RE: Multiple occurrence data structure anomaly -- RPG400-L

I find it hard to accept that "There is absolutely, positively no
difference in the way params are handled between RPG III and RPG IV."
when the observed behavior seems to disprove this. In both instances,
the programs were passing occurrence 50 of a MODS to a second program.
The second program populated occurrence 1. When first program was OPM it
found occurrence 1 populated. When the first program was ILE it found
occurrence 50 populated. Something is different somewhere!

Trevor Briggs
Analyst/Programmer
Lincare, Inc.
(727) 431-1246
TBriggs2@xxxxxxxxxxx

-----Original Message-----
From: rpg400-l-bounces@xxxxxxxxxxxx
[mailto:rpg400-l-bounces@xxxxxxxxxxxx] On Behalf Of Charles Wilt
Sent: Friday, July 05, 2013 1:39 PM
To: RPG programming on the IBM i (AS/400 and iSeries)
Subject: Re: Multiple occurrence data structure anomaly

"appeared to work just fine" is the key point...

There is absolutely, positively no difference in the way params are
handled
between RPG III and RPG IV.

However, automatic stack memory is allocated differently. Meaning you
can
be doing something wrong in RPG III and get lucky that the corrupted
memory
doesn't seem to effect you, but once you convert to RPG IV it can bite
you.

I had RPG III program passing a 3 character variable to another program
that was actually expecting a 5 character variable. Never had an issue,
till we converted them to RPG IV. Suddenly, we were corrupting memory
that
mattered. :)

HTH,
Charles

On Fri, Jul 5, 2013 at 11:44 AM, Briggs, Trevor (TBriggs2) <
TBriggs2@xxxxxxxxxxx> wrote:

The called program is an old program that I don't want to mess with,

and

expects (and populates) a MODS - not the way I would do it, but there

are.

The calling program is actually a file maintenance program template.

used to be OPM and appeared to work just fine. The template has been
upgraded to ILE and I was "lucky" enough to be the first person to use
it to create a new maintenance pgm. While testing the function that
calls the second program I encountered what appears to be a rule

change

between OPM and ILE functionality.

Trevor Briggs
Analyst/Programmer
Lincare, Inc.
(727) 431-1246
TBriggs2@xxxxxxxxxxx

-----Original Message-----
From: rpg400-l-bounces@xxxxxxxxxxxx
[mailto:rpg400-l-bounces@xxxxxxxxxxxx] On Behalf Of Alan Campin
Sent: Friday, July 05, 2013 11:36 AM
To: RPG programming on the IBM i (AS/400 and iSeries)
Subject: Re: Multiple occurrence data structure anomaly

I would agree with Jon. The question I have is why are you doing this?
it
sounds like you are trying to apply a monolith solution to a an ILE
world
but I might be misunderstanding what you are trying to do.

On Fri, Jul 5, 2013 at 7:54 AM, Briggs, Trevor (TBriggs2) <
TBriggs2@xxxxxxxxxxx> wrote:

Barbara,

You say:
" When you pass a MODS as a prototyped parameter, it passes the

current

occurrence. (As you've seen.)"

What I interpret you are saying is that ONLY the current occurrence

passed. Yet in practice, I see that if Pgm B populates occurrences 1

and

2, then Pgm A sees this on return. What is apparently happening is

that

the whole MODS is being passed (at least, is being returned), but
"positioned at" the current occurrence.

What I find really odd is that without the setting of the occurrence

to

1 before the call, when Pgm B populates occurrences 1 and 2, Pgm A

sees

the results in occurrences 50 and 51 - of a 50-occurrence MODS!

(This

is

observed by investigating the MODS with Debug - i.e. eval
MYMODS(50..51). Attempting to access occurrence 51 in the program
generates error RNX0122: OCCUR value is out of range, as one would
expect.)

Curious!

Trevor Briggs
Analyst/Programmer
Lincare, Inc.
(727) 431-1246
TBriggs2@xxxxxxxxxxx

-----Original Message-----
From: rpg400-l-bounces@xxxxxxxxxxxx
[mailto:rpg400-l-bounces@xxxxxxxxxxxx] On Behalf Of Barbara Morris
Sent: Wednesday, July 03, 2013 9:42 PM
To: rpg400-l@xxxxxxxxxxxx
Subject: Re: Multiple occurrence data structure anomaly

On 7/2/2013 2:46 PM, Briggs, Trevor (TBriggs2) wrote:

...
When control is returned to Pgm A, value is in
occurrence 50 of the MODS.

When you pass a MODS as a prototyped parameter, it passes the

current

occurrence. (As you've seen.)

I assume you didn't add the DIM keyword for the prototyped, so I

think

it makes sense that it would pass the current occurrence.

Just by the way, if you use an array of data structures (DIM keyword
instead of OCCURS keyword), you can distinguish between the whole

array

ARR, and an element ARR(i).

For sure I would recommend using a DS array for new code, since it's
easier (I think) to code array indexes than to manage occurrences.

But for existing code, it's not usually easy to change a MODS to a
DS-array, since it involves changing every reference to the

subfields.

For example, if a MODS named INFO was previously not qualified, and

INFO

was changed to a qualified ds array, the reference to subfield ADDR
would change from simply ADDR to INFO(index).ADDR.

--
Barbara
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the

contents of this message.
All personal messages express views solely of the sender, which are

not to

be attributed to Lincare Holdings Inc., and may not be copied or
distributed without this disclaimer.
If you received this message in error, please notify us immediately at
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