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

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Date:   Tue, 16 Mar 2021 01:21:55 +0900
From:   Masahiro Yamada <masahiroy@...nel.org>
To:     Nathan Chancellor <nathan@...nel.org>
Cc:     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>,
        Sedat Dilek <sedat.dilek@...il.com>,
        Fangrui Song <maskray@...gle.com>
Subject: Re: [PATCH v2 1/2] Makefile: Remove '--gcc-toolchain' flag

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.





> 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