AW: CALLPRC parameter usage

Hi Mike,

first how your prototype looks like?

A temporary variable gets only declared if the parameter is passed by
constant reference (Keyword CONST in the prototype) and the passed parameter
is not an exact match of the parameter definition in the prototype. This is
independent from specifying the keyword OPTIONS(*VARSIZE). Specifying
OPTIONS(*VARSIZE) will accept any length up to the maximum length. Keep in
mind, not the duplicate is passed to the called procedure but only the
address of either the original field or the duplicate. For input only
parameters, a shorter length may not be a problem, because you cannot change
it. But for input/output parameters you have to check the incomming number
of bytes (with API CEEDOD) and only this number of bytes can be changed in
your program. Otherwise you'll change bytes that belong to other variables
in your global storage.

For CL-Procedures it's also possible to define prototypes that can be
embedded in RPG.
>From RPGIV reference:
"EXTPROC(*CL: 'MYPROC') specifies an external procedure that is written in
ILE CL, or an RPG procedure to be called by ILE CL. Use *CL if your program
uses return values with data types that CL handles differently from RPG. For
example, use *CL when prototyping an RPG procedure that is to be called by a
CL procedure when the return value is 1A."

When using a prototype for CL-Procedures, the parameter passing works as if
it would be a RPG procedure. In case of OPTIONS(*VARSIZE) you have to check
the incomming number of parameters in your CL procedure as you have to do it
in your RPG procedure.

When calling RPG-Procedures from CL, no parameter conversion can happen,
because there is no way to specify a prototype.

Mit freundlichen Gru?en / Best regards

Birgitta

"Shoot for the moon, even if you miss, you'll land among the stars."
(Les Brown)

-----Ursprungliche Nachricht-----
Von: rpg400-l-bounces@xxxxxxxxxxxx
[mailto:rpg400-l-bounces@xxxxxxxxxxxx]Im Auftrag von Mike Pantzopoulos -
(H/O)
Gesendet: Sonntag, 5. Marz 2006 10:20
An: RPG programming on the AS400 / iSeries
Betreff: RE: CALLPRC parameter usage


Ok. Last question (I hope).

I understood from the manual that the system converts the parameter passed
from the calling RPG into a temporary vatiable length field if the prototype
is declared as *varsize.  In the calling RPG, the parameter can be declared
as any length up to the prototype declaration. It's declared as a noraml
variable, and If that's the case, then why can't they convert the CL
variable in the same fashion and avoid this low-level explicitness?

-----Original Message-----
From: rpg400-l-bounces@xxxxxxxxxxxx
[mailto:rpg400-l-bounces@xxxxxxxxxxxx]On Behalf Of Simon Coulter
Sent: Friday, 3 March 2006 4:49 PM
To: RPG programming on the AS400 / iSeries
Subject: Re: CALLPRC parameter usage



On 03/03/2006, at 3:20 PM, Mike Pantzopoulos - (H/O) wrote:

> I found the problem with the &RETURN parameter in midrange and got
> that to work as well by extracting only the first byte. Is this some
> issue with the way the compiler returns a value through the procedure
> name that can't be mapped directly to how CL works internally?

It has nothing to do with how CL works internally. It has everything to
do with really dumb design.

When ILE CL was created the only other ILE language was C. C has the
rather stupid habit of widening parameters and return values. Thus
whoever implemented the CL CALLPRC tried to be compatible with C and
gave little or no thought to the possibility that other ILE languages
might be callable from CL in some future release.

This problem also exists when calling CL procedures from RPG. RPG has a
(relatively recently) provided options on the EXTPROC keyword to
control this behaviour. CL should have provided the same set of
options.

Regards,
Simon Coulter.
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