>
>             begin
>                return Error_Page
>                  (AWS.Messages.S405,
>                   Dispatcher.DB.Query.Data.Error_Template);
>             end;
>       end case;
>
> How can an anonymous block change anything?
[...]
> At this point, I'm completely lost on how to proceed. I would love to
> report the bug, so that hopefully it might eventually be fixed, but
> without a smallish reproducer I don't dare bothering AdaCore.

Back when I was working on a supported project, I had a somewhat similar
problem with a deeply-nested loop; AdaCore suggested using an anonymous
block around some of the inner levels, which turned out to be a good
workround.

I suppose that the block resets some of the compiler internals, enough
to prevent the problem manifesting itself.

I don't think you should worry too much about the size of the
reproducer; if they're interested they'll look, if not, not. But it
might be best to supply all the source needed to compile the problematic
unit (in a zip archive, for example).

Is there any chance that you can reproduce the problem using GNAT GPL?
You stand a *much* better chance of getting the problem looked at if so.