linux-kernel - Re: [PATCH 01/17] kbuild: Disable -Waddress-of-packed-member for gcc 9

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Message-ID: <CAK7LNAR3qUuNwQFfqcjyiA3Qus1x_zUFHbvop88Y1UReRwvgHA@mail.gmail.com>
Date:   Mon, 1 Apr 2019 10:04:34 +0900
From:   Masahiro Yamada <yamada.masahiro@...ionext.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Andi Kleen <andi@...stfloor.org>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH 01/17] kbuild: Disable -Waddress-of-packed-member for gcc 9

Hi,

On Fri, Mar 22, 2019 at 10:59 PM Arnd Bergmann <arnd@...db.de> wrote:
>
> On Thu, Mar 21, 2019 at 11:00 PM Andi Kleen <andi@...stfloor.org> wrote:
> >
> > From: Andi Kleen <ak@...ux.intel.com>
> >
> > This warning is very noisy in a default build with gcc 9.
> > Move it into W=2 only.
> >
> > Cc: arnd@...db.de
> > Cc: Masahiro Yamada <yamada.masahiro@...ionext.com>
> > Signed-off-by: Andi Kleen <ak@...ux.intel.com>
>
> I think W=2 is too aggressive. On many architectures, this finds
> real bugs and the false positives tend to be trivial to fix
> (by removing the bogus __packed annotation), which improves
> the generated code in the process.
>
> Moving it to W=1 for the moment is probably fine, but ideally
> I think we should fix the kernel to behave according to the
> C standard.
>
>       Arnd



I agree to disable this warning option
since we see a lot of instances.

The room of argument is W=1 or W=2?
I do not have a strong opinion either way.

Arnd most actively takes care of warnings like this.
If he looks into these warnings, W=1 is fine with me.


-- 
Best Regards
Masahiro Yamada