From: Nick Desaulniers <ndesaulniers@google.com>
To: Segher Boessenkool <segher@kernel.crashing.org>,
Nathan Chancellor <nathan@kernel.org>
Cc: kernel test robot <lkp@intel.com>,
linux-kbuild@vger.kernel.org, trix@redhat.com,
masahiroy@kernel.org, llvm@lists.linux.dev, npiggin@gmail.com,
linuxppc-dev@lists.ozlabs.org, nicolas@fjasle.eu
Subject: Re: [PATCH 06/14] powerpc/vdso: Remove unused '-s' flag from ASFLAGS
Date: Mon, 9 Jan 2023 15:14:33 -0800 [thread overview]
Message-ID: <CAKwvOdn3En6kdGBmDF4nFYpMgR0Dx0cgaTH1pPZdEcAJTZWaPg@mail.gmail.com> (raw)
In-Reply-To: <20230109222337.GM25951@gate.crashing.org>
On Mon, Jan 9, 2023 at 2:29 PM Segher Boessenkool
<segher@kernel.crashing.org> wrote:
>
> Hi! Happy new year all.
HNY Segher! :)
>
> On Mon, Jan 09, 2023 at 01:58:32PM -0800, Nick Desaulniers wrote:
> > On Wed, Jan 4, 2023 at 11:55 AM Nathan Chancellor <nathan@kernel.org> wrote:
> > >
> > > When clang's -Qunused-arguments is dropped from KBUILD_CPPFLAGS, it
> > > warns that ASFLAGS contains '-s', which is a linking phase option, so it
> > > is unused.
> > >
> > > clang-16: error: argument unused during compilation: '-s' [-Werror,-Wunused-command-line-argument]
> > >
> > > Looking at the GAS sources, '-s' is only useful when targeting Solaris
> > > and it is ignored for the powerpc target so just drop the flag
> > > altogether, as it is not needed.
> >
> > Do you have any more info where you found this? I don't see -s
> > documented as an assembler flag.
> > https://sourceware.org/binutils/docs/as/PowerPC_002dOpts.html
> > https://sourceware.org/binutils/docs/as/Invoking.html
>
> It is required by POSIX (for the c99 command, anyway). It *also* is
> required to be supported when producing object files (so when no linking
> is done).
>
> It is a GCC flag, and documented just fine:
> https://gcc.gnu.org/onlinedocs/gcc/Link-Options.html#index-s
>
> (Yes, that says it is for linking; but the option is allowed without
> error of any kind always).
>
> (ASFLAGS sounds like it is for assembler commands, but it really is
> for compiler commands that just happen to get .S input files).
>
> > The patch seems fine to me, but what was this ever supposed to be?
> > FWICT it predates git history (looking at
> > arch/powerpc/kernel/vdso32/Makefile at fc15351d9d63)
>
> Yeah, good question. This compiler flag does the moral equivalent of
> strip -s (aka --strip-all). Maybe this was needed at some point, or
> the symbol or debug info was just annoying (during bringup or similar)?
Ah right! Ok then, I think we might keep the patch's diff, but update
the commit message to mention this is a linker flag that's unused
since the compiler is being invoked but not the linker (the compiler
is being used as the driver to assemble a single assembler source
without linking it; linking is then driven by the linker in a separate
make rule).
Then we might want to revisit that s390 patch, too?
