From: Geoff Keating <geoffk@geoffk.org>
To: Alexandre Oliva <aoliva@redhat.com>
Cc: dewar@gnat.com (Robert Dewar)
Subject: Re: Bug in loop optimize (invalid postinc to preinc transformation)
Date: Thu, 28 Dec 2000 14:32:00 -0000 [thread overview]
Message-ID: <jm1yusp47z.fsf@geoffk.org> (raw)
In-Reply-To: <orsnn89u6j.fsf@guarana.lsd.ic.unicamp.br>
Alexandre Oliva <aoliva@redhat.com> writes:
> On Dec 28, 2000, dewar@gnat.com (Robert Dewar) wrote:
>
> > then this is defined only if the resulting pointer remains within the
> > same object, or in the csae of arrays it can go just past the end. Overflow
> > per se does not arise with pointers because of this stricter rule.
>
> Only if the compiler guarantees that no array will ever be placed
> across the wrapping boundary.
Since 0 is not a valid pointer---that is, no pointer to an object
should ever compare equal to 0---this makes pointers a case of
unsigned integers for which overflow is not permitted.
I know that there are 32-bit architectures on which GCC runs in which
it's perfectly possible that an array will be placed across
0x80000000.
--
- Geoffrey Keating <geoffk@geoffk.org>
next prev parent reply other threads:[~2000-12-28 14:32 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2000-12-28 5:40 Robert Dewar
2000-12-28 12:21 ` Alexandre Oliva
2000-12-28 14:32 ` Geoff Keating [this message]
2000-12-28 15:22 ` Tim Hollebeek
2000-12-28 22:20 ` Dave Korn
2000-12-29 0:52 ` Richard Henderson
2000-12-29 1:51 ` Tim Hollebeek
-- strict thread matches above, loose matches on Subject: below --
2000-12-31 8:30 dewar
2001-01-03 0:52 ` Jamie Lokier
2000-12-29 18:43 dewar
2000-12-30 15:18 ` Toon Moene
2000-12-28 20:33 dewar
2000-12-28 1:14 Richard Kenner
2000-12-27 22:40 Robert Dewar
2000-12-29 18:36 ` Jamie Lokier
2000-12-27 3:04 Bug in loop optimize (TREE stage) David Korn
2000-12-27 15:42 ` Bug in loop optimize (invalid postinc to preinc transformation) Peter Osterlund
2000-12-27 19:55 ` Alexandre Oliva
2000-12-27 21:09 ` Torbjorn Granlund
2000-12-27 21:20 ` Alexandre Oliva
2000-12-27 22:24 ` Jamie Lokier
2000-12-31 8:25 ` Andreas Schwab
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