linux-kernel - Re: [PATCH] Kbuild: Move -Wmaybe-uninitialized to W=1

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Date:	Thu, 28 Jul 2016 06:20:11 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Sam Ravnborg <sam@...nborg.org>,
	lkml <linux-kernel@...r.kernel.org>, Michael Matz <matz@...e.de>,
	linux-kbuild@...r.kernel.org, x86-ml <x86@...nel.org>
Subject: Re: [PATCH] Kbuild: Move -Wmaybe-uninitialized to W=1

Hi Linus,

about 6e8d666e9253 ("Disable "maybe-uninitialized" warning globally"):

Good! Finally!

This thing was really getting on my nerves.

Btw, I tried at the time to move it to W=1 insted of completely
disabling it, see below. That got nowhere though.

On Mon, Jul 07, 2014 at 12:53:39PM +0200, Borislav Petkov wrote:
> Ok, here's a v2 which goes ontop of
> 
> http://lkml.kernel.org/r/1404175346-12330-1-git-send-email-behanw@converseincode.com
> 
> After this, all warnings stuff should be back to normal.
> 
> ---
> From: Borislav Petkov <bp@...e.de>
> Subject: [PATCH -v2] Kbuild: Move -Wmaybe-uninitialized to W=1
> 
> This warning is enabled by -Wall or -Wextra, says the gcc manpage. It
> also says that gcc cannot always know whether the warning is issued
> correctly:
> 
> "These warnings are made optional because GCC is not smart enough to see
> all the reasons why the code might be correct in spite of appearing to
> have an error."
> 
> And, as expected, it fires for perfectly valid use cases, thus making it
> not really useful. Let's move it to the W=1 bunch in case people want to
> enable it with the additional checks.
> 
> Signed-off-by: Borislav Petkov <bp@...e.de>
> ---
>  Makefile                   | 5 ++++-
>  scripts/Makefile           | 1 +
>  scripts/Makefile.extrawarn | 1 +
>  3 files changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/Makefile b/Makefile
> index 4d75b4bceedd..b58c94261960 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -613,7 +613,7 @@ include $(srctree)/arch/$(SRCARCH)/Makefile
>  KBUILD_CFLAGS	+= $(call cc-option,-fno-delete-null-pointer-checks,)
>  
>  ifdef CONFIG_CC_OPTIMIZE_FOR_SIZE
> -KBUILD_CFLAGS	+= -Os $(call cc-disable-warning,maybe-uninitialized,)
> +KBUILD_CFLAGS	+= -Os
>  else
>  KBUILD_CFLAGS	+= -O2
>  endif
> @@ -742,6 +742,9 @@ KBUILD_CFLAGS   += $(call cc-option,-Werror=date-time)
>  # use the deterministic mode of AR if available
>  KBUILD_ARFLAGS := $(call ar-option,D)
>  
> +# disable -Wmaybe-uninitialized as too noisy, see Makefile.extrawarn instead
> +KBUILD_CFLAGS   += $(call cc-disable-warning, maybe-uninitialized)
> +
>  # check for 'asm goto'
>  ifeq ($(shell $(CONFIG_SHELL) $(srctree)/scripts/gcc-goto.sh $(CC)), y)
>  	KBUILD_CFLAGS += -DCC_HAVE_ASM_GOTO
> diff --git a/scripts/Makefile b/scripts/Makefile
> index 890df5c6adfb..a483d9988a2e 100644
> --- a/scripts/Makefile
> +++ b/scripts/Makefile
> @@ -19,6 +19,7 @@ hostprogs-$(CONFIG_BUILDTIME_EXTABLE_SORT) += sortextable
>  hostprogs-$(CONFIG_ASN1)	 += asn1_compiler
>  
>  HOSTCFLAGS_sortextable.o = -I$(srctree)/tools/include
> +HOSTCFLAGS_sortextable.o += $(call cc-disable-warning, maybe-uninitialized)
>  HOSTCFLAGS_asn1_compiler.o = -I$(srctree)/include
>  
>  always		:= $(hostprogs-y) $(hostprogs-m)
> diff --git a/scripts/Makefile.extrawarn b/scripts/Makefile.extrawarn
> index e3501272cd93..9657d5778e06 100644
> --- a/scripts/Makefile.extrawarn
> +++ b/scripts/Makefile.extrawarn
> @@ -25,6 +25,7 @@ warning-1 += -Wold-style-definition
>  warning-1 += $(call cc-option, -Wmissing-include-dirs)
>  warning-1 += $(call cc-option, -Wunused-but-set-variable)
>  warning-1 += $(call cc-disable-warning, missing-field-initializers)
> +warning-1 += $(call cc-option, -Wmaybe-uninitialized)
>  
>  ifeq ($(COMPILER),clang)
>  warning-1 += $(call cc-disable-warning, initializer-overrides)
> -- 
> 2.0.0
> 
> -- 
> Regards/Gruss,
>     Boris.
> 
> Sent from a fat crate under my desk. Formatting is fine.
> --
> 

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
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