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From: Masahiro Yamada <masahiroy@kernel.org>
To: Arnd Bergmann <arnd@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>,
	Nathan Chancellor <nathan@kernel.org>,
	Nick Desaulniers <ndesaulniers@google.com>,
	Nicolas Schier <nicolas@fjasle.eu>,
	Guenter Roeck <linux@roeck-us.net>, Lee Jones <lee@kernel.org>,
	Stephen Rothwell <sfr@canb.auug.org.au>,
	linux-kbuild@vger.kernel.org, linux-arch@vger.kernel.org
Subject: Re: [PATCH 3/9] Kbuild: avoid duplicate warning options
Date: Sat, 12 Aug 2023 18:21:39 +0900	[thread overview]
Message-ID: <CAK7LNAT0BZ107ngRNQvVO4DjOKj8AOrD2860rOgQ84WP9QfaFw@mail.gmail.com> (raw)
In-Reply-To: <20230811140327.3754597-4-arnd@kernel.org>

On Sat, Aug 12, 2023 at 5:50 PM Arnd Bergmann <arnd@kernel.org> wrote:
>
> From: Arnd Bergmann <arnd@arndb.de>
>
> Some warning options are disabled at one place and then conditionally
> re-enabled later in scripts/Makefile.extrawarn.
>
> For consistency, rework this file so each of those warnings only
> gets etiher enabled or disabled based on the W= flags but not both.
>
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
>  scripts/Makefile.extrawarn | 43 +++++++++++++++++++++++---------------
>  1 file changed, 26 insertions(+), 17 deletions(-)
>
> diff --git a/scripts/Makefile.extrawarn b/scripts/Makefile.extrawarn
> index 9cc0e52ebd7eb..8afbe4706ff11 100644
> --- a/scripts/Makefile.extrawarn
> +++ b/scripts/Makefile.extrawarn
> @@ -56,20 +56,12 @@ KBUILD_CFLAGS += -Wno-pointer-sign
>  # globally built with -Wcast-function-type.
>  KBUILD_CFLAGS += $(call cc-option, -Wcast-function-type)
>
> -# disable stringop warnings in gcc 8+
> -KBUILD_CFLAGS += $(call cc-disable-warning, stringop-truncation)
> -
>  # We'll want to enable this eventually, but it's not going away for 5.7 at least
>  KBUILD_CFLAGS += $(call cc-disable-warning, stringop-overflow)
>
>  # Another good warning that we'll want to enable eventually
>  KBUILD_CFLAGS += $(call cc-disable-warning, restrict)
>
> -# Enabled with W=2, disabled by default as noisy
> -ifdef CONFIG_CC_IS_GCC
> -KBUILD_CFLAGS += -Wno-maybe-uninitialized
> -endif
> -
>  # The allocators already balk at large sizes, so silence the compiler
>  # warnings for bounds checks involving those possible values. While
>  # -Wno-alloc-size-larger-than would normally be used here, earlier versions
> @@ -96,8 +88,6 @@ KBUILD_CFLAGS += $(call cc-option,-Werror=designated-init)
>  # Warn if there is an enum types mismatch
>  KBUILD_CFLAGS += $(call cc-option,-Wenum-conversion)
>
> -KBUILD_CFLAGS += $(call cc-disable-warning, packed-not-aligned)
> -
>  # backward compatibility
>  KBUILD_EXTRA_WARN ?= $(KBUILD_ENABLE_EXTRA_GCC_CHECKS)
>
> @@ -122,11 +112,6 @@ KBUILD_CFLAGS += $(call cc-option, -Wunused-but-set-variable)
>  KBUILD_CFLAGS += $(call cc-option, -Wunused-const-variable)
>  KBUILD_CFLAGS += $(call cc-option, -Wpacked-not-aligned)
>  KBUILD_CFLAGS += $(call cc-option, -Wstringop-truncation)
> -# The following turn off the warnings enabled by -Wextra
> -KBUILD_CFLAGS += -Wno-missing-field-initializers
> -KBUILD_CFLAGS += -Wno-sign-compare
> -KBUILD_CFLAGS += -Wno-type-limits
> -KBUILD_CFLAGS += -Wno-shift-negative-value
>
>  KBUILD_CPPFLAGS += -Wundef
>  KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN1
> @@ -135,9 +120,12 @@ else
>
>  # Some diagnostics enabled by default are noisy.
>  # Suppress them by using -Wno... except for W=1.
> +KBUILD_CFLAGS += $(call cc-disable-warning, unused-but-set-variable)
> +KBUILD_CFLAGS += $(call cc-disable-warning, unused-const-variable)
> +KBUILD_CFLAGS += $(call cc-disable-warning, packed-not-aligned)
> +KBUILD_CFLAGS += $(call cc-disable-warning, stringop-truncation)
>
>  ifdef CONFIG_CC_IS_CLANG
> -KBUILD_CFLAGS += -Wno-initializer-overrides
>  # Clang before clang-16 would warn on default argument promotions.
>  ifneq ($(call clang-min-version, 160000),y)
>  # Disable -Wformat
> @@ -151,7 +139,6 @@ ifeq ($(call clang-min-version, 120000),y)
>  KBUILD_CFLAGS += -Wformat-insufficient-args
>  endif
>  endif
> -KBUILD_CFLAGS += -Wno-sign-compare
>  KBUILD_CFLAGS += $(call cc-disable-warning, pointer-to-enum-cast)
>  KBUILD_CFLAGS += -Wno-tautological-constant-out-of-range-compare
>  KBUILD_CFLAGS += $(call cc-disable-warning, unaligned-access)
> @@ -173,8 +160,25 @@ KBUILD_CFLAGS += -Wtype-limits
>  KBUILD_CFLAGS += $(call cc-option, -Wmaybe-uninitialized)
>  KBUILD_CFLAGS += $(call cc-option, -Wunused-macros)
>
> +ifdef CONFIG_CC_IS_CLANG
> +KBUILD_CFLAGS += -Winitializer-overrides
> +endif
> +
>  KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN2
>
> +else
> +
> +# The following turn off the warnings enabled by -Wextra
> +KBUILD_CFLAGS += -Wno-missing-field-initializers
> +KBUILD_CFLAGS += -Wno-type-limits
> +KBUILD_CFLAGS += -Wno-shift-negative-value
> +
> +ifdef CONFIG_CC_IS_CLANG
> +KBUILD_CFLAGS += -Wno-initializer-overrides
> +else
> +KBUILD_CFLAGS += -Wno-maybe-uninitialized




