RE: Calling similiar (overloaded) procedure that has *nopass *omit in the parameter

Here is a clip from the V5R4 RPG manual.

--------------------------------------
if OPTIONS(*NOPASS) is coded and you choose not to pass the parameter, the
procedure must check that the parameter was passed before it accesses it.

If the unpassed parameter is accessed in the called program or procedure,
unpredictable results will occur.
--------------------------------------




-----Original Message-----
From: Dennis [mailto:iseries@xxxxxxxxxxxx]
Sent: Wednesday, March 09, 2011 2:28 PM
To: RPG programming on the IBM i / System i
Subject: Re: Calling similiar (overloaded) procedure that has *nopass *omit
in the parameter

I didn't se Paul questioning Barbara's knowledge/expertise. (Maybe I
missed that.) I _did_ see him ask a valid question about where this may be
documented. One could argue, I suppose that we should 'just know,' but I,
for one, would disagree in this case since rules have changed to a point.

"Scott Klement" <rpg400-l@xxxxxxxxxxxxxxxx> wrote:

hi Paul,

Here's a program that should demonstrate the problem. Not sure why
you're arguing the point (do you really think you know more about this
than the lead developer of the RPG compiler?!) but I've known about
this
for QUITE a long time (longer even than ILE has existed) and I can
vouch
for her.

But, anyway... try this program, you will (most likely) see the
problem:

H DFTACTGRP(*NO)

D myProc PR
D parm1 10a
D parm2 10a options(*nopass)

D one s 10a inz('blah')
D two s 10a inz('blah')
/free
// For this call, %ADDR() will PROBABLY (but not guaranteed)
// work, because nothing in the parm stack has been used yet.

myProc(one);

// This call passes both parameters, so will work.

myProc(one: two);

// This call will PROBABLY (but not guaranteed) show that
// only one parm was passed, but %addr(parm2) won't be null.

myProc(one);

return;
/end-free


P myProc B
D PI
D parm1 10a
D parm2 10a options(*nopass)
D count s 10i 0
D msg s 52a
/free
count = %parms();
msg = 'You passed ' + %char(count) + ' parms.';
dsply msg;

if %addr(parm1) = *null;
dsply ('parm1 = *NULL');
else;
dsply ('parm1 <> *NULL');
endif;

if %addr(parm2) = *null;
dsply ('parm2 = *NULL');
else;
dsply ('parm2 <> *NULL');
endif;
/end-free
P E

When I call this, I get:

CALL MYPGM

DSPLY You passed 1 parms.
DSPLY parm1 <> *NULL
DSPLY parm2 = *NULL
DSPLY You passed 2 parms.
DSPLY parm1 <> *NULL
DSPLY parm2 <> *NULL
DSPLY You passed 1 parms.
DSPLY parm1 <> *NULL
DSPLY parm2 <> *NULL

Note that on the final call, it says you've passed only 1 parameter
(which makes sense, since that's what the code does) but parm2<>*NULL.



On 3/9/2011 8:28 AM, Morgan, Paul wrote:

I'm curious where in the V5R4 documentation it mentions that using

%addr() on a *NOPASS parameter is unreliable? With my testing on
program subprocedures it works. Maybe with further testing it won't.
Maybe it won't work with a service program procedure. The RPG
documentation (reference and user guide) talks about using %addr() on
an *OMIT parameter but no mention of results on a *NOPASS parameter.

Paul Morgan

Principal Programmer Analyst
IT Supply Chain/Replenishment

-----Original Message-----
From: rpg400-l-bounces@xxxxxxxxxxxx

[mailto:rpg400-l-bounces@xxxxxxxxxxxx] On Behalf Of John McKay

Sent: Wednesday, March 09, 2011 1:35 AM
To: RPG programming on the IBM i / System i
Subject: Re: Calling similiar (overloaded) procedure that has*nopass

*omitinthe parameter

Barbara,

Lucky programmers document and test, test and document. They

also

read the documentation and the code.

Regards,
John McKay mba

On 08/03/2011 23:00, Barbara Morris wrote:

On 2011/3/8 3:18 PM, Morgan, Paul wrote:

Have you tried to check the address of a *nopass parameter if it
wasn't passed? I get *NULL when I check in my test program and the
program doesn't break.

You've been unlucky then. If you were lucky, you would have seen a
non-null pointer that just happened to be lying around where your
program was looking for it, and your program would have broken

because

it thought the parameter had actually been passed.

Sometimes programs and procedures that access unpassed parameters

can

work for years, and then something changes about what happens before

the

program or procedure gets called, and *boom*, you get an error.

Everything might seem to work fine until you demo it to your boss,

or

until just after it goes into production, or until just before you

go on

vacation, or ...

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