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For information on the data types supported by different HLLs, consult the appro-
priate language manual.
Table 11. RPG Parameter Passing Methods
Passing By Reference
ILE RPG – prototype
D proc PR
D parm 1A
C CALLP proc(fld)
ILE C
void proc(char *parm);
proc(&fld);
ILE COBOL
CALL PROCEDURE "PROC" USING BY REFERENCE PARM
RPG – non-prototyped
C CALL 'PROC'
C PARM FLD
ILE CL
CALL PROC (&FLD)
Passing By Value
ILE RPG – prototype
D proc PR
D parm 1A VALUE
C CALLP proc('a')
ILE C
void proc(char parm);
proc('a');
ILE COBOL
CALL PROCEDURE "PROC" USING BY VALUE PARM
RPG – non-prototyped N/A
ILE CL N/A
Passing By Read-Only Reference
ILE RPG – prototype
D proc PR
D parm 1A CONST
C CALLP proc(fld)
ILE C
void proc(const char *parm);
proc(&fld);
ILE COBOL N/A
1
RPG – non-prototyped N/A
ILE CL N/A
Notes:
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.
|
Interlanguage Calling Considerations
| 1. When returning a 1-byte character value to or from ILE C or ILE CL, the
| returned value must be declared in a special way.
| For ILE CL, declare the returned value as a 2-byte character and then use
| %SUBSTRING to obtain the actual returned value.
|
DCL &RET2 TYPE(*CHAR) LEN(2)
| DCL &RET1 TYPE(*CHAR) LEN(1)
| CALLPRC RPGPROC RTNVAL(&RET2)
| CHGVAR &RET1 VALUE(%SUBSTRING(&RET2 1 1))
Chapter 10. Calling Programs and Procedures 147