From 64a91907c896247c19f8314add2c9baa573fbd3c Mon Sep 17 00:00:00 2001 From: Masahiro Yamada Date: Sun, 1 Sep 2019 01:25:54 +0900 Subject: kbuild: refactor scripts/Makefile.extrawarn Instead of the warning-[123] magic, let's accumulate compiler options to KBUILD_CFLAGS directly as the top Makefile does. I think this makes it 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 Reviewed-by: Nathan Chancellor Tested-by: Sedat Dilek Acked-by: Nick Desaulniers Acked-by: Miguel Ojeda --- scripts/Makefile.extrawarn | 106 ++++++++++++++++++++++++--------------------- 1 file changed, 56 insertions(+), 50 deletions(-) (limited to 'scripts/Makefile.extrawarn') 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 -- cgit v1.2.3 From e27128db62834c5b906585c2d97f0ddd431fa28f Mon Sep 17 00:00:00 2001 From: Masahiro Yamada Date: Sun, 1 Sep 2019 01:25:55 +0900 Subject: kbuild: rename KBUILD_ENABLE_EXTRA_GCC_CHECKS to KBUILD_EXTRA_WARN KBUILD_ENABLE_EXTRA_GCC_CHECKS started as a switch to add extra warning options for GCC, but now it is a historical misnomer since we use it also for Clang, DTC, and even kernel-doc. Rename it to more sensible, shorter KBUILD_EXTRA_WARN. For the backward compatibility, KBUILD_ENABLE_EXTRA_GCC_CHECKS is still supported (but not advertised in the documentation). I also fixed up 'make help', and updated the documentation. Signed-off-by: Masahiro Yamada Reviewed-by: Nathan Chancellor Reviewed-by: Nick Desaulniers Reviewed-by: Sedat Dilek --- Documentation/kbuild/kbuild.rst | 14 +++++++++----- Makefile | 2 +- scripts/Makefile.build | 2 +- scripts/Makefile.extrawarn | 13 +++++++++---- scripts/Makefile.lib | 4 ++-- scripts/genksyms/Makefile | 2 +- 6 files changed, 23 insertions(+), 14 deletions(-) (limited to 'scripts/Makefile.extrawarn') diff --git a/Documentation/kbuild/kbuild.rst b/Documentation/kbuild/kbuild.rst index 62f9d86c082c..f1e5dce86af7 100644 --- a/Documentation/kbuild/kbuild.rst +++ b/Documentation/kbuild/kbuild.rst @@ -105,6 +105,15 @@ The output directory can also be specified using "O=...". Setting "O=..." takes precedence over KBUILD_OUTPUT. +KBUILD_EXTRA_WARN +----------------- +Specify the extra build checks. The same value can be assigned by passing +W=... from the command line. + +See `make help` for the list of the supported values. + +Setting "W=..." takes precedence over KBUILD_EXTRA_WARN. + KBUILD_DEBARCH -------------- For the deb-pkg target, allows overriding the normal heuristics deployed by @@ -241,11 +250,6 @@ To get all available archs you can also specify all. E.g.:: $ make ALLSOURCE_ARCHS=all tags -KBUILD_ENABLE_EXTRA_GCC_CHECKS ------------------------------- -If enabled over the make command line with "W=1", it turns on additional -gcc -W... options for more extensive build-time checking. - KBUILD_BUILD_TIMESTAMP ---------------------- Setting this to a date string overrides the timestamp used in the diff --git a/Makefile b/Makefile index 06e1e21c0f45..adc0cabe2382 100644 --- a/Makefile +++ b/Makefile @@ -1538,7 +1538,7 @@ help: @echo ' make C=1 [targets] Check re-compiled c source with $$CHECK (sparse by default)' @echo ' make C=2 [targets] Force check of all c source with $$CHECK' @echo ' make RECORDMCOUNT_WARN=1 [targets] Warn about ignored mcount sections' - @echo ' make W=n [targets] Enable extra gcc checks, n=1,2,3 where' + @echo ' make W=n [targets] Enable extra build checks, n=1,2,3 where' @echo ' 1: warnings which may be relevant and do not occur too often' @echo ' 2: warnings which occur quite often but may still be relevant' @echo ' 3: more obscure warnings, can most likely be ignored' diff --git a/scripts/Makefile.build b/scripts/Makefile.build index 2a21ca86b720..f72aba64d611 100644 --- a/scripts/Makefile.build +++ b/scripts/Makefile.build @@ -85,7 +85,7 @@ else ifeq ($(KBUILD_CHECKSRC),2) cmd_force_checksrc = $(CHECK) $(CHECKFLAGS) $(c_flags) $< endif -ifneq ($(KBUILD_ENABLE_EXTRA_GCC_CHECKS),) +ifneq ($(KBUILD_EXTRA_WARN),) cmd_checkdoc = $(srctree)/scripts/kernel-doc -none $< endif diff --git a/scripts/Makefile.extrawarn b/scripts/Makefile.extrawarn index d226c5fb13e2..53eb7e0c6a5a 100644 --- a/scripts/Makefile.extrawarn +++ b/scripts/Makefile.extrawarn @@ -8,14 +8,19 @@ KBUILD_CFLAGS += $(call cc-disable-warning, packed-not-aligned) +# backward compatibility +KBUILD_EXTRA_WARN ?