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 how large that
save area is. My assumption would be that it is 18 fullwords, just
because it's not documented as being any different in VSE or z/OS and
REXX is a 31-bit application.
The fact that is not explicitly documented is troublesome, since as was
pointed out, the writer of the routine sets the requirements for the
users of the routine, and it would be reassuring to know that REXX
always meets those requirements.
On 2022-01-24 2:14 p.m., Dave Clark wrote:
"IBM Mainframe Assembler List"<[email protected]> 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
F8SA,
offset X'80' from R13 is the address of the save area, and I know what
format it is.
That is all well and good -- when you're looking at a dump. But
I'm given to understand that none of that information is helpful when a
called program receives control from a 2nd- or 3rd-party caller (i.e., any
caller not written on-site) in terms of being able to tell how much
storage the caller allocated for the savearea whose address is passed to
the called program. Now, if I've got that wrong, then please enlighten
me. Thanks.
Sincerely,
Dave Clark
Gary Weinhold
Senior Application Architect
DATAKINETICS | Data Performance & Optimization
Phone:+1.613.523.5500 x216
Email: [email protected]
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