On Tue, Feb 08, 2022 at 01:23:32PM +0900, Masahiro Yamada wrote:
On Thu, Feb 3, 2022 at 8:12 AM Nick Desaulniers ndesaulniers@google.com wrote:
On Wed, Feb 2, 2022 at 3:07 PM Nathan Chancellor nathan@kernel.org wrote:
-Wunaligned-access is a new warning in clang that is default enabled for arm and arm64 under certain circumstances within the clang frontend (see LLVM commit below). On v5.17-rc2, an ARCH=arm allmodconfig build shows 1284 total/70 unique instances of this warning (most of the instances are in header files), which is quite noisy.
To keep a normal build green through CONFIG_WERROR, only show this warning with W=1, which will allow automated build systems to catch new instances of the warning so that the total number can be driven down to zero eventually since catching unaligned accesses at compile time would be generally useful.
Cc: stable@vger.kernel.org Link: https://github.com/llvm/llvm-project/commit/35737df4dcd28534bd3090157c224c19... Link: https://github.com/ClangBuiltLinux/linux/issues/1569 Link: https://github.com/ClangBuiltLinux/linux/issues/1576 Signed-off-by: Nathan Chancellor nathan@kernel.org
Thanks to you and Arnd for working out whether this is important to pursue. Sounds like it is. Reviewed-by: Nick Desaulniers ndesaulniers@google.com
I assume this should be considered as a bug fix to avoid the error for the combination of CONFIG_WERROR=y and the latest Clang.
Applied to linux-kbuild/fixes. Thanks.
Yes, this is what I was hoping for! Thank you, I'll try to make that more clear in the future.
Cheers, Nathan
v1 -> v2: https://lore.kernel.org/r/20220201232229.2992968-1-nathan@kernel.org/
- Move to W=1 instead of W=2 so that new instances are caught (Arnd).
- Add links to the ClangBuiltLinux issue tracker.
scripts/Makefile.extrawarn | 1 + 1 file changed, 1 insertion(+)
diff --git a/scripts/Makefile.extrawarn b/scripts/Makefile.extrawarn index d53825503874..8be892887d71 100644 --- a/scripts/Makefile.extrawarn +++ b/scripts/Makefile.extrawarn @@ -51,6 +51,7 @@ KBUILD_CFLAGS += -Wno-sign-compare KBUILD_CFLAGS += -Wno-format-zero-length KBUILD_CFLAGS += $(call cc-disable-warning, pointer-to-enum-cast) KBUILD_CFLAGS += -Wno-tautological-constant-out-of-range-compare +KBUILD_CFLAGS += $(call cc-disable-warning, unaligned-access) endif
endif
base-commit: 26291c54e111ff6ba87a164d85d4a4e134b7315c
2.35.1
-- Thanks, ~Nick Desaulniers
-- Best Regards Masahiro Yamada