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Date: Tue, 27 Feb 2018 14:42:43 -0600
From: Segher Boessenkool <segher@kernel.crashing.org>
To: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Mathieu Malaterre <malat@debian.org>,
        "open list:LINUX FOR POWERPC PA SEMI PWRFICIENT"
        <linuxppc-dev@lists.ozlabs.org>,
        Paul Mackerras <paulus@samba.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Jiri Slaby <jslaby@suse.com>
Subject: Re: [PATCH 01/21] powerpc: Remove warning on array size when empty
Message-ID: <20180227204243.GW21977@gate.crashing.org>
References: <20180225172236.29650-1-malat@debian.org> <20180225172236.29650-2-malat@debian.org> <CAHp75Vdpdr-0-vdvo0SBx2XcM=HePrUbbb4SM9+ExT_i-1B69Q@mail.gmail.com> <CAHp75Ve_zxp4_N_YzzvJ=H8Qs65G5j7bgGBv_TvsZ6Ye2nuECA@mail.gmail.com> <CA+7wUszK++8Tr9j1=4jQtRSu-36MH=dqgimq-ST9D9hvacrJSQ@mail.gmail.com> <603d5335-6220-73f2-d902-b92bc74bc79e@c-s.fr> <CA+7wUsys=J8vkEOtzd26B6MGEhfTBRzaA_myuUWNzf24rMvn+A@mail.gmail.com> <CAHp75VePco3hNo_vM916CiLzBAd18i=O1TaecD5YEDewvMpYYQ@mail.gmail.com>
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On Tue, Feb 27, 2018 at 05:52:06PM +0200, Andy Shevchenko wrote:
> On Tue, Feb 27, 2018 at 9:44 AM, Mathieu Malaterre <malat@debian.org> wrote:
> > On Tue, Feb 27, 2018 at 8:33 AM, Christophe LEROY
> > <christophe.leroy@c-s.fr> wrote:
> 
> >>>>> Much simpler is just add
> >>>>>
> >>>>> if (ARRAY_SIZE() == 0)
> >>>>>   return;
> 
> >> Or add in front:
> >> if (!ARRAY_SIZE(feature_properties))
> >>         return;
> >
> > (not tested) I believe the compiler still go over the for() loop and
> > will complain about the original unsigned comparison.
> 
> Did you run tests? Did you look into object file?
> 
> In kernel we much rely on the compiling away the code which is
> deterministically not in use.
> Here I'm pretty sure it will compile away entire function.

It does, but it also still warns (this warning is done very early in the
compiler pipeline).


Segher