Okay, let's run with this one. If program A has an entry, B, and the program is compiled with NAME(ALIAS), when the program is linked, there will be an entry for A and an entry for B as an ALIAS of A.
When A is executed, a statement in the program says SET XXXX TO ENTRY B where XXXX is defined as PROCEDURE-POINTER. Does a separate copy of the load module get loaded as B when this SET statement is executed or does the runtime simply gain access to the entry point B within the currently loaded version of A? If a separate copy of the load module is loaded as B, where is the recursion? If a separate copy of the load module is not loaded, I can see the recursion. C- Charles (Chuck) Hardee Senior Systems Engineer/Database Administration EAS Information Technology Thermo Fisher Scientific 300 Industry Drive | Pittsburgh, PA 15275 Phone +1 (724) 517-2633 | Mobile +1 (412) 877-2809 | FAX: +1 (412) 490-9230 [email protected] | www.thermofisher.com WORLDWIDE CONFIDENTIALITY NOTE: Dissemination, distribution or copying of this e-mail or the information herein by anyone other than the intended recipient, or an employee or agent of a system responsible for delivering the message to the intended recipient, is prohibited. If you are not the intended recipient, please inform the sender and delete all copies. -----Original Message----- From: IBM Mainframe Discussion List [mailto:[email protected]] On Behalf Of Mike Schwab Sent: Tuesday, August 09, 2016 12:29 PM To: [email protected] Subject: Re: How does COBOL detect a recursive call? http://www.ibm.com/support/knowledgecenter/SSLTBW_2.1.0/com.ibm.zos.v2r1.ieab100/reus.htm When you link edit, you indicate the re-usability of the program. When the program runs, it reuses the same program if re-entrant. Each use has a different set of registers and working storage. Serially reusable can be self modifying (storing into load module areas), but can be reused after completing. Needs a new copy for a simultaneous use. None means the program must be reloaded from disk for every use. When you run a program, the LOAD macro examines the directory and loads as appropriate. http://www.longpelaexpertise.com/ezine/ReentrantBeginners.php On Tue, Aug 9, 2016 at 9:59 AM, John McKown <[email protected]> wrote: > On Tue, Aug 9, 2016 at 9:40 AM, John McKown <[email protected]> > wrote: > >> This is a kind of curiosity question. Unless a COBOL program is compiled >> with the THREAD option and the RECURSIVE clause on the PROGRAM-ID, the >> program cannot CALL itself. I have also found out that if you use an ENTRY >> statement and the compile NAME(ALIAS), you cannot do a CALL of the alias >> from the "main" program either. E.g. if you have a PROGRAM-ID. A. and an >> ENTRY 'B', then you cannot CALL 'B' while running A. I am thinking this >> must be in some way related to the fact that 'A' and 'B' share the same >> WORKING-STORAGE area. But I was just wondering if anybody knows how this is >> implemented. Of course, it is probably likely to change between releases, >> so it's not something I could depend on. >> >> Why the interest? Because while talking with Chuck Hardee about having an >> LE condition handler in the same source member (as an ENTRY) as the main >> COBOL routine, we found that the run-unit will abend with a U4087-2 and >> some messages about recursive invocation. So as a test, I compiled a sample >> which got the U4087-2 with the THREAD option and RECURSIVE clause, and that >> ran successfully. However the THREAD option comes with some possibley nasty >> side restrictions. In particular, no INITIAL clause in the PROGRAM-ID >> sentence and, worse, no use of SORT / MERGE verbs. >> > > Well, here I am talking to myself again. At least I'm not, yet, into the 3 > way arguments with myself. But it turns out that I misread the manual. > RECURSIVE is required on the PROGRAM-ID if THREAD is used, but not vice > versa. So it appears that all I really need is the RECURSIVE clause on the > PROGRAM-ID and not the THREAD compile option. But I'm still mildly curious > about how COBOL detects recursion, if you know off-hand. > > -- > Klein bottle for rent -- inquire within. > > Maranatha! <>< > John McKown > > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, > send email to [email protected] with the message: INFO IBM-MAIN -- Mike A Schwab, Springfield IL USA Where do Forest Rangers go to get away from it all? ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
