In this particular case, why not allow the mainline to have full addressabilty and drop the base at the point where it's no longer valid?
-- Shmuel (Seymour J.) Metz http://mason.gmu.edu/~smetz3 עַם יִשְׂרָאֵל חַי ________________________________________ From: IBM Mainframe Assembler List <[email protected]> on behalf of Farley, Peter <[email protected]> Sent: Wednesday, November 8, 2023 5:13 PM To: [email protected] Subject: Re: Internal Exit Routine Handling The “why” of using adcons instead of direct instruction reference with my suggested USING setup: Because the mainline USING that I suggested limits the use of R11 to just the mainline code and data, the labels on your exit routines are not addressable using R11 since they are outside of that range of addresses. Loading an A(exitname) constant means the assembler can resolve the adcon value to “offset from start of code” because it knows where that name is in the object code, but it won’t let you use that name directly in LA or LAY because there is no base register that covers the area where the exit name is coded. Then the loader can fully resolve the adcon value at program load time because the ESD entry is “CSECT start + offset”. Peter From: IBM Mainframe Assembler List <[email protected]> On Behalf Of Dave Clark Sent: Wednesday, November 8, 2023 4:49 PM To: [email protected] Subject: Re: Internal Exit Routine Handling "IBM Mainframe Assembler List" <[email protected]> wrote on 11/08/2023 04:31:21 PM: > If in the mainline code you need the address of any exit routine, > use “L Rx,=A(exit name)” rather than simply “LA Rx,exitname”. I get the rest of what you said. But could you explain why the above is needed? It seems related to using a V address constant for an external subroutine which is resolved by the linkage editor. To start with, I guess that this is because of limiting the range of the code base? Does the linkage editor still get involved in adjusting the =A constant after the fact? I do have the following in the mainline code when I set up to call to the IBM system utility. Obviously, I could simply change this as you describe but I wouldn't know why -- and I always like to know why. ;-) LA R2,IPTEXIT GET EXIT RTN ADDRESS LA R3,IPTAREA GET I/O AREA ADDRESS STM R2,R3,INLCIPTA PUT ADDRESSES IN CONTROL BLOCK LA R2,LSTEXIT GET EXIT RTN ADDRESS LA R3,LSTAREA GET I/O AREA ADDRESS STM R2,R3,INLCLSTA PUT ADDRESSES IN CONTROL BLOCK LA R2,PCHEXIT GET EXIT RTN ADDRESS LA R3,PCHAREA GET I/O AREA ADDRESS STM R2,R3,INLCPCHA PUT ADDRESSES IN CONTROL BLOCK Sincerely, Dave Clark -- This message and any attachments are intended only for the use of the addressee and may contain information that is privileged and confidential. If the reader of the message is not the intended recipient or an authorized representative of the intended recipient, you are hereby notified that any dissemination of this communication is strictly prohibited. If you have received this communication in error, please notify us immediately by e-mail and delete the message and any attachments from your system.
