Nathan Chancellor <nathan@xxxxxxxxxx> writes:
> When clang's -Qunused-arguments is dropped from KBUILD_CPPFLAGS, it
> points out that KBUILD_AFLAGS contains a linker flag, which will be
> used:
Should that say "unused" ?
> clang: error: -Wl,-a32: 'linker' input unused [-Werror,-Wunused-command-line-argument]
>
> This was likely supposed to be '-Wa,-a$(BITS)'. However, this change is
> unnecessary, as all supported versions of clang and gcc will pass '-a64'
> or '-a32' to GNU as based on the value of '-m'; the behavior of the
> latest stable release of the oldest supported major version of each
> compiler is shown below and each compiler's latest release exhibits the
> same behavior (GCC 12.2.0 and Clang 15.0.6).
>
> $ powerpc64-linux-gcc --version | head -1
> powerpc64-linux-gcc (GCC) 5.5.0
>
> $ powerpc64-linux-gcc -m64 -### -x assembler-with-cpp -c -o /dev/null /dev/null &| grep 'as '
> .../as -a64 -mppc64 -many -mbig -o /dev/null /tmp/cctwuBzZ.s
>
> $ powerpc64-linux-gcc -m32 -### -x assembler-with-cpp -c -o /dev/null /dev/null &| grep 'as '
> .../as -a32 -mppc -many -mbig -o /dev/null /tmp/ccaZP4mF.sg
>
> $ clang --version | head -1
> Ubuntu clang version 11.1.0-++20211011094159+1fdec59bffc1-1~exp1~20211011214622.5
>
> $ clang --target=powerpc64-linux-gnu -fno-integrated-as -m64 -### \
> -x assembler-with-cpp -c -o /dev/null /dev/null &| grep gnu-as
> "/usr/bin/powerpc64-linux-gnu-as" "-a64" "-mppc64" "-many" "-o" "/dev/null" "/tmp/null-80267c.s"
>
> $ clang --target=powerpc64-linux-gnu -fno-integrated-as -m64 -### \
> -x assembler-with-cpp -c -o /dev/null /dev/null &| grep gnu-as
> "/usr/bin/powerpc64-linux-gnu-as" "-a32" "-mppc" "-many" "-o" "/dev/null" "/tmp/null-ab8f8d.s"
>
> Remove this flag altogether to avoid future issues.
>
> Fixes: 1421dc6d4829 ("powerpc/kbuild: Use flags variables rather than overriding LD/CC/AS")
> Signed-off-by: Nathan Chancellor <nathan@xxxxxxxxxx>
> Reviewed-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
> ---
> Cc: mpe@xxxxxxxxxxxxxx
Acked-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx> (powerpc)
cheers
