> -----Original Message-----
> From: IBM Mainframe Discussion List On Behalf Of Bill Fairchild
>
> What you showed will do a STH of some register somewhere, but not
necessarily R4. For it to be R4,
> you need another blank character after the IEFUJV, or else delete the
AL1(7) byte, or change the CL8
> to CL9, etc. Adding 3 more blank characters would allow this code to
store R4 somewhere and then not
> skip over the execution of the next instruction after the IEFUJV
eye-catcher.
>
> Bill Fairchild
Indeed, if an executable instruction is intended to follow the DC, and
if the assembler back then ensured to assemble instructions to begin on
a halfword address, it would seem that the sequence shown would attempt
to store Reg0 somewhere because of the x'00' slack byte following the
second blank shown. It also seems to imply that that "next" instruction
was a two-byte instruction; else "strange and wonderful" things would
occur immediately thereafter.
Of course, it's necessary to assume that in this example, R15 contains
the address of the B instruction....
-jc-
>
> -----Original Message-----
> From: IBM Mainframe Discussion List [mailto:IBM-MAIN@bama.ua.edu] On
Behalf Of Rick Fochtman
> Sent: Friday, August 19, 2011 1:56 PM
> To: IBM-MAIN@bama.ua.edu
> Subject: Re: Last card reader?
>
>
--------------------------------------<snip>----------------------------
-----
> And I've had a few doozies - one program should have had an LA
instruction that got keypunched as an
> LH; the error was discovered fourteen years later when IBM changed a
control block around so the
> referenced field wound up on an odd boundary.
>
------------------------------------<unsnip>----------------------------
----
> This one took me 8 months to isolate:
>
> B 12(,R15) X'47F0F00C'
> DC AL1(7),CL8'IEFUJV' X'07C9C5C6E4D1E54040'
>
> Ended up doing a STH of R4 at what appeared to be a totally random
address. Only failed when the
> clobbered storage was executed. :-)
>
> Our systems staff had its own sandbox to play, and test, all changes,
but that guy's "under-
> confidence" was such that he wouldn't even test on our sandbox.
>
> Rick
>
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