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From: "sven.koehler at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/51628] __attribute__((packed)) is unsafe in some cases
Date: Tue, 10 Mar 2015 13:40:00 -0000 [thread overview]
Message-ID: <bug-51628-4-t4ZBqPFKv3@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-51628-4@http.gcc.gnu.org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=51628
--- Comment #24 from Sven <sven.koehler at gmail dot com> ---
Comment #4 mentions typedef int myint __attribute__((aligned(1)));
That shouldn't even work. The GCC documentation on Type Attributes mentions
that "The aligned attribute can only increase the alignment". It goes on to
mention the packed attribute, which can be used to decrease alignment. But as
far as I know, that attributes was designed for structs. Anyhow, it seems that
the aligned attribute is intended for increasing the alignment only - not for
decreasing.
Yet, when I checked __alignof(myint) with both gcc and clang, it was in fact
decreased from 4 to 1. Not sure why. That seems to contradict the
documentation.
prev parent reply other threads:[~2015-03-10 13:40 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-12-19 23:00 [Bug c/51628] New: " Keith.S.Thompson at gmail dot com
2011-12-19 23:17 ` [Bug c/51628] " Keith.S.Thompson at gmail dot com
2011-12-19 23:38 ` pinskia at gcc dot gnu.org
2011-12-20 0:43 ` Keith.S.Thompson at gmail dot com
2011-12-20 10:22 ` rguenth at gcc dot gnu.org
2011-12-20 10:54 ` ebotcazou at gcc dot gnu.org
2011-12-20 11:19 ` rguenther at suse dot de
2011-12-20 11:20 ` ebotcazou at gcc dot gnu.org
2011-12-20 11:34 ` rguenther at suse dot de
2011-12-20 11:57 ` ebotcazou at gcc dot gnu.org
2011-12-20 12:00 ` rguenther at suse dot de
2011-12-20 12:29 ` ebotcazou at gcc dot gnu.org
2011-12-20 13:11 ` jakub at gcc dot gnu.org
2011-12-20 13:29 ` rguenther at suse dot de
2011-12-20 17:45 ` ebotcazou at gcc dot gnu.org
2013-04-02 0:58 ` peter at axium dot co.nz
2013-04-02 8:30 ` rguenth at gcc dot gnu.org
2013-04-02 8:31 ` rguenth at gcc dot gnu.org
2013-04-02 20:21 ` peter at axium dot co.nz
2013-04-03 7:30 ` ebotcazou at gcc dot gnu.org
2013-04-03 7:55 ` rguenther at suse dot de
2013-04-03 8:51 ` ebotcazou at gcc dot gnu.org
2013-04-03 9:20 ` rguenther at suse dot de
2015-03-10 13:29 ` sven.koehler at gmail dot com
2015-03-10 13:40 ` sven.koehler at gmail dot com [this message]
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