On Sat, 1 Jan 2011 17:39:51 -0500 "Robert A. Rosenberg" <[email protected]>
wrote:
:>At 12:01 -0700 on 01/01/2011, Paul Gilmartin wrote about Re: A bug or
:>a feature?:
:>>On Dec 30, 2010, at 10:05, Tom Marchant wrote:
:>>> <quote from HLASM V1R6 Language Reference>
:>>> 5.46.4.3 Range of an ordinary USING instruction
:>>> The range of an ordinary USING instruction (called the ordinary
:>>> USING range, or simply the USING range) is the 4096 bytes
:>>> beginning at the base address specified in the USING instruction,
:>>> or the range as specified by the range end, whichever is the
:>>> lesser. For long-displacement instructions, the range is the
:>>> addresses between (base_address-524288) and (base_address+524287)
:>>> </quote>
:>>> You'll notice that the range in not addressed at all for long
:>>> displacement instructions.
:>>That's bizarre. I wonder what rationale there might be for
:>>ignoring a range end explicitly coded by the programmer when
:>>the displacement is long.
:>Possibly due to the range being from the defined base address to the
:>defined range end (or Base+4095 in the absence of the definition).
:>For long instructions, while you could in theory define a cut-off
:>point (which could be enforced by the assembler) there is no way to
:>define a range that starts BEFORE the base.
You forgot, "with the current USING syntax".
A new value could be added to USING, i.e.,
USING (base,start,end)
or
USING (base,end[,start])
(for those who may object to the reordering which is compatible as USING only
supports an END value currently)
:> Thus the range is
:>Base-512K to Base+512K. Since it is a displacement off a base
:>register, why would you want to restrict the range? You would get a
:>protection error if you try to access data you should not have access
:>to (ie: It is a programming error to reference the location).
For the same reason that there is a END value in the USING right now.
--
Binyamin Dissen <[email protected]>
http://www.dissensoftware.com
Director, Dissen Software, Bar & Grill - Israel
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