linux-kernel - Re: [PATCH v2 1/2] Makefile: Remove '--gcc-toolchain' flag

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Date:   Mon, 15 Mar 2021 17:41:47 +0100
From:   Sedat Dilek <sedat.dilek@...il.com>
To:     Masahiro Yamada <masahiroy@...nel.org>
Cc:     Nathan Chancellor <nathan@...nel.org>,
        Michal Marek <michal.lkml@...kovi.net>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        clang-built-linux <clang-built-linux@...glegroups.com>,
        Fangrui Song <maskray@...gle.com>
Subject: Re: [PATCH v2 1/2] Makefile: Remove '--gcc-toolchain' flag

On Mon, Mar 15, 2021 at 5:22 PM Masahiro Yamada <masahiroy@...nel.org> wrote:
>
> On Wed, Mar 10, 2021 at 5:59 AM Nathan Chancellor <nathan@...nel.org> wrote:
> >
> > This flag was originally added to allow clang to find the GNU cross
> > tools in commit 785f11aa595b ("kbuild: Add better clang cross build
> > support"). This flag was not enough to find the tools at times so
> > '--prefix' was added to the list in commit ef8c4ed9db80 ("kbuild: allow
> > to use GCC toolchain not in Clang search path") and improved upon in
> > commit ca9b31f6bb9c ("Makefile: Fix GCC_TOOLCHAIN_DIR prefix for Clang
> > cross compilation"). Now that '--prefix' specifies a full path and
> > prefix, '--gcc-toolchain' serves no purpose because the kernel builds
> > with '-nostdinc' and '-nostdlib'.
> >
> > This has been verified with self compiled LLVM 10.0.1 and LLVM 13.0.0 as
> > well as a distribution version of LLVM 11.1.0 without binutils in the
> > LLVM toolchain locations.
> >
> > Link: https://reviews.llvm.org/D97902
> > Signed-off-by: Nathan Chancellor <nathan@...nel.org>
> > ---
> >
> > v1 -> v2:
> >
> > * Improve commit message (add history behind flag and link to Fangrui's
> >   documentation improvement).
>
>
> Both applied to linux-kbuild. Thanks.
>

Sorry for being pedantic: This misses my Tested-by#s (see [1]).

Tested-by: Sedat Dilek <sedat.dilek@...il.com> # LLVM/Clang v13-git

AFAICS v2 changes some comments in the commit only but not code?

- Sedat -

[1] https://marc.info/?l=linux-kernel&m=161480031518629&w=2
[2] https://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild.git/commit/?h=kbuild&id=d4aa405bc9cd506532f075456645716cdd1739c1

>
>
>
>
> > I did not carry tags forward so that people could re-review and test.
> >
> >  Makefile | 4 ----
> >  1 file changed, 4 deletions(-)
> >
> > diff --git a/Makefile b/Makefile
> > index 31dcdb3d61fa..182e93d91198 100644
> > --- a/Makefile
> > +++ b/Makefile
> > @@ -568,10 +568,6 @@ ifneq ($(CROSS_COMPILE),)
> >  CLANG_FLAGS    += --target=$(notdir $(CROSS_COMPILE:%-=%))
> >  GCC_TOOLCHAIN_DIR := $(dir $(shell which $(CROSS_COMPILE)elfedit))
> >  CLANG_FLAGS    += --prefix=$(GCC_TOOLCHAIN_DIR)$(notdir $(CROSS_COMPILE))
> > -GCC_TOOLCHAIN  := $(realpath $(GCC_TOOLCHAIN_DIR)/..)
> > -endif
> > -ifneq ($(GCC_TOOLCHAIN),)
> > -CLANG_FLAGS    += --gcc-toolchain=$(GCC_TOOLCHAIN)
> >  endif
> >  ifneq ($(LLVM_IAS),1)
> >  CLANG_FLAGS    += -no-integrated-as
> >
> > base-commit: a38fd8748464831584a19438cbb3082b5a2dab15
> > --
> > 2.31.0.rc1
> >
>
>
> --
> Best Regards
> Masahiro Yamada