It was a (not the only) common coding technique "in the old days" to put the fields referenced by a subroutine at the end of that subroutine. If the last field were an odd length then if the next subroutine began with label EQU * you ended up with the alignment problem referenced in these posts. Nowadays putting data near instructions is a terrible technique never minding alignment because it drives the hardware's cache management crazy. Actually you code use that technique now and avoid both alignment and caching problems through the use of LOCTR.
Charles -----Original Message----- From: IBM Mainframe Assembler List [mailto:ASSEMBLER-LIST@LISTSERV.UGA.EDU] On Behalf Of Schmitt, Michael Sent: Tuesday, June 2, 2020 9:18 AM To: ASSEMBLER-LIST@LISTSERV.UGA.EDU Subject: Re: z/OS HLASM: EQU for statement labels Thank you for your replies. I too was originally taught to use DS 0H for a label statement, because it guaranteed halfword instruction alignment. But I recently started using EQU * because a) it seemed to be clearer as to the intent, and b) I figured that if your instructions weren't aligned you've got bigger problems. I hadn't considered someone intentionally embedding an odd size storage area in the instruction stream without taking care to realign. I may rethink this, perhaps with Charles Mills suggestion to use DS 0H at the start of routines but continue to use EQU * inside them. As for the question of stand-alone labels vs. putting the label on the next instruction, I like the stand-alone labels because it promotes maintainable code. You can put comments on the label, but more important is that you can code multiple labels for the same address. For example, if you have this kind of structure (begging Outlook not to collapse the leading spaces): if x if y do a endif else do b endif you can code one label for the first ENDIF and another for the ELSE. Then later if you want to insert more instructions immediately before the ELSE, it is very clear where to put them and none of the labels change. DXC Technology Company - Headquarters: 1775 Tysons Boulevard, Tysons, Virginia 22102, USA. DXC Technology Company -- This message is transmitted to you by or on behalf of DXC Technology Company or one of its affiliates. It is intended exclusively for the addressee. The substance of this message, along with any attachments, may contain proprietary, confidential or privileged information or information that is otherwise legally exempt from disclosure. Any unauthorized review, use, disclosure or distribution is prohibited. If you are not the intended recipient of this message, you are not authorized to read, print, retain, copy or disseminate any part of this message. If you have received this message in error, please destroy and delete all copies and notify the sender by return e-mail. Regardless of content, this e-mail shall not operate to bind DXC Technology Company or any of its affiliates to any order or other contract unless pursuant to explicit written agreement or government initiative expressly permitting the use of e-mail for such purpose. --.
