linux-kernel - Re: [PATCH] ftrace: Build with CPPFLAGS to get -Qunused-arguments

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Date:   Wed, 19 Sep 2018 23:54:44 +0900
From:   Masahiro Yamada <yamada.masahiro@...ionext.com>
To:     Nick Desaulniers <ndesaulniers@...gle.com>
Cc:     Joel Stanley <joel@....id.au>,
        Michal Marek <michal.lkml@...kovi.net>,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ftrace: Build with CPPFLAGS to get -Qunused-arguments

2018-09-18 2:24 GMT+09:00 Nick Desaulniers <ndesaulniers@...gle.com>:
> On Mon, Sep 17, 2018 at 12:38 AM Joel Stanley <joel@....id.au> wrote:
>>
>> When building to record the mcount locations the kernel uses
>> KBUILD_CFLAGS but not KBUILD_CPPFLAGS. This means it lacks
>> -Qunused-arguments when building with clang, resulting in a lot of
>> noisy warnings.
>>
>> Signed-off-by: Joel Stanley <joel@....id.au>
>> ---
>> Not sure why -Qunused-arguments is in CPP instead of KBUILD_CFLAGS. We
>> could instead put it in KBUILD_CFLAGS, and not need this patch.
>
> The preprocessor has flags that can change the definitions of macros.
> So there might be unused flags there.  I'm not a fan of covering up
> those warnings via -Qunused-arguments; the flags should be feature
> detected via cc-option and friends rather than always added then
> silenced if excessive.  That hides flags that are long dead/unused.
>
> Thanks for this patch!
> Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>
>
>>
>>  scripts/Makefile.build | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>


Applied to linux-kbuild/fixes. Thanks!


-- 
Best Regards
Masahiro Yamada