[GnuCOBOL-users] Interfacing COBOL with C

[Simon Sobisch]

The following thread was originally posted to the bug mailing list (the
last messages under "Bug-GnuCOBOL Digest, Vol 17, Issue 5") and is
hereby "forwarded" to this, more appropriate, list

Simon

Am 04.08.2018 um 13:13 schrieb Ron Norman:
> FYI, There was a fair bit of work that I put into C <--> COBOL interface
> a while ago, but this was done in the reportwriter branch and I don't
> think it has all been merged into the trunk yet.
> 
> What I do is generate a a small C 'main' routine that is then link with
> the 1st COBOL module: Example:
> 
> extern void tsp();
> extern void tipMainEntry();
> extern void c_tiprtn();
> int
> main(int argc, char **argv)
> {
>     /*  GnuCOBOL  */
>     cob_init (0,(void*)0);
>     tipMainEntry(tsp,argc,argv,(void*)0,(void*)0);
>     c_tiprtn();
>     exit(0);
>     tsp();
>     return 0;   
> 
> 
> 
> On Fri, Aug 3, 2018 at 10:20 PM, Michael Potter <address@hidden
> <mailto:address@hidden>> wrote:
> 
>     I dug into the cobcrun code and saw they were copying the
>     COB_LIBRARY_PATH into a separate environment.
> 
>     I coded that in my .c file _something_ like this:
> 
>        (void) cob_setenv ("COB_LIBRARY_PATH",
>     getenv("COB_LIBRARY_PATH"), 1);
>        (void) cob_setenv ("COB_PRE_LOAD", "UNDATE", 1);
> 
>        LibHandle = dlopen("MYPROG.so", RTLD_NOW);
> 
>        cob_init();  // Added per James' suggestion.
> 
>        ProgramEntry = (ProgramEntryType)dlsym(LibHandle, "MYPROG");
> 
>        ProgramEntry();
> 
>     If anyone has a good idea of what I should change please speak up. 
>     If I don't hear anything I will code up a minimal test case and post it.
> 
>     One issue I have with James' suggestion is it seemed to imply that I
>     needed to do cob_init() after dlopen, but will I need to do a dlopen
>     before every cobol call.
> 
>     My code is structured such that c calls COBOL calls c calls COBOL
>     calls c ....
> 
> 
> 
> 
>     On Fri, Aug 3, 2018 at 3:12 PM James K. Lowden
>     <address@hidden <mailto:address@hidden>> wrote:
> 
>         On Wed, 1 Aug 2018 23:21:44 -0400
>         Michael Potter <address@hidden <mailto:address@hidden>> wrote:
> 
>         > libcob: user-defined FUNCTION 'UNDATE' not found
>         > when I attempt to load the COBOL program using my own dlopen in my
>         > own c program (I am not using cobcrun).
>         >
>         > I suspect that COB_LIBRARY_PATH is part of cobcrun and
>         therefore not
>         > used in my c program.
> 
>         Are you calling cob_init after dlopen and before calling any cobol
>         function? 
> 
>         I would expect COB_LIBRARY_PATH to affect the Cobol runtime support,
>         not cobcrun per se. 
> 
>         --jkl
> 
> 
> 
> 
> 
> -- 
> Cheers
> Ron Norman