I thought of a better solution, perhaps a bit clearer (and telling the
assembler exactly what you want it to do):
Leave your mainline USING as it is, covering the entire module. Leave your
LA,exitname instructions as they are.
At the end of all mainline code and subroutines and private data:
END_OF_MAIN_CODE_AND_CONSTANTS DS 0H
After each label EXITX that starts an exit, code:
DROP R11
USING (EXITX_START,EXITX_END),R12
USING (MAIN_CSECT_NAME,END_OF_MAIN_CODE_AND_CONSTANTS),R11
At the end of each EXITX routine, code:
EXITX_END DS 0H
DROP R12
Now you are telling the assembler exactly which register to use for which
labels in the program.
Peter
From: IBM Mainframe Assembler List <[email protected]> On Behalf
Of Farley, Peter
Sent: Wednesday, November 8, 2023 5:57 PM
To: [email protected]
Subject: Re: Internal Exit Routine Handling
Oops, Tony is correct – you can use LARL even if the exit labels are outside of
the mainline USING I suggested. That’s a much better solution than my adcon
suggestion. If you decide to use my USING suggestions then change your LA’s to
LARL’s
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Oops, Tony is correct – you can use LARL even if the exit labels are outside of
the mainline USING I suggested.
That’s a much better solution than my adcon suggestion. If you decide to use
my USING suggestions then change your LA’s to LARL’s for the exit addresses.
Peter
From: IBM Mainframe Assembler List
<[email protected]<mailto:[email protected]>> On
Behalf Of Tony Harminc
Sent: Wednesday, November 8, 2023 5:25 PM
To: [email protected]<mailto:[email protected]>
Subject: Re: Internal Exit Routine Handling
On Wed, 8 Nov 2023 at 17:13, Farley, Peter <
[email protected]<mailto:[email protected]>>
wrote:
> The “why” of using adcons instead of direct instruction reference with my
> suggested USING setup:
>
> Because the mainline USING that I suggested limits the use of R11 to just
> the mainline code and data, the labels on your exit routines are not
> addressable using R11 since they are outside of that range of addresses.
>
> Loading an A(exitname) constant means the assembler can resolve the adcon
> value to “offset from start of code” because it knows where that name is in
> the object code, but it won’t let you use that name directly in LA or LAY
> because there is no base register that covers the area where the exit name
> is coded. Then the loader can fully resolve the adcon value at program
> load time because the ESD entry is “CSECT start + offset”.
>
In the case where the routines are in the same assembly/CSECT, but don't
have addressibility via a register, LARL is your friend. For that matter
LARL is generally useful in all sorts of such cases. For example, where you
have a main routine and some sort of exits or callbacks that don't get
passed the original base register value, in old-style coding you might need
something like:
BALR Rx,EXIT
USING EXIT,Rx
L Rn,=A(MAIN)
USING MAIN,Rn
to establish a base. Now you can use
LARL Rn,MAIN
USING MAIN,Rn
to get the main base back.
Tony H.
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