scripts/Makefile.extrawarn - linux - Git at Google

 # SPDX-License-Identifier: GPL-2.0
 # ==========================================================================
 # make W=... settings
 #
 # There are four warning groups enabled by W=1, W=2, W=3, and W=e
 # They are independent, and can be combined like W=12 or W=123e.
 # ==========================================================================

 # Default set of warnings, always enabled
 KBUILD_CFLAGS += -Wall
 KBUILD_CFLAGS += -Wundef
 KBUILD_CFLAGS += -Werror=implicit-function-declaration
 KBUILD_CFLAGS += -Werror=implicit-int
 KBUILD_CFLAGS += -Werror=return-type
 KBUILD_CFLAGS += -Werror=strict-prototypes
 KBUILD_CFLAGS += -Wno-format-security
 KBUILD_CFLAGS += -Wno-trigraphs
 KBUILD_CFLAGS += $(call cc-disable-warning,frame-address,)
 KBUILD_CFLAGS += $(call cc-disable-warning, address-of-packed-member)
 KBUILD_CFLAGS += -Wmissing-declarations
 KBUILD_CFLAGS += -Wmissing-prototypes

 ifneq ($(CONFIG_FRAME_WARN),0)
 KBUILD_CFLAGS += -Wframe-larger-than=$(CONFIG_FRAME_WARN)
 endif

 KBUILD_CPPFLAGS-$(CONFIG_WERROR) += -Werror
 KBUILD_CPPFLAGS += $(KBUILD_CPPFLAGS-y)
 KBUILD_CFLAGS-$(CONFIG_CC_NO_ARRAY_BOUNDS) += -Wno-array-bounds

 ifdef CONFIG_CC_IS_CLANG
 # The kernel builds with '-std=gnu11' so use of GNU extensions is acceptable.
 KBUILD_CFLAGS += -Wno-gnu
 else

 # gcc inanely warns about local variables called 'main'
 KBUILD_CFLAGS += -Wno-main
 endif

 # These result in bogus false positives
 KBUILD_CFLAGS += $(call cc-disable-warning, dangling-pointer)

 # Variable Length Arrays (VLAs) should not be used anywhere in the kernel
 KBUILD_CFLAGS += -Wvla

 # disable pointer signed / unsigned warnings in gcc 4.0
 KBUILD_CFLAGS += -Wno-pointer-sign

 # In order to make sure new function cast mismatches are not introduced
 # in the kernel (to avoid tripping CFI checking), the kernel should be
 # globally built with -Wcast-function-type.
 KBUILD_CFLAGS += $(call cc-option, -Wcast-function-type)

 # The allocators already balk at large sizes, so silence the compiler
 # warnings for bounds checks involving those possible values. While
 # -Wno-alloc-size-larger-than would normally be used here, earlier versions
 # of gcc (<9.1) weirdly don't handle the option correctly when _other_
 # warnings are produced (?!). Using -Walloc-size-larger-than=SIZE_MAX
 # doesn't work (as it is documented to), silently resolving to "0" prior to
 # version 9.1 (and producing an error more recently). Numeric values larger
 # than PTRDIFF_MAX also don't work prior to version 9.1, which are silently
 # ignored, continuing to default to PTRDIFF_MAX. So, left with no other
 # choice, we must perform a versioned check to disable this warning.
 # https://lore.kernel.org/lkml/20210824115859.187f272f@canb.auug.org.au
 KBUILD_CFLAGS-$(call gcc-min-version, 90100) += -Wno-alloc-size-larger-than
 KBUILD_CFLAGS += $(KBUILD_CFLAGS-y) $(CONFIG_CC_IMPLICIT_FALLTHROUGH)

 # Prohibit date/time macros, which would make the build non-deterministic
 KBUILD_CFLAGS += -Werror=date-time

 # enforce correct pointer usage
 KBUILD_CFLAGS += $(call cc-option,-Werror=incompatible-pointer-types)

 # Require designated initializers for all marked structures
 KBUILD_CFLAGS += $(call cc-option,-Werror=designated-init)

 # Warn if there is an enum types mismatch
 KBUILD_CFLAGS += $(call cc-option,-Wenum-conversion)

 KBUILD_CFLAGS += -Wextra
 KBUILD_CFLAGS += -Wunused

 #
 # W=1 - warnings which may be relevant and do not occur too often
 #
 ifneq ($(findstring 1, $(KBUILD_EXTRA_WARN)),)

 KBUILD_CFLAGS += -Wmissing-format-attribute
 KBUILD_CFLAGS += -Wmissing-include-dirs
 KBUILD_CFLAGS += $(call cc-option, -Wunused-const-variable)

