Re: [PATCH] drm/i915: Clean up disabled warnings

[Nathan Chancellor]

On 8/25/2021 4:03 PM, Nick Desaulniers wrote:
> On Tue, Aug 24, 2021 at 4:23 PM Nathan Chancellor <nathan@xxxxxxxxxx> wrote:
> > i915 enables a wider set of warnings with '-Wall -Wextra' then disables
> > several with cc-disable-warning. If an unknown flag gets added to
> > KBUILD_CFLAGS when building with clang, all subsequent calls to
> > cc-{disable-warning,option} will fail, meaning that all of these
> > warnings do not get disabled [1].
> >
> > A separate series will address the root cause of the issue by not adding
> > these flags when building with clang [2]; however, the symptom of these
> > extra warnings appearing can be addressed separately by just removing
> > the calls to cc-disable-warning, which makes the build ever so slightly
> > faster because the compiler does not need to be called as much before
> > building.
> >
> > The following warnings are supported by GCC 4.9 and clang 10.0.1, which
> > are the minimum supported versions of these compilers so the call to
> > cc-disable-warning is not necessary. Masahiro cleaned this up for the
> > reset of the kernel in commit 4c8dd95a723d ("kbuild: add some extra
> > warning flags unconditionally").
> >
> > * -Wmissing-field-initializers
> > * -Wsign-compare
> > * -Wtype-limits
> > * -Wunused-parameter
> >
> > -Wunused-but-set-variable was implemented in clang 13.0.0 and
> > -Wframe-address was implemented in clang 12.0.0 so the
> > cc-disable-warning calls are kept for these two warnings.
> >
> > Lastly, -Winitializer-overrides is clang's version of -Woverride-init,
> > which is disabled for the specific files that are problematic. clang
> > added a compatibility alias in clang 8.0.0 so -Winitializer-overrides
> > can be removed.
> >
> > [1]: https://lore.kernel.org/r/202108210311.CBtcgoUL-lkp@xxxxxxxxx/
> > [2]: https://lore.kernel.org/r/20210824022640.2170859-1-nathan@xxxxxxxxxx/
> >
> > Signed-off-by: Nathan Chancellor <nathan@xxxxxxxxxx>
>
> Thanks for the patch! Do you need to re-ping, rebase, or resend that
> other series?
> Reviewed-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>

I assume you mean the series below rather than above? I sent this patch 
right after that series and it has one set of reviews so I am hoping the 
i915 maintainers will pick them up soon so this one can be applied 
afterwards or resent.

Thank you for the review!

Cheers,
Nathan

> > ---
> >
> > NOTE: This is based on my series to enable -Wsometimes-initialized here:
> >
> > https://lore.kernel.org/r/20210824225427.2065517-1-nathan@xxxxxxxxxx/
> >
> > I sent it separately as this can go into whatever release but I would
> > like for that series to go into 5.15.
> >
> >   drivers/gpu/drm/i915/Makefile | 10 ++++------
> >   1 file changed, 4 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/Makefile b/drivers/gpu/drm/i915/Makefile
> > index 335ba9f43d8f..6b38547543b1 100644
> > --- a/drivers/gpu/drm/i915/Makefile
> > +++ b/drivers/gpu/drm/i915/Makefile
> > @@ -13,13 +13,11 @@
> >   # will most likely get a sudden build breakage... Hopefully we will fix
> >   # new warnings before CI updates!
> >   subdir-ccflags-y := -Wall -Wextra
> > -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 += -Wno-unused-parameter
> > +subdir-ccflags-y += -Wno-type-limits
> > +subdir-ccflags-y += -Wno-missing-field-initializers
> > +subdir-ccflags-y += -Wno-sign-compare
> >   subdir-ccflags-y += $(call cc-disable-warning, unused-but-set-variable)
> > -# clang warnings
> > -subdir-ccflags-y += $(call cc-disable-warning, sign-compare)
> > -subdir-ccflags-y += $(call cc-disable-warning, initializer-overrides)
> >   subdir-ccflags-y += $(call cc-disable-warning, frame-address)
> >   subdir-ccflags-$(CONFIG_DRM_I915_WERROR) += -Werror
> >
> >
> > base-commit: fb43ebc83e069625cfeeb2490efc3ffa0013bfa4
> > prerequisite-patch-id: 31c28450ed7e8785dce967a16db6d52eff3d7d6d
> > prerequisite-patch-id: 372dfa0e07249f207acc1942ab0e39b13ff229b2
> > prerequisite-patch-id: 1a585fa6cda50c32ad1e3ac8235d3cff1b599978
> > --
> > 2.33.0