From what I understand that you are right. However OP Mark indicates
there is a convention at his shop which allows the calling program (the
presumed allocater of the save area) to indicate to the called program
how large the save area is by using the F4SA eyecatcher. It's a
convention at his shop, but it's no different in my mind from
conventions that use enqueues or Compare and Swap to control access to
code paths. They only work if everyone plays by the rules.
On 2021-11-30 9:36 a.m., Charles Mills wrote:
Ah! I have not been clear on the convention. As I read it now, the called
program puts one of the FnSA strings in its *new* save area to indicate how
*it* previously stored the registers in its entry save area.
So the OP's premise is incorrect. A program cannot learn the length or
format of the incoming save area by examining it (although an FnSA string
there would give you a clue of what the caller was up to in general).
I am inferring that there is no way for a called program to determine
programmatically the length or expected format of the incoming save area. It
must be agreed upon by the two programs, or phrasing it differently, the
called program's save area expectations must be documented and respected by
the caller.
Am I right, or off (pardon the pun) base?
Charles
Gary Weinhold
Senior Application Architect
DATAKINETICS | Data Performance & Optimization
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-----Original Message-----
From: IBM Mainframe Assembler List [mailto:ASSEMBLER-LIST@LISTSERV.UGA.EDU]
On Behalf Of Peter Relson
Sent: Tuesday, November 30, 2021 5:39 AM
To: ASSEMBLER-LIST@LISTSERV.UGA.EDU
Subject: Re: Base-less macros
Steve Smith wrote:
And there are other bizarre ways to return without
restoring R14, which is not actually required by documented conventions.
Only restoring of AR14 and the high half of R14 are required (for
non-AMODE 64 cases), in general.
(Although I would guess that there are many violations of preserving the
high half of R14).
Some interfaces might define that they preserve R14 completely. Most do
not.
Mark Hammack wrote
I have a macro that switches between a regular (24/31 bit style)
save area and an extended (64 bit "F4SA") save area.
What do you mean by "switches between"? It is fine to use a different
style than the style your caller was using (as long as the savearea
provided is big enough to accommodate your needs), without having any care
about what was being used by your caller. The string at +4 identifies how
you saved your caller's registers.
Peter Relson
z/OS Core Technology Design
