This problem is complex in theory but simple in (your) practice.
Save/restore the lower halves with an STM/LM R14,R12,12(R13) on entry/exit.
Save and restore the upper half of any register you destroy using a save
area of your choice. The lower half of an otherwise unused register is good.
A
I'm a bit confused. I understand that there is no way to determine whether the
the caller has provided a 144-byte save area. However, I don't understand the
issue for running the forward chain, assuming that all called routines have set
the forward pointer, other than detecting the end of the
Especially since in z/OS it is now documented to pass a 144-byte save area to
the step-level "PGM=" executable. AFAIK, what size save area either the online
TMP or the batch TMP's (IKJEFTxx, IRXJCL) pass to Rexx is not documented.
I don’t know what z/VSE documents as the program-level save
On Friday I submitted this to IBM: Chapter 12. TSO/E REXX programming services
of z/OS 2.5 TSO/E REXX Reference, SA32-0972-50 does not specify whether
external functions are called with a 72-byte save area or a 144-byte save area.
--
Shmuel (Seymour J.) Metz
http://mason.gmu.edu/~smetz3
For both VSE and zOS, there is REXX documentation (VSE'sis at
https://www.ibm.com/docs/en/zvse/6.2?topic=packages-interface-writing-external-function-subroutine-code
that states that on entry to the called routine Register 13 contains the
address of a register save area. What it doesn't say is
"IBM Mainframe Assembler List" wrote on
01/24/2022 02:01:29 PM:
> When I'm following save area chains in a dump, starting with R13, I look
> at the second word. If it is an address, I know that the save area at
that
> address is a standard 72-byte save area. If it is F4SA, F5SA, F7SA, or
Replying to my own post to elaborate a little.
When a program allocates a save area to pass to its callers, there is only
one word, the second word, that it can use in the new save area.
Everything else is reserved for the called program. The oldest documentation
for the standard 72-byte save
When you say that it "makes no sense", I think you mean that you don't
understand it.
The second word of a save area cannot be set by the caller. Or, rather,
if it is, it will be destroyed by the called program.
How does a program know how a caller will use the save area that is
passed to
If your program can be called by a program that you don't control, and that
doesn't document that it provides something more, you have to assume
that you re only provided a 72-byte save area.
There is no code that a program can provide in the first word of a save area
that could describe the
