linux-kernel - Re: [PATCH] ARC: build: Turn off -Wmaybe-uninitialized for ARC gcc 4.8

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Message-ID: <23667289.mNa1Q2STbY@wuerfel>
Date:	Fri, 18 Mar 2016 10:52:12 +0100
From:	Arnd Bergmann <arnd@...db.de>
To:	Vineet Gupta <Vineet.Gupta1@...opsys.com>
Cc:	linux-snps-arc@...ts.infradead.org,
	Claudiu Zissulescu <Claudiu.Zissulescu@...opsys.com>,
	Michal Marek <mmarek@...e.cz>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ARC: build: Turn off -Wmaybe-uninitialized for ARC gcc 4.8

On Friday 18 March 2016 14:16:23 Vineet Gupta wrote:
> diff --git a/arch/arc/Makefile b/arch/arc/Makefile
> index fed12f39d8ce..aeb101e8e674 100644
> --- a/arch/arc/Makefile
> +++ b/arch/arc/Makefile
> @@ -48,9 +48,14 @@ endif
>  upto_gcc44    :=  $(call cc-ifversion, -le, 0404, y)
>  atleast_gcc44 :=  $(call cc-ifversion, -ge, 0404, y)
>  atleast_gcc48 :=  $(call cc-ifversion, -ge, 0408, y)
> +is_gcc48      :=  $(call cc-ifversion, -eq, 0408, y)
>  
>  cflags-$(atleast_gcc44)                        += -fsection-anchors
>  
> +# gcc 4.8 spits out false positives for default -O3
> +# disable these for 4.8 and revisit when we upgrade to newer ver
> +cflags-$(is_gcc48)                     += $(call cc-disable-warning,maybe-uninitialized,)
> +
>  cflags-$(CONFIG_ARC_HAS_LLSC)          += -mlock
>  cflags-$(CONFIG_ARC_HAS_SWAPE)         += -mswape

Is this any better with gcc-4.9 or gcc-5? Maybe it's better to add the flag to
the line that adds -O3 for consistency. We do the same thing for -Os in the
global Makefile, as that triggers a similar load of warnings.

	Arnd