linux-kernel - Re: [PATCH] drm/i915: Disable some extra clang warnings

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Message-ID: <87vads1nn5.fsf@intel.com>
Date:   Mon, 19 Mar 2018 10:21:34 +0200
From:   Jani Nikula <jani.nikula@...ux.intel.com>
To:     Matthias Kaehlcke <mka@...omium.org>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        David Airlie <airlied@...ux.ie>
Cc:     intel-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, Guenter Roeck <groeck@...omium.org>,
        Matthias Kaehlcke <mka@...omium.org>
Subject: Re: [PATCH] drm/i915: Disable some extra clang warnings

On Fri, 16 Mar 2018, Matthias Kaehlcke <mka@...omium.org> wrote:
> Commit 39bf4de89ff7 ("drm/i915: Add -Wall -Wextra to our build, set
> warnings to full") enabled extra warnings for i915 to spot possible
> bugs in new code, and then disabled a subset of these warnings to keep
> the current code building without warnings (with gcc). Enabling the
> extra warnings also enabled some additional clang-only warnings, as a
> result building i915 with clang currently is extremely noisy. For now
> also disable the clang warnings sign-compare, sometimes-uninitialized,
> unneeded-internal-declaration and initializer-overrides. If desired
> they can be re-enabled after the code has been fixed.
>
> Fixes: 39bf4de89ff7 ("drm/i915: Add -Wall -Wextra to our build, set
> warnings to full")
> Signed-off-by: Matthias Kaehlcke <mka@...omium.org>

Thanks for the patch, I think it's the right thing to do. I'm afraid it
doesn't apply to current code, however. Please rebase on top of drm-tip
branch of [1].

> ---
>  drivers/gpu/drm/i915/Makefile | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/Makefile b/drivers/gpu/drm/i915/Makefile
> index 091aef281963..ad05796a96ba 100644
> --- a/drivers/gpu/drm/i915/Makefile
> +++ b/drivers/gpu/drm/i915/Makefile
> @@ -17,6 +17,10 @@ subdir-ccflags-y += $(call cc-disable-warning, unused-parameter)
>  subdir-ccflags-y += $(call cc-disable-warning, type-limits)
>  subdir-ccflags-y += $(call cc-disable-warning, missing-field-initializers)
>  subdir-ccflags-y += $(call cc-disable-warning, implicit-fallthrough)

While at it, please add a comment here noting that the below disables
are for Clang.

Thanks,
Jani.

[1] https://bugs.freedesktop.org/enter_bug.cgi?product=DRI&component=DRM/Intel


> +subdir-ccflags-y += $(call cc-disable-warning, sign-compare)
> +subdir-ccflags-y += $(call cc-disable-warning, sometimes-uninitialized)
> +subdir-ccflags-y += $(call cc-disable-warning, unneeded-internal-declaration)
> +subdir-ccflags-y += $(call cc-disable-warning, initializer-overrides)
>  subdir-ccflags-$(CONFIG_DRM_I915_WERROR) += -Werror
>  
>  # Fine grained warnings disable

-- 
Jani Nikula, Intel Open Source Technology Center