# git rev-parse -q --verify 736116436e5b99b46e1a49c17cae6f6ee0a30e84^{commit}
736116436e5b99b46e1a49c17cae6f6ee0a30e84
already have revision, skipping fetch
# git checkout -q -f -B kisskb 736116436e5b99b46e1a49c17cae6f6ee0a30e84
# git clean -qxdf
# < git log -1
# commit 736116436e5b99b46e1a49c17cae6f6ee0a30e84
# Author: Gustavo A. R. Silva <gustavoars@kernel.org>
# Date:   Wed Sep 2 23:25:55 2020 -0500
# 
#     include: jhash/signal: Fix fall-through warnings for Clang
#     
#     In preparation to enable -Wimplicit-fallthrough for Clang, explicitly
#     add break statements instead of letting the code fall through to the
#     next case.
#     
#     This patch adds four break statements that, together, fix almost 80,000
#     warnings when building Linux 5.9-rc3 with Clang 12.0.0 and this[1] change
#     reverted. Notice that in order to enable -Wimplicit-fallthrough for Clang,
#     such change[1] is meant to be reverted at some point. So, this patch helps
#     to move in that direction.
#     
#     Something important to mention is that there is currently a discrepancy
#     between GCC and Clang when dealing with switch fall-through to empty case
#     statements or to cases that only contain a break/continue/return
#     statement[2][3][4].
#     
#     Now that the -Wimplicit-fallthrough option has been globally enabled[5],
#     any compiler should really warn on missing either a fallthrough annotation
#     or any of the other case-terminating statements (break/continue/return/
#     goto) when falling through to the next case statement. Making exceptions
#     to this introduces variation in case handling which may continue to lead
#     to bugs, misunderstandings, and a general lack of robustness. The point
#     of enabling options like -Wimplicit-fallthrough is to prevent human error
#     and aid developers in spotting bugs before their code is even built/
#     submitted/committed, therefore eliminating classes of bugs. So, min order
#     to really accomplish this, we should, and can, move in the direction of
#     addressing any error-prone scenarios and get rid of the unintentional
#     fallthrough bug-class in the kernel, entirely, even if there is some minor
#     redundancy. Better to have explicit case-ending statements than continue to
#     have exceptions where one must guess as to the right result. The compiler
#     will eliminate any actual redundancy.
#     
#     [1] commit e2079e93f562c ("kbuild: Do not enable -Wimplicit-fallthrough for clang for now")
#     [2] https://github.com/ClangBuiltLinux/linux/issues/636
#     [3] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91432
#     [4] https://godbolt.org/z/xgkvIh
#     [5] commit a035d552a93b ("Makefile: Globally enable fall-through warning")
#     
#     Co-developed-by: Kees Cook <keescook@chromium.org>
#     Signed-off-by: Kees Cook <keescook@chromium.org>
#     Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
# < /opt/cross/kisskb/korg/gcc-4.9.4-nolibc/i386-linux/bin/i386-linux-gcc --version
# < /opt/cross/kisskb/korg/gcc-4.9.4-nolibc/i386-linux/bin/i386-linux-ld --version
# < git log --format=%s --max-count=1 736116436e5b99b46e1a49c17cae6f6ee0a30e84
# < make -s -j 8 ARCH=i386 O=/kisskb/build/gustavoars_i386-allnoconfig_i386-gcc4.9 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-4.9.4-nolibc/i386-linux/bin/i386-linux-  allnoconfig
# < make -s -j 8 ARCH=i386 O=/kisskb/build/gustavoars_i386-allnoconfig_i386-gcc4.9 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-4.9.4-nolibc/i386-linux/bin/i386-linux-  help
# make -s -j 8 ARCH=i386 O=/kisskb/build/gustavoars_i386-allnoconfig_i386-gcc4.9 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-4.9.4-nolibc/i386-linux/bin/i386-linux-  olddefconfig
# make -s -j 8 ARCH=i386 O=/kisskb/build/gustavoars_i386-allnoconfig_i386-gcc4.9 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-4.9.4-nolibc/i386-linux/bin/i386-linux-  
Completed OK
# rm -rf /kisskb/build/gustavoars_i386-allnoconfig_i386-gcc4.9
# Build took: 0:00:26.331796