Commit 28bc20dc authored by Sam Ravnborg's avatar Sam Ravnborg Committed by Michal Marek
Browse files

kbuild: implement several W= levels 

Building a kernel with "make W=1" produces far too much noise to be
useful.

Divide the warning options in three groups:

    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

When building the whole kernel, those levels produce:

W=1 - 4859 warnings
W=2 - 1394 warnings
W=3 - 86666 warnings

respectively. Warnings have been counted with Geert's script at

http://www.kernel.org/pub/linux/kernel/people/geert/linux-log/linux-log-summary.pl



Many warnings occur from .h files so fixing one file may have a nice
effect on the total number of warnings.

With these changes I am actually tempted to try W=1 now and then.
Previously there was just too much noise.

Borislav:

- make the W= levels exclusive
- move very noisy and making little sense for the kernel warnings to W=3
- drop -Woverlength-strings due to useless warning message
- copy explanatory text for the different warning levels to 'make help'
- recount warnings per level

Signed-off-by: default avatarSam Ravnborg <sam@ravnborg.org>
Signed-off-by: default avatarBorislav Petkov <bp@alien8.de>
Cc: Dave Jones <davej@redhat.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: default avatarMichal Marek <mmarek@suse.cz>
parent 40df759e

Makefile

+6 −2
Original line number Diff line number Diff line
@@ -103,7 +103,7 @@ ifeq ("$(origin O)", "command line") 
endif



ifeq ("$(origin W)", "command line")

  export KBUILD_ENABLE_EXTRA_GCC_CHECKS := 1

  export KBUILD_ENABLE_EXTRA_GCC_CHECKS := $(W)

endif



# That's our default target when none is given on the command line
@@ -1274,7 +1274,11 @@ help: 
	@echo  '  make O=dir [targets] Locate all output files in "dir", including .config'

	@echo  '  make C=1   [targets] Check all c source with $$CHECK (sparse by default)'

	@echo  '  make C=2   [targets] Force check of all c source with $$CHECK'

	@echo  '  make W=1   [targets] Enable extra gcc checks'

	@echo  '  make W=n   [targets] Enable extra gcc 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'



	@echo  ''

	@echo  'Execute "make" or "make all" to build all targets marked with [*] '

	@echo  'For further info see the ./README file'

scripts/Makefile.build

+38 −27
Original line number Diff line number Diff line
@@ -51,36 +51,47 @@ ifeq ($(KBUILD_NOPEDANTIC),) 
endif



#

# make W=1 settings

# make W=... settings

#

# $(call cc-option... ) handles gcc -W.. options which

# 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

ifdef KBUILD_ENABLE_EXTRA_GCC_CHECKS

KBUILD_EXTRA_WARNINGS := -Wextra

KBUILD_EXTRA_WARNINGS += -Wunused -Wno-unused-parameter

KBUILD_EXTRA_WARNINGS += -Waggregate-return

KBUILD_EXTRA_WARNINGS += -Wbad-function-cast

KBUILD_EXTRA_WARNINGS += -Wcast-qual

KBUILD_EXTRA_WARNINGS += -Wcast-align

KBUILD_EXTRA_WARNINGS += -Wconversion

KBUILD_EXTRA_WARNINGS += -Wdisabled-optimization

KBUILD_EXTRA_WARNINGS += -Wlogical-op

KBUILD_EXTRA_WARNINGS += -Wmissing-declarations

KBUILD_EXTRA_WARNINGS += -Wmissing-format-attribute

KBUILD_EXTRA_WARNINGS += $(call cc-option, -Wmissing-include-dirs,)

KBUILD_EXTRA_WARNINGS += -Wmissing-prototypes

KBUILD_EXTRA_WARNINGS += -Wnested-externs

KBUILD_EXTRA_WARNINGS += -Wold-style-definition

KBUILD_EXTRA_WARNINGS += $(call cc-option, -Woverlength-strings,)

KBUILD_EXTRA_WARNINGS += -Wpacked

KBUILD_EXTRA_WARNINGS += -Wpacked-bitfield-compat

KBUILD_EXTRA_WARNINGS += -Wpadded

KBUILD_EXTRA_WARNINGS += -Wpointer-arith

KBUILD_EXTRA_WARNINGS += -Wredundant-decls

KBUILD_EXTRA_WARNINGS += -Wshadow

KBUILD_EXTRA_WARNINGS += -Wswitch-default

KBUILD_EXTRA_WARNINGS += $(call cc-option, -Wvla,)

KBUILD_CFLAGS += $(KBUILD_EXTRA_WARNINGS)

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 += $(call cc-option, -Wmissing-include-dirs)



warning-2 := -Waggregate-return

warning-2 += -Wcast-align

warning-2 += -Wdisabled-optimization

warning-2 += -Wnested-externs

warning-2 += -Wshadow

warning-2 += $(call cc-option, -Wlogical-op)



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-3 += $(call cc-option, -Wvla)



warning := $(warning-$(KBUILD_ENABLE_EXTRA_GCC_CHECKS))



ifeq ("$(warning)","")

        $(error W=$(KBUILD_ENABLE_EXTRA_GCC_CHECKS) is unknown)

endif



KBUILD_CFLAGS += $(warning)

endif



include scripts/Makefile.lib

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