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

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Message-ID: <20210302214358.qr6enl6majzplhij@google.com>
Date:   Tue, 2 Mar 2021 13:43:58 -0800
From:   Fangrui Song <maskray@...gle.com>
To:     Nathan Chancellor <nathan@...nel.org>
Cc:     Masahiro Yamada <masahiroy@...nel.org>,
        Michal Marek <michal.lkml@...kovi.net>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org,
        clang-built-linux@...glegroups.com
Subject: Re: [PATCH 1/2] Makefile: Remove '--gcc-toolchain' flag

Reviewed-by: Fangrui Song <maskray@...gle.com>

Thanks for the clean-up!
--gcc-toolchain= is an obsscure way searching for GCC installation prefixes (--prefix).
The logic is complex and different for different distributions/architectures.

If we specify --prefix= (-B) explicitly, --gcc-toolchain is not needed.

On 2021-03-02, Nathan Chancellor wrote:
>This is not necessary anymore now that we specify '--prefix=', which
>tells clang exactly where to find the GNU cross tools. 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.
>
>Signed-off-by: Nathan Chancellor <nathan@...nel.org>
>---
> Makefile | 4 ----
> 1 file changed, 4 deletions(-)
>
>diff --git a/Makefile b/Makefile
>index f9b54da2fca0..c20f0ad8be73 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: 7a7fd0de4a9804299793e564a555a49c1fc924cb
>-- 
>2.31.0.rc0.75.gec125d1bc1
>
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