linux-kernel - Re: [PATCH 2/2] kbuild: clang: Disable the 'duplicate-decl-specifier' warning

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Date:   Tue, 16 May 2017 14:41:18 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     Matthias Kaehlcke <mka@...omium.org>
Cc:     Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Michal Marek <mmarek@...e.com>, linux-kbuild@...r.kernel.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Grant Grundler <grundler@...omium.org>,
        Greg Hackmann <ghackmann@...gle.com>,
        Michael Davidson <md@...gle.com>, Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH 2/2] kbuild: clang: Disable the 'duplicate-decl-specifier' warning

Hi

On Fri, Apr 21, 2017 at 2:39 PM, Matthias Kaehlcke <mka@...omium.org> wrote:
> clang generates plenty of these warnings in different parts of the code.
> They are mostly caused by container_of() and other macros which declare
> a "const <type> *" variable for their internal use which triggers a
> "duplicate 'const' specifier" warning if the <type> is already const
> qualified.
>
> Wording-mostly-from: Michael Davidson <md@...gle.com>
> Signed-off-by: Matthias Kaehlcke <mka@...omium.org>
> ---
>  Makefile | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/Makefile b/Makefile
> index df5abf346354..6cd6d428db43 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -704,6 +704,7 @@ KBUILD_CFLAGS += $(call cc-disable-warning, unused-variable)
>  KBUILD_CFLAGS += $(call cc-disable-warning, format-invalid-specifier)
>  KBUILD_CFLAGS += $(call cc-disable-warning, gnu)
>  KBUILD_CFLAGS += $(call cc-disable-warning, address-of-packed-member)
> +KBUILD_CFLAGS += $(call cc-disable-warning, duplicate-decl-specifier)
>  # Quiet clang warning: comparison of unsigned expression < 0 is always false
>  KBUILD_CFLAGS += $(call cc-disable-warning, tautological-compare)
>  # CLANG uses a _MergedGlobals as optimization, but this breaks modpost, as the

It seems like gcc 7 may have the same warning.  Specifically I saw a
patch fly by from Arnd, which you can find in Mark Brown's tree now:

https://git.kernel.org/pub/scm/linux/kernel/git/broonie/sound.git/commit/?h=topic/rt5614&id=03ba791df98d15d07ea74075122af71e35c7611c


+Arnd since he may be trying to solve the same issues?

-Doug