linux-kernel - Re: [PATCH] Remove deductively redundant NULL pointer checks

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Date:   Tue, 26 Feb 2019 16:00:28 +0800
From:   kbuild test robot <lkp@...el.com>
To:     Shaobo He <shaobo@...utah.edu>
Cc:     kbuild-all@...org, linux-media@...r.kernel.org,
        laurent.pinchart@...asonboard.com, shaobo@...utah.edu,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Rick Chang <rick.chang@...iatek.com>,
        Bin Liu <bin.liu@...iatek.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Tiffany Lin <tiffany.lin@...iatek.com>,
        Andrew-CT Chen <andrew-ct.chen@...iatek.com>,
        Kieran Bingham <kieran.bingham+renesas@...asonboard.com>,
        Mikhail Ulyanov <mikhail.ulyanov@...entembedded.com>,
        Jacob chen <jacob2.chen@...k-chips.com>,
        Heiko Stuebner <heiko@...ech.de>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Kamil Debski <kamil@...as.org>,
        Andrzej Hajda <a.hajda@...sung.com>,
        Andrzej Pietrasiewicz <andrzej.p@...sung.com>,
        Jacek Anaszewski <jacek.anaszewski@...il.com>,
        Benoit Parrot <bparrot@...com>,
        Hans Verkuil <hans.verkuil@...co.com>,
        Ezequiel Garcia <ezequiel@...labora.com>,
        Anton Leontiev <scileont@...il.com>,
        Kees Cook <keescook@...omium.org>,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        open list <linux-kernel@...r.kernel.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-arm-kernel@...ts.infradead.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@...ts.infradead.org>,
        "open list:MEDIA DRIVERS FOR RENESAS - FDP1" 
        <linux-renesas-soc@...r.kernel.org>,
        "open list:ARM/Rockchip SoC support" 
        <linux-rockchip@...ts.infradead.org>
Subject: Re: [PATCH] Remove deductively redundant NULL pointer checks

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@...sung.com>
:::::: CC: Mauro Carvalho Chehab <mchehab@...hat.com>

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