Calling between C++ and COBOL

The following tables describe the types of calls that are supported between C++ and COBOL when running with Language Environment®.

Table 1 shows which calls are supported from COBOL programs to C++ routines.
Table 2 shows which calls are supported from C++ routines to COBOL programs.

Within a given enclave containing ILC between COBOL and C++, the application may be structured in one of the following ways:

As a single statically-bound load module.
As a DLL application, with multiple DLL load modules, each containing DLL-enabled COBOL and C++ routines.
As an application using multiple load modules and using COBOL dynamic CALLs. In this case, all instances of C++ ILC must be statically-bound within the main load module. The only exception would be if extern "COBOL" or extern "C" is specified for all C++ functions called by COBOL that are in dynamically called load modules that do not contain any DLL routines that export functions or variables.
As an application using multiple load modules and using fetch.

Table 1. Support for calls from COBOL to C++
Caller	Call type	Target
Caller	Call type	C++ with extern "COBOL"	C++ with extern "C"	C++ without extern
VS COBOL II (1)	static	Yes with restrictions (2)	No	No
COBOL/370 (1)	static	Yes	No	No
COBOL (5) compiled with NODLL	static	Yes	Yes	No
VS COBOL II (1)	dynamic	No	No	No
COBOL/370 (1)	dynamic	No	No	No
COBOL (5) compiled with NODLL	dynamic	Yes (3)	Yes (3)	No
COBOL (6) compiled with DLL	CALL "literal" to a function within the module	Yes	Yes	No
COBOL (6) compiled with DLL	CALL "literal" to a function exported from a DLL	Yes (4)	Yes (4)	No
COBOL (6) compiled with DLL	CALL identifier to a function exported from a DLL	Yes (4)	Yes (4)	No
Note: When the caller is VS COBOL II or COBOL/370, all calls must be to void functions. Static calls are supported from VS COBOL II to C++ with extern "COBOL" in the following cases: The call is done in the main load module. The call is done in a load module whose entry point is a Language Environment-conforming program or routine that was called using COBOL dynamic call. The call is done in a module that was called using fetch. The call is done in a DLL that was called using DLL linkage. Dynamically called load modules cannot contain any DLL routines that export functions or variables. Use the binder DYNAM(NO) control statement to prevent marking the load module as a DLL. The XL C/C++ compiler may mark certain internal symbols as exported, resulting in the C++ executable being a DLL. To prevent the XL C++ compiler from doing this, use the NOEXPORT(NOSYS) compiler option. In this case, the C++ code can also be compiled with the XPLINK option. The XPLINK C++ code must reside in a separate module from the COBOL caller. COBOL for MVS™ & VM, COBOL for OS/390® & VM, or Enterprise COBOL for z/OS COBOL for OS/390 & VM or Enterprise COBOL for z/OS

Table 2. Support for calls from C++ to COBOL
Caller	Call type	Target
Caller	Call type	VS COBOL II or COBOL/370	COBOL (4) compiled with NODLL	COBOL (5) compiled with DLL
C++ with extern "COBOL"	function is within the module	Yes (1)	Yes	Yes
C++ with extern "C"	function is within the module	No	Yes	Yes
C++ without extern	function is within the module	No	Yes	No
C++ with extern "COBOL"	fetch	Yes (1, 2)	Yes (2, 3)	No
C++ with extern "C"	fetch	No	Yes (2, 3)	No
C++ without extern	fetch	No	No	No
C++ with extern "COBOL"	function is exported from a DLL	No	No	Yes (3)
C++ with extern "C"	function is exported from a DLL	No	No	Yes (3)
C++ without extern	function is exported from a DLL	No	No	No
Note: When the target of the call is VS COBOL II or COBOL/370, the called COBOL program must be declared as a void function. Fetched load modules cannot contain any DLL routines that export functions or variables. In this case, the C++ code can also be compiled with the XPLINK option. The XPLINK C++ code must reside in a separate module from the COBOL caller. COBOL for MVS & VM, COBOL for OS/390 & VM, or Enterprise COBOL for z/OS COBOL for OS/390 & VM or Enterprise COBOL for z/OS