linux-kernel - Re: [PATCH 5/5] gcov: disable -Wmaybe-uninitialized warning

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Message-ID: <56C1E229.4050308@linux.vnet.ibm.com>
Date:	Mon, 15 Feb 2016 15:35:21 +0100
From:	Peter Oberparleiter <oberpar@...ux.vnet.ibm.com>
To:	Arnd Bergmann <arnd@...db.de>, Michal Marek <mmarek@...e.com>
Cc:	linux-arm-kernel@...ts.infradead.org, linux-kbuild@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/5] gcov: disable -Wmaybe-uninitialized warning

On 12.02.2016 17:06, Arnd Bergmann wrote:
> When gcov profiling is enabled, we see a lot of spurious warnings about
> possibly uninitialized variables being used:
> 
> arch/arm/mm/dma-mapping.c: In function 'arm_coherent_iommu_map_page':
> arch/arm/mm/dma-mapping.c:1085:16: warning: 'start' may be used uninitialized in this function [-Wmaybe-uninitialized]
> drivers/clk/st/clk-flexgen.c: In function 'st_of_flexgen_setup':
> drivers/clk/st/clk-flexgen.c:323:9: warning: 'num_parents' may be used uninitialized in this function [-Wmaybe-uninitialized]
> kernel/cgroup.c: In function 'cgroup_mount':
> kernel/cgroup.c:2119:11: warning: 'root' may be used uninitialized in this function [-Wmaybe-uninitialized]
> 
> All of these are false positives, so it seems better to just disable
> the warnings whenever GCOV is enabled. Most users don't enable GCOV,
> and based on a prior patch, it is now also disabled for 'allmodconfig'
> builds, so there should be no downsides of doing this.
> 
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

Sounds sane.

Acked-by: Peter Oberparleiter <oberpar@...ux.vnet.ibm.com>

> ---
>  Makefile | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/Makefile b/Makefile
> index 6bb89728a9d1..7b6900931a47 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -364,7 +364,7 @@ AFLAGS_MODULE   =
>  LDFLAGS_MODULE  =
>  CFLAGS_KERNEL	=
>  AFLAGS_KERNEL	=
> -CFLAGS_GCOV	= -fprofile-arcs -ftest-coverage -fno-tree-loop-im
> +CFLAGS_GCOV	= -fprofile-arcs -ftest-coverage -fno-tree-loop-im -Wno-maybe-uninitialized
>  CFLAGS_KCOV	= -fsanitize-coverage=trace-pc
> 
> 


-- 
Peter Oberparleiter
Linux on z Systems Development - IBM Germany