Pointer concept in Cobol

sedireswarapu · New User Joined: 18 Jun 2008 Posts: 28 Location: India

Hi..
Am new to this pointer concept in Cobol programming and
in my project trying to send a Character pointer from C program to Cobol.

LINKAGE SECTION.
01 MYPOINTER USAGE IS POINTER.
01 MYCHAR-POINTER.
05 MYCHARS PIC X(20).

PROCEDURE DIVISION USING MYPOINTER,MYCHAR-POINTER.
SET ADDRESS OF MYCHAR-POINTER TO MYPOINTER

also tried

SET ADDRESS OF MYPOINTER TO MYCHAR-POINTER .. but no luck

As per above code, Cobol module will get Pointer in Linkage section and tries to assign it to a group Item. And i also tried to display the pointer as such but i see only some random numbers.

Am getting SOC4 abend while trying to Set the address.

Could you pls throw some light on this pointer handling in cobol.

CICS Guy · Posted: Wed Sep 24, 2008 6:05 pm

sedireswarapu · New User Joined: 18 Jun 2008 Posts: 28 Location: India

Sorry for the confusion.

Actually am doing :

PROCEDURE DIVISION USING MYPOINTER

and the MYCHAR-POINTER group item is declared in Workstorage division.
What am trying to do is :

1. printing the pointer content - its not working ( shows me some random number)

2. Trying to assign the MYPOINTER (usually COBOL gets pointer like VOID pointer) to a String of Chars variable.

Is it possible to assign a pointer ( in future i will be sending a structure pointer from C to COBOL and have to assign it to a group item to get the fields out of it ..) to a data item of similar type ?

Thanks.

hchinnam · New User Joined: 18 Oct 2006 Posts: 73

Can you try changing it as follows.

sedireswarapu · New User Joined: 18 Jun 2008 Posts: 28 Location: India

Thanks for your reply.

But it abends with SOC4 during the SET statement.

LINKAGE SECTION.
01 MYCHAR-POINTER.
05 MYCHARS PIC X(20).
01 MYPOINTER USAGE IS POINTER.

PROCEDURE DIVISION USING MYPOINTER.
DISPLAY "TESTING COBOL WITH POINTERS".
SET ADDRESS OF MYCHAR-POINTER TO MYPOINTER
DISPLAY "MYCHARS = " MYCHAR-POINTER.
GOBACK.

This cobol module is invoked from a C module

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#pragma linkage (TESTCOB,COBOL)
void TESTCOB (char*);
void main()
{
char *pName = "BALAJI";
printf ("Testing pointers with cobol\n");
printf ("Name : %s\n", pName);
TESTCOB(pName);
printf ("Exit\n");
}

At this point all am trying is to set the pointer that i get in the COBOL to another variable.. Since bcoz in future i will be sending STRUCTURE POINTER from C program and have to map that pointer in COBOL to a GROUP ITEM.

Not sure whether this is possible but this is my idea of doing things with COBOL on this design. Please help as this sounds very new to me but yet challenging ..

Thanks.

hchinnam · New User Joined: 18 Oct 2006 Posts: 73

Looks like MYPOINTER is not set.

Are you sure about the SYNTAX/OPTIONs of call from C to COBOL.

Because back when we tried doing similar thing between PL/I and COBOL, we used to mention some specific option, which signifies it is a call between different languages.

Robert Sample · Posted: Wed Sep 24, 2008 9:22 pm

Your program is violating COBOL standards:

CICS Guy · Posted: Wed Sep 24, 2008 9:52 pm

Robert Sample · Posted: Thu Sep 25, 2008 12:02 am

Actually, in this case it does not matter what the CALL has. Sriram's program has 2 01 levels in the LINKAGE SECTION. The PROCEDURE DIVISION is USING the second 01 level but not the first; trying to reference both LINKAGE SECTION 01 fields will cause the S0C4 because COBOL isn't setting up addressability for two fields.

Sriram: why do you think you need a pointer variable in COBOL? If your C program does a CALL to a COBOL routine and the CALL includes a struct, just define the LINKAGE SECTION in the COBOL program to include each item in the structure, then reference the items in your COBOL program. The PROCEDURE DIVISION USING <linkage section 01> establishes the addressability of the variables. I have tested this and passed data both ways successfully.

CICS Guy · Posted: Thu Sep 25, 2008 12:24 am

Robert Sample · Posted: Thu Sep 25, 2008 12:49 am

From the manual, LINKAGE SECTION description:

CICS Guy · Posted: Thu Sep 25, 2008 2:05 am

You can set the address of a linkage area to a working storage address, a record (FD) address or an address passed by a called/calling program and those ws & fd addresses do not need to be 01 levels.

That one passed argument is (if done correctly) an address. Setting the other linkage area to that address establishes addressability to it.

Picture the linkage section 01s as assembler DSECTs (just as the 01s in the FD are) and the 01s in working storage as CSECTs......

sedireswarapu · New User Joined: 18 Jun 2008 Posts: 28 Location: India

Thanks for all your suggestions.

Things i tried earlier:
1. Passed only one pointer arg from C and had two data items in Linkage

Now i have changed the linkage section to accept the pointer arg from C and now am trying to set it to a POINTER in WS section.

But my compilation keeps failing saying