linux-kernel - Re: [Patch v3] x86/build: don't add -maccumulate-outgoing-args w/o compiler support

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Message-ID: <20170508032650.lefwzesoyv2pzbsz@treble>
Date:   Sun, 7 May 2017 22:26:50 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Nick Desaulniers <nick.desaulniers@...il.com>
Cc:     tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
        x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [Patch v3] x86/build: don't add -maccumulate-outgoing-args w/o
 compiler support

On Fri, May 05, 2017 at 08:05:09PM -0700, Nick Desaulniers wrote:
> Clang does not support this machine dependent option.
> 
> Older versions of GCC (pre 3.0) may not support this option, added in
> 2000, but it's unlikely they can still compile the kernel.
> 
> Signed-off-by: Nick Desaulniers <nick.desaulniers@...il.com>
> ---
>  arch/x86/Makefile | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/x86/Makefile b/arch/x86/Makefile
> index 4430dd489620..5a0ac8411792 100644
> --- a/arch/x86/Makefile
> +++ b/arch/x86/Makefile
> @@ -179,7 +179,7 @@ ifdef CONFIG_JUMP_LABEL
>  endif
>  
>  ifeq ($(ACCUMULATE_OUTGOING_ARGS), 1)
> -	KBUILD_CFLAGS += -maccumulate-outgoing-args
> +	KBUILD_CFLAGS += $(call cc-option,-maccumulate-outgoing-args,)
>  endif
>  
>  # Stackpointer is addressed different for 32 bit and 64 bit x86

It would be useful to add a comment in the Makefile above the
KBUILD_CFLAGS line stating that clang doesn't support this flag.

-- 
Josh