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From: Arnd Bergmann <arnd@arndb.de>
To: Masahiro Yamada <masahiroy@kernel.org>
Cc: Andrew Lunn <andrew@lunn.ch>,
	Nick Desaulniers <ndesaulniers@google.com>,
	netdev <netdev@vger.kernel.org>,
	David Miller <davem@davemloft.net>,
	Jakub Kicinski <kuba@kernel.org>,
	Michal Marek <michal.lkml@markovi.net>,
	Rohit Maheshwari <rohitm@chelsio.com>,
	Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
	clang-built-linux <clang-built-linux@googlegroups.com>
Subject: Re: [PATCH net-next v2 1/2] Makefile.extrawarn: Add symbol for W=1 warnings for today
Date: Mon, 12 Oct 2020 10:11:53 +0200
Message-ID: <CAK8P3a2LxR7BXhMktQN-Q-JpYq0ziMZVPHhu47k3CQ9OuKWUTg@mail.gmail.com> (raw)
In-Reply-To: <CAK7LNASB6ashOzmL5XntkPSq9a+8VoWCowP5CAt+oX0o=0y=dA@mail.gmail.com>

On Sun, Oct 11, 2020 at 3:04 PM Masahiro Yamada <masahiroy@kernel.org> wrote:
> On Tue, Oct 6, 2020 at 6:08 AM Andrew Lunn <andrew@lunn.ch> wrote:
>
>
> I am not a big fan of KBUILD_CFLAGS_W1_<timestamp>
> since it is ugly.
>
> I'd like to start with adding individual flags
> like drivers/gpu/drm/i915/Makefile, and see
> how difficult it would be to maintain it.

I don't really like that either, to be honest, mostly because that is
somewhat incompatible with my plan to move all the warning flags
out the command line and into _Pragma() lines in header files.

> One drawback of your approach is that
> you cannot set KBUILD_CFLAGS_W1_20200930
> until you eliminate all the warnings in the
> sub-directory in interest.
> (i.e. all or nothing approach)
>
> At best, you can only work out from 'old -> new' order
> because KBUILD_CFLAGS_W1_20200326 is a suer-set of
> KBUILD_CFLAGS_W1_20190907, which is a suer-set of
> KBUILD_CFLAGS_W1_20190617 ...
>
>
>
> If you add flags individually, you can start with
> low-hanging fruits, or ones with higher priority
> as Arnd mentions about -Wmissing-{declaration,prototypes}.
>
>
> For example, you might be able to set
> 'subdir-ccflags-y += -Wmissing-declarations'
> to drivers/net/Makefile, while
> 'subdir-ccflags-y += -Wunused-but-set-variable'
> stays in drivers/net/ethernet/Makefile.

I agree with the goal though. In particular it may be helpful to pick
a set of warning flags to always be enabled without also setting
-Wextra, which has different meanings depending on compiler
version, or between gcc and clang.

I wonder how different they really are, and we can probably find
out from https://github.com/Barro/compiler-warnings, but I have
not checked myself.

      Arnd

  reply index

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-01  1:12 [RFC PATCH net-next v2 0/2] driver/net/ethernet W=1 by default Andrew Lunn
2020-10-01  1:12 ` [PATCH net-next v2 1/2] Makefile.extrawarn: Add symbol for W=1 warnings for today Andrew Lunn
2020-10-01 23:09   ` Nick Desaulniers
2020-10-02  1:44     ` Andrew Lunn
2020-10-02 12:20       ` Arnd Bergmann
2020-10-02 12:51         ` Andrew Lunn
2020-10-02 13:15           ` Arnd Bergmann
2020-10-12  1:00         ` Masahiro Yamada
2020-10-12  8:05           ` Arnd Bergmann
2020-10-05 17:31       ` Nick Desaulniers
2020-10-05 19:49         ` Andrew Lunn
2020-10-05 20:03           ` Arnd Bergmann
2020-10-05 21:08             ` Andrew Lunn
2020-10-11 13:03               ` Masahiro Yamada
2020-10-12  8:11                 ` Arnd Bergmann [this message]
2020-10-16 14:12                 ` Andrew Lunn
     [not found]                   ` <CAK8P3a1nBhmf1PQwHHbEjiVgRTXi4UuJAbwuK92CKEbR=yKGWw@mail.gmail.com>
2020-10-17 14:57                     ` Andrew Lunn
2020-10-02 11:08   ` kernel test robot
2020-10-01  1:12 ` [PATCH net-next v2 2/2] driver/net/ethernet: Sign up for W=1 as defined on 20200930 Andrew Lunn

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