linux-kernel - Re: [PATCH] kbuild, LLVMLinux: Add -Werror to cc-option to support clang

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Date:   Thu, 6 Apr 2017 02:11:32 +0900
From:   Masahiro Yamada <yamada.masahiro@...ionext.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Mark Charlebois <charlebm@...il.com>,
        Behan Webster <behanw@...verseincode.com>,
        Michal Marek <mmarek@...e.com>,
        Nicolas Pitre <nicolas.pitre@...aro.org>,
        Kees Cook <keescook@...omium.org>,
        Emese Revfy <re.emese@...il.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        masahiroy@...nel.org
Subject: Re: [PATCH] kbuild, LLVMLinux: Add -Werror to cc-option to support clang

Hi Arnd,

2017-04-03 6:46 GMT+09:00 Masahiro Yamada <yamada.masahiro@...ionext.com>:
> Hi Arnd,
>
>
> 2017-04-01 5:38 GMT+09:00 Arnd Bergmann <arnd@...db.de>:
>> From: Mark Charlebois <charlebm@...il.com>
>>
>> Clang will warn about unknown warnings but will not return false
>> unless -Werror is set. GCC will return false if an unknown
>> warning is passed.
>>
>> Adding -Werror make both compiler behave the same.
>>
>> [arnd: it turns out we need the same patch for testing whether -ffunction-sections
>>        works right with gcc. I've build tested extensively with this patch
>>        applied, so let's just merge this one now.]
>>
>> Signed-off-by: Mark Charlebois <charlebm@...il.com>
>> Signed-off-by: Behan Webster <behanw@...verseincode.com>
>> Reviewed-by: Jan-Simon Möller <dl9pf@....de>
>> Signed-off-by: Arnd Bergmann <arnd@...db.de>
>
>
> Thank you for forwarding this patch.
>
>
> The code diff looks good to me,
> but I'd like to be sure about git-log before applying it.
>
>
> As far as I tested, the statement
> "Clang will warn about unknown warnings but will not
> return false unless -Werror is set." does not seem true
> on recent versions.
>
>
>
> [1] When I use version 3.3
>
> masahiro@...ver:~$ clang --version
> clang version 3.3 (tags/RELEASE_33/final)
> Target: x86_64-unknown-linux-gnu
> Thread model: posix
> masahiro@...ver:~$ clang  -foobar -c -x c /dev/null
> clang: warning: argument unused during compilation: '-foobar'
> masahiro@...ver:~$ echo $?
> 0
>
>
> [2] When I use version 3.4
>
> masahiro@...ver:~$ clang --version
> clang version 3.4 (tags/RELEASE_34/final)
> Target: x86_64-unknown-linux-gnu
> Thread model: posix
> masahiro@...ver:~$ clang  -foobar -c -x c /dev/null
> clang: error: unknown argument: '-foobar'
> masahiro@...ver:~$ echo $?
> 1
>
>
>
>
> I agree we can apply this patch anyway
> even if the original motivation is not true anymore.
>
>
> Can you check it out,
> and add a little more comments if you agree?


Sorry.  This was my misunderstanding.
You do not have to answer my question.

I found this patch is still useful for recent clang versions.

I will apply this patch shortly.  Thanks!




-- 
Best Regards
Masahiro Yamada