# 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/gcc-4.6.3-nolibc/sh4-linux/bin/sh4-linux-gcc --version
# < /opt/cross/kisskb/gcc-4.6.3-nolibc/sh4-linux/bin/sh4-linux-ld --version
# < git log --format=%s --max-count=1 e2079e93f562c7f7a030eb7642017ee5eabaaa10
# < make -s -j 120 ARCH=sh O=/kisskb/build/kbuild_sh-defconfig_sh4 CROSS_COMPILE=/opt/cross/kisskb/gcc-4.6.3-nolibc/sh4-linux/bin/sh4-linux-  defconfig
# make -s -j 120 ARCH=sh O=/kisskb/build/kbuild_sh-defconfig_sh4 CROSS_COMPILE=/opt/cross/kisskb/gcc-4.6.3-nolibc/sh4-linux/bin/sh4-linux-  
  Generating include/generated/machtypes.h
<stdin>:1511:2: warning: #warning syscall clone3 not implemented [-Wcpp]
/kisskb/src/arch/sh/kernel/cpu/sh4/../sh3/../../entry-common.S: Assembler messages:
/kisskb/src/arch/sh/kernel/cpu/sh4/../sh3/../../entry-common.S:385: Warning: overflow in branch to syscall_exit_work; converted into longer instruction sequence
/kisskb/src/arch/sh/kernel/cpu/sh4/../sh3/../../entry-common.S:388: Warning: overflow in branch to syscall_exit_work; converted into longer instruction sequence
/kisskb/src/kernel/rcu/srcutree.c: In function 'init_srcu_struct_fields':
/kisskb/src/kernel/rcu/srcutree.c:140:32: warning: 'levelspread[<U7140>]' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/kernel/rcu/srcutree.c:88:6: note: 'levelspread[<U7140>]' was declared here
/kisskb/src/fs/proc/inode.c: In function 'proc_reg_open':
/kisskb/src/include/linux/list.h:65:12: warning: 'pdeo' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/fs/proc/inode.c:338:21: note: 'pdeo' was declared here
/kisskb/src/kernel/printk/printk.c: In function 'devkmsg_sysctl_set_loglvl':
/kisskb/src/kernel/printk/printk.c:194:16: warning: 'old' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/drivers/base/regmap/regmap.c: In function 'regmap_raw_read':
/kisskb/src/drivers/base/regmap/regmap.c:2591:6: warning: 'ret' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/drivers/base/regmap/regmap.c: In function '_regmap_raw_write':
/kisskb/src/drivers/base/regmap/regmap.c:1852:6: warning: 'ret' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/drivers/sh/clk/cpg.c: In function 'r8':
/kisskb/src/drivers/sh/clk/cpg.c:41:2: warning: passing argument 1 of 'ioread8' discards 'const' qualifier from pointer target type [enabled by default]
/kisskb/src/include/asm-generic/iomap.h:29:21: note: expected 'void *' but argument is of type 'const void *'
/kisskb/src/drivers/sh/clk/cpg.c: In function 'r16':
/kisskb/src/drivers/sh/clk/cpg.c:46:2: warning: passing argument 1 of 'ioread16' discards 'const' qualifier from pointer target type [enabled by default]
/kisskb/src/include/asm-generic/iomap.h:30:21: note: expected 'void *' but argument is of type 'const void *'
/kisskb/src/drivers/sh/clk/cpg.c: In function 'r32':
/kisskb/src/drivers/sh/clk/cpg.c:51:2: warning: passing argument 1 of 'ioread32' discards 'const' qualifier from pointer target type [enabled by default]
/kisskb/src/include/asm-generic/iomap.h:32:21: note: expected 'void *' but argument is of type 'const void *'
/kisskb/src/mm/vmstat.c: In function 'sysctl_vm_numa_stat_handler':
/kisskb/src/mm/vmstat.c:90:5: warning: 'oldval' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/fs/ext4/readpage.c: In function 'ext4_mpage_readpages':
/kisskb/src/fs/ext4/readpage.c:295:1: warning: the frame size of 1200 bytes is larger than 1024 bytes [-Wframe-larger-than=]
/kisskb/src/fs/mpage.c: In function 'do_mpage_readpage':
/kisskb/src/fs/mpage.c:338:1: warning: the frame size of 1108 bytes is larger than 1024 bytes [-Wframe-larger-than=]
/kisskb/src/fs/mpage.c: In function '__mpage_writepage':
/kisskb/src/fs/mpage.c:690:1: warning: the frame size of 1148 bytes is larger than 1024 bytes [-Wframe-larger-than=]
/kisskb/src/drivers/usb/core/devio.c: In function 'async_completed':
/kisskb/src/drivers/usb/core/devio.c:613:23: warning: 'errno' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/mm/hugetlb.c: In function 'alloc_pool_huge_page':
/kisskb/src/mm/hugetlb.c:1465:5: warning: 'page' may be used uninitialized in this function [-Wuninitialized]
WARNING: "ftrace_set_clr_event" [vmlinux] is a static EXPORT_SYMBOL_GPL
WARNING: "ftrace_set_clr_event" [vmlinux] is a static EXPORT_SYMBOL_GPL
  Kernel: arch/sh/boot/zImage is ready
Completed OK
# rm -rf /kisskb/build/kbuild_sh-defconfig_sh4
# Build took: 0:00:26.997061