linux-kernel - Re: kbuild: move cc-option and cc-disable-warning after incl. arch Makefile

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Date:   Mon, 19 Mar 2018 11:37:41 +0900
From:   Masahiro Yamada <yamada.masahiro@...ionext.com>
To:     Stefan Agner <stefan@...er.ch>
Cc:     Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Michal Marek <michal.lkml@...kovi.net>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Matthias Kaehlcke <mka@...omium.org>,
        Arnd Bergmann <arnd@...db.de>
Subject: Re: kbuild: move cc-option and cc-disable-warning after incl. arch Makefile

2018-03-19 9:41 GMT+09:00 Stefan Agner <stefan@...er.ch>:
> Hi Masahiro,
>
> On 27.11.2017 13:15, Masahiro Yamada wrote:
>> Geert reported commit ae6b289a3789 ("kbuild: Set KBUILD_CFLAGS before
>> incl. arch Makefile") broke cross-compilation using a cross-compiler
>> that supports less compiler options than the host compiler.
>>
>> For example,
>>
>>   cc1: error: unrecognized command line option "-Wno-unused-but-set-variable"
>>
>> This problem happens on architectures that setup CROSS_COMPILE in their
>> arch/*/Makefile.
>>
>> Move the cc-option and cc-disable-warning back to the original position,
>> but keep the Clang target options.
>
> This seems to break arm (32-bit) clang support for me. It seems to break
> correct compiler flag detection in some way.
>
> Just moving no-integrated-as back to before including the arch Makefile
> seems to fix the issue:

Sorry, looks like I broke it.



> --- a/Makefile
> +++ b/Makefile
> @@ -487,6 +487,7 @@ CLANG_GCC_TC        :=
> --gcc-toolchain=$(GCC_TOOLCHAIN)
>  endif
>  KBUILD_CFLAGS += $(CLANG_TARGET) $(CLANG_GCC_TC)
>  KBUILD_AFLAGS += $(CLANG_TARGET) $(CLANG_GCC_TC)
> +KBUILD_CFLAGS += $(call cc-option, -no-integrated-as)
>  endif
>
>  RETPOLINE_CFLAGS_GCC := -mindirect-branch=thunk-extern
> -mindirect-branch-register
> @@ -744,7 +745,6 @@ KBUILD_CFLAGS += $(call cc-disable-warning,
> tautological-compare)
>  # See modpost pattern 2
>  KBUILD_CFLAGS += $(call cc-option, -mno-global-merge,)
>  KBUILD_CFLAGS += $(call cc-option, -fcatch-undefined-behavior)
> -KBUILD_CFLAGS += $(call cc-option, -no-integrated-as)
>  KBUILD_AFLAGS += $(call cc-option, -no-integrated-as)
>  else
>
> Does that sound like a reasonable fix?


Yes, I think so.


For consistency, please move
KBUILD_AFLAGS += $(call cc-option, -no-integrated-as)
as well.




-- 
Best Regards
Masahiro Yamada