https://lore.kernel.org/llvm/20221228-drop-qunused-arguments-v1-9-658cbc8fc592@kernel.org/
>
> > Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
> Reviewed-by: Segher Boessenkool <segher@kernel.crashing.org>
>
>
> Segher
--
Thanks,
~Nick Desaulniers
next prev parent reply other threads:[~2023-01-09 23:14 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-04 19:54 [PATCH 00/14] Remove clang's -Qunused-arguments from KBUILD_CPPFLAGS Nathan Chancellor
2023-01-04 19:54 ` [PATCH 01/14] x86/boot/compressed: prefer cc-option for CFLAGS additions Nathan Chancellor
2023-01-04 19:54 ` [PATCH 02/14] MIPS: Always use -Wa,-msoft-float and eliminate GAS_HAS_SET_HARDFLOAT Nathan Chancellor
2023-01-09 21:18 ` Nick Desaulniers
2023-01-10 7:45 ` Philippe Mathieu-Daudé
2023-01-10 8:30 ` Thomas Bogendoerfer
2023-01-04 19:54 ` [PATCH 03/14] MIPS: Prefer cc-option for additions to cflags Nathan Chancellor
2023-01-09 21:21 ` Nick Desaulniers
2023-01-10 7:42 ` Philippe Mathieu-Daudé
2023-01-10 8:30 ` Thomas Bogendoerfer
2023-01-04 19:54 ` [PATCH 04/14] kbuild: Update assembler calls to use proper flags and language target Nathan Chancellor
2023-01-04 19:54 ` [PATCH 05/14] powerpc: Remove linker flag from KBUILD_AFLAGS Nathan Chancellor
2023-01-09 21:24 ` Nick Desaulniers
2023-01-04 19:54 ` [PATCH 06/14] powerpc/vdso: Remove unused '-s' flag from ASFLAGS Nathan Chancellor
2023-01-09 21:58 ` Nick Desaulniers
2023-01-09 22:15 ` Nathan Chancellor
2023-01-09 22:21 ` Nick Desaulniers
2023-01-09 22:23 ` Segher Boessenkool
2023-01-09 22:37 ` Nathan Chancellor
2023-01-09 22:47 ` Segher Boessenkool
2023-01-09 23:14 ` Nick Desaulniers [this message]
2023-01-10 0:51 ` Nathan Chancellor
2023-01-10 11:45 ` Segher Boessenkool
2023-01-10 15:02 ` Nathan Chancellor
[not found] ` <20230109222337.GM25951__25255.3859770828$1673303520$gmane$org@gate.crashing.org>
2023-01-10 0:22 ` Andreas Schwab
2023-01-10 0:43 ` Segher Boessenkool
2023-01-04 19:54 ` [PATCH 07/14] powerpc/vdso: Improve linker flags Nathan Chancellor
2023-01-09 22:08 ` Nick Desaulniers
2023-01-09 22:15 ` Nathan Chancellor
2023-01-04 19:54 ` [PATCH 08/14] powerpc/vdso: Remove an unsupported flag from vgettimeofday-32.o with clang Nathan Chancellor
2023-01-09 22:12 ` Nick Desaulniers
2023-01-09 22:38 ` Nathan Chancellor
2023-01-09 23:16 ` Nick Desaulniers
2023-01-04 19:54 ` [PATCH 09/14] s390/vdso: Drop unused '-s' flag from KBUILD_AFLAGS_64 Nathan Chancellor
2023-01-05 7:27 ` Sven Schnelle
2023-01-04 19:54 ` [PATCH 10/14] s390/vdso: Drop '-shared' from KBUILD_CFLAGS_64 Nathan Chancellor
2023-01-05 7:31 ` Sven Schnelle
2023-01-04 19:54 ` [PATCH 11/14] s390/purgatory: Remove unused '-MD' and unnecessary '-c' flags Nathan Chancellor
2023-01-05 7:33 ` Sven Schnelle
2023-01-04 19:54 ` [PATCH 12/14] drm/amd/display: Do not add '-mhard-float' to dml_ccflags for clang Nathan Chancellor
2023-01-05 14:21 ` Alex Deucher
2023-01-04 19:54 ` [PATCH 13/14] kbuild: Turn a couple more of clang's unused option warnings into errors Nathan Chancellor
2023-01-09 22:15 ` Nick Desaulniers
2023-01-04 19:54 ` [PATCH 14/14] kbuild: Stop using '-Qunused-arguments' with clang Nathan Chancellor
2023-01-09 22:17 ` Nick Desaulniers
2023-01-05 8:00 ` [PATCH 00/14] Remove clang's -Qunused-arguments from KBUILD_CPPFLAGS Heiko Carstens
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