Commit 5241ab4c authored Jul 29, 2019 by Masahiro Yamada

kbuild: initialize CLANG_FLAGS correctly in the top Makefile



CLANG_FLAGS is initialized by the following line:

  CLANG_FLAGS     := --target=$(notdir $(CROSS_COMPILE:%-=%))

..., which is run only when CROSS_COMPILE is set.

Some build targets (bindeb-pkg etc.) recurse to the top Makefile.

When you build the kernel with Clang but without CROSS_COMPILE,
the same compiler flags such as -no-integrated-as are accumulated
into CLANG_FLAGS.

If you run 'make CC=clang' and then 'make CC=clang bindeb-pkg',
Kbuild will recompile everything needlessly due to the build command
change.

Fix this by correctly initializing CLANG_FLAGS.

Fixes: 238bcbc4 ("kbuild: consolidate Clang compiler flags")
Cc: <stable@vger.kernel.org> # v5.0+
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Acked-by: Nick Desaulniers <ndesaulniers@google.com>

parent 62244554

Makefile

+2 −1

Original line number	Diff line number	Diff line
		@@ -472,6 +472,7 @@ KBUILD_CFLAGS_MODULE := -DMODULE
		KBUILD_LDFLAGS_MODULE := -T $(srctree)/scripts/module-common.lds
		KBUILD_LDFLAGS :=
		GCC_PLUGINS_CFLAGS :=
		CLANG_FLAGS :=

		export ARCH SRCARCH CONFIG_SHELL HOSTCC KBUILD_HOSTCFLAGS CROSS_COMPILE AS LD CC
		export CPP AR NM STRIP OBJCOPY OBJDUMP PAHOLE KBUILD_HOSTLDFLAGS KBUILD_HOSTLDLIBS
		@@ -519,7 +520,7 @@ endif

		ifneq ($(shell $(CC) --version 2>&1 \| head -n 1 \| grep clang),)
		ifneq ($(CROSS_COMPILE),)
		CLANG_FLAGS := --target=$(notdir $(CROSS_COMPILE:%-=%))
		CLANG_FLAGS += --target=$(notdir $(CROSS_COMPILE:%-=%))
		GCC_TOOLCHAIN_DIR := $(dir $(shell which $(CROSS_COMPILE)elfedit))
		CLANG_FLAGS += --prefix=$(GCC_TOOLCHAIN_DIR)
		GCC_TOOLCHAIN := $(realpath $(GCC_TOOLCHAIN_DIR)/..)

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