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

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Message-ID: <87ee3b1qsy.fsf@intel.com>
Date:   Wed, 09 Mar 2022 10:19:25 +0200
From:   Jani Nikula <jani.nikula@...el.com>
To:     Arnd Bergmann <arnd@...nel.org>,
        Masahiro Yamada <masahiroy@...nel.org>
Cc:     alexs@...nel.org, arnd@...db.de, arnd@...nel.org, dsterba@...e.com,
        elver@...gle.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: Re: [PATCH 1/4] [v4] Kbuild: add -Wno-shift-negative-value where
 -Wextra is used

On Tue, 08 Mar 2022, Arnd Bergmann <arnd@...nel.org> wrote:
> 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>

Acked-by: Jani Nikula <jani.nikula@...el.com>

> ---
> [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

-- 
Jani Nikula, Intel Open Source Graphics Center