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From: "W. Wesley Groleau (Wes)" <wwgrol@PSESERV3.FW.HAC.COM>
Subject: Alternative for AQS-95 para. 5.6.6
Date: 1996/04/04
Message-ID: <9604041602.AA04748@most>#1/1
X-Deja-AN: 145827669
sender: Ada programming language <INFO-ADA@VM1.NoDak.EDU>
comments: cc: ausnit@software.org
mailer: Elm [revision: 70.85]
newsgroups: comp.lang.ada
Date: 1996-04-04T00:00:00+00:00
List-Id: <comp.lang.ada>

Ada 95 Quality and Style carries forward the AQS-83 recommendation for
a safety check to prevent runaway looping or recursion.  The suggestion
is based on a counter and a limit check.  For real-time or safety critical
systems, a time limit may be more useful than a count.  Is there any
detail I've missed that would prevent using the following technique?

select
  delay Message_Interval * 0.75;
  raise Processing_Took_Too_Long;
then abort
  loop          |or| Recursive_Subprogram;
  end loop;     |  |
end select;

For Ada 83, please critique this:

Runaway.Start_Checking
             ( Check_ID   => Local_Check,  -- initializes ID which
<EITHER>       Time_Limit => <duration> ); -- contains discriminant
  <OR>         Iter_Limit => <count>    ); -- set by choice of start

[ while xxx | for xxx ] loop

   Runaway.Check ( Local_Check );
   -- raises Too_Much_Time or Too_Many_Times

Actual package Runaway is trivial to implement (and these are not my
original names).  But I'm not sure it's worth the time.  I had already
done the spec, but the file seems to have Run Away  :-)

The above is not any easier than the AQS approach, but it does have the
advantage of standardizing the technique for a whole project.

I know I can count on c.l.a for plenty of useful feedback (and probably
a flame or two).

--
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