RE: Large Return values (was Re: Variable Length Field Question)

I just did a (very) short article on this in my Midrange Developer
newsletter.
The solution is to pass parameters along with perhaps the length of the data
(if necessary). This will avoid temporary variables from being created and
returned. Also with a reference parm that will be updated, no temp variable
is created. 
For some large parameters that are passed by VALUE or CONST, you do get the
temp work variable being declared, and your data is copied to that temp
value which is subsequently passed to the subprocedure. You can't do
anything about this for VALUE parms, however for CONST parms, you can add
the OPTIONS(*VARSIZE) and the compiler will avoid creating a temp variable
and copying your data to it before passing. 

I know IBM is working on this but that doesn't help up now. It is
unfortunate that a similar issue was raised/red-flagged back in the late
1980s when IBM initially implemented the so called "String Opcodes" in
RPGIII. When SCAN/CAT/XLATE/CHECK came out, I ran a test using a 6000-byte
work field. The implementation of these opcodes was so poorly designed that
they actually created copies of your Factor 1, Factor 2 and Result field and
then did the operation and copied the data back to your variable. 
I was on the phone discussing it with the developer (how is now the RPG
Manager) and talked him into changing it. 
It is disappointing that something similarly poor in resource utilization
has made its way into such a vital part of RPG IV.
-Bob Cozzi


-----Original Message-----
From: rpg400-l-bounces@xxxxxxxxxxxx [mailto:rpg400-l-bounces@xxxxxxxxxxxx]
On Behalf Of Brad Stone
Sent: Thursday, May 20, 2004 7:47 AM
To: RPG programming on the AS400 / iSeries
Subject: Large Return values (was Re: Variable Length Field Question)

Ya, I've heard about this as well.  Is the suggestion then
to return pointers?  Does this also apply to passing
parameters that are large values, or just returning large
values?

Brad

On Thu, 20 May 2004 11:48:34 +1200
 "Peter Connell" <Peter.Connell@xxxxxxxxxxxxxxxxxxxx>
wrote:
> Brad,
> A warning on large variable length return values.
> 
> Previous responses I've had on this list by the IBM guys
> indicate that
> it appears the compiler has not been designed to
> accommodate these as
> well as might be hoped.
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