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From: "tsv at solvo dot ru" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/24178] GCC 4.0/4.1 generates code that produces unaligned access exceptions
Date: Tue, 04 Oct 2005 05:59:00 -0000 [thread overview]
Message-ID: <20051004055903.6298.qmail@sourceware.org> (raw)
In-Reply-To: <bug-24178-3055@http.gcc.gnu.org/bugzilla/>
------- Comment #3 from tsv at solvo dot ru 2005-10-04 05:59 -------
(In reply to comment #2)
> (In reply to comment #0)
>
> > The offset of "p5" member is 25 bytes, but compiler thinks that "p5" is aligned
> > in "foo" function
>
> You are casting a pointer to a Foo* that doesn't have proper alignment for
> a Foo. This is undefined behavior, so anything can happen, including an
> unaligned access at some later point. This is not a gcc bug.
Correct me if I wrong, but loading long from passed pointer to char minus 4
is not correct too. I could agree if the compiler did substruct 25 from pointer
and added 24 and that did load (it does it in not optimized version). In this
case it would me me who passed incorrect pointer (in fact DEC C did that) and I
agree with compiler that warns me about it.
I can't test right now, but if I recall gcc 3.4 didn't have such problems.
>
> > It might be not very good coding practice, but it taken from Mozilla source.
>
> Please report it there instead.
>
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24178
next prev parent reply other threads:[~2005-10-04 5:59 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-10-03 18:36 [Bug c/24178] New: " tsv at solvo dot ru
2005-10-03 19:03 ` [Bug middle-end/24178] " pinskia at gcc dot gnu dot org
2005-10-03 20:48 ` falk at debian dot org
2005-10-04 5:59 ` tsv at solvo dot ru [this message]
2005-10-04 7:32 ` falk at debian dot org
2005-10-04 7:36 ` [Bug middle-end/24178] [4.0/4.1 regression] " falk at debian dot org
2005-10-14 13:30 ` tsv at solvo dot ru
2005-10-15 15:04 ` falk at debian dot org
2005-10-22 21:59 ` pinskia at gcc dot gnu dot org
2005-10-22 22:42 ` falk at debian dot org
2005-10-23 18:22 ` tsv at solvo dot ru
2005-10-23 18:29 ` [Bug target/24178] " pinskia at gcc dot gnu dot org
2005-10-30 23:32 ` pinskia at gcc dot gnu dot org
2005-11-02 7:13 ` rth at gcc dot gnu dot org
2005-11-02 7:43 ` rth at gcc dot gnu dot org
2005-11-02 18:20 ` rth at gcc dot gnu dot org
2005-11-02 22:26 ` tsv at solvo dot ru
2005-11-03 0:33 ` rth at gcc dot gnu dot org
2005-11-03 0:34 ` rth at gcc dot gnu dot org
2010-08-06 19:33 ` ubizjak at gmail dot com
2010-08-06 19:44 ` [Bug target/24178] [4.6 Regression] " ubizjak at gmail dot com
2010-08-06 19:46 ` [Bug target/24178] [4.0/4.1 regression] " rguenth at gcc dot gnu dot org
2010-08-06 20:00 ` ubizjak at gmail dot com
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