Re: Fwd: GnuCOBOL call parameter problem.

[James K. Lowden]

On Sat, 6 Jun 2020 15:00:00 -0400
Ron Norman <rjn@inglenet.com> wrote:

I *do* appreciate your attention to this, Ron.  I haven't looked at
r3587, but I recognize the priority you gave it.  Thank you.  

What I want to forge is an agreement in principle about how C and Cobol
should interact. I'm not sure were there yet.  

> Parameters can be optional and the variable NUMBER-OF-CALL-PARAMETERS
> needs to be set correctly.

Variadic functions have been part of standard C since 1999.  

NUMBER-OF-CALL-PARAMETERS should be eliminated from libcob.  Any
function with an optional number of parameters should be defined as per
stdarg (3).   

Unused optional arguments are conventionally passed as a compile-time
constant, recognized by the called function.  One popular choice is a
NULL pointer.  

If you want to use NUMBER-OF-CALL-PARAMETERS from Cobol, and a helper
function like cobcall because you think that helps, or because that's
the MF way, that's fine.  Put it in the compiler.  Let's not let
concerns like that define the libcob API.  

> Also some parameters can be defined as ANY LENGTH or ANY NUMERIC and
> for those to work the caller should be COBOL.

Define a C type to represent an array of ANY LENGTH, and another for
ANY NUMERIC, probably a discriminated union.  Pass the pointer.
Next?  

--jkl