Re: [PATCH] Remove deductively redundant NULL pointer checks

From: kbuild test robot <lkp@intel.com>
To: Shaobo He <shaobo@cs.utah.edu>
Cc: Andrew-CT Chen <andrew-ct.chen@mediatek.com>,
	Heiko Stuebner <heiko@sntech.de>,
	Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>,
	"Gustavo A. R. Silva" <gustavo@embeddedor.com>,
	Kamil Debski <kamil@wypas.org>,
	Sakari Ailus <sakari.ailus@linux.intel.com>,
	Andrzej Hajda <a.hajda@samsung.com>,
	laurent.pinchart@ideasonboard.com,
	"open list:MEDIA DRIVERS FOR RENESAS - FDP1"
	<linux-renesas-soc@vger.kernel.org>,
	Mauro Carvalho Chehab <mchehab@kernel.org>,
	Rick Chang <rick.chang@mediatek.com>,
	"open list:ARM/Rockchip SoC support"
	<linux-rockchip@lists.infradead.org>,
	Matthias Brugger <matthias.bgg@gmail.com>,
	Mikhail Ulyanov <mikhail.ulyanov@cogentembedded.com>,
	Hans Verkuil <hans.verkuil@cisco.com>,
	linux-media@vger.kernel.org, Bin Liu <bin.liu@mediatek.com>,
	Anton Leontiev <scileont@gmail.com>,
	Kees Cook <keescook@chromium.org>, Benoit Parrot <bparrot@ti.com>,
	"moderated list:ARM/Mediatek SoC support"
	<linux-mediatek@lists.infradead.org>,
	Jacek Anaszewski <jacek.anaszewski@gmail.com>,
	Andrzej Pietrasiewicz <andrzej.p@samsung.com>,
	Tiffany Lin <tiffany.lin@mediatek.com>,
	Ezequiel Garcia <ezequiel@collabora.com>,
	"moderated list:ARM/Mediatek SoC support"
	<linux-arm-kernel@lists.infradead.org>,
	Jacob chen <jacob2.chen@rock-chips.com>,
	open list <linux-kernel@vger.kernel.org>,
	shaobo@cs.utah.edu, Kyungmin Park <kyungmin.park@samsung.com>,
	Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>,
	kbuild-all@01.org, Philipp Zabel <p.zabel@pengutronix.de>
Subject: Re: [PATCH] Remove deductively redundant NULL pointer checks
Date: Tue, 26 Feb 2019 16:00:28 +0800	[thread overview]
Message-ID: <201902261552.mpkZMJAZ%fengguang.wu@intel.com> (raw)
In-Reply-To: <1551128631-19713-1-git-send-email-shaobo@cs.utah.edu>

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Hi Shaobo,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on linuxtv-media/master]
[also build test WARNING on v5.0-rc8 next-20190225]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/Shaobo-He/Remove-deductively-redundant-NULL-pointer-checks/20190226-133616
base:   git://linuxtv.org/media_tree.git master
config: xtensa-allyesconfig (attached as .config)
compiler: xtensa-linux-gcc (GCC) 8.2.0
reproduce:
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # save the attached .config to linux build tree
        GCC_VERSION=8.2.0 make.cross ARCH=xtensa 

Note: it may well be a FALSE warning. FWIW you are at least aware of it now.
http://gcc.gnu.org/wiki/Better_Uninitialized_Warnings

All warnings (new ones prefixed by >>):

   In file included from include/media/videobuf2-v4l2.h:16,
                    from include/media/v4l2-mem2mem.h:20,
                    from drivers/media//platform/vim2m.c:27:
   drivers/media//platform/vim2m.c: In function 'vidioc_s_fmt':
>> include/media/videobuf2-core.h:1098:11: warning: 'vq' may be used uninitialized in this function [-Wmaybe-uninitialized]
     return (q->num_buffers > 0);
             ~^~~~~~~~~~~~~
   drivers/media//platform/vim2m.c:683:20: note: 'vq' was declared here
     struct vb2_queue *vq;
                       ^~
--
   In file included from include/media/videobuf2-v4l2.h:16,
                    from include/media/v4l2-mem2mem.h:20,
                    from drivers/media/platform/vim2m.c:27:
   drivers/media/platform/vim2m.c: In function 'vidioc_s_fmt':
>> include/media/videobuf2-core.h:1098:11: warning: 'vq' may be used uninitialized in this function [-Wmaybe-uninitialized]
     return (q->num_buffers > 0);
             ~^~~~~~~~~~~~~
   drivers/media/platform/vim2m.c:683:20: note: 'vq' was declared here
     struct vb2_queue *vq;
                       ^~

vim +/vq +1098 include/media/videobuf2-core.h

74753cff Hans Verkuil          2014-04-07  1089  
74753cff Hans Verkuil          2014-04-07  1090  /**
2b141324 Mauro Carvalho Chehab 2017-10-06  1091   * vb2_is_busy() - return busy status of the queue.
2b141324 Mauro Carvalho Chehab 2017-10-06  1092   * @q:		pointer to &struct vb2_queue with videobuf2 queue.
e23ccc0a Pawel Osciak          2010-10-11  1093   *
e23ccc0a Pawel Osciak          2010-10-11  1094   * This function checks if queue has any buffers allocated.
e23ccc0a Pawel Osciak          2010-10-11  1095   */
e23ccc0a Pawel Osciak          2010-10-11  1096  static inline bool vb2_is_busy(struct vb2_queue *q)
e23ccc0a Pawel Osciak          2010-10-11  1097  {
e23ccc0a Pawel Osciak          2010-10-11 @1098  	return (q->num_buffers > 0);
e23ccc0a Pawel Osciak          2010-10-11  1099  }
e23ccc0a Pawel Osciak          2010-10-11  1100  

:::::: The code at line 1098 was first introduced by commit
:::::: e23ccc0ad9258634e6d52cedf473b35dc34416c7 [media] v4l: add videobuf2 Video for Linux 2 driver framework

:::::: TO: Pawel Osciak <p.osciak@samsung.com>
:::::: CC: Mauro Carvalho Chehab <mchehab@redhat.com>

---
0-DAY kernel test infrastructure                Open Source Technology Center
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