Enterprise COBOL for z/OS, Version 4.2, Programming Guide

You can set procedure-pointer and function-pointer data items only by using format 6 of the SET statement.

Procedure pointers are data items defined with the USAGE IS PROCEDURE-POINTER clause.
Function pointers are data items defined with the USAGE IS FUNCTION-POINTER clause.
In this information, "pointer" refers to either a procedure-pointer data item or a function-pointer data item.

• Another COBOL program that is not nested.
  For example, to have a user-written error-handling routine take control when an exception condition occurs, you must first pass the entry address of the routine to CEEHDLR, a condition-management Language Environment callable service, so that the routine is registered.
• A program written in another language.
  For example, to receive the entry address of a C function, call the function with the CALL RETURNING statement.
  It will return a pointer that you can either use as a function pointer or convert to a procedure pointer by using a form of the SET statement.
• An alternate entry point in another COBOL program (as defined in an ENTRY statement).

The SET statement sets the pointer to refer either to an entry point in the same load module as your program, to a separate load module, or to an entry point that is exported from a DLL, depending on the DYNAM|NODYNAM and DLL|NODLL compiler options.
Therefore, consider these factors when using these pointer data items:

• If you compile a program with the NODYNAM and NODLL options and set a pointer item to a literal value (to an actual name of an entry point), the value must refer to an entry point in the same load module.
  Otherwise the reference cannot be resolved.


• If you compile a program with the NODLL option and either set a pointer item to an identifier that will contain the name of the entry point at run time or set the pointer item to a literal and compile with the DYNAM option, then the pointer item, whether a literal or variable, must point to an entry point in a separate load module.
  The entry point can be either the primary entry point or an alternate entry point named in an ALIAS linkage-editor or binder statement.


• If you compile with the NODYNAM and DLL options and set a pointer item to a literal value (the actual name of an entry point), the value must refer to an entry point in the same load module or to an entry-point name that is exported from a DLL module.
  In the latter case you must include the DLL side file for the target DLL module in the link edit of your program load module.


• If you compile with the NODYNAM and DLL options and set a pointer item to an identifier (a data item that contains the entry point name at run time), the identifier value must refer to the entry-point name that is exported from a DLL module.
  In this case the DLL module name must match the name of the exported entry point.

If you set a pointer item to an entry address in a dynamically called load module, and your program subsequently cancels that dynamically called module, then that pointer item becomes undefined.
Reference to it thereafter is not reliable.