 KBUILD_CPPFLAGS += -Wundef
 KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN1

 else

 # Some diagnostics enabled by default are noisy.
 # Suppress them by using -Wno... except for W=1.
 KBUILD_CFLAGS += $(call cc-disable-warning, unused-but-set-variable)
 KBUILD_CFLAGS += $(call cc-disable-warning, unused-const-variable)
 KBUILD_CFLAGS += $(call cc-disable-warning, packed-not-aligned)
 KBUILD_CFLAGS += $(call cc-disable-warning, format-overflow)
 ifdef CONFIG_CC_IS_GCC
 KBUILD_CFLAGS += $(call cc-disable-warning, format-truncation)
 else
 # Clang checks for overflow/truncation with '%p', while GCC does not:
 # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111219
 KBUILD_CFLAGS += $(call cc-disable-warning, format-overflow-non-kprintf)
 KBUILD_CFLAGS += $(call cc-disable-warning, format-truncation-non-kprintf)
 endif
 KBUILD_CFLAGS += $(call cc-disable-warning, stringop-truncation)

 KBUILD_CFLAGS += -Wno-override-init # alias for -Wno-initializer-overrides in clang

 ifdef CONFIG_CC_IS_CLANG
 # Clang before clang-16 would warn on default argument promotions.
 ifneq ($(call clang-min-version, 160000),y)
 # Disable -Wformat
 KBUILD_CFLAGS += -Wno-format
 # Then re-enable flags that were part of the -Wformat group that aren't
 # problematic.
 KBUILD_CFLAGS += -Wformat-extra-args -Wformat-invalid-specifier
 KBUILD_CFLAGS += -Wformat-zero-length -Wnonnull
 # Requires clang-12+.
 ifeq ($(call clang-min-version, 120000),y)
 KBUILD_CFLAGS += -Wformat-insufficient-args
 endif
 endif
 KBUILD_CFLAGS += $(call cc-disable-warning, pointer-to-enum-cast)
 KBUILD_CFLAGS += -Wno-tautological-constant-out-of-range-compare
 KBUILD_CFLAGS += $(call cc-disable-warning, unaligned-access)
 KBUILD_CFLAGS += -Wno-enum-compare-conditional
 KBUILD_CFLAGS += -Wno-enum-enum-conversion
 endif

 endif

 #
 # W=2 - warnings which occur quite often but may still be relevant
 #
 ifneq ($(findstring 2, $(KBUILD_EXTRA_WARN)),)

 KBUILD_CFLAGS += -Wdisabled-optimization
 KBUILD_CFLAGS += -Wshadow
 KBUILD_CFLAGS += $(call cc-option, -Wlogical-op)
 KBUILD_CFLAGS += $(call cc-option, -Wunused-macros)

 KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN2

 else

 # The following turn off the warnings enabled by -Wextra
 KBUILD_CFLAGS += -Wno-missing-field-initializers
 KBUILD_CFLAGS += -Wno-type-limits
 KBUILD_CFLAGS += -Wno-shift-negative-value

 ifdef CONFIG_CC_IS_GCC
 KBUILD_CFLAGS += -Wno-maybe-uninitialized
 endif

 endif

 #
 # W=3 - more obscure warnings, can most likely be ignored
 #
 ifneq ($(findstring 3, $(KBUILD_EXTRA_WARN)),)

 KBUILD_CFLAGS += -Wbad-function-cast
 KBUILD_CFLAGS += -Wcast-align
 KBUILD_CFLAGS += -Wcast-qual
 KBUILD_CFLAGS += -Wconversion
 KBUILD_CFLAGS += -Wpacked
 KBUILD_CFLAGS += -Wpadded
 KBUILD_CFLAGS += -Wpointer-arith
 KBUILD_CFLAGS += -Wredundant-decls
 KBUILD_CFLAGS += -Wsign-compare
 KBUILD_CFLAGS += -Wswitch-default

 KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN3

 else

 # The following turn off the warnings enabled by -Wextra
 KBUILD_CFLAGS += -Wno-sign-compare
 KBUILD_CFLAGS += -Wno-unused-parameter

 endif

 #
 # W=e - error out on warnings
 #
 ifneq ($(findstring e, $(KBUILD_EXTRA_WARN)),)

 KBUILD_CFLAGS += -Werror

 endif
	# SPDX-License-Identifier: GPL-2.0
	# ==========================================================================
	# make W=... settings
	#
	# There are four warning groups enabled by W=1, W=2, W=3, and W=e
	# They are independent, and can be combined like W=12 or W=123e.
	# ==========================================================================

