From mboxrd@z Thu Jan  1 00:00:00 1970
From: dewar@gnat.com (Robert Dewar)
To: aoliva@redhat.com, egcs@tantalophile.demon.co.uk
Cc: denisc@overta.ru, dkorn@pixelpower.com, gcc@gcc.gnu.org, peter.osterlund@mailbox.swipnet.se
Subject: Re: Bug in loop optimize (invalid postinc to preinc transformation)
Date: Wed, 27 Dec 2000 22:40:00 -0000
Message-id: <20001228063958.B325234D80@nile.gnat.com>
X-SW-Source: 2000-12/msg00791.html

<<Overflow of unsigned integers has defined behaviour -- they wrap.  The
question is, what rule applies to pointer comparisons?
>>

This is a malformed question. Any pointer increment is constrained 
to require that the resulting pointer be valid. Wrapping is simply
not an issue.

If p points to a valid address in an allocated array, then P+1 is also
valid, and there is no question of wrap. But P+2 may be beyond the
array and therefore ill-defined, and this has nothing to do with wrapping.