# git rev-parse -q --verify e2079e93f562c7f7a030eb7642017ee5eabaaa10^{commit}
e2079e93f562c7f7a030eb7642017ee5eabaaa10
already have revision, skipping fetch
# git checkout -q -f -B kisskb e2079e93f562c7f7a030eb7642017ee5eabaaa10
# git clean -qxdf
# < git log -1
# commit e2079e93f562c7f7a030eb7642017ee5eabaaa10
# Author: Nathan Chancellor <natechancellor@gmail.com>
# Date:   Mon Aug 26 17:41:55 2019 -0700
# 
#     kbuild: Do not enable -Wimplicit-fallthrough for clang for now
#     
#     This functionally reverts commit bfd77145f35c ("Makefile: Convert
#     -Wimplicit-fallthrough=3 to just -Wimplicit-fallthrough for clang").
#     
#     clang enabled support for -Wimplicit-fallthrough in C in r369414 [1],
#     which causes a lot of warnings when building the kernel for two reasons:
#     
#     1. Clang does not support the /* fall through */ comments. There seems
#        to be a general consensus in the LLVM community that this is not
#        something they want to support. Joe Perches wrote a script to convert
#        all of the comments to a "fallthrough" keyword that will be added to
#        compiler_attributes.h [2] [3], which catches the vast majority of the
#        comments. There doesn't appear to be any consensus in the kernel
#        community when to do this conversion.
#     
#     2. Clang and GCC disagree about falling through to final case statements
#        with no content or cases that simply break:
#     
#        https://godbolt.org/z/c8csDu
#     
#        This difference contributes at least 50 warnings in an allyesconfig
#        build for x86, not considering other architectures. This difference
#        will need to be discussed to see which compiler is right [4] [5].
#     
#     [1]: https://github.com/llvm/llvm-project/commit/1e0affb6e564b7361b0aadb38805f26deff4ecfc
#     [2]: https://lore.kernel.org/lkml/61ddbb86d5e68a15e24ccb06d9b399bbf5ce2da7.camel@perches.com/
#     [3]: https://lore.kernel.org/lkml/1d2830aadbe9d8151728a7df5b88528fc72a0095.1564549413.git.joe@perches.com/
#     [4]: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91432
#     [5]: https://github.com/ClangBuiltLinux/linux/issues/636
#     
#     Given these two problems need discussion and coordination, do not enable
#     -Wimplicit-fallthrough with clang right now. Add a comment to explain
#     what is going on as well. This commit should be reverted once these two
#     issues are fully flushed out and resolved.
#     
#     Suggested-by: Masahiro Yamada <yamada.masahiro@socionext.com>
#     Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
#     Acked-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
#     Acked-by: Nick Desaulniers <ndesaulniers@google.com>
#     Acked-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
#     Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
# < /opt/cross/kisskb/br-sparc64-full-2016.08-613-ge98b4dd/bin/sparc64-linux-gcc --version
# < /opt/cross/kisskb/br-sparc64-full-2016.08-613-ge98b4dd/bin/sparc64-linux-ld --version
# < git log --format=%s --max-count=1 e2079e93f562c7f7a030eb7642017ee5eabaaa10
# < make -s -j 120 ARCH=sparc64 O=/kisskb/build/kbuild_sparc64-defconfig_sparc64 CROSS_COMPILE=/opt/cross/kisskb/br-sparc64-full-2016.08-613-ge98b4dd/bin/sparc64-linux-  defconfig
# make -s -j 120 ARCH=sparc64 O=/kisskb/build/kbuild_sparc64-defconfig_sparc64 CROSS_COMPILE=/opt/cross/kisskb/br-sparc64-full-2016.08-613-ge98b4dd/bin/sparc64-linux-  
<stdin>:1511:2: warning: #warning syscall clone3 not implemented [-Wcpp]
WARNING: EXPORT symbol "_mcount" [vmlinux] version generation failed, symbol will not be versioned.
WARNING: "ftrace_set_clr_event" [vmlinux] is a static EXPORT_SYMBOL_GPL
WARNING: EXPORT symbol "_mcount" [vmlinux] version generation failed, symbol will not be versioned.
  kernel: arch/sparc/boot/image is ready
WARNING: "ftrace_set_clr_event" [vmlinux] is a static EXPORT_SYMBOL_GPL
  kernel: arch/sparc/boot/zImage is ready
Completed OK
# rm -rf /kisskb/build/kbuild_sparc64-defconfig_sparc64
# Build took: 0:00:42.591427