Every time a CALL statement executes, it calls a C routine called "sub". This routine is passed the name of the called program and its USING parameters. You may modify this routine to recognize the call name that you want to assign to a C subprogram and perform the appropriate code. This routine is contained in the "sub.c" file.
The "sub" routine is passed two arguments: argc and argv. The argv parameter is an array of character pointers. The argc parameter is an integer count of the number of elements in the argv array. The first element in argv points to the call name exactly as it appears in the COBOL CALL statement. This name is terminated with a NULL character. The remaining elements of argv point to each of the USING arguments.
The "sub" function should check to see if the called name is one that should be handled in C. It can do this by comparing "argv[0]" with the desired routine name using the "strcmp" C library routine. If the routine is one that is not handled by a C subroutine, then "sub" should return a negative value. This indicates to runcbl that the CALL statement has not been fulfilled and that it should try to find a COBOL subprogram by that name. If the routine is handled by the "sub" function, then a zero should be returned. In this case, runcbl will assume that the CALL statement has been completed and it will continue with the next statement. Finally, if "sub" returns a positive value, then runcbl will execute a STOP RUN, returning the value to the operating system as runcbl's exit value.
See "sub.c" for an example of this interface.
When processing a USING parameter, note that the C subroutine must know what internal format the parameter uses. Also note, that in COBOL, literal values are not terminated by a NULL character. Thus, you should not treat a passed value as a C string unless the calling program ensures that the passed value is NULL terminated. This can be accomplished in the following fashion:
STRING "literal", LOW-VALUES, DELIMITED BY SIZE
INTO ITEM-1
CALL NAME-1 USING ITEM-1.
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