= $(KBUILD_ENABLE_EXTRA_GCC_CHECKS) + ifeq ("$(origin W)", "command line") - export KBUILD_ENABLE_EXTRA_GCC_CHECKS := $(W) + KBUILD_EXTRA_WARN := $(W) endif +export KBUILD_EXTRA_WARN + # # W=1 - warnings which may be relevant and do not occur too often # -ifneq ($(findstring 1, $(KBUILD_ENABLE_EXTRA_GCC_CHECKS)),) +ifneq ($(findstring 1, $(KBUILD_EXTRA_WARN)),) KBUILD_CFLAGS += -Wextra -Wunused -Wno-unused-parameter KBUILD_CFLAGS += -Wmissing-declarations @@ -48,7 +53,7 @@ endif # # W=2 - warnings which occur quite often but may still be relevant # -ifneq ($(findstring 2, $(KBUILD_ENABLE_EXTRA_GCC_CHECKS)),) +ifneq ($(findstring 2, $(KBUILD_EXTRA_WARN)),) KBUILD_CFLAGS += -Wcast-align KBUILD_CFLAGS += -Wdisabled-optimization @@ -65,7 +70,7 @@ endif # # W=3 - more obscure warnings, can most likely be ignored # -ifneq ($(findstring 3, $(KBUILD_ENABLE_EXTRA_GCC_CHECKS)),) +ifneq ($(findstring 3, $(KBUILD_EXTRA_WARN)),) KBUILD_CFLAGS += -Wbad-function-cast KBUILD_CFLAGS += -Wcast-qual diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib index 380a7d11a573..4a0cdd6f5909 100644 --- a/scripts/Makefile.lib +++ b/scripts/Makefile.lib @@ -251,7 +251,7 @@ quiet_cmd_gzip = GZIP $@ DTC ?= $(objtree)/scripts/dtc/dtc # Disable noisy checks by default -ifeq ($(findstring 1,$(KBUILD_ENABLE_EXTRA_GCC_CHECKS)),) +ifeq ($(findstring 1,$(KBUILD_EXTRA_WARN)),) DTC_FLAGS += -Wno-unit_address_vs_reg \ -Wno-unit_address_format \ -Wno-avoid_unnecessary_addr_size \ @@ -262,7 +262,7 @@ DTC_FLAGS += -Wno-unit_address_vs_reg \ -Wno-pci_device_reg endif -ifneq ($(findstring 2,$(KBUILD_ENABLE_EXTRA_GCC_CHECKS)),) +ifneq ($(findstring 2,$(KBUILD_EXTRA_WARN)),) DTC_FLAGS += -Wnode_name_chars_strict \ -Wproperty_name_chars_strict endif diff --git a/scripts/genksyms/Makefile b/scripts/genksyms/Makefile index baf44ed0a93a..78629f515e78 100644 --- a/scripts/genksyms/Makefile +++ b/scripts/genksyms/Makefile @@ -12,7 +12,7 @@ genksyms-objs := genksyms.o parse.tab.o lex.lex.o # # Just in case, run "$(YACC) --version" without suppressing stderr # so that 'bison: not found' will be displayed if it is missing. -ifeq ($(findstring 1,$(KBUILD_ENABLE_EXTRA_GCC_CHECKS)),) +ifeq ($(findstring 1,$(KBUILD_EXTRA_WARN)),) quiet_cmd_bison_no_warn = $(quiet_cmd_bison) cmd_bison_no_warn = $(YACC) --version >/dev/null; \ -- cgit v1.2.3 From 6863f5643dd717376c2fdc85a47a00f9d738a834 Mon Sep 17 00:00:00 2001 From: Masahiro Yamada Date: Sat, 7 Sep 2019 11:52:36 +0900 Subject: kbuild: allow Clang to find unused static inline functions for W=1 build GCC and Clang have different policy for -Wunused-function; GCC does not warn unused static inline functions at all whereas Clang does if they are defined in source files instead of included headers although it has been suppressed since commit abb2ea7dfd82 ("compiler, clang: suppress warning for unused static inline functions"). We often miss to delete unused functions where 'static inline' is used in *.c files since there is no tool to detect them. Unused code remains until somebody notices. For example, commit 075ddd75680f ("regulator: core: remove unused rdev_get_supply()"). Let's remove __maybe_unused from the inline macro to allow Clang to start finding unused static inline functions. For now, we do this only for W=1 build since it is not a good idea to sprinkle warnings for the normal build (e.g. 35 warnings for arch/x86/configs/x86_64_defconfig). My initial attempt was to add -Wno-unused-function for no W= build (https://lore.kernel.org/patchwork/patch/1120594/) Nathan Chancellor pointed out that would weaken Clang's checks since we would no longer get -Wunused-function without W=1. It is true GCC would