RE: Cancel & Condition Handlers (was: File update after abnormal programtermination)

>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