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From: Nathan Chancellor <nathan@kernel.org>
To: Masahiro Yamada <masahiroy@kernel.org>,
	Michal Marek <michal.lkml@markovi.net>,
	Nick Desaulniers <ndesaulniers@google.com>
Cc: linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org,
	clang-built-linux@googlegroups.com,
	Sedat Dilek <sedat.dilek@gmail.com>,
	Fangrui Song <maskray@google.com>,
	Nathan Chancellor <nathan@kernel.org>
Subject: [PATCH v2 1/2] Makefile: Remove '--gcc-toolchain' flag
Date: Tue,  9 Mar 2021 13:59:14 -0700
Message-ID: <20210309205915.2340265-1-nathan@kernel.org> (raw)
In-Reply-To: <20210302210646.3044738-1-nathan@kernel.org>

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@kernel.org>
---

v1 -> v2:

* Improve commit message (add history behind flag and link to Fangrui's
  documentation improvement).

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


  parent reply index

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-02 21:06 [PATCH " Nathan Chancellor
2021-03-02 21:06 ` [PATCH 2/2] Makefile: Only specify '--prefix=' when building with clang + GNU as Nathan Chancellor
2021-03-02 22:02   ` Fangrui Song
2021-03-02 22:09     ` Nick Desaulniers
2021-03-02 22:40       ` Nick Desaulniers
2021-03-09 19:55   ` Masahiro Yamada
2021-03-09 19:58     ` Masahiro Yamada
2021-03-02 21:43 ` [PATCH 1/2] Makefile: Remove '--gcc-toolchain' flag Fangrui Song
2021-03-03  8:33   ` Masahiro Yamada
2021-03-02 22:33 ` Nick Desaulniers
2021-03-03  3:25 ` Sedat Dilek
2021-03-03 14:22   ` Sedat Dilek
2021-03-09 20:59 ` Nathan Chancellor [this message]
2021-03-09 20:59   ` [PATCH v2 2/2] Makefile: Only specify '--prefix=' when building with clang + GNU as Nathan Chancellor
2021-03-09 21:15   ` [PATCH v2 1/2] Makefile: Remove '--gcc-toolchain' flag Fangrui Song
2021-03-15 16:21   ` Masahiro Yamada
2021-03-15 16:41     ` Sedat Dilek
2021-03-16 15:36       ` Masahiro Yamada

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