catch unused static non-inline functions, but it would weaken Clang as a standalone compiler, at least. Hence, here is a counter implementation. The current problem is, W=... only controls compiler flags, which are globally effective. There is no way to address only 'static inline' functions. This commit defines KBUILD_EXTRA_WARN[123] corresponding to W=[123]. When KBUILD_EXTRA_WARN1 is defined, __maybe_unused is omitted from the 'inline' macro. The new macro __inline_maybe_unused makes the code a bit uglier, so I hope we can remove it entirely after fixing most of the warnings. If you contribute to code clean-up, please run "make CC=clang W=1" and check -Wunused-function warnings. You will find lots of unused functions. Some of them are false-positives because the call-sites are disabled by #ifdef. I do not like to abuse the inline keyword for suppressing unused-function warnings because it is intended to be a hint for the compiler optimization. I prefer #ifdef around the definition, or __maybe_unused if #ifdef would make the code too ugly. Signed-off-by: Masahiro Yamada Reviewed-by: Nathan Chancellor Tested-by: Nathan Chancellor --- include/linux/compiler_types.h | 20 ++++++++++++++------ scripts/Makefile.extrawarn | 6 ++++++ 2 files changed, 20 insertions(+), 6 deletions(-) (limited to 'scripts/Makefile.extrawarn') diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h index 599c27b56c29..b056a40116da 100644 --- a/include/linux/compiler_types.h +++ b/include/linux/compiler_types.h @@ -130,10 +130,6 @@ struct ftrace_likely_data { /* * Force always-inline if the user requests it so via the .config. - * GCC does not warn about unused static inline functions for - * -Wunused-function. This turns out to avoid the need for complex #ifdef - * directives. Suppress the warning in clang as well by using "unused" - * function attribute, which is redundant but not harmful for gcc. * Prefer gnu_inline, so that extern inline functions do not emit an * externally visible function. This makes extern inline behave as per gnu89 * semantics rather than c99. This prevents multiple symbol definition errors @@ -144,15 +140,27 @@ struct ftrace_likely_data { */ #if !defined(CONFIG_OPTIMIZE_INLINING) #define inline inline __attribute__((__always_inline__)) __gnu_inline \ - __maybe_unused notrace + __inline_maybe_unused notrace #else #define inline inline __gnu_inline \ - __maybe_unused notrace + __inline_maybe_unused notrace #endif #define __inline__ inline #define __inline inline +/* + * GCC does not warn about unused static inline functions for -Wunused-function. + * Suppress the warning in clang as well by using __maybe_unused, but enable it + * for W=1 build. This will allow clang to find unused functions. Remove the + * __inline_maybe_unused entirely after fixing most of -Wunused-function warnings. + */ +#ifdef KBUILD_EXTRA_WARN1 +#define __inline_maybe_unused +#else +#define __inline_maybe_unused __maybe_unused +#endif + /* * Rather then using noinline to prevent stack consumption, use * noinline_for_stack instead. For documentation reasons. diff --git a/scripts/Makefile.extrawarn b/scripts/Makefile.extrawarn index 53eb7e0c6a5a..ecddf83ac142 100644 --- a/scripts/Makefile.extrawarn +++ b/scripts/Makefile.extrawarn @@ -36,6 +36,8 @@ KBUILD_CFLAGS += $(call cc-option, -Wstringop-truncation) KBUILD_CFLAGS += -Wno-missing-field-initializers KBUILD_CFLAGS += -Wno-sign-compare +KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN1 + else # Some diagnostics enabled by default are noisy. @@ -65,6 +67,8 @@ KBUILD_CFLAGS += -Wsign-compare KBUILD_CFLAGS += $(call cc-option, -Wmaybe-uninitialized) KBUILD_CFLAGS += $(call cc-option, -Wunused-macros) +KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN2 + endif # @@ -82,4 +86,6 @@ KBUILD_CFLAGS += -Wredundant-decls KBUILD_CFLAGS += -Wswitch-default KBUILD_CFLAGS += $(call cc-option, -Wpacked-bitfield-compat) +KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN3 + endif -- cgit v1.2.3