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From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada
Subject: Re: Barrier re-evaluation issue with GNAT 4.3.2
Date: Sat, 10 Oct 2009 00:41:38 -0500
Organization: Jacob Sparre Andersen
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Date: 2009-10-10T00:41:38-05:00
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"Jeffrey R. Carter" <spam.jrcarter.not@spam.acm.org> wrote in message 
news:h9rco8$u58$1@news.tornevall.net...
> Robert A Duff wrote:
>>
>> Pragma Detect_Blocking will cause GNAT to raise Program_Error.
>> If you want to write portable code, you should use this
>> pragma.
>
> I thought there would be a way to make GNAT be an Ada compiler, but a 
> quick look at the secret documentation didn't find it.

GNAT does some weird things, but this isn't one of them. Pragma 
Detect_Blocking is standard Ada 2005 (added for the Ravenscar profile). It 
should be the default, but it isn't because various real-time people who 
ought to know better don't want to pay the miniscule cost of the check. [I 
think the check should be the default with the possibility of check 
suppression -- which hardly ever would be used. But some people think 
possible deadlocks are a better outcome. Bah!] Because of that, almost all 
Ada compilers will behave as GNAT does in this case. If you want portable 
Ada code (at runtime), you need to include the pragma -- for *all* 
compilers, not just GNAT. (If you are doing pure Ada 95, you are out of 
luck, unfortunately.)

                                              Randy.