RE: Calling an RPG procedure with optional parameters from C code

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

> RPG doesn't allow optional parameters to be specified before 
> required ones either.

That is true for *NOPASS but not for *OMIT

> When you pass *OMIT to an RPG IV procedure, what you are 
> really doing is passing a NULL pointer.

I am not sure that is true.  In the called procedure you test the field's
address for NULL, not its value.

> Thus, in your C/C++ program just make sure you pass a NULL 
> pointer for the *OMITted parameter.

I tried that, before I asked a question here, and it didn't work.  The
procedure prototype said that an INT is being passed as the first parameter
and when I specified a NULL there the module would not compile.

However I just changed the first parameter of the procedure prototype to be
pointer to INT and now NULL is acceptable and it is now working.

As RPG, by default, uses pass by reference, in a C procedure prototype the
declarations should be of type 'pointer to xxx'.  All the other fields in my
C procedure prototype were 'pointer to xxx' so that one was probably just a
typo.

Thanks for your assistance.

regards

Stephen Osborn
 

> -----Original Message-----
> From: rpg400-l-bounces@xxxxxxxxxxxx 
> [mailto:rpg400-l-bounces@xxxxxxxxxxxx] On Behalf Of Wilt, Charles
> Sent: 01 November 2006 15:56
> To: RPG programming on the AS400 / iSeries
> Subject: RE: Calling an RPG procedure with optional 
> parameters from C code
>
> RPG doesn't allow optional parameters to be specified before 
> required ones either.
>
> Note the RPG offers omittable (*OMIT) and optional (*NOPASS) 
> parameters.
>
> C/C++ don't have the equivalent of an omittable param.  Or 
> rather, all C/C++ parms passed by reference could be (are by 
> default) omittable.
>
> When you pass *OMIT to an RPG IV procedure, what you are 
> really doing is passing a NULL pointer.
>
> Thus, in your C/C++ program just make sure you pass a NULL 
> pointer for the *OMITted parameter.
>
> HTH,
>
> Charles Wilt
> --
> iSeries Systems Administrator / Developer Mitsubishi Electric 
> Automotive America
> ph: 513-573-4343
> fax: 513-398-1121
>