Buildresult: linus/mmu_defconfig/microblaze-gcc5 built on Jul 18 2021, 03:03

kisskb

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Status:	OK
Date/Time:	Jul 18 2021, 03:03
Duration:	0:01:05.885652
Builder:	blade46
Revision:	Revert "Makefile: Enable -Wimplicit-fallthrough for Clang" (`d936eb23874433caa3e3d841cfa16f5434b85dcf)`
Target:	linus/mmu_defconfig/microblaze-gcc5
Branch:	linus
Compiler:	microblaze-gcc5 (microblazeel-linux-gcc.br_real (Buildroot 2016.11-git-00613-ge98b4dd) 5.4.0 / GNU ld (GNU Binutils) 2.26.1)
Config:	mmu_defconfig (download)
Log:	Download original No warnings found in log. Full Log # git rev-parse -q --verify d936eb23874433caa3e3d841cfa16f5434b85dcf^{commit} d936eb23874433caa3e3d841cfa16f5434b85dcf already have revision, skipping fetch # git checkout -q -f -B kisskb d936eb23874433caa3e3d841cfa16f5434b85dcf # git clean -qxdf # < git log -1 # commit d936eb23874433caa3e3d841cfa16f5434b85dcf # Author: Linus Torvalds <torvalds@linux-foundation.org> # Date: Thu Jul 15 18:05:31 2021 -0700 # # Revert "Makefile: Enable -Wimplicit-fallthrough for Clang" # # This reverts commit b7eb335e26a9c7f258c96b3962c283c379d3ede0. # # It turns out that the problem with the clang -Wimplicit-fallthrough # warning is not about the kernel source code, but about clang itself, and # that the warning is unusable until clang fixes its broken ways. # # In particular, when you enable this warning for clang, you not only get # warnings about implicit fallthroughs. You also get this: # # warning: fallthrough annotation in unreachable code [-Wimplicit-fallthrough] # # which is completely broken becasue it # # (a) doesn't even tell you where the problem is (seriously: no line # numbers, no filename, no nothing). # # (b) is fundamentally broken anyway, because there are perfectly valid # reasons to have a fallthrough statement even if it turns out that # it can perhaps not be reached. # # In the kernel, an example of that second case is code in the scheduler: # # switch (state) { # case cpuset: # if (IS_ENABLED(CONFIG_CPUSETS)) { # cpuset_cpus_allowed_fallback(p); # state = possible; # break; # } # fallthrough; # case possible: # # where if CONFIG_CPUSETS is enabled you actually never hit the # fallthrough case at all. But that in no way makes the fallthrough # wrong. # # So the warning is completely broken, and enabling it for clang is a very # bad idea. # # In the meantime, we can keep the gcc option enabled, and make the gcc # build use # # -Wimplicit-fallthrough=5 # # which means that we will at least continue to require a proper # fallthrough statement, and that gcc won't silently accept the magic # comment versions. Because gcc does this all correctly, and while the odd # "=5" part is kind of obscure, it's documented in [1]: # # "-Wimplicit-fallthrough=5 doesn’t recognize any comments as # fallthrough comments, only attributes disable the warning" # # so if clang ever fixes its bad behavior we can try enabling it there again. # # Link: https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html [1] # Cc: Kees Cook <keescook@chromium.org> # Cc: Gustavo A. R. Silva <gustavoars@kernel.org> # Cc: Nathan Chancellor <nathan@kernel.org> # Cc: Nick Desaulniers <ndesaulniers@google.com> # Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> # < /opt/cross/kisskb/br-microblaze-full-2016.08-613-ge98b4dd/bin/microblazeel-linux-gcc --version # < /opt/cross/kisskb/br-microblaze-full-2016.08-613-ge98b4dd/bin/microblazeel-linux-ld --version # < git log --format=%s --max-count=1 d936eb23874433caa3e3d841cfa16f5434b85dcf # < make -s -j 32 ARCH=microblaze O=/kisskb/build/linus_mmu_defconfig_microblaze CROSS_COMPILE=/opt/cross/kisskb/br-microblaze-full-2016.08-613-ge98b4dd/bin/microblazeel-linux- mmu_defconfig # < make -s -j 32 ARCH=microblaze O=/kisskb/build/linus_mmu_defconfig_microblaze CROSS_COMPILE=/opt/cross/kisskb/br-microblaze-full-2016.08-613-ge98b4dd/bin/microblazeel-linux- help # make -s -j 32 ARCH=microblaze O=/kisskb/build/linus_mmu_defconfig_microblaze CROSS_COMPILE=/opt/cross/kisskb/br-microblaze-full-2016.08-613-ge98b4dd/bin/microblazeel-linux- olddefconfig # make -s -j 32 ARCH=microblaze O=/kisskb/build/linus_mmu_defconfig_microblaze CROSS_COMPILE=/opt/cross/kisskb/br-microblaze-full-2016.08-613-ge98b4dd/bin/microblazeel-linux- Kernel: arch/microblaze/boot/linux.bin is ready (#1) Completed OK # rm -rf /kisskb/build/linus_mmu_defconfig_microblaze # Build took: 0:01:05.885652

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