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On 9 Feb 2020, at 23:25, Dave Wade <dave.g4ugm@...> wrote:

To see what CMS mods there are in the n-Pack logon to maint and type

CMSACC

This accesses the CMS modifications disk as "B" and then do

EE HRCMODS MEMO B

You will see HRC371DS implements this change. So

MEMO HRC371DS B1

Will contain details of how this is implemented.

Dave

-----Original Message-----
From: [email protected] <[email protected]> On Behalf Of
rvjansen@...
Sent: 09 February 2020 20:15
To: [email protected]
Subject: Re: [h390-vm] building BREXX

One piece of the puzzle is this:

There is no DMSREX module in VM/370. René Ferland confirmed this.

The RESLIB command is used to load BREXX TEXT into resident storage.
RESLIB itself is not documented in the official VM/370 documents, I just read
the System Programmer’s guide and the CMS Commands and Macros guide.
It is documented by HELP RESLIB, and was written by Andrew Hanushevsky,
Langmuir Laboratory, Cornell University in 1980.

The HELP RESLIB (MORE command states that every program that is loaded in
this way, needs to be serially reusable (which is one step above/below
reentrant/reenterable, depending on how you see it). This means BREXX
may not have compiler initialized static variables. I wonder if GCC has an
option to make sure it does not, and I would be more at ease if it was
reentrant.

The loading is done for each VM/user by an exec called SYSPROF EXEC. I
found out by doing a RESLIB DELETE GCCLIB, RESLIB DELETE DMSREX for my
MAINT user, and trying to make it work again afterwards. It did not, because
the botched builds left a wrong SYSPROF EXEC on MAINT’s A disk, or that is
what I think.

As soon as I found this, and deleted the one on the A disk, the one on the V
disk is executed at logon and the info is correct again. Interestingly, the
modules GCCLIB and DMSREXX are loaded at different (virtual) address in
different userid’s. Then I remembered that the release notes for Sixpack 1.2
say:

? During initialization, CMS executes "SYSPROF EXEC" before
executing "PROFILE EXEC". This allows you to ensure certain commands are
always executed for users.


These commands are the RESLIB commands for BREXX; it then chains
SYSPROX EXEC for the mecaff programs.

I’ll keep you posted on more progress, for example whe I find out how the
exec processor finds it is a REXX exec, which is rather anachronistic for this
level of VM.

best regards,

René Jansen.