| Message ID | 20221228-drop-qunused-arguments-v1-5-658cbc8fc592@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Remove clang's -Qunused-arguments from KBUILD_CPPFLAGS | expand |
On Wed, Jan 4, 2023 at 11:54 AM Nathan Chancellor <nathan@kernel.org> wrote: > > When clang's -Qunused-arguments is dropped from KBUILD_CPPFLAGS, it > points out that KBUILD_AFLAGS contains a linker flag, which will be > used: > > 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@kernel.org> Thanks for the patch! Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> > --- > Cc: mpe@ellerman.id.au > Cc: npiggin@gmail.com > Cc: christophe.leroy@csgroup.eu > Cc: linuxppc-dev@lists.ozlabs.org > --- > arch/powerpc/Makefile | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile > index dc4cbf0a5ca9..4fd630efe39d 100644 > --- a/arch/powerpc/Makefile > +++ b/arch/powerpc/Makefile > @@ -90,7 +90,7 @@ aflags-$(CONFIG_CPU_LITTLE_ENDIAN) += -mlittle-endian > > ifeq ($(HAS_BIARCH),y) > KBUILD_CFLAGS += -m$(BITS) > -KBUILD_AFLAGS += -m$(BITS) -Wl,-a$(BITS) > +KBUILD_AFLAGS += -m$(BITS) > KBUILD_LDFLAGS += -m elf$(BITS)$(LDEMULATION) > endif > > > -- > 2.39.0
diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile index dc4cbf0a5ca9..4fd630efe39d 100644 --- a/arch/powerpc/Makefile +++ b/arch/powerpc/Makefile @@ -90,7 +90,7 @@ aflags-$(CONFIG_CPU_LITTLE_ENDIAN) += -mlittle-endian ifeq ($(HAS_BIARCH),y) KBUILD_CFLAGS += -m$(BITS) -KBUILD_AFLAGS += -m$(BITS) -Wl,-a$(BITS) +KBUILD_AFLAGS += -m$(BITS) KBUILD_LDFLAGS += -m elf$(BITS)$(LDEMULATION) endif
When clang's -Qunused-arguments is dropped from KBUILD_CPPFLAGS, it points out that KBUILD_AFLAGS contains a linker flag, which will be used: 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@kernel.org> --- Cc: mpe@ellerman.id.au Cc: npiggin@gmail.com Cc: christophe.leroy@csgroup.eu Cc: linuxppc-dev@lists.ozlabs.org --- arch/powerpc/Makefile | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)