linux-kernel - Re: [RESEND PATCH v3 05/11] mtd: rawnand: vf610_nfc: add initializer to avoid -Wmaybe-uninitialized

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Date:   Fri, 3 May 2019 13:11:52 +0200
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Masahiro Yamada <yamada.masahiro@...ionext.com>
Cc:     linux-arch <linux-arch@...r.kernel.org>,
        Christophe Leroy <christophe.leroy@....fr>,
        Arnd Bergmann <arnd@...db.de>,
        linux-s390 <linux-s390@...r.kernel.org>,
        Mathieu Malaterre <malat@...ian.org>, X86 ML <x86@...nel.org>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        linux-mips@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...hat.com>,
        linux-mtd <linux-mtd@...ts.infradead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [RESEND PATCH v3 05/11] mtd: rawnand: vf610_nfc: add
 initializer to avoid -Wmaybe-uninitialized

Hi Masahiro,

Masahiro Yamada <yamada.masahiro@...ionext.com> wrote on Fri, 3 May
2019 19:36:35 +0900:

> Hi Miquel,
> 
> On Thu, May 2, 2019 at 11:14 PM Miquel Raynal <miquel.raynal@...tlin.com> wrote:
> >
> > Hi Masahiro,
> >
> > Masahiro Yamada <yamada.masahiro@...ionext.com> wrote on Tue, 23 Apr
> > 2019 12:49:53 +0900:
> >  
> > > This prepares to move CONFIG_OPTIMIZE_INLINING from x86 to a common
> > > place. We need to eliminate potential issues beforehand.
> > >
> > > Kbuild test robot has never reported -Wmaybe-uninitialized warning
> > > for this probably because vf610_nfc_run() is inlined by the x86
> > > compiler's inlining heuristic.
> > >
> > > If CONFIG_OPTIMIZE_INLINING is enabled for a different architecture
> > > and vf610_nfc_run() is not inlined, the following warning is reported:
> > >
> > > drivers/mtd/nand/raw/vf610_nfc.c: In function ‘vf610_nfc_cmd’:
> > > drivers/mtd/nand/raw/vf610_nfc.c:455:3: warning: ‘offset’ may be used uninitialized in this function [-Wmaybe-uninitialized]
> > >    vf610_nfc_rd_from_sram(instr->ctx.data.buf.in + offset,
> > >    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > >             nfc->regs + NFC_MAIN_AREA(0) + offset,
> > >             ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > >             trfr_sz, !nfc->data_access);
> > >             ~~~~~~~~~~~~~~~~~~~~~~~~~~~  
> >
> > IMHO this patch has no dependencies with this series.  
> 
> 
> This patch is the prerequisite for 11/11.
> https://lore.kernel.org/patchwork/patch/1064959/
> 
> 
> Without the correct patch order,
> the kbuild test robot reports the warning.
> 
> 
> > Would you mind sending it alone with the proper Fixes tag?  
> 
> 
> I do not think Fixes is necessary.

IMHO it is. Even if today the warning does not spawn, there is a
real C error which might already be an issue.

> 
> Nobody has noticed this potential issue before.
> Without 11/11, probably we cannot reproduce this warning.
> 
> 
> BTW, this series has been for a while in linux-next.

Missed that. Ok, nevermind.


Thanks,
Miquèl