44929bface
Commit 4a5838ad9d ("kbuild: Add extra gcc checks") added the
-Wpacked-bitfield-compat flag, but there is no need to add it
explicitly.
GCC manual says:
"This warning is enabled by default. Use -Wno-packed-bitfield-compat
to disable this warning."
The test code in the manual:
struct foo
{
char a:4;
char b:8;
} __attribute__ ((packed));
... emits "note: offset of packed bit-field ‘b’ has changed in GCC 4.4"
without W=3.
Let's remove it, as it is a default with GCC.
Clang does not support this flag, so its removal will not affect Clang
builds.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
208 lines
7.1 KiB
Makefile
208 lines
7.1 KiB
Makefile
# SPDX-License-Identifier: GPL-2.0
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# ==========================================================================
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# make W=... settings
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#
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# There are four warning groups enabled by W=1, W=2, W=3, and W=e
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# They are independent, and can be combined like W=12 or W=123e.
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# ==========================================================================
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# Default set of warnings, always enabled
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KBUILD_CFLAGS += -Wall
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KBUILD_CFLAGS += -Wundef
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KBUILD_CFLAGS += -Werror=implicit-function-declaration
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KBUILD_CFLAGS += -Werror=implicit-int
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KBUILD_CFLAGS += -Werror=return-type
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KBUILD_CFLAGS += -Werror=strict-prototypes
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KBUILD_CFLAGS += -Wno-format-security
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KBUILD_CFLAGS += -Wno-trigraphs
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KBUILD_CFLAGS += $(call cc-disable-warning,frame-address,)
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KBUILD_CFLAGS += $(call cc-disable-warning, address-of-packed-member)
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KBUILD_CFLAGS += -Wmissing-declarations
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KBUILD_CFLAGS += -Wmissing-prototypes
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ifneq ($(CONFIG_FRAME_WARN),0)
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KBUILD_CFLAGS += -Wframe-larger-than=$(CONFIG_FRAME_WARN)
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endif
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KBUILD_CPPFLAGS-$(CONFIG_WERROR) += -Werror
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KBUILD_CPPFLAGS += $(KBUILD_CPPFLAGS-y)
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KBUILD_CFLAGS-$(CONFIG_CC_NO_ARRAY_BOUNDS) += -Wno-array-bounds
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ifdef CONFIG_CC_IS_CLANG
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# The kernel builds with '-std=gnu11' so use of GNU extensions is acceptable.
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KBUILD_CFLAGS += -Wno-gnu
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else
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# gcc inanely warns about local variables called 'main'
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KBUILD_CFLAGS += -Wno-main
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endif
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# These warnings generated too much noise in a regular build.
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# Use make W=1 to enable them (see scripts/Makefile.extrawarn)
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KBUILD_CFLAGS += $(call cc-disable-warning, unused-but-set-variable)
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KBUILD_CFLAGS += $(call cc-disable-warning, unused-const-variable)
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# These result in bogus false positives
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KBUILD_CFLAGS += $(call cc-disable-warning, dangling-pointer)
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# Variable Length Arrays (VLAs) should not be used anywhere in the kernel
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KBUILD_CFLAGS += -Wvla
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# disable pointer signed / unsigned warnings in gcc 4.0
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KBUILD_CFLAGS += -Wno-pointer-sign
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# In order to make sure new function cast mismatches are not introduced
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# in the kernel (to avoid tripping CFI checking), the kernel should be
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# globally built with -Wcast-function-type.
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KBUILD_CFLAGS += $(call cc-option, -Wcast-function-type)
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# The allocators already balk at large sizes, so silence the compiler
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# warnings for bounds checks involving those possible values. While
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# -Wno-alloc-size-larger-than would normally be used here, earlier versions
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# of gcc (<9.1) weirdly don't handle the option correctly when _other_
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# warnings are produced (?!). Using -Walloc-size-larger-than=SIZE_MAX
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# doesn't work (as it is documented to), silently resolving to "0" prior to
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# version 9.1 (and producing an error more recently). Numeric values larger
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# than PTRDIFF_MAX also don't work prior to version 9.1, which are silently
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# ignored, continuing to default to PTRDIFF_MAX. So, left with no other
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# choice, we must perform a versioned check to disable this warning.
