On Thu, Aug 29, 2019 at 11:12 AM Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx> wrote: > > Instead of the warning-[123] magic, let's accumulate compiler options > to KBUILD_CFLAGS directly as the top Makefile does. I think this makes > easier to understand what is going on in this file. > > This commit slightly changes the behavior, I think all of which are OK. > > [1] Currently, cc-option calls are needlessly evaluated. For example, > warning-3 += $(call cc-option, -Wpacked-bitfield-compat) > needs evaluating only when W=3, but it is actually evaluated for > W=1, W=2 as well. With this commit, only relevant cc-option calls > will be evaluated. This is a slight optimization. > > [2] Currently, unsupported level like W=4 is checked by: > $(error W=$(KBUILD_ENABLE_EXTRA_GCC_CHECKS) is unknown) > This will no longer be checked, but I do not think it is a big > deal. > > [3] Currently, 4 Clang warnings (Winitializer-overrides, Wformat, > Wsign-compare, Wformat-zero-length) are shown by any of W=1, W=2, > and W=3. With this commit, they will be warned only by W=1. I > think this is a more correct behavior since each warning belongs > to only one group. > > For understanding this commit correctly: > > We have 3 warning groups, W=1, W=2, and W=3. You may think W=3 has a > higher level than W=1, but they are actually independent. If you like, What?! Ok now things make much more sense. (This is a great addition to this patch). Maybe this should additionally be a comment in the source code? > you can combine them like W=13. To enable all the warnings, you can > pass W=123. This is shown by 'make help', but it is often missed > unfortunately. Since we support W= combination, there should not exist > intersection among the three groups. If we enable Winitializer-overrides > for W=1, we do not need to for W=2 or W=3. This is why I believe the > change [3] makes sense. > > The documentation says -Winitializer-overrides is enabled by default. > (https://clang.llvm.org/docs/DiagnosticsReference.html#winitializer-overrides) > We negate it by passing -Wno-initializer-overrides for the normal > build, but we do not do that for W=1. This means, W=1 effectively > enables -Winitializer-overrides by the clang's default. The same for > the other three. I wonder if this logic needs detailed commenting, > but I do not want to be bothered any more. I added comments. > > Signed-off-by: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx> > Reviewed-by: Nathan Chancellor <natechancellor@xxxxxxxxx> Acked-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx> > --- > > Changes in v2: > - Added comments and more commit log > > scripts/Makefile.extrawarn | 105 +++++++++++++++++++------------------ > 1 file changed, 54 insertions(+), 51 deletions(-) > > diff --git a/scripts/Makefile.extrawarn b/scripts/Makefile.extrawarn > index a74ce2e3c33e..3680445823b7 100644 > --- a/scripts/Makefile.extrawarn > +++ b/scripts/Makefile.extrawarn > @@ -1,14 +1,6 @@ > # SPDX-License-Identifier: GPL-2.0 > # ========================================================================== > -# > # make W=... settings > -# > -# W=1 - warnings that may be relevant and does not occur too often > -# W=2 - warnings that occur quite often but may still be relevant > -# W=3 - the more obscure warnings, can most likely be ignored > -# > -# $(call cc-option, -W...) handles gcc -W.. options which > -# are not supported by all versions of the compiler > # ========================================================================== > > KBUILD_CFLAGS += $(call cc-disable-warning, packed-not-aligned) > @@ -17,58 +9,69 @@ ifeq ("$(origin W)", "command line") > export KBUILD_ENABLE_EXTRA_GCC_CHECKS := $(W) > endif > > -ifdef KBUILD_ENABLE_EXTRA_GCC_CHECKS > -warning- := $(empty) > +# > +# W=1 - warnings that may be relevant and does not occur too often > +# > +ifneq ($(findstring 1, $(KBUILD_ENABLE_EXTRA_GCC_CHECKS)),) > > -warning-1 := -Wextra -Wunused -Wno-unused-parameter > -warning-1 += -Wmissing-declarations > -warning-1 += -Wmissing-format-attribute > -warning-1 += -Wmissing-prototypes > -warning-1 += -Wold-style-definition > -warning-1 += -Wmissing-include-dirs > -warning-1 += $(call cc-option, -Wunused-but-set-variable) > -warning-1 += $(call cc-option, -Wunused-const-variable) > -warning-1 += $(call cc-option, -Wpacked-not-aligned) > -warning-1 += $(call cc-option, -Wstringop-truncation) > +KBUILD_CFLAGS += -Wextra -Wunused -Wno-unused-parameter > +KBUILD_CFLAGS += -Wmissing-declarations > +KBUILD_CFLAGS += -Wmissing-format-attribute > +KBUILD_CFLAGS += -Wmissing-prototypes > +KBUILD_CFLAGS += -Wold-style-definition > +KBUILD_CFLAGS += -Wmissing-include-dirs > +KBUILD_CFLAGS += $(call cc-option, -Wunused-but-set-variable) > +KBUILD_CFLAGS += $(call cc-option, -Wunused-const-variable) > +KBUILD_CFLAGS += $(call cc-option, -Wpacked-not-aligned) > +KBUILD_CFLAGS += $(call cc-option, -Wstringop-truncation) > # The following turn off the warnings enabled by -Wextra > -warning-1 += -Wno-missing-field-initializers > -warning-1 += -Wno-sign-compare > - > -warning-2 += -Wcast-align > -warning-2 += -Wdisabled-optimization > -warning-2 += -Wnested-externs > -warning-2 += -Wshadow > -warning-2 += $(call cc-option, -Wlogical-op) > -warning-2 += -Wmissing-field-initializers > -warning-2 += -Wsign-compare > -warning-2 += $(call cc-option, -Wmaybe-uninitialized) > -warning-2 += $(call cc-option, -Wunused-macros) > - > -warning-3 := -Wbad-function-cast > -warning-3 += -Wcast-qual > -warning-3 += -Wconversion > -warning-3 += -Wpacked > -warning-3 += -Wpadded > -warning-3 += -Wpointer-arith > -warning-3 += -Wredundant-decls > -warning-3 += -Wswitch-default > -warning-3 += $(call cc-option, -Wpacked-bitfield-compat) > - > -warning := $(warning-$(findstring 1, $(KBUILD_ENABLE_EXTRA_GCC_CHECKS))) > -warning += $(warning-$(findstring 2, $(KBUILD_ENABLE_EXTRA_GCC_CHECKS))) > -warning += $(warning-$(findstring 3, $(KBUILD_ENABLE_EXTRA_GCC_CHECKS))) > - > -ifeq ("$(strip $(warning))","") > - $(error W=$(KBUILD_ENABLE_EXTRA_GCC_CHECKS) is unknown) > -endif > +KBUILD_CFLAGS += -Wno-missing-field-initializers > +KBUILD_CFLAGS += -Wno-sign-compare > > -KBUILD_CFLAGS += $(warning) > else > > +# Some diagnostics such as -Winitializer-overrides are enabled by default. > +# We suppress them by using -Wno... except for W=1. > + > ifdef CONFIG_CC_IS_CLANG > KBUILD_CFLAGS += -Wno-initializer-overrides > KBUILD_CFLAGS += -Wno-format > KBUILD_CFLAGS += -Wno-sign-compare > KBUILD_CFLAGS += -Wno-format-zero-length > endif > + > +endif > + > +# > +# W=2 - warnings that occur quite often but may still be relevant > +# > +ifneq ($(findstring 2, $(KBUILD_ENABLE_EXTRA_GCC_CHECKS)),) > + > +KBUILD_CFLAGS += -Wcast-align > +KBUILD_CFLAGS += -Wdisabled-optimization > +KBUILD_CFLAGS += -Wnested-externs > +KBUILD_CFLAGS += -Wshadow > +KBUILD_CFLAGS += $(call cc-option, -Wlogical-op) > +KBUILD_CFLAGS += -Wmissing-field-initializers > +KBUILD_CFLAGS += -Wsign-compare > +KBUILD_CFLAGS += $(call cc-option, -Wmaybe-uninitialized) > +KBUILD_CFLAGS += $(call cc-option, -Wunused-macros) > + > +endif > + > +# > +# W=3 - the more obscure warnings, can most likely be ignored > +# > +ifneq ($(findstring 3, $(KBUILD_ENABLE_EXTRA_GCC_CHECKS)),) > + > +KBUILD_CFLAGS += -Wbad-function-cast > +KBUILD_CFLAGS += -Wcast-qual > +KBUILD_CFLAGS += -Wconversion > +KBUILD_CFLAGS += -Wpacked > +KBUILD_CFLAGS += -Wpadded > +KBUILD_CFLAGS += -Wpointer-arith > +KBUILD_CFLAGS += -Wredundant-decls > +KBUILD_CFLAGS += -Wswitch-default > +KBUILD_CFLAGS += $(call cc-option, -Wpacked-bitfield-compat) > + > endif > -- > 2.17.1 > -- Thanks, ~Nick Desaulniers
