RE: Cancel & Condition Handlers (was: File update after abnormal program termination) -- RPG400-L

I guess what I had in mind was an application I have in which any I/O errors
are logged, and then an email is sent to me, and then the user is notified
about it and then the application is shut down.  Works nicely, but only
handles I/O errors.  Everything else gets the normal exception handling
which isn't so gentle.

> -----Original Message-----
> From: bmorris@ca.ibm.com [SMTP:bmorris@ca.ibm.com]
> Sent: Friday, February 22, 2002 12:11 PM
> To:   rpg400-l@midrange.com
> Subject:      RE: Cancel & Condition Handlers (was: File update after
> abnormal program termination)
>
>
> >From: "Smith, Nelson" <NSmith@lincare.com>
> >Date: Fri, 22 Feb 2002 10:24:31 -0500
> Reply-To: rpg400-l@midrange.com
> >
> >Has anyone implemented a generic or set of Cancel and/or Condition
> Handlers
> >to use across an entire application and what would such an animal look
> like=
> >?
> >Is there a list somewhere of all possible conditions a handler can
> handle?
> >I know, RTFM.  At this point it's just a general question, not a real
> >project I'm getting into.
>
> Nelson, if by "handle" you mean "make it go away", then for a generic
> condition handler (or any condition handler for that matter) the list
> of conditions it can handle should be empty, in my opinion.  It can be
> dangerous to handle conditions with an ILE condition handler, because
> it causes the failing procedure to continue at the next MI instruction
> rather than the next HLL instruction.  If this is a "store" instruction,
> you now have bad data in the target variable.  The scariest part of
> going to the next MI instruction is that what instruction is next can
> change from release to release or even PTF to PTF, and what may be
> benign one day can be destructive the next.
>
> Safe things for condition handlers to do are
> - look at the condition and do some cleanup or reporting tasks, but
>   then let the language's exception handling take over
> - as above, but also promote (change) the exception into something
>   else (maybe your own message with nicer wording)
>
> Condition handlers are called for any exception (escape, notify and
> status), so there's probably no list of conditions they can handle.
>
> Barbara Morris
>
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