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Makefile: Enable -Wimplicit-fallthrough for Clang

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With the recent fixes for fallthrough warnings, it is now possible to
enable -Wimplicit-fallthrough for Clang.

It's important to mention that since we have adopted the use of the
pseudo-keyword macro fallthrough; we also want to avoid having more
/* fall through */ comments being introduced. Notice that contrary
to GCC, Clang doesn't recognize any comments as implicit fall-through
markings when the -Wimplicit-fallthrough option is enabled. So, in
order to avoid having more comments being introduced, we have to use
the option -Wimplicit-fallthrough=5 for GCC, which similar to Clang,
will cause a warning in case a code comment is intended to be used
as a fall-through marking.

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>
This commit is contained in:
Gustavo A. R. Silva 2021-07-12 00:57:54 -05:00
parent 104aba8dd7
commit b7eb335e26
1 changed files with 3 additions and 6 deletions
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Makefile
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@ -797,12 +797,6 @@ KBUILD_CFLAGS += -Wno-gnu
# source of a reference will be _MergedGlobals and not on of the whitelisted names.
# See modpost pattern 2
KBUILD_CFLAGS += -mno-global-merge
else
# Warn about unmarked fall-throughs in switch statement.
# Disabled for clang while comment to attribute conversion happens and
# https://github.com/ClangBuiltLinux/linux/issues/636 is discussed.
KBUILD_CFLAGS += $(call cc-option,-Wimplicit-fallthrough,)
endif
# These warnings generated too much noise in a regular build.
@ -983,6 +977,9 @@ NOSTDINC_FLAGS += -nostdinc -isystem $(shell $(CC) -print-file-name=include)
# warn about C99 declaration after statement
KBUILD_CFLAGS += -Wdeclaration-after-statement
# Warn about unmarked fall-throughs in switch statement.
KBUILD_CFLAGS += $(call cc-option,-Wimplicit-fallthrough=5,$(call cc-option,-Wimplicit-fallthrough,))
# Variable Length Arrays (VLAs) should not be used anywhere in the kernel
KBUILD_CFLAGS += -Wvla