RE: Passing pointers as parms

[Joel Fritz <JFritz@xxxxxxxxxxxxxxxx>]

Maybe it was something like this:

You have a data structure in your calling program you want to update in the
called program.  If you pass a pointer, which appears to be legal and well
behaved in the very limited test I just ran, all you do is copy the data
structure definition into the called program and base it on the pointer
that's passed in.  It's the same thing you're doing with slightly and maybe
even inconseqentially fewer lines of code.  You are absolutely right that
passing by reference is passing by reference and that's the default in RPG.
Here's my test:

                     Calling program:

Fqsysprt   o    f   80        printer

D ptrtst2         pr                  extpgm('PTRTST2')

D pointer                         *

D

D datastruct      ds

D packed                         5p 0 inz(99999)

D char                           5    inz('five')

D

D ptrparm                         *   inz(%addr(datastruct))

C

C                   except    before

C                   callp     ptrtst2(ptrparm)

C                   except    after

C                   eval      *inlr = *on

Oqsysprt   e            before

O                                              'Before--packed = '

O                       packed        j

O                                           +1 'char = '

O                       char

O          e            after

O                                              'After--packed = '

O                       packed        j

O                                           +1 'char = '

O                       char



                      Called program:

D ptrtst2         pr

D pointer                         *

D

D ptrtst2         pi

D pointer                         *

D

D datastruct      ds                  based(pointer)

D packed                         5p 0

D char                           5

D

C                   eval      packed = 11111

C                   eval      char = 'after'

C                   eval      *inlr = *on


> -----Original Message-----
> From: Scott Klement [mailto:klemscot@klements.com]
> Sent: Tuesday, November 28, 2000 9:08 AM
> To: RPG400-L@midrange.com
> Subject: Re: Passing pointers as parms
> 
> 
> 
> If this is a program calling a program (within the same job) 
> the program
> _is_ (implicitly) passing a pointer...     Thats the way 
> parameters work,
> they're passed by "reference" (i.e. a reference to an address in main
> storage)
> 
> The exception to this, of course, is when using something 
> like QCMDEXC or
> SBMJOB...   
> 
> So I'm a bit confused as to why you want to pass a pointer 
> instead of the
> buffer directly?   if you really want to just pass the 
> pointer, you could
> do something like this:
> 
> Program 1:
> 
> D MyBuffer        S          32766A
> D pointer         S               *   inz(%addr(MyBuffer))
> D MyField         S              1A   based(pointer)
> C                   CALL      'PROGRAM2'
> C                   PARM                    MyField
> 
> 
> Program 2:
> 
> D pointer         S               *   
> D MyField         S              1A   
> D MyBuffer        S          32766A     based(pointer)
> C     *ENTRY        PLIST
> C                   PARM                    MyField
> C                   eval      pointer = %addr(MyField)
>  
> 
> But this would yield the same exact results as just passing "MyBuffer"
> directly... so why would you bother??
> 
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