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

[Masahiro Yamada]

Hi Arnd,


2017-04-01 5:38 GMT+09:00 Arnd Bergmann <arnd@xxxxxxxx>:
> From: Mark Charlebois <charlebm@xxxxxxxxx>
>
> 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@xxxxxxxxx>
> Signed-off-by: Behan Webster <behanw@xxxxxxxxxxxxxxxxxx>
> Reviewed-by: Jan-Simon MÃller <dl9pf@xxxxxx>
> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>


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@grover:~$ clang --version
clang version 3.3 (tags/RELEASE_33/final)
Target: x86_64-unknown-linux-gnu
Thread model: posix
masahiro@grover:~$ clang  -foobar -c -x c /dev/null
clang: warning: argument unused during compilation: '-foobar'
masahiro@grover:~$ echo $?
0


[2] When I use version 3.4

masahiro@grover:~$ clang --version
clang version 3.4 (tags/RELEASE_34/final)
Target: x86_64-unknown-linux-gnu
Thread model: posix
masahiro@grover:~$ clang  -foobar -c -x c /dev/null
clang: error: unknown argument: '-foobar'
masahiro@grover:~$ 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?


-- 
Best Regards
Masahiro Yamada