RE: Getting into pointers

Sorry, I meant to replace wMrsAdh with MyDS.


Just to make things worse, or more interesting depending on how you look at it, MyDS will have this kind of structure :

MyDS
Field1
Field2
Field3 LIKEDS( otherDS ) DIM ( 100 )

As I'm incapable of calculating the size needed, I'm hoping %ALLOC ( %size(MyDS:*ALL)) will work on this kind of DS.

I think I like Stuart's suggestion as I'm passing back a pointer from PGM2 to tell PGM1 where to find the DS.

Thanks.

-----Message d'origine-----
De : rpg400-l-bounces@xxxxxxxxxxxx
[mailto:rpg400-l-bounces@xxxxxxxxxxxx] De la part de Charles Wilt
Envoyé : mercredi 12 août 2009 15:37
À : RPG programming on the IBM i / System i
Objet : Re: Getting into pointers

Using %alloc() is the right way.

But this doesn't make sense:
wLen = %LEN ( wMrsAdh ( 1 ));

where is wMrsAdh defined?

Then you use a "magic number" here, which is never a good idea.
MyPtr = %ALLOC ( wLen * 100 );

If you wanted to do it that way, a better idea would have
been the %elem() bif.

However, I would have just coded:

MyPtr = %ALLOC ( %size(MyDS:*ALL));


HTH,
Charles

On Wed, Aug 12, 2009 at 8:41 AM, David
FOXWELL<David.FOXWELL@xxxxxxxxx> wrote:

Hi,

I just wrote my first program ever that passed a pointer

from one program to another. I used it to access a data
structure in the calling program that was alimented by the
program being called. I won't explain why I did not just pass
the data structure as a parameter. Anyway, it seems to work.
I was a little surprised and found it good fun. However,
having rather stumbled upon the solution when it didn't work,
I ask the experts out there for confirmation :

Code simplified.
D PGM2 PR EXTPGM ( 'PGM2' )
D OutParm *


D MyDS DS LIKEDS ( gMyOtherDS )

DIM ( 100 )

D BASED ( MyPtr )
D MyPtr S *

/free

PGM2 ( MyPtr );

/end-free



This crashed because I understand I need to allocate

storage for MyPtr before the call.

So I inserted this and it worked :
wLen = %LEN ( wMrsAdh ( 1 ));
MyPtr = %ALLOC ( wLen * 100 );

Is this the right way to initialize the pointer?

Thanks.
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