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# https://lore.kernel.org/lkml/20210824115859.187f272f@canb.auug.org.au
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KBUILD_CFLAGS-$(call gcc-min-version, 90100) += -Wno-alloc-size-larger-than
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KBUILD_CFLAGS += $(KBUILD_CFLAGS-y) $(CONFIG_CC_IMPLICIT_FALLTHROUGH)
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# Prohibit date/time macros, which would make the build non-deterministic
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KBUILD_CFLAGS += -Werror=date-time
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# enforce correct pointer usage
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KBUILD_CFLAGS += $(call cc-option,-Werror=incompatible-pointer-types)
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# Require designated initializers for all marked structures
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KBUILD_CFLAGS += $(call cc-option,-Werror=designated-init)
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# Warn if there is an enum types mismatch
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KBUILD_CFLAGS += $(call cc-option,-Wenum-conversion)
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#
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# W=1 - warnings which may be relevant and do not occur too often
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#
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ifneq ($(findstring 1, $(KBUILD_EXTRA_WARN)),)
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KBUILD_CFLAGS += -Wextra -Wunused -Wno-unused-parameter
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KBUILD_CFLAGS += $(call cc-option, -Wrestrict)
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KBUILD_CFLAGS += -Wmissing-format-attribute
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KBUILD_CFLAGS += -Wold-style-definition
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KBUILD_CFLAGS += -Wmissing-include-dirs
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KBUILD_CFLAGS += $(call cc-option, -Wunused-but-set-variable)
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KBUILD_CFLAGS += $(call cc-option, -Wunused-const-variable)
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KBUILD_CFLAGS += $(call cc-option, -Wpacked-not-aligned)
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KBUILD_CFLAGS += $(call cc-option, -Wformat-overflow)
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KBUILD_CFLAGS += $(call cc-option, -Wformat-truncation)
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KBUILD_CFLAGS += $(call cc-option, -Wstringop-truncation)
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KBUILD_CPPFLAGS += -Wundef
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KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN1
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else
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# Some diagnostics enabled by default are noisy.
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# Suppress them by using -Wno... except for W=1.
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KBUILD_CFLAGS += $(call cc-disable-warning, unused-but-set-variable)
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KBUILD_CFLAGS += $(call cc-disable-warning, unused-const-variable)
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KBUILD_CFLAGS += $(call cc-disable-warning, restrict)
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KBUILD_CFLAGS += $(call cc-disable-warning, packed-not-aligned)
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KBUILD_CFLAGS += $(call cc-disable-warning, format-overflow)
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KBUILD_CFLAGS += $(call cc-disable-warning, format-truncation)
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KBUILD_CFLAGS += $(call cc-disable-warning, stringop-truncation)
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ifdef CONFIG_CC_IS_CLANG
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# Clang before clang-16 would warn on default argument promotions.
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ifneq ($(call clang-min-version, 160000),y)
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# Disable -Wformat
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KBUILD_CFLAGS += -Wno-format
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# Then re-enable flags that were part of the -Wformat group that aren't
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# problematic.
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KBUILD_CFLAGS += -Wformat-extra-args -Wformat-invalid-specifier
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KBUILD_CFLAGS += -Wformat-zero-length -Wnonnull
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# Requires clang-12+.
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ifeq ($(call clang-min-version, 120000),y)
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KBUILD_CFLAGS += -Wformat-insufficient-args
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endif
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endif
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KBUILD_CFLAGS += $(call cc-disable-warning, pointer-to-enum-cast)
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KBUILD_CFLAGS += -Wno-tautological-constant-out-of-range-compare
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KBUILD_CFLAGS += $(call cc-disable-warning, unaligned-access)
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KBUILD_CFLAGS += $(call cc-disable-warning, cast-function-type-strict)
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KBUILD_CFLAGS += -Wno-enum-compare-conditional
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KBUILD_CFLAGS += -Wno-enum-enum-conversion
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endif
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endif
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#
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# W=2 - warnings which occur quite often but may still be relevant
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#
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ifneq ($(findstring 2, $(KBUILD_EXTRA_WARN)),)
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KBUILD_CFLAGS += -Wdisabled-optimization
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KBUILD_CFLAