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From: Robert Dewar <robert_dewar@my-deja.com>
Subject: Re: Help Me Please :)
Date: 2000/03/29
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In article <8brm79$jm3$1@slb6.atl.mindspring.net>,
  Richard D Riehle <laoXhai@ix.netcom.com> wrote:
> I agree it is useful to track such things.  That is why I like
> the addition of Exception_Occurrence to the language in
> Ada.Exceptions.
>
>       when Some_Nasty_Error : Constraint_Error =>
>         Error_Manager.Log(Ada.Exceptions.
>           Exception_Information(Some_Nasty_Error));
>
> This is where Dr. Dewar and I differ.  I see this feature as
> important for applications such as command and control
> systems.  He sees it, as of our last discussion of the
> subject, as less important than I.

Well I am not quite sure what the disagreement is, but let
me make a couple of comments on the above code.

It is highly implementation dependent, on some implementations
it may give a useful symbolic traceback, on another, no output
at all, and on a third, may generate a complete core dump. The
output is "implementation defined", which means you know
absolutely nothing about what the above code does from a
portable point of view.

On a given compiler it may do something useful to you, but you
have to examine any such logging code wrt the implementation
you are using, and adjust the code accordingly. But in practice
most Ada 83 implementations provided facilities like this in
any case (actually many Ada 83 implementations provided much
more extensive capabilities, and the Ada 95 facilities are not
sufficient, we have had to add quite a bit to GNAT here, see
for example, GNAT.Exceptions.

Also, you hope that compilers have extended capabilities like
dumping the results of an exception EVEN if there are dependent
tasks that prevent propagation. Or dump exceptions that
otherwise terminate tasks silently.



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