Ed,
By the 'rules' express in this thread, if the caller places one of the
literals at x'04', he then *must* place the back-pointer at offset
x'80'. Is that not what you and others have been saying?
If the back-pointer *must* be at x'80', then the area from x'08'-x'7F'
*must* therefore be a valid area for the caller to store R14-R12 as
double-words.
Tony Thigpen
Ed Jaffe wrote on 1/27/22 11:05 AM:
On 1/27/2022 6:24 AM, Tony Thigpen wrote:
The answer seems to be that, while not fully known, if one of the
literals is present, the called program can safely know that they have
at least the x'08' to x'7F' are to start double-word registers. Do you
at least agree to that conclusion?
Whaaaat?! You're saying that you want to depend on what a previous
callee put at +4 to determine something about the length of the caller's
save area? That makes no sense!
Suppose that previous callee put an incorrect literal at +4 (e.g., F4SA)
and then abended attempting to use bytes that didn't exist in the
caller's save area. And, after recovering from that abend, the caller is
now calling you. Why would you wish to depend on that incorrect value at
+4?
Why must we have these "Rube Goldberg" discussions in the first place?
Can't we just follow the linkage conventions as documented and leave it
at that?
--
Phoenix Software International
Edward E. Jaffe
831 Parkview Drive North
El Segundo, CA 90245
https://www.phoenixsoftware.com/
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