| Message ID | 20190831162555.31887-1-yamada.masahiro@socionext.com |
|---|---|
| State | Accepted |
| Commit | 64a91907c896247c19f8314add2c9baa573fbd3c |
| Headers | show |
| Series | [v3,1/2] kbuild: refactor scripts/Makefile.extrawarn | expand |
On Sat, Aug 31, 2019 at 6:26 PM Masahiro Yamada <yamada.masahiro@socionext.com> wrote: > +# Some diagnostics enabled by default are noisy. > +# 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 FWIW, I just found out I missed a bug that clang failed to warn about because of the -Wno-format. Apparently gcc warns only about type mismatches that result in incompatible calling conventions (e.g. int vs int64_t) but not smaller types (int, short) that get converted to an int anyway. Passing -Wno-format turns both off. Arnd
On Wed, Sep 04, 2019 at 11:46:45PM +0200, Arnd Bergmann wrote: > On Sat, Aug 31, 2019 at 6:26 PM Masahiro Yamada > <yamada.masahiro@socionext.com> wrote: > > > +# Some diagnostics enabled by default are noisy. > > +# 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 > > FWIW, I just found out I missed a bug that clang failed to warn about > because of the -Wno-format. Apparently gcc warns only about type > mismatches that result in incompatible calling conventions (e.g. > int vs int64_t) but not smaller types (int, short) that get converted to an > int anyway. Passing -Wno-format turns both off. > > Arnd Hi Arnd, This has been fixed in clang 10.0.0 but this areas has not been updated as nobody has sent a patch yet: https://github.com/ClangBuiltLinux/linux/issues/378#issuecomment-524411147 Cheers, Nathan
On Thu, Sep 5, 2019 at 12:40 AM Nathan Chancellor <natechancellor@gmail.com> wrote: > On Wed, Sep 04, 2019 at 11:46:45PM +0200, Arnd Bergmann wrote: > > On Sat, Aug 31, 2019 at 6:26 PM Masahiro Yamada > > <yamada.masahiro@socionext.com> wrote: > > > > FWIW, I just found out I missed a bug that clang failed to warn about > > because of the -Wno-format. Apparently gcc warns only about type > > mismatches that result in incompatible calling conventions (e.g. > > int vs int64_t) but not smaller types (int, short) that get converted to an > > int anyway. Passing -Wno-format turns both off. > > > > Arnd > > Hi Arnd, > > This has been fixed in clang 10.0.0 but this areas has not been updated > as nobody has sent a patch yet: > > https://github.com/ClangBuiltLinux/linux/issues/378#issuecomment-524411147 Ok, that's good. I see that on clang-9, the documentation also mentions that -Wformat control -Wformat-extra-args -Wformat-invalid-specifier -Wformat-y2k -Wformat-zero-length -Wnonnull and -Wformat-security. We can probably turn these all on, regardless. The only warning that produces output here is -Wformat-security, and only in a couple of files (number of warnings per file from a few hundred randconfig builds): 384 kernel/trace/ring_buffer_benchmark.c 176 samples/trace_printk/trace-printk.c 174 kernel/debug/kdb/kdb_io.c 102 arch/x86/kernel/e820.c 80 fs/btrfs/check-integrity.c 67 fs/reiserfs/prints.c 63 fs/xfs/xfs_log_recover.c 54 fs/quota/dquot.c 53 lib/test_printf.c 39 sound/core/sound.c 28 arch/x86/kernel/cpu/mce/core.c 21 kernel/trace/preemptirq_delay_test.c 19 sound/core/seq/seq_clientmgr.c 17 sound/pci/hda/hda_bind.c 16 sound/usb/mixer_quirks.c 16 arch/x86/kernel/cpu/mce/amd.c 15 net/smc/smc_ism.c 12 kernel/debug/kdb/kdb_main.c 8 net/netfilter/nf_conntrack_helper.c 4 kernel/power/suspend_test.c 3 sound/pci/rme32.c 3 net/dsa/dsa.c 2 sound/pci/rme96.c 1 sound/soc/sof/intel/hda-codec.c 1 sound/pci/korg1212/korg1212.c Arnd
On Sun, Sep 1, 2019 at 1:26 AM Masahiro Yamada <yamada.masahiro@socionext.com> 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, > you can combine them like W=13. To enable all the warnings, you can > pass W=123. It is shown by 'make help', but not noticed much. 