From: Thomas Zimmermann <tzimmermann@suse.de>
To: "Gustavo A. R. Silva" <gustavo@embeddedor.com>,
Jani Nikula <jani.nikula@linux.intel.com>,
Lucas Stach <l.stach@pengutronix.de>,
Russell King <linux+etnaviv@armlinux.org.uk>,
Christian Gmeiner <christian.gmeiner@gmail.com>,
David Airlie <airlied@linux.ie>, Daniel Vetter <daniel@ffwll.ch>,
Patrik Jakobsson <patrik.r.jakobsson@gmail.com>,
Joonas Lahtinen <joonas.lahtinen@linux.intel.com>,
Rodrigo Vivi <rodrigo.vivi@intel.com>,
Rob Clark <robdclark@gmail.com>, Sean Paul <sean@poorly.run>,
Dave Airlie <airlied@redhat.com>,
Gerd Hoffmann <kraxel@redhat.com>,
Hans de Goede <hdegoede@redhat.com>,
Eric Anholt <eric@anholt.net>,
VMware Graphics <linux-graphics-maintainer@vmware.com>,
Thomas Hellstrom <thellstrom@vmware.com>,
Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
Maxime Ripard <mripard@kernel.org>
Cc: etnaviv@lists.freedesktop.org, dri-devel@lists.freedesktop.org,
linux-kernel@vger.kernel.org, intel-gfx@lists.freedesktop.org,
linux-arm-msm@vger.kernel.org, freedreno@lists.freedesktop.org,
virtualization@lists.linux-foundation.org,
spice-devel@lists.freedesktop.org
Subject: Re: [PATCH][next] drm: Replace zero-length array with flexible-array member
Date: Mon, 9 Mar 2020 08:49:45 +0100 [thread overview]
Message-ID: <67c46a2b-8127-a4b7-c825-8cba6f28db8c@suse.de> (raw)
In-Reply-To: <138ff691-94b3-1ce5-e7fa-e6d7c436bf8e@embeddedor.com>
[-- Attachment #1.1: Type: text/plain, Size: 3000 bytes --]
Hi Gustavo
Am 03.03.20 um 19:20 schrieb Gustavo A. R. Silva:
>
>
> On 2/25/20 08:17, Jani Nikula wrote:
>> On Tue, 25 Feb 2020, "Gustavo A. R. Silva" <gustavo@embeddedor.com> wrote:
>>> The current codebase makes use of the zero-length array language
>>> extension to the C90 standard, but the preferred mechanism to declare
>>> variable-length types such as these ones is a flexible array member[1][2],
>>> introduced in C99:
>>>
>>> struct foo {
>>> int stuff;
>>> struct boo array[];
>>> };
>>>
>>> By making use of the mechanism above, we will get a compiler warning
>>> in case the flexible array does not occur last in the structure, which
>>> will help us prevent some kind of undefined behavior bugs from being
>>> inadvertently introduced[3] to the codebase from now on.
>>>
>>> Also, notice that, dynamic memory allocations won't be affected by
>>> this change:
>>>
>>> "Flexible array members have incomplete type, and so the sizeof operator
>>> may not be applied. As a quirk of the original implementation of
>>> zero-length arrays, sizeof evaluates to zero."[1]
>>>
>>> This issue was found with the help of Coccinelle.
>>>
>>> [1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
>>> [2] https://github.com/KSPP/linux/issues/21
>>> [3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour")
>>>
>>> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
>>> ---
>>> drivers/gpu/drm/etnaviv/etnaviv_gem.h | 2 +-
>>> drivers/gpu/drm/gma500/intel_bios.h | 2 +-
>>> drivers/gpu/drm/i915/display/intel_vbt_defs.h | 4 ++--
>>> drivers/gpu/drm/i915/gt/intel_lrc.c | 2 +-
>>> drivers/gpu/drm/i915/i915_gpu_error.h | 2 +-
>>
>> Please split out the i915 changes to a separate patch.
>>
>
> Sure thing. I can do that.
I think each driver deserves it's own patch. Makes backporting easier.
Best regards
Thomas
>
>>> drivers/gpu/drm/msm/msm_gem.h | 2 +-
>>> drivers/gpu/drm/qxl/qxl_cmd.c | 2 +-
>>> drivers/gpu/drm/vboxvideo/vboxvideo.h | 2 +-
>>> drivers/gpu/drm/vc4/vc4_drv.h | 2 +-
>>> drivers/gpu/drm/vmwgfx/vmwgfx_page_dirty.c | 2 +-
>>> drivers/gpu/drm/vmwgfx/vmwgfx_surface.c | 2 +-
>>> include/drm/bridge/mhl.h | 4 ++--
>>> include/drm/drm_displayid.h | 2 +-
>>> include/uapi/drm/i915_drm.h | 4 ++--
>>
>> Not sure it's worth touching uapi headers. They're full of both [0] and
>> []. Again, please at least split it to a separate patch to be decided
>> separately.
>>
>
> Yeah, it's worth it; the purpose of these patches is to replace [0] with [] across
> the whole tree.
>
> Thanks
> --
> Gustavo
>
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Felix Imendörffer
[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 488 bytes --]
next prev parent reply other threads:[~2020-03-09 7:49 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-25 14:03 [PATCH][next] drm: Replace zero-length array with flexible-array member Gustavo A. R. Silva
2020-02-25 14:17 ` Jani Nikula
2020-03-03 18:20 ` Gustavo A. R. Silva
2020-03-09 7:49 ` Thomas Zimmermann [this message]
2020-02-25 15:04 ` Chris Wilson
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=67c46a2b-8127-a4b7-c825-8cba6f28db8c@suse.de \
--to=tzimmermann@suse.de \
--cc=airlied@linux.ie \
--cc=airlied@redhat.com \
--cc=christian.gmeiner@gmail.com \
--cc=daniel@ffwll.ch \
--cc=dri-devel@lists.freedesktop.org \
--cc=eric@anholt.net \
--cc=etnaviv@lists.freedesktop.org \
--cc=freedreno@lists.freedesktop.org \
--cc=gustavo@embeddedor.com \
--cc=hdegoede@redhat.com \
--cc=intel-gfx@lists.freedesktop.org \
--cc=jani.nikula@linux.intel.com \
--cc=joonas.lahtinen@linux.intel.com \
--cc=kraxel@redhat.com \
--cc=l.stach@pengutronix.de \
--cc=linux+etnaviv@armlinux.org.uk \
--cc=linux-arm-msm@vger.kernel.org \
--cc=linux-graphics-maintainer@vmware.com \
--cc=linux-kernel@vger.kernel.org \
--cc=maarten.lankhorst@linux.intel.com \
--cc=mripard@kernel.org \
--cc=patrik.r.jakobsson@gmail.com \
--cc=robdclark@gmail.com \
--cc=rodrigo.vivi@intel.com \
--cc=sean@poorly.run \
--cc=spice-devel@lists.freedesktop.org \
--cc=thellstrom@vmware.com \
--cc=virtualization@lists.linux-foundation.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).