On Tue, 14 Sep 2021, Nathan Chancellor nathan@kernel.org 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.
Reviewed-by: Nick Desaulniers ndesaulniers@google.com Signed-off-by: Nathan Chancellor nathan@kernel.org
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/20210824232237.2085342-1-nathan@kernel.org/
Rebase on drm-intel-gt-next now that the prerequisite patch series has been merged: https://lore.kernel.org/r/87wnnj13t5.fsf@intel.com/
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