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From: "Douglas A. Gwyn" <DAGwyn@null.net>
To: 9fans@cse.psu.edu
Subject: Re: [9fans] Bounds checking bug ifcall(2) functions
Date: Mon, 19 Nov 2007 10:14:52 +0000	[thread overview]
Message-ID: <473E4CC5.9FF9EDDA@null.net> (raw)
In-Reply-To: <c03ff139454ba47fe3365466ffc8a5e4@quanstro.net>

erik quanstrom wrote:
> i don't think it means you have to allocate an extra byte. there's
> no requirement that you may indirect the "one-past the end" address.

No, but (a) the arithmetic has to work properly, including
relations like "p < q", and on some architectures merely
loading a past-the-segment-end address into an address
register can cause an invalid-address trap.  Thus, the C
implementation when it lays out the data objects in
segments may have to make sure that the segment contains
an extra unused byte at the end, just so its address will
be valid.


      reply	other threads:[~2007-11-19 10:14 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-11-09 22:20 [9fans] Bounds checking bug in fcall(2) functions Erik Dalén
2007-11-09 22:42 ` Charles Forsyth
2007-11-09 23:01   ` Erik Dalén
2007-11-09 23:41     ` Charles Forsyth
2007-11-10 17:55     ` Russ Cox
2007-11-16 10:18     ` [9fans] Bounds checking bug ifcall(2) functions Douglas A. Gwyn
2007-11-16 10:38       ` erik quanstrom
2007-11-19 10:14         ` Douglas A. Gwyn [this message]

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