linux-kernel - Re: [PATCH 1/2] kbuild: replace cc-name test with CONFIG_CC_IS

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Date:   Tue, 30 Oct 2018 21:40:27 +0900
From:   Masahiro Yamada <yamada.masahiro@...ionext.com>
To:     Michael Ellerman <mpe@...erman.id.au>
Cc:     Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        Linux-MIPS <linux-mips@...ux-mips.org>,
        James Hogan <jhogan@...nel.org>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Michal Marek <michal.lkml@...kovi.net>,
        Paul Mackerras <paulus@...ba.org>,
        Paul Burton <paul.burton@...s.com>,
        Ralf Baechle <ralf@...ux-mips.org>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>
Subject: Re: [PATCH 1/2] kbuild: replace cc-name test with CONFIG_CC_IS_CLANG

On Tue, Oct 30, 2018 at 9:36 PM Michael Ellerman <mpe@...erman.id.au> wrote:
>
> Masahiro Yamada <yamada.masahiro@...ionext.com> writes:
> > diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile
> > index 17be664..338e827 100644
> > --- a/arch/powerpc/Makefile
> > +++ b/arch/powerpc/Makefile
> > @@ -96,7 +96,7 @@ aflags-$(CONFIG_CPU_BIG_ENDIAN)             += $(call cc-option,-mabi=elfv1)
> >  aflags-$(CONFIG_CPU_LITTLE_ENDIAN)   += -mabi=elfv2
> >  endif
> >
> > -ifneq ($(cc-name),clang)
> > +ifneq ($(CONFIG_CC_IS_CLANG),y)
> >    cflags-$(CONFIG_CPU_LITTLE_ENDIAN) += -mno-strict-align
> >  endif
> >
> > @@ -175,7 +175,7 @@ endif
> >  # Work around gcc code-gen bugs with -pg / -fno-omit-frame-pointer in gcc <= 4.8
> >  # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=44199
> >  # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=52828
> > -ifneq ($(cc-name),clang)
> > +ifneq ($(CONFIG_CC_IS_CLANG),y)
> >  CC_FLAGS_FTRACE      += $(call cc-ifversion, -lt, 0409, -mno-sched-epilog)
> >  endif
> >  endif
>
> Does this behave like other CONFIG variables, ie. it will not be defined
> when it's false?

Right.


> And if so can't we use ifdef/ifndef? eg:
>
> ifndef CONFIG_CC_IS_CLANG
>   CC_FLAGS_FTRACE       += $(call cc-ifversion, -lt, 0409, -mno-sched-epilog)
>
> That reads cleaner to me.


OK, will do respin if you prefer ifdef/ifndef style.




> Still this patch is fine as is:
>
> Acked-by: Michael Ellerman <mpe@...erman.id.au> (powerpc)
>
> cheers



-- 
Best Regards
Masahiro Yamada