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Date:   Mon, 20 Jun 2022 21:14:28 +0200
From:   Michal Hocko <mhocko@suse.com>
To:     Julia Lawall <julia.lawall@inria.fr>
Cc:     Charan Teja Kalla <quic_charante@quicinc.com>,
        kernel test robot <lkp@intel.com>,
        Minchan Kim <minchan@kernel.org>, kbuild-all@lists.01.org,
        linux-kernel@vger.kernel.org,
        Andrew Morton <akpm@linux-foundation.org>,
        Linux Memory Management List <linux-mm@kvack.org>
Subject: Re: [kbuild-all] Re: mm/madvise.c:1438:6: warning: Redundant
 assignment of 'ret' to itself. [selfAssignment]
Message-ID: <YrDHFJkwcn5Ga3yy@dhcp22.suse.cz>
References: <202206180617.UzO7ymnD-lkp@intel.com>
 <5ec7b561-551b-f02a-9b7b-65d05ccdabbc@quicinc.com>
 <YrCgcEGKxjN7mNu9@dhcp22.suse.cz>
 <alpine.DEB.2.22.394.2206201253480.2243@hadrien>
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On Mon 20-06-22 12:54:56, Julia Lawall wrote:
> 
> 
> On Mon, 20 Jun 2022, Michal Hocko wrote:
> 
> > On Sat 18-06-22 11:25:43, Charan Teja Kalla wrote:
> > > Hello Andrew,
> > >
> > > On 6/18/2022 4:34 AM, kernel test robot wrote:
> > > > tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> > > > head:   4b35035bcf80ddb47c0112c4fbd84a63a2836a18
> > > > commit: 5bd009c7c9a9e888077c07535dc0c70aeab242c3 mm: madvise: return correct bytes advised with process_madvise
> > > > date:   3 months ago
> > > > compiler: mips-linux-gcc (GCC) 11.3.0
> > > > reproduce (cppcheck warning):
> > > >         # apt-get install cppcheck
> > > >         git checkout 5bd009c7c9a9e888077c07535dc0c70aeab242c3
> > > >         cppcheck --quiet --enable=style,performance,portability --template=gcc FILE
> > > >
> > > > If you fix the issue, kindly add following tag where applicable
> > > > Reported-by: kernel test robot <lkp@intel.com>
> > > >
> > > >
> > > > cppcheck warnings: (new ones prefixed by >>)
> > > >>> mm/madvise.c:1438:6: warning: Redundant assignment of 'ret' to itself. [selfAssignment]
> > > >     ret = (total_len - iov_iter_count(&iter)) ? : ret;
> > >
> > > Other way to avoid this warning is by creating another local variable
> > > that holds the total bytes processed. Having another local variable to
> > > get rid off some compilation warning doesn't seem proper to me. So,
> > > leaving this warning unless you ask me to fix this.
> >
> > Is this a new warning? I do not see it supported by my gcc 10.x. Do we
> 
> cppcheck is a static analysis tool.  It looks like it doesn't have a
> proper understanding of ?:

Ohh, thanks for the clarification! I thought this was a gcc feature.
Then I would suggest to report a bug report against the static checker
rather than making any changes to the kernel to workaround it.
-- 
Michal Hocko
SUSE Labs