GCC manual says -Wall implies -Wmaybe-uninitialized.

If you move -Wno-maybe-uninitialize to the "W != 2" part,
-Wmaybe-uninitialized is unneeded in the 'W == 2" part.

Maybe, the same applies to -Wunused-but-set-parameter.

Shall we drop warnings implied by another, or
is it clearer to explicitly add either -Wfoo or -Wno-foo?

If desired, we can do such a clean-up later, though.







--
Best Regards
Masahiro Yamada

  reply	other threads:[~2023-08-12  9:22 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-08-11 14:03 [PATCH 0/9] Kbuild: warning options cleanup and more warnings Arnd Bergmann
2023-08-11 14:03 ` [PATCH 1/9] Kbuild: only pass -fno-inline-functions-called-once for gcc Arnd Bergmann
2023-08-11 14:14   ` Nathan Chancellor
2023-08-11 14:23     ` Arnd Bergmann
2023-08-11 14:03 ` [PATCH 2/9] Kbuild: consolidate warning flags in scripts/Makefile.extrawarn Arnd Bergmann
2023-08-11 14:19   ` Nathan Chancellor
2023-08-11 14:26     ` Arnd Bergmann
2023-08-12  7:21       ` Masahiro Yamada
2023-08-20  1:36       ` Masahiro Yamada
2023-08-11 14:03 ` [PATCH 3/9] Kbuild: avoid duplicate warning options Arnd Bergmann
2023-08-12  9:21   ` Masahiro Yamada [this message]
2023-08-12  9:28     ` Arnd Bergmann
2023-08-20  1:38       ` Masahiro Yamada
2023-08-11 14:03 ` [PATCH 4/9] extrawarn: don't turn off -Wshift-negative-value for gcc-9 Arnd Bergmann
2023-08-12 12:04   ` Masahiro Yamada
2023-08-11 14:03 ` [PATCH 5/9] extrawarn: enable format and stringop overflow warnings in W=1 Arnd Bergmann
2023-08-12 13:10   ` Masahiro Yamada
2023-08-20  1:40     ` Masahiro Yamada
2023-08-21 18:26     ` Nick Desaulniers
2023-08-11 14:03 ` [PATCH 6/9] extrawarn: move -Wrestrict into W=1 warnings Arnd Bergmann
2023-08-12 13:20   ` Masahiro Yamada
2023-08-20  1:45   ` Masahiro Yamada
2023-08-11 14:03 ` [PATCH 7/9] extrawarn: do not disable -Wmain at W=1 level Arnd Bergmann
2023-08-11 14:03 ` [PATCH 8/9] extrawarn: enable more warnings in W=2 Arnd Bergmann
2023-08-11 14:03 ` [PATCH 9/9] [RFC] extrawarn: enable more W=1 warnings by default Arnd Bergmann
2023-08-11 16:09   ` Nathan Chancellor
2023-08-11 18:23     ` Arnd Bergmann
2023-08-14 19:52       ` Nathan Chancellor

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