Re: CALL, CALLP, & CALLB - for Hans -- RPG400-L


Hi Hans,

what about error handling and CALLP (it's a comment rather than question :)))

Take care,

Vanja


On Fri, 26 Feb 1999 boldt@ca.ibm.com wrote:

> 
> 
> 
> Patrick wrote:
> >I am trying to distinguish the differences in the CALLP & CALLB commands
> >vs. the CALL command in RPG IV. I am trying to locate a web site or
> >document that summarizes the differences between these and to give me some
> >ideas as when to use these.
> >
> >We use a LOT of CALLs to subprograms (verifying account numbers, returning
> >employee information, returning item file information). I assume that both
> >CALLP and CALLB will be faster than a CALL. Does anyone have any hints as
> >to best convert the subprogram to a module, and what prototypes should be
> >used for this?
> >
> >And if you know of a good website with code examples that are easy to
> >follow, please let me know.
> 
> Have you read the RPG IV Reference Manual and the RPG IV Programmers
> Guide?
> 
> First, CALLB is faster than CALL since it is calling something thats
> statically bound.
> 
> CALLP is a replacement for both CALL and CALLB in that it can do both
> static and dynamic calls.  When you use CALLP, you must code a procedure
> prototype in your D-Specs.  On the prototype, you can define either
> bound or dynamic call linkage.  Keyword EXTPROC is used to specify bound
> linkage and EXTPGM is used for dynamic linkage.  (The default is bound
> linkage.)
> 
> The main difference is that CALLP provides better error checking on the
> parameter types than CALL/CALLB.  It also provides additional function
> such as value and constant reference parameters.
> 
> Programs that you call currently using CALL or CALLB can easily be
> called using CALLP by defining a prototype for that program.  Just look
> at the types of the fields defined in the *ENTRY PLIST for the program
> and define the parameters in the prototype to match.  Note that type
> checking on a CALLP is much more rigorous than on a CALL, so you have
> to be careful defining the parameters.  For example, if you want to be
> able to pass character fields of different lengths or arrays with
> different numbers of elements, you need to specify OPTIONS(*VARSIZE).
> If certain parameters are optional, you need to specify OPTIONS(*OMIT)
> or OPTIONS(*NOPASS).
> 
> You don't have to change anything in the called program to be able to
> call it using CALLP.  If you want to take advantage of new language
> features, though, you could define a procedure interface for that
> program to replace the *ENTRY PLIST.  When adding new functionality,
> you could code that using sub-procedures.
> 
> When defining the prototypes for a module, the approach we recommend is
> to place the prototypes for a module in a /COPY member.  Include that
> /COPY member in the modules source as well as the source files of all
> other modules that call procedures in that module.
> 
> Cheers!  Hans
> 
> Hans Boldt, ILE RPG Development, IBM Toronto Lab, boldt@ca.ibm.com
> 
> 
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