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 the reason why I think 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. > > Add comments in case people are confused with the code. > > Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> > Reviewed-by: Nathan Chancellor <natechancellor@gmail.com> > Tested-by: Sedat Dilek <sedat.dilek@gmail.com> > Acked-by: Nick Desaulniers <ndesaulniers@google.com> > Acked-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com> > --- Both applied to linux-kbuild. > Changes in v3: > - Added yet more comments. > Fix grammatical mistake 'does' -> 'do'. > > Changes in v2: > - Added comments and more commit log > > scripts/Makefile.extrawarn | 106 ++++++++++++++++++++----------------- > 1 file changed, 56 insertions(+), 50 deletions(-) > > diff --git a/scripts/Makefile.extrawarn b/scripts/Makefile.extrawarn > index a74ce2e3c33e..d226c5fb13e2 100644 > --- a/scripts/Makefile.extrawarn > +++ b/scripts/Makefile.extrawarn > @@ -1,14 +1,9 @@ > # 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 > +# There are three warning groups enabled by W=1, W=2, W=3. > +# They are independent, and can be combined like W=12 or W=123. > # ========================================================================== > > KBUILD_CFLAGS += $(call cc-disable-warning, packed-not-aligned) > @@ -17,58 +12,69 @@ ifeq ("$(origin W)", "command line") > export KBUILD_ENABLE_EXTRA_GCC_CHECKS := $(W) > endif > > -ifdef KBUILD_ENABLE_EXTRA_GCC_CHECKS > -warning- := $(empty) > +# > +# W=1 - warnings which may be relevant and do not occur too often > +# > +ifneq ($(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 += $(warning) > else > > +# Some diagnostics enabled by default are noisy. > +# Suppress them by using -Wno... except for W=1. > + > ifdef CONFIG_CC_IS_CLANG > KBUILD_CFLAGS += -Wno-initializer-overrides > KBUILD_CFLAGS += -Wno-format > KBUILD_CFLAGS += -Wno-sign-compare > KBUILD_CFLAGS += -Wno-format-zero-length > endif > + > +endif > + > +# > +# W=2 - warnings which occur quite often but may still be relevant > +# > +ifneq ($(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 += $(call cc-option, -Wunused-macros) > + > +endif > + > +# > +# W=3 - more obscure warnings, can most likely be ignored > +# > +ifneq ($(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 > -- Best Regards Masahiro Yamada
diff --git a/scripts/Makefile.extrawarn b/scripts/Makefile.extrawarn index a74ce2e3c33e..d226c5fb13e2 100644 --- a/scripts/Makefile.extrawarn +++ b/scripts/Makefile.extrawarn @@ -1,14 +1,9 @@ # 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 +# There are three warning groups enabled by W=1, W=2, W=3. +# They are independent, and can be combined like W=12 or W=123. # ========================================================================== KBUILD_CFLAGS += $(call cc-disable-warning, packed-not-aligned) @@ -17,58 +12,69 @@ ifeq ("$(origin W)", "command line") export KBUILD_ENABLE_EXTRA_GCC_CHECKS := $(W) endif -ifdef KBUILD_ENABLE_EXTRA_GCC_CHECKS -warning- := $(empty) +# +# W=1 - warnings which may be relevant and do not occur too often +# +ifneq ($(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 += $(warning) else +# Some diagnostics enabled by default are noisy. +# Suppress them by using -Wno... except for W=1. + ifdef CONFIG_CC_IS_CLANG KBUILD_CFLAGS += -Wno-initializer-overrides KBUILD_CFLAGS += -Wno-format KBUILD_CFLAGS += -Wno-sign-compare KBUILD_CFLAGS += -Wno-format-zero-length endif + +endif + +# +# W=2 - warnings which occur quite often but may still be relevant +# +ifneq ($(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 += $(call cc-option, -Wunused-macros) + +endif + +# +# W=3 - more obscure warnings, can most likely be ignored +# +ifneq ($(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
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, you can combine them like W=13. To enable all the warnings, you can pass W=123. It is shown by 'make help', but not noticed much. 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 the reason why I think 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. Add comments in case people are confused with the code. Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> Reviewed-by: Nathan Chancellor <natechancellor@gmail.com> Tested-by: Sedat Dilek <sedat.dilek@gmail.com> Acked-by: Nick Desaulniers <ndesaulniers@google.com> Acked-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com> --- Changes in v3: - Added yet more comments. Fix grammatical mistake 'does' -> 'do'. Changes in v2: - Added comments and more commit log scripts/Makefile.extrawarn | 106 ++++++++++++++++++++----------------- 1 file changed, 56 insertions(+), 50 deletions(-) -- 2.17.1