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From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada
Subject: Re: Is Text_IO.Put_Line() thread-safe?
Date: Thu, 21 Jun 2012 14:01:16 -0500
Organization: Jacob Sparre Andersen Research & Innovation
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Date: 2012-06-21T14:01:16-05:00
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"Robert A Duff" <bobduff@shell01.TheWorld.com> wrote in message 
news:wccy5npwxmh.fsf@shell01.TheWorld.com...
> "J-P. Rosen" <rosen@adalog.fr> writes:
>
>> Asynchronous raising of exceptions was in preliminary Ada, the issue was
>> studied, and removed for Ada 83.
>
> Not really.  It was renamed to be "abort".  The semantics of
> "abort" in Ada 83 are essentially the same as the semantics
> of T'Failure in preliminary Ada.
>
> In all Ada implementations I have worked on (which is a lot),
> abort is implemented internally via a special exception that
> is invisible to user code.

Really? No wonder we spent so much time on "abort"! :-)

There are no exceptions in our tasking implementation. There is a special 
entry that takes an exception_occurrence that gets called in the exception 
handler of a rendezvous (and all rendezvous have such a handler for all 
exception, added by the compiler if necessary); that's used to generate the 
needed replication of the exception. Abort is handled by a lot of code 
implementing the "abnormal" state; some of it shares the mechanism for 
finalizating a task upon completion.

I don't know what happens if an exception is raised in the "abnormal" state, 
I wouldn't expect it to be special.

                                         Randy.