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From: "rguenth at gcc dot gnu dot org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/27214] The C frontend introduces undefined pointer overflow
Date: Wed, 19 Apr 2006 15:31:00 -0000	[thread overview]
Message-ID: <20060419153154.31016.qmail@sourceware.org> (raw)
In-Reply-To: <bug-27214-10053@http.gcc.gnu.org/bugzilla/>



------- Comment #4 from rguenth at gcc dot gnu dot org  2006-04-19 15:31 -------
How's that "the same"?  Either you say that pointers follow unsigned integer
types in overflow behavior (quote me the standard for that) or explain why

     p + -4  is treated as  p + (char *)-4

but  p -  4  is treated as  p - (char *)4

which are different in overflow behavior as (char *) is "unsigned" as far as
the middle-end concerns.

I see 6.5.6/8 where it says

If both the pointer operand and the result point to elements of the same array
object, or one past the last element of the array object, the evaluation shall
not produce an overflow; otherwise, the behavior is undefined.


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |UNCONFIRMED
         Resolution|INVALID                     |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27214


  parent reply	other threads:[~2006-04-19 15:31 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2006-04-19 11:44 [Bug c/27214] New: " rguenth at gcc dot gnu dot org
2006-04-19 15:06 ` [Bug c/27214] " pinskia at gcc dot gnu dot org
2006-04-19 15:13 ` rguenth at gcc dot gnu dot org
2006-04-19 15:22 ` pinskia at gcc dot gnu dot org
2006-04-19 15:31 ` rguenth at gcc dot gnu dot org [this message]
2006-04-19 15:34 ` pinskia at gcc dot gnu dot org
2006-04-19 16:32 ` rakdver at gcc dot gnu dot org
2006-04-19 17:15 ` joseph at codesourcery dot com
2006-05-05  9:23 ` pinskia at gcc dot gnu dot org
2007-12-11  0:46 ` pinskia at gcc dot gnu dot org
2008-01-03 16:25 ` rguenth at gcc dot gnu dot org
     [not found] <bug-27214-4@http.gcc.gnu.org/bugzilla/>
2012-05-06  4:23 ` bugdal at aerifal dot cx
2012-05-07  9:21 ` rguenth at gcc dot gnu.org
2021-03-25 14:11 ` rguenth at gcc dot gnu.org

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