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From: "ebotcazou at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/46488] [4.5 regression] server/core_filters.c from apache httpd 2.2.17 miscompiled at -O3
Date: Mon, 29 Nov 2010 13:34:00 -0000 [thread overview]
Message-ID: <bug-46488-4-mXqrvNjOHx@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-46488-4@http.gcc.gnu.org/bugzilla/>
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46488
--- Comment #22 from Eric Botcazou <ebotcazou at gcc dot gnu.org> 2010-11-29 12:09:30 UTC ---
> The pointers are constructed explicitly to never be dereferenced, only
> compared for equality; if a dereference exists it would be a bug, but
> I don't see one.
APR_RING_SPLICE_HEAD does such a dereference as far I can see:
#define APR_RING_SPLICE_HEAD(hp, ep1, epN, elem, link) \
APR_RING_SPLICE_AFTER(APR_RING_SENTINEL((hp), elem, link), \
(ep1), (epN), link)
#define APR_RING_SPLICE_AFTER(lep, ep1, epN, link) do { \
APR_RING_PREV((ep1), link) = (lep); \
APR_RING_NEXT((epN), link) = APR_RING_NEXT((lep), link); \
APR_RING_PREV(APR_RING_NEXT((lep), link), link) = (epN); \
APR_RING_NEXT((lep), link) = (ep1); \
} while (0)
#define APR_RING_NEXT(ep, link) (ep)->link.next
#define APR_RING_PREV(ep, link) (ep)->link.prev
> In the absence of such a smoking gun, can an C99 aliasing issue occur merely
> in handling pointer equivalence?
That would be a real compiler bug. :-)
You seem to be quite familiar with the httpd code. Can you pinpoint what is
miscompiled exactly in ap_core_input_filter or ap_core_output_filter? I'm not
saying that the miscompilation comes from this strict aliasing issue, only that
it might at this point.
next prev parent reply other threads:[~2010-11-29 12:10 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-11-15 18:55 [Bug c/46488] New: server/core_filters.c from apache httpd 2.2.17 does not produce good code with optimizations (-O) used on Solaris Sparc 64-bit lk0946 at att dot com
2010-11-16 8:37 ` [Bug middle-end/46488] [4.5 regression] server/core_filters.c from apache httpd 2.2.17 miscompiled with optimization ebotcazou at gcc dot gnu.org
2010-11-16 16:48 ` lk0946 at att dot com
2010-11-16 16:55 ` lk0946 at att dot com
2010-11-16 17:16 ` ebotcazou at gcc dot gnu.org
2010-11-17 0:10 ` lk0946 at att dot com
2010-11-17 0:31 ` ebotcazou at gcc dot gnu.org
2010-11-17 6:43 ` lk0946 at att dot com
2010-11-17 7:44 ` ebotcazou at gcc dot gnu.org
2010-11-25 16:06 ` rguenth at gcc dot gnu.org
2010-11-25 16:58 ` ebotcazou at gcc dot gnu.org
2010-11-26 22:34 ` lk0946 at att dot com
2010-11-26 23:09 ` [Bug middle-end/46488] server/core_filters.c from apache httpd 2.2.17 miscompiled with optimization -O3 rguenth at gcc dot gnu.org
2010-11-27 0:12 ` lk0946 at att dot com
2010-11-27 14:11 ` ebotcazou at gcc dot gnu.org
2010-11-27 23:59 ` LpSolit at netscape dot net
2010-11-28 9:49 ` [Bug middle-end/46488] [4.5 regression] server/core_filters.c from apache httpd 2.2.17 miscompiled at -O3 ebotcazou at gcc dot gnu.org
2010-11-28 13:22 ` ebotcazou at gcc dot gnu.org
2010-11-28 14:33 ` ebotcazou at gcc dot gnu.org
2010-11-29 11:05 ` jorton at redhat dot com
2010-11-29 11:59 ` ebotcazou at gcc dot gnu.org
2010-11-29 12:10 ` jorton at redhat dot com
2010-11-29 13:34 ` ebotcazou at gcc dot gnu.org [this message]
2010-11-29 14:03 ` rguenth at gcc dot gnu.org
2010-11-29 14:07 ` rguenth at gcc dot gnu.org
2010-11-29 14:31 ` jorton at redhat dot com
2010-11-29 14:41 ` rguenther at suse dot de
2010-11-29 21:39 ` pcpa at mandriva dot com.br
2010-11-30 7:47 ` ebotcazou at gcc dot gnu.org
2010-11-30 10:00 ` ebotcazou at gcc dot gnu.org
2010-11-30 10:57 ` rguenth at gcc dot gnu.org
2010-11-30 13:14 ` ebotcazou at gcc dot gnu.org
2010-11-30 15:18 ` ebotcazou at gcc dot gnu.org
2010-11-30 15:47 ` rguenther at suse dot de
2010-11-30 23:43 ` pcpa at mandriva dot com.br
2010-11-30 23:52 ` ebotcazou at gcc dot gnu.org
2010-12-01 10:13 ` rguenther at suse dot de
2010-12-01 12:15 ` ebotcazou at gcc dot gnu.org
2010-12-01 18:23 ` pcpa at mandriva dot com.br
2010-12-01 18:26 ` pcpa at mandriva dot com.br
2010-12-01 18:56 ` ebotcazou at gcc dot gnu.org
2010-12-01 21:54 ` ebotcazou at gcc dot gnu.org
2010-12-01 22:15 ` rguenth at gcc dot gnu.org
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