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From: dennison@telepath.com
Subject: Re: Exception Propagation
Date: 1999/06/09
Message-ID: <7jluvt$lfr$1@nnrp1.deja.com>#1/1
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Date: 1999-06-09T00:00:00+00:00
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In article <m3wvxef8zw.fsf@mheaney.ni.net>,
  Matthew Heaney <matthew_heaney@acm.org> wrote:
> Robert Dewar <robert_dewar@my-deja.com> writes:
>
> > I would have preferred that an unhandled exception in a task
> > caused termination of the entire program, you can always get
> > the bizarre effect in the RM if you really want it by doing:
> >
> >       exception when others => null;
> >
> > at the outer level of a task
>
> I don't understand this comment.
>
> Given this task body:
>
>   task body T is
>     ...
>   begin
>     ...
>   exception
>     when others => null;
>
>   end T;
>
> Are you saying that if an exception occurs, that that exception
handler
> will cause behavior other than silent termination of task T?

I think you missed the subjunctive clause. He's talking about a
hypothecital scheme where termination of an Ada task via an
unhandled exception causes the entire program to terminate, not actual
Ada. In such a scheme, the *current* behavior of Ada programs (silent
termination) could be achieved by the code above.

The only way I can think of to implement Matt's suggestion would be to
indeed raise the exception in the parent task (in a non-determinstic
location) when a child task is terminated by it, as in my hypothetical
TERD language. :-)

--
T.E.D.


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