Hi Masahiro,
Nit: s/CLANG_CFLAGS/CLANG_FLAGS/ in the title and a small typo below.
On Sun, Apr 09, 2023 at 11:53:57PM +0900, Masahiro Yamada wrote:
> When preprocessing arch/*/kernel/vmlinux.lds.S, the target triple is
> not passed to $(CPP) because we add it only to KBUILD_{C,A}FLAGS.
>
> As a result, the linker script is preprocessed with predefined macros
> for the build host instead of the target.
>
> Assuming you use an x86 build machine, compare the following:
>
> $ clang -dM -E -x c /dev/null
> $ clang -dM -E -x c /dev/null -target aarch64-linux-gnu
>
> There is no actual problem presumably because our linker scripts do not
> rely on such predefined macros, but it is better to define correct ones.
>
> Move $(CFLAGS_CFLAGS) to KBUILD_CPPFLAGS, so that all *.c, *.S, *.lds.S
^ CLANG_FLAGS
> will be processed with the proper target triple.
>
> Reported-by: Tom Rini <trini@xxxxxxxxxxxx>
> Signed-off-by: Masahiro Yamada <masahiroy@xxxxxxxxxx>
We will need to sort out the report from the kbuild test robot before we
can do this. Otherwise, I think this should be fine, although I am
curious if -Wunused-command-line-argument might fire more because there
may be flags are unused while preprocessing. I will run this through my
test matrix once the other report has been addressed to make sure there
is nothing else obviously wrong with this change.
Cheers,
Nathan
> ---
>
> scripts/Makefile.clang | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/scripts/Makefile.clang b/scripts/Makefile.clang
> index 70b354fa1cb4..93ca059cc3b8 100644
> --- a/scripts/Makefile.clang
> +++ b/scripts/Makefile.clang
> @@ -38,6 +38,5 @@ CLANG_FLAGS += -Werror=unknown-warning-option
> CLANG_FLAGS += -Werror=ignored-optimization-argument
> CLANG_FLAGS += -Werror=option-ignored
> CLANG_FLAGS += -Werror=unused-command-line-argument
> -KBUILD_CFLAGS += $(CLANG_FLAGS)
> -KBUILD_AFLAGS += $(CLANG_FLAGS)
> +KBUILD_CPPFLAGS += $(CLANG_FLAGS)
> export CLANG_FLAGS
> --
> 2.37.2
>
