tjh.dev / kernel
Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel os linux
1
fork

Configure Feed

Select the types of activity you want to include in your feed.

kconfig: Add support for -Wimplicit-fallthrough

Add Kconfig support for -Wimplicit-fallthrough for both GCC and Clang.

The compiler option is under configuration CC_IMPLICIT_FALLTHROUGH,
which is enabled by default.

Special thanks to Nathan Chancellor who fixed the Clang bug[1][2]. This
bugfix only appears in Clang 14.0.0, so older versions still contain
the bug and -Wimplicit-fallthrough won't be enabled for them, for now.

This concludes a long journey and now we are finally getting rid
of the unintentional fallthrough bug-class in the kernel, entirely. :)

Link: https://github.com/llvm/llvm-project/commit/9ed4a94d6451046a51ef393cd62f00710820a7e8 [1]
Link: https://bugs.llvm.org/show_bug.cgi?id=51094 [2]
Link: https://github.com/KSPP/linux/issues/115
Link: https://github.com/ClangBuiltLinux/linux/issues/236
Co-developed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Co-developed-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

authored by

Gustavo A. R. Silva and committed by
Linus Torvalds dee2b702 ce49bfc8

+6 -5
+1 -5
Makefile
··· 789 789 KBUILD_CFLAGS += $(stackp-flags-y) 790 790 791 791 KBUILD_CFLAGS-$(CONFIG_WERROR) += -Werror 792 - KBUILD_CFLAGS += $(KBUILD_CFLAGS-y) 792 + KBUILD_CFLAGS += $(KBUILD_CFLAGS-y) $(CONFIG_CC_IMPLICIT_FALLTHROUGH) 793 793 794 794 ifdef CONFIG_CC_IS_CLANG 795 795 KBUILD_CPPFLAGS += -Qunused-arguments ··· 801 801 KBUILD_CFLAGS += -mno-global-merge 802 802 else 803 803 804 - # Warn about unmarked fall-throughs in switch statement. 805 - # Disabled for clang while comment to attribute conversion happens and 806 - # https://github.com/ClangBuiltLinux/linux/issues/636 is discussed. 807 - KBUILD_CFLAGS += $(call cc-option,-Wimplicit-fallthrough=5,) 808 804 # gcc inanely warns about local variables called 'main' 809 805 KBUILD_CFLAGS += -Wno-main 810 806 endif
+5
init/Kconfig
··· 885 885 config CC_HAS_INT128 886 886 def_bool !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) && 64BIT 887 887 888 + config CC_IMPLICIT_FALLTHROUGH 889 + string 890 + default "-Wimplicit-fallthrough=5" if CC_IS_GCC 891 + default "-Wimplicit-fallthrough" if CC_IS_CLANG && $(cc-option,-Wunreachable-code-fallthrough) 892 + 888 893 # 889 894 # For architectures that know their GCC __int128 support is sound 890 895 #