Re: [block:for-linus 20/23] include/linux/kernel.h:62:48: warning: 'zone_blocks' may be used uninitialized in this function

From: Damien Le Moal <Damien.LeMoal@wdc.com>
To: Jens Axboe <axboe@kernel.dk>,
	"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>
Cc: Christoph Hellwig <hch@lst.de>,
	"Martin K. Petersen" <martin.petersen@oracle.com>
Subject: Re: [block:for-linus 20/23] include/linux/kernel.h:62:48: warning: 'zone_blocks' may be used uninitialized in this function
Date: Mon, 15 Jul 2019 05:43:24 +0000	[thread overview]
Message-ID: <BYAPR04MB5816C2EFC9D3C9FEF6DCCD2CE7CF0@BYAPR04MB5816.namprd04.prod.outlook.com> (raw)
In-Reply-To: 201907131730.Br9OqtbO%lkp@intel.com

On 2019/07/13 18:10, kbuild test robot wrote:
> tree:   https://kernel.googlesource.com/pub/scm/linux/kernel/git/axboe/linux-block.git for-linus
> head:   787c79d6393fc028887cc1b6066915f0b094e92f
> commit: b091ac616846a1da75b1f2566b41255ce7f0e0a6 [20/23] sd_zbc: Fix report zones buffer allocation
> config: c6x-allyesconfig (attached as .config)
> compiler: c6x-elf-gcc (GCC) 7.4.0
> reproduce:
>         wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
>         chmod +x ~/bin/make.cross
>         git checkout b091ac616846a1da75b1f2566b41255ce7f0e0a6
>         # save the attached .config to linux build tree
>         GCC_VERSION=7.4.0 make.cross ARCH=c6x 
> 
> If you fix the issue, kindly add following tag
> Reported-by: kbuild test robot <lkp@intel.com>
> 
> 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/asm-generic/bug.h:18:0,
>                     from arch/c6x/include/asm/bug.h:12,
>                     from include/linux/bug.h:5,
>                     from include/linux/thread_info.h:12,
>                     from include/asm-generic/current.h:5,
>                     from ./arch/c6x/include/generated/asm/current.h:1,
>                     from include/linux/sched.h:12,
>                     from include/linux/blkdev.h:5,
>                     from drivers//scsi/sd_zbc.c:11:
>    drivers//scsi/sd_zbc.c: In function 'sd_zbc_read_zones':
>>> include/linux/kernel.h:62:48: warning: 'zone_blocks' may be used uninitialized in this function [-Wmaybe-uninitialized]
>     #define __round_mask(x, y) ((__typeof__(x))((y)-1))
>                                                    ^
>    drivers//scsi/sd_zbc.c:464:6: note: 'zone_blocks' was declared here
>      u32 zone_blocks;
>          ^~~~~~~~~~~
[...]

Jens,

This warning does not show up on x86_64 native build with gcc 9.1.
I just sent a patch to remove the warning, but I do not have a c6x cross
compilation environment available so the patch was checked only on x86.

Best regards.

-- 
Damien Le Moal
Western Digital Research