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/[email protected]/
[2]: https://lore.kernel.org/r/[email protected]/
Reviewed-by: Nick Desaulniers <[email protected]>
Signed-off-by: Nathan Chancellor <[email protected]>
---
v1 -> v2: https://lore.kernel.org/r/[email protected]/
* Rebase on drm-intel-gt-next now that the prerequisite patch series has
been merged: https://lore.kernel.org/r/[email protected]/
* Add Nick's reviewed-by tag.
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 c584188aa15a..fd99374583d5 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: 43192617f7816bb74584c1df06f57363afd15337
--
2.33.0
On Tue, 14 Sep 2021, Nathan Chancellor <[email protected]> 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/[email protected]/
> [2]: https://lore.kernel.org/r/[email protected]/
>
> Reviewed-by: Nick Desaulniers <[email protected]>
> Signed-off-by: Nathan Chancellor <[email protected]>
Thanks for the patch, and sorry for the delay.
Exceptionally pushed to drm-intel-gt-next instead of drm-intel-next
because some of the dependencies such as 43192617f781 ("drm/i915: Enable
-Wsometimes-uninitialized") were queued there too.
BR,
Jani.
> ---
>
> v1 -> v2: https://lore.kernel.org/r/[email protected]/
>
> * Rebase on drm-intel-gt-next now that the prerequisite patch series has
> been merged: https://lore.kernel.org/r/[email protected]/
>
> * Add Nick's reviewed-by tag.
>
> 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 c584188aa15a..fd99374583d5 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: 43192617f7816bb74584c1df06f57363afd15337
--
Jani Nikula, Intel Open Source Graphics Center