	# Default set of warnings, always enabled
	KBUILD_CFLAGS += -Wall
	KBUILD_CFLAGS += -Wundef
	KBUILD_CFLAGS += -Werror=implicit-function-declaration
	KBUILD_CFLAGS += -Werror=implicit-int
	KBUILD_CFLAGS += -Werror=return-type
	KBUILD_CFLAGS += -Werror=strict-prototypes
	KBUILD_CFLAGS += -Wno-format-security
	KBUILD_CFLAGS += -Wno-trigraphs
	KBUILD_CFLAGS += $(call cc-disable-warning,frame-address,)
	KBUILD_CFLAGS += $(call cc-disable-warning, address-of-packed-member)
	KBUILD_CFLAGS += -Wmissing-declarations
	KBUILD_CFLAGS += -Wmissing-prototypes

	ifneq ($(CONFIG_FRAME_WARN),0)
	KBUILD_CFLAGS += -Wframe-larger-than=$(CONFIG_FRAME_WARN)
	endif

	KBUILD_CPPFLAGS-$(CONFIG_WERROR) += -Werror
	KBUILD_CPPFLAGS += $(KBUILD_CPPFLAGS-y)
	KBUILD_CFLAGS-$(CONFIG_CC_NO_ARRAY_BOUNDS) += -Wno-array-bounds

	ifdef CONFIG_CC_IS_CLANG
	# The kernel builds with '-std=gnu11' so use of GNU extensions is acceptable.
	KBUILD_CFLAGS += -Wno-gnu
	else

	# gcc inanely warns about local variables called 'main'
	KBUILD_CFLAGS += -Wno-main
	endif

	# These result in bogus false positives
	KBUILD_CFLAGS += $(call cc-disable-warning, dangling-pointer)

	# Variable Length Arrays (VLAs) should not be used anywhere in the kernel
	KBUILD_CFLAGS += -Wvla

	# disable pointer signed / unsigned warnings in gcc 4.0
	KBUILD_CFLAGS += -Wno-pointer-sign

	# In order to make sure new function cast mismatches are not introduced
	# in the kernel (to avoid tripping CFI checking), the kernel should be
	# globally built with -Wcast-function-type.
	KBUILD_CFLAGS += $(call cc-option, -Wcast-function-type)

	# The allocators already balk at large sizes, so silence the compiler
	# warnings for bounds checks involving those possible values. While
	# -Wno-alloc-size-larger-than would normally be used here, earlier versions
	# of gcc (<9.1) weirdly don't handle the option correctly when _other_
	# warnings are produced (?!). Using -Walloc-size-larger-than=SIZE_MAX
	# doesn't work (as it is documented to), silently resolving to "0" prior to
	# version 9.1 (and producing an error more recently). Numeric values larger
	# than PTRDIFF_MAX also don't work prior to version 9.1, which are silently
	# ignored, continuing to default to PTRDIFF_MAX. So, left with no other
	# choice, we must perform a versioned check to disable this warning.
	# https://lore.kernel.org/lkml/20210824115859.187f272f@canb.auug.org.au
	KBUILD_CFLAGS-$(call gcc-min-version, 90100) += -Wno-alloc-size-larger-than
	KBUILD_CFLAGS += $(KBUILD_CFLAGS-y) $(CONFIG_CC_IMPLICIT_FALLTHROUGH)

	# Prohibit date/time macros, which would make the build non-deterministic
	KBUILD_CFLAGS += -Werror=date-time

	# enforce correct pointer usage
	KBUILD_CFLAGS += $(call cc-option,-Werror=incompatible-pointer-types)

	# Require designated initializers for all marked structures
	KBUILD_CFLAGS += $(call cc-option,-Werror=designated-init)

	# Warn if there is an enum types mismatch
	KBUILD_CFLAGS += $(call cc-option,-Wenum-conversion)

	KBUILD_CFLAGS += -Wextra
	KBUILD_CFLAGS += -Wunused

	#
	# W=1 - warnings which may be relevant and do not occur too often
	#
	ifneq ($(findstring 1, $(KBUILD_EXTRA_WARN)),)

	KBUILD_CFLAGS += -Wmissing-format-attribute
	KBUILD_CFLAGS += -Wmissing-include-dirs
	KBUILD_CFLAGS += $(call cc-option, -Wunused-const-variable)

