linux-kernel - Re: [PATCH 1/2] kbuild: refactor scripts/Makefile.extrawarn

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Date:   Wed, 28 Aug 2019 11:17:19 -0700
From:   Nathan Chancellor <natechancellor@...il.com>
To:     Masahiro Yamada <yamada.masahiro@...ionext.com>
Cc:     linux-kbuild@...r.kernel.org,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Miguel Ojeda <miguel.ojeda.sandonis@...il.com>,
        Arnd Bergmann <arnd@...db.de>,
        Michal Marek <michal.lkml@...kovi.net>,
        clang-built-linux@...glegroups.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] kbuild: refactor scripts/Makefile.extrawarn

On Wed, Aug 28, 2019 at 02:54:24PM +0900, Masahiro Yamada wrote:
> Instead of the warning-[123] magic, let's accumulate compiler options
> to KBUILD_CFLAGS directly as the top Makefile does. I think this makes
> easier to understand what is going on in this file.
> 
> This commit slightly changes the behavior, I think all of which are OK.
> 
> [1] Currently, cc-option calls are needlessly evaluated. For example,
>       warning-3 += $(call cc-option, -Wpacked-bitfield-compat)
>     needs evaluating only when W=3, but it is actually evaluated for
>     W=1, W=2 as well. With this commit, only relevant cc-option calls
>     will be evaluated. This is a slight optimization.
> 
> [2] Currently, unsupported level like W=4 is checked by:
>       $(error W=$(KBUILD_ENABLE_EXTRA_GCC_CHECKS) is unknown)
>     This will no longer be checked, but I do not think it is a big
>     deal.
> 
> [3] Currently, 4 Clang warnings (Winitializer-overrides, Wformat,
>     Wsign-compare, Wformat-zero-length) are shown by any of W=1, W=2,
>     and W=3. With this commit, they will be warned only by W=1. I
>     think this is a more correct behavior since each warning belongs
>     to only one warning level.
> 
> Signed-off-by: Masahiro Yamada <yamada.masahiro@...ionext.com>

Reviewed-by: Nathan Chancellor <natechancellor@...il.com>