Re: Ending a program from within a procedure

[Simon Coulter <shc@xxxxxxxxxxxxxxxxx>]

On 26/07/2005, at 8:26 AM, Paul Morgan wrote:

> All just because the exception handling model on the 400 (escape 
> messages)
> doesn't allow for automatic propagation up the call stack.

Not quite true. In an ILE environment exceptions are propagated up the 
call stack until a control boundary is reached.

> You either
> handle it at the target of the escape message or the system takes over 
> with
> some default handling.  Because of that model your subroutine has to 
> have
> knowledge of the top level entry point.  That's unnecessary cohesion 
> between
> the subroutine and the 'top level' point.

Not true. You can send to *PGMBDY plus 1 relative invocation level and 
know that the message will be sent to the caller of the program 
containing your sub-routine or procedure regardless of what program is 
the caller.

> Better would be the subroutine throwing an exception to it's caller 
> (where's
> the RPG THROW opcode?).  Let the caller decide to handle the exception 
> or if
> it's ignored it gets automatically bubbled up to it's own caller.

That's exactly what happens with ILE procedures but it stops at the the 
first control boundary. Easy solution is to have each program that 
starts a control boundary catch all exceptions. They can either handle 
them or throw them on. Eventually someone will either handle it or the 
system default handler will deal with it.

> Eventually it would then reach your 'top level' point that would 
> handle the
> exception. If it's not handled it would reach the top of the call 
> stack and
> get some default handling like ending the job or breaking on QSYSOPR.

Sounds like the above description. Easy enough to do with existing 
functions.

Regards,
Simon Coulter.
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