linux-kernel - [PATCH 1/4] [v4] Kbuild: add -Wno-shift-negative-value where -Wextra is used

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Date:   Tue,  8 Mar 2022 22:56:12 +0100
From:   Arnd Bergmann <arnd@...nel.org>
To:     Masahiro Yamada <masahiroy@...nel.org>
Cc:     alexs@...nel.org, arnd@...db.de, arnd@...nel.org, dsterba@...e.com,
        elver@...gle.com, jani.nikula@...el.com, linux-doc@...r.kernel.org,
        linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org,
        llvm@...ts.linux.dev, mark.rutland@....com,
        ndesaulniers@...gle.com, ojeda@...nel.org,
        torvalds@...ux-foundation.org
Subject: [PATCH 1/4] [v4] Kbuild: add -Wno-shift-negative-value where -Wextra is used

From: Arnd Bergmann <arnd@...db.de>

As a preparation for moving to -std=gnu11, turn off the
-Wshift-negative-value option. This warning is enabled by gcc when
building with -Wextra for c99 or higher, but not for c89. Since
the kernel already relies on well-defined overflow behavior,
the warning is not helpful and can simply be disabled in
all locations that use -Wextra.

Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
[v4]
  split into a separate patch
---
 drivers/gpu/drm/i915/Makefile          | 1 +
 drivers/staging/greybus/tools/Makefile | 3 ++-
 fs/btrfs/Makefile                      | 1 +
 scripts/Makefile.extrawarn             | 1 +
 4 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/Makefile b/drivers/gpu/drm/i915/Makefile
index 1b62b9f65196..1618a6e0af4e 100644
--- a/drivers/gpu/drm/i915/Makefile
+++ b/drivers/gpu/drm/i915/Makefile
@@ -17,6 +17,7 @@ subdir-ccflags-y += -Wno-unused-parameter
 subdir-ccflags-y += -Wno-type-limits
 subdir-ccflags-y += -Wno-missing-field-initializers
 subdir-ccflags-y += -Wno-sign-compare
+subdir-ccflags-y += -Wno-shift-negative-value
 subdir-ccflags-y += $(call cc-disable-warning, unused-but-set-variable)
 subdir-ccflags-y += $(call cc-disable-warning, frame-address)
 subdir-ccflags-$(CONFIG_DRM_I915_WERROR) += -Werror
diff --git a/drivers/staging/greybus/tools/Makefile b/drivers/staging/greybus/tools/Makefile
index ad0ae8053b79..a3bbd73171f2 100644
--- a/drivers/staging/greybus/tools/Makefile
+++ b/drivers/staging/greybus/tools/Makefile
@@ -12,7 +12,8 @@ CFLAGS	+= -std=gnu99 -Wall -Wextra -g \
 	    -Wredundant-decls \
 	    -Wcast-align \
 	    -Wsign-compare \
-	    -Wno-missing-field-initializers
+	    -Wno-missing-field-initializers \
+	    -Wno-shift-negative-value
 
 CC	:= $(CROSS_COMPILE)gcc
 
diff --git a/fs/btrfs/Makefile b/fs/btrfs/Makefile
index 4188ba3fd8c3..99f9995670ea 100644
--- a/fs/btrfs/Makefile
+++ b/fs/btrfs/Makefile
@@ -17,6 +17,7 @@ subdir-ccflags-y += $(condflags)
 subdir-ccflags-y += -Wno-missing-field-initializers
 subdir-ccflags-y += -Wno-sign-compare
 subdir-ccflags-y += -Wno-type-limits
+subdir-ccflags-y += -Wno-shift-negative-value
 
 obj-$(CONFIG_BTRFS_FS) := btrfs.o
 
diff --git a/scripts/Makefile.extrawarn b/scripts/Makefile.extrawarn
index 8be892887d71..650d0b8ceec3 100644
--- a/scripts/Makefile.extrawarn
+++ b/scripts/Makefile.extrawarn
@@ -36,6 +36,7 @@ KBUILD_CFLAGS += $(call cc-option, -Wstringop-truncation)
 KBUILD_CFLAGS += -Wno-missing-field-initializers
 KBUILD_CFLAGS += -Wno-sign-compare
 KBUILD_CFLAGS += -Wno-type-limits
+KBUILD_CFLAGS += -Wno-shift-negative-value
 
 KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN1
 
-- 
2.29.2