linux-kernel - [PATCH] Makefile: Convert -Wimplicit-fallthrough=3 to just -Wimplicit-fallthrough for clang

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Date:   Mon, 05 Aug 2019 15:11:15 -0700
From:   Joe Perches <joe@...ches.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        LKML <linux-kernel@...r.kernel.org>,
        clang-built-linux@...glegroups.com
Subject: [PATCH] Makefile: Convert -Wimplicit-fallthrough=3 to just
 -Wimplicit-fallthrough for clang

A compilation -Wimplicit-fallthrough warning was enabled by
commit a035d552a93b ("Makefile: Globally enable fall-through warning")

Even though clang 10.0.0 does not currently support this warning
without a patch, clang currently does not support a value for this
option.

Link: https://bugs.llvm.org/show_bug.cgi?id=39382

The gcc default for this warning is 3 so removing the =3 has no
effect for gcc and enables the warning for patched versions of clang.

Also remove the =3 from an existing use in a parisc Makefile:
arch/parisc/math-emu/Makefile

Signed-off-by: Joe Perches <joe@...ches.com>
---
 Makefile                      | 2 +-
 arch/parisc/math-emu/Makefile | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/Makefile b/Makefile
index 5ee6f6889869..a3985421fd29 100644
--- a/Makefile
+++ b/Makefile
@@ -845,7 +845,7 @@ NOSTDINC_FLAGS += -nostdinc -isystem $(shell $(CC) -print-file-name=include)
 KBUILD_CFLAGS += -Wdeclaration-after-statement
 
 # Warn about unmarked fall-throughs in switch statement.
-KBUILD_CFLAGS += $(call cc-option,-Wimplicit-fallthrough=3,)
+KBUILD_CFLAGS += $(call cc-option,-Wimplicit-fallthrough,)
 
 # Variable Length Arrays (VLAs) should not be used anywhere in the kernel
 KBUILD_CFLAGS += -Wvla
diff --git a/arch/parisc/math-emu/Makefile b/arch/parisc/math-emu/Makefile
index 55c1396580a4..3747a0cbd3b8 100644
--- a/arch/parisc/math-emu/Makefile
+++ b/arch/parisc/math-emu/Makefile
@@ -18,4 +18,4 @@ obj-y	 := frnd.o driver.o decode_exc.o fpudispatch.o denormal.o \
 # other very old or stripped-down PA-RISC CPUs -- not currently supported
 
 obj-$(CONFIG_MATH_EMULATION)	+= unimplemented-math-emulation.o
-CFLAGS_REMOVE_fpudispatch.o	= -Wimplicit-fallthrough=3
+CFLAGS_REMOVE_fpudispatch.o	= -Wimplicit-fallthrough