Interlanguage Calls

When passing or receiving data from a program or procedure written in another language, it is important to know whether the other language supports the same parameter passing methods and the same data types as ILE RPG. RPG Parameter Passing Methods shows the different parameter passing methods allowed by ILE RPG and, where applicable, how they would be coded in the other the ILE languages. The table also includes the OPM RPG/400® compiler for comparison.

RPG Parameter Passing Methods

Table 1. Passing By Reference

Calling mechanism	Example
ILE RPG – prototype	rpgle D proc PR D parm 1A C CALLP proc(fld)
ILE C®	rpgle void proc(char *parm); proc(&fld);
ILE COBOL	rpgle CALL PROCEDURE "PROC" USING BY REFERENCE PARM
RPG – non-prototyped	rpgle C CALL 'PROC' C PARM FLD
ILE CL	rpgle CALL PROC (&FLD)

Table 2. Passing By Value

Calling mechanism	Example
ILE RPG – prototype	rpgle D proc PR D parm 1A VALUE C CALLP proc('a')
ILE C	rpgle void proc(char parm); proc('a');
ILE COBOL	rpgle CALL PROCEDURE "PROC" USING BY VALUE PARM
RPG – non-prototyped	N/A
ILE CL	N/A

Table 3. Passing By Read-Only Reference

Calling mechanism	Example
ILE RPG – prototype	rpgle D proc PR D parm 1A CONST C CALLP proc(fld)
ILE C	rpgle void proc(const char *parm); proc(&fld);
ILE COBOL	N/A1
RPG – non-prototyped	N/A
ILE CL	N/A

Note:

1. Do not confuse passing by read-only reference with COBOL’s passing BY CONTENT. In RPG terms, to pass Fld1 by content, you would code:

        C                   PARM      Fld1          TEMP

   Fld1 is protected from being changed, but TEMP is not. There is no expectation that the parameter will not be changed.

For information on the data types supported by different HLLs, consult the appropriate language manual.