	KBUILD_CPPFLAGS += -Wundef
	KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN1

	else

	# Some diagnostics enabled by default are noisy.
	# Suppress them by using -Wno... except for W=1.
	KBUILD_CFLAGS += $(call cc-disable-warning, unused-but-set-variable)
	KBUILD_CFLAGS += $(call cc-disable-warning, unused-const-variable)
	KBUILD_CFLAGS += $(call cc-disable-warning, packed-not-aligned)
	KBUILD_CFLAGS += $(call cc-disable-warning, format-overflow)
	ifdef CONFIG_CC_IS_GCC
	KBUILD_CFLAGS += $(call cc-disable-warning, format-truncation)
	else
	# Clang checks for overflow/truncation with '%p', while GCC does not:
	# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111219
	KBUILD_CFLAGS += $(call cc-disable-warning, format-overflow-non-kprintf)
	KBUILD_CFLAGS += $(call cc-disable-warning, format-truncation-non-kprintf)
	endif
	KBUILD_CFLAGS += $(call cc-disable-warning, stringop-truncation)

	KBUILD_CFLAGS += -Wno-override-init # alias for -Wno-initializer-overrides in clang

	ifdef CONFIG_CC_IS_CLANG
	# Clang before clang-16 would warn on default argument promotions.
	ifneq ($(call clang-min-version, 160000),y)
	# Disable -Wformat
	KBUILD_CFLAGS += -Wno-format
	# Then re-enable flags that were part of the -Wformat group that aren't
	# problematic.
	KBUILD_CFLAGS += -Wformat-extra-args -Wformat-invalid-specifier
	KBUILD_CFLAGS += -Wformat-zero-length -Wnonnull
	# Requires clang-12+.
	ifeq ($(call clang-min-version, 120000),y)
	KBUILD_CFLAGS += -Wformat-insufficient-args
	endif
	endif
	KBUILD_CFLAGS += $(call cc-disable-warning, pointer-to-enum-cast)
	KBUILD_CFLAGS += -Wno-tautological-constant-out-of-range-compare
	KBUILD_CFLAGS += $(call cc-disable-warning, unaligned-access)
	KBUILD_CFLAGS += -Wno-enum-compare-conditional
	KBUILD_CFLAGS += -Wno-enum-enum-conversion
	endif

	endif

	#
	# W=2 - warnings which occur quite often but may still be relevant
	#
	ifneq ($(findstring 2, $(KBUILD_EXTRA_WARN)),)

	KBUILD_CFLAGS += -Wdisabled-optimization
	KBUILD_CFLAGS += -Wshadow
	KBUILD_CFLAGS += $(call cc-option, -Wlogical-op)
	KBUILD_CFLAGS += $(call cc-option, -Wunused-macros)

	KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN2

	else

	# The following turn off the warnings enabled by -Wextra
	KBUILD_CFLAGS += -Wno-missing-field-initializers
	KBUILD_CFLAGS += -Wno-type-limits
	KBUILD_CFLAGS += -Wno-shift-negative-value

	ifdef CONFIG_CC_IS_GCC
	KBUILD_CFLAGS += -Wno-maybe-uninitialized
	endif

	endif

	#
	# W=3 - more obscure warnings, can most likely be ignored
	#
	ifneq ($(findstring 3, $(KBUILD_EXTRA_WARN)),)

	KBUILD_CFLAGS += -Wbad-function-cast
	KBUILD_CFLAGS += -Wcast-align
	KBUILD_CFLAGS += -Wcast-qual
	KBUILD_CFLAGS += -Wconversion
	KBUILD_CFLAGS += -Wpacked
	KBUILD_CFLAGS += -Wpadded
	KBUILD_CFLAGS += -Wpointer-arith
	KBUILD_CFLAGS += -Wredundant-decls
	KBUILD_CFLAGS += -Wsign-compare
	KBUILD_CFLAGS += -Wswitch-default

	KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN3

	else

	# The following turn off the warnings enabled by -Wextra
	KBUILD_CFLAGS += -Wno-sign-compare
	KBUILD_CFLAGS += -Wno-unused-parameter

	endif

	#
	# W=e - error out on warnings
	#
	ifneq ($(findstring e, $(KBUILD_EXTRA_WARN)),)

	KBUILD_CFLAGS += -Werror

	endif