linux-kernel - Re: [PATCH] qed: add missing header dependencies

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Message-ID: <5820324.xrfiu7KHci@wuerfel>
Date:   Wed, 07 Sep 2016 14:52:56 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Yuval Mintz <Yuval.Mintz@...gic.com>
Cc:     Baoyou Xie <baoyou.xie@...aro.org>,
        netdev <netdev@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        "xie.baoyou@....com.cn" <xie.baoyou@....com.cn>,
        Ariel Elior <Ariel.Elior@...gic.com>
Subject: Re: [PATCH] qed: add missing header dependencies

On Wednesday, September 7, 2016 12:31:03 PM CEST Yuval Mintz wrote:
> > > While I obviously have no strong objection for including
> > > qed_selftest.h from qed_selftest.c, I'm not sure I understand which C
> > > standard dictates this requirement.
> > > Why should a function definition [not call] be preceded by a prototype?
> > 
> > - When a function is defined in one file and used in another, you want
> >   both files to include the same header that has the declaration to
> >   ensure that the types are identical. There are cases where the
> >   prototype is changed after the fact in an incompatible way, causing
> >   silent data corruption on some configurations but maybe not on others.
> 
> O.k., motivation is clear.
> But this really isn't enforced by the ansi-c standard, right?

No, ansi-c doesn't enforce this, and even the regular kernel build
flags don't enable the warning in question, we only get it when
either building with "make C=1" using sparse, or "make W=1" to
enable extra warnings from gcc.

The warning is however really useful, and I hope that we go through
all drivers in the kernel and eliminate these warnings in order
to turn them on by default for all drivers.

> Acked-by: Yuval Mintz <Yuval.Mintz@...gic.com>

Thanks,

	Arnd