Re: Calling an RPG procedure with optional parameters fr om C code

["Osborn, Stephen" <stephen.osborn@xxxxxxxxx>]

I understood the difference in calling methods but I had implemented it
incorrectly.

In both my RPG & C prototypes I had an INT, whereas I should have had an INT
in the RPG one and a pointer to INT in the C one.

Once I had corrected the C prototype I was able to pass NULL and get it
working.


regards

Stephen Osborn
Financial Messaging & Integration
Misys Banking Systems
+44 (0)20 8486 1790
stephen.osborn@xxxxxxxxx
 

> -----Original Message-----
> From: c400-l-bounces+stephen.osborn=misys.com@xxxxxxxxxxxx 
> [mailto:c400-l-bounces+stephen.osborn=misys.com@xxxxxxxxxxxx] 
> On Behalf Of Scott Klement
> Sent: 01 November 2006 17:35
> To: C programming iSeries / AS400
> Subject: Re: [C400-L] Calling an RPG procedure with optional 
> parameters from C code
>
>
> RPG (by default) passes parameters by reference.  C (by 
> default) passes 
> parameters by value.   To pass a parameter by reference from 
> C, you put a 
> pointer on the prototype, and you pass the address of a 
> variable to that pointer.
>
> RPG's *OMIT is equivalent to passing a NULL pointer.
>
> So, from C, you simply pass NULL instead of a variable.  For example:
>
>
> prototype:
>
> void procname(char *param1, char *param2, char *param3, char *param4);
>
> code:
>
>     char val1[50], val2[50], val3[30], val4[50];
>
> // set the "val" variables to useful values here
>
>     procname( val1, NULL, val3, val4);
>
>     - or -
>
>     procname( NULL, val2, val3, val4);
>
>
> etc, etc.
>
> --
> Scott Klement  http://www.scottklement.com
>
> On Wed, 1 Nov 2006, Osborn, Stephen wrote:
>
> > I have RPG procedures where the first two parameters are 
> alternates, i.e.
> > values must be supplied for
> > param1, param3, param4, etc
> > or
> > param2, param3, param4, etc
> >
> > Using *OMIT I can call these in either mode from RPG, e.g.
> > callp procname(value1 : *OMIT : value3 : value4) or callp 
> > procname(*OMIT : value2 : value3 : value4)
> >
> > However I need to call some of these routines from some 
> legacy C code.
> > How do I specify in C (both the prototype and the code) 
> that param1 & 
> > param2 can be *OMIT'd?