Nice! Now we don't need to invoke $CC to find out info about linker support.
Signed-off-by: Nick Desaulniers
Tested-by: Nick Desaulniers
On Thu, Feb 22, 2018 at 8:57 PM Masahiro Yamada <
yamada.masah...@socionext.com> wrote:
> Currently, linker options are tested by the coordination of $(CC) and
> $(LD) because LD needs some object to link.
> As commit 86a9df597cdd ("kbuild: fix linker feature test macros when
> cross compiling with Clang") addressed, we need to make sure $(CC)
> and $(LD) agree the underlying architecture of the passed object.
> This could be a bit complex when we combine tools from different groups.
> For example, we can use clang for $(CC), but we still need to rely on
> GCC toolchain for $(LD).
> So, I was searching a way for standalone testing of linker options.
> A trick I found is to use '-v'. This prints the version string, but
> also tests if the given option is recognized.
> If a given option is supported,
>$ aarch64-linux-gnu-ld -v --fix-cortex-a53-843419
>GNU ld (Linaro_Binutils-2017.11) 2.28.2.20170706
>$ echo $?
>0
> If unsupported,
>$ aarch64-linux-gnu-ld -v --fix-cortex-a53-843419
>GNU ld (crosstool-NG linaro-1.13.1-4.7-2013.04-20130415 - Linaro GCC
> 2013.04) 2.23.1
>aarch64-linux-gnu-ld: unrecognized option '--fix-cortex-a53-843419'
>aarch64-linux-gnu-ld: use the --help option for usage information
>$ echo $?
>1
> Gold works likewise.
>$ aarch64-linux-gnu-ld.gold -v --fix-cortex-a53-843419
>GNU gold (Linaro_Binutils-2017.11 2.28.2.20170706) 1.14
>masahiro@pug:~/ref/linux$ echo $?
>0
>$ aarch64-linux-gnu-ld.gold -v --fix-cortex-a53-99
>GNU gold (Linaro_Binutils-2017.11 2.28.2.20170706) 1.14
>aarch64-linux-gnu-ld.gold: --fix-cortex-a53-99: unknown option
>aarch64-linux-gnu-ld.gold: use the --help option for usage information
>$ echo $?
>1
> LLD too.
>$ ld.lld -v --gc-sections
>LLD 7.0.0 (http://llvm.org/git/lld.git
> 4a0e4190e74cea19f8a8dc625ccaebdf8b5d1585) (compatible with GNU linkers)
>$ echo $?
>0
>$ ld.lld -v --fix-cortex-a53-843419
>LLD 7.0.0 (http://llvm.org/git/lld.git
> 4a0e4190e74cea19f8a8dc625ccaebdf8b5d1585) (compatible with GNU linkers)
>$ echo $?
>0
>$ ld.lld -v --fix-cortex-a53-99
>ld.lld: error: unknown argument: --fix-cortex-a53-99
>LLD 7.0.0 (http://llvm.org/git/lld.git
> 4a0e4190e74cea19f8a8dc625ccaebdf8b5d1585) (compatible with GNU linkers)
>$ echo $?
>1
> Signed-off-by: Masahiro Yamada
> ---
> scripts/Kbuild.include | 4 +---
> 1 file changed, 1 insertion(+), 3 deletions(-)
> diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include
> index 34cbd81..f9c2f07 100644
> --- a/scripts/Kbuild.include
> +++ b/scripts/Kbuild.include
> @@ -237,9 +237,7 @@ cc-ldoption = $(call try-run-cached,\
> # ld-option
> # Usage: LDFLAGS += $(call ld-option, -X)
> -ld-option = $(call try-run-cached,\
> - $(CC) $(KBUILD_CPPFLAGS) $(CC_OPTION_CFLAGS) -x c /dev/null -c -o
> "$$TMPO"; \
> - $(LD) $(LDFLAGS) $(1) "$$TMPO" -o "$$TMP",$(1),$(2))
> +ld-option = $(call try-run-cached, $(LD) $(LDFLAGS) $(1) -v,$(1),$(2))
> # ar-option
> # Usage: KBUILD_ARFLAGS := $(call ar-option,D)
> --
> 2.7.4
--
Thanks,
~Nick Desaulniers
