On 17.09.2018 20:06, Masahiro Yamada wrote: > Hi Stefan, > > 2018-09-18 11:31 GMT+09:00 Stefan Agner <stefan@xxxxxxxx>: >> When using a GCC cross toolchain which is not in a compiled in >> Clang search path, Clang reverts to the system assembler and >> linker. This leads to assembler or linker errors, depending on >> which tool is first used for a given architecture. >> >> It seems that Clang is not searching $PATH for a matching >> assembler or linker. > > > The current code passes the absolute path of toolchains > to --gcc-toolchain option. > In my understanding, this is enough for Clang > to find the proper linker and the assembler. > > > Why is the --prefix option also needed ? > It seems that Clang makes a difference between "toolchain" and search path for toolchain binaries. Without this patch building fails for the described use case, see the github link for more context. -- Stefan > > Am I missing something? > > > >> Make sure that Clang picks up the correct assembler or linker by >> passing the cross compilers bin directory as search path. >> >> This allows to use Clang provided by distributions with GCC >> toolchains not in /usr/bin. >> >> Link: https://github.com/ClangBuiltLinux/linux/issues/78 >> Signed-off-by: Stefan Agner <stefan@xxxxxxxx> >> --- >> Nick, I removed your Reviewed-by since I had to change variable >> assignment slightly... >> >> Makefile | 8 +++++--- >> 1 file changed, 5 insertions(+), 3 deletions(-) >> >> diff --git a/Makefile b/Makefile >> index 4d5c883a98e5..d5de2db4b549 100644 >> --- a/Makefile >> +++ b/Makefile >> @@ -495,13 +495,15 @@ endif >> ifeq ($(cc-name),clang) >> ifneq ($(CROSS_COMPILE),) >> CLANG_TARGET := --target=$(notdir $(CROSS_COMPILE:%-=%)) >> -GCC_TOOLCHAIN := $(realpath $(dir $(shell which $(LD)))/..) >> +GCC_TOOLCHAIN_DIR := $(dir $(shell which $(LD))) >> +CLANG_PREFIX := --prefix=$(GCC_TOOLCHAIN_DIR) >> +GCC_TOOLCHAIN := $(realpath $(GCC_TOOLCHAIN_DIR)/..) >> endif >> ifneq ($(GCC_TOOLCHAIN),) >> CLANG_GCC_TC := --gcc-toolchain=$(GCC_TOOLCHAIN) >> endif >> -KBUILD_CFLAGS += $(CLANG_TARGET) $(CLANG_GCC_TC) >> -KBUILD_AFLAGS += $(CLANG_TARGET) $(CLANG_GCC_TC) >> +KBUILD_CFLAGS += $(CLANG_TARGET) $(CLANG_GCC_TC) $(CLANG_PREFIX) >> +KBUILD_AFLAGS += $(CLANG_TARGET) $(CLANG_GCC_TC) $(CLANG_PREFIX) >> KBUILD_CFLAGS += $(call cc-option, -no-integrated-as) >> KBUILD_AFLAGS += $(call cc-option, -no-integrated-as) >> endif >> -- >> 2.19.0 >>
