On Tue, Jul 21, 2020 at 10:31 AM Fangrui Song <maskray@xxxxxxxxxx> wrote: > > When CROSS_COMPILE is set (e.g. aarch64-linux-gnu-), if > $(CROSS_COMPILE)elfedit is found at /usr/bin/aarch64-linux-gnu-elfedit, > GCC_TOOLCHAIN_DIR will be set to /usr/bin/. --prefix= will be set to > /usr/bin/ and Clang as of 11 will search for both > $(prefix)aarch64-linux-gnu-$needle and $(prefix)$needle. > > GCC searchs for $(prefix)aarch64-linux-gnu/$version/$needle, > $(prefix)aarch64-linux-gnu/$needle and $(prefix)$needle. In practice, > $(prefix)aarch64-linux-gnu/$needle rarely contains executables. > > To better model how GCC's -B/--prefix takes in effect in practice, newer > Clang (since > https://github.com/llvm/llvm-project/commit/3452a0d8c17f7166f479706b293caf6ac76ffd90) > only searches for $(prefix)$needle. Currently it will find /usr/bin/as > instead of /usr/bin/aarch64-linux-gnu-as. > > Set --prefix= to $(GCC_TOOLCHAIN_DIR)$(CROSS_COMPILE) > (/usr/bin/aarch64-linux-gnu-) so that newer Clang can find the > appropriate cross compiling GNU as (when -no-integrated-as is in > effect). > > Cc: stable@xxxxxxxxxxxxxxx > Reported-by: Nathan Chancellor <natechancellor@xxxxxxxxx> > Signed-off-by: Fangrui Song <maskray@xxxxxxxxxx> > Reviewed-by: Nathan Chancellor <natechancellor@xxxxxxxxx> > Tested-by: Nathan Chancellor <natechancellor@xxxxxxxxx> > Tested-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx> Reviewed-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx> > Link: https://github.com/ClangBuiltLinux/linux/issues/1099 > --- > Changes in v2: > * Updated description to add tags and the llvm-project commit link. > * Fixed a typo. > > Changes in v3: > * Add Cc: stable@xxxxxxxxxxxxxxx > --- > Makefile | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/Makefile b/Makefile > index 0b5f8538bde5..3ac83e375b61 100644 > --- a/Makefile > +++ b/Makefile > @@ -567,7 +567,7 @@ ifneq ($(shell $(CC) --version 2>&1 | head -n 1 | grep clang),) > ifneq ($(CROSS_COMPILE),) > CLANG_FLAGS += --target=$(notdir $(CROSS_COMPILE:%-=%)) > GCC_TOOLCHAIN_DIR := $(dir $(shell which $(CROSS_COMPILE)elfedit)) > -CLANG_FLAGS += --prefix=$(GCC_TOOLCHAIN_DIR) > +CLANG_FLAGS += --prefix=$(GCC_TOOLCHAIN_DIR)$(CROSS_COMPILE) > GCC_TOOLCHAIN := $(realpath $(GCC_TOOLCHAIN_DIR)/..) > endif > ifneq ($(GCC_TOOLCHAIN),) > -- > 2.28.0.rc0.105.gf9edc3c819-goog > -- Thanks, ~Nick Desaulniers
