linux-kernel - Re: [PATCH] Kbuild: use cc-disable-warning consistently for maybe-uninitialized

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Date:   Fri, 27 Jan 2017 17:03:45 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Michal Marek <mmarek@...e.com>
Cc:     linux-kbuild@...r.kernel.org, fengguang.wu@...el.com,
        kbuild-all@...org, Arnd Bergmann <arnd@...db.de>,
        stable@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] Kbuild: use cc-disable-warning consistently for maybe-uninitialized

On Fri, Jan 13, 2017 at 4:40 PM, Arnd Bergmann <arnd@...db.de> wrote:
> In commit a76bcf557ef4 ("Kbuild: enable -Wmaybe-uninitialized warning
> for "make W=1""), I reverted another change that happened to fix a problem
> with old compilers, and now we get this report again with old compilers
> (prior to gcc-4.8) and GCOV enabled:
>
>    cc1: warnings being treated as errors
>    drivers/gpu/drm/i915/intel_ringbuffer.c: In function 'intel_ring_setup_status_page':
>    drivers/gpu/drm/i915/intel_ringbuffer.c:438: error: 'mmio.reg' may be used uninitialized in this function
>    At top level:
>>> cc1: error: unrecognized command line option "-Wno-maybe-uninitialized"
>
> The problem is that we turn off the warning conditionally in a number
> of places as we should, but one of them does it unconditionally.
> Instead, change it to call cc-disable-warning as we do elsewhere.
>
> The original patch that caused it was merged into linux-4.7, then
> 4.8 removed the change and 4.9 brought it back, so we probably want
> a backport to 4.9 once this is merged.
>
> Cc: stable@...r.kernel.org
> Fixes: a76bcf557ef4 ("Kbuild: enable -Wmaybe-uninitialized warning for "make W=1"")
> Fixes: e72e2dfe7c16 ("gcov: disable -Wmaybe-uninitialized warning")
> Reported-by: kbuild test robot <fengguang.wu@...el.com>
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---

Hi Michal,

any plans to pick this up for v4.10?

   Arnd

>  Makefile | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/Makefile b/Makefile
> index 4fcc0f2dd93c..dbe9ce5d0e96 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -370,7 +370,7 @@ LDFLAGS_MODULE  =
>  CFLAGS_KERNEL  =
>  AFLAGS_KERNEL  =
>  LDFLAGS_vmlinux =
> -CFLAGS_GCOV    = -fprofile-arcs -ftest-coverage -fno-tree-loop-im -Wno-maybe-uninitialized
> +CFLAGS_GCOV    = -fprofile-arcs -ftest-coverage -fno-tree-loop-im $(call cc-disable-warning,maybe-uninitialized,)
>  CFLAGS_KCOV    := $(call cc-option,-fsanitize-coverage=trace-pc,)
>
>
> --
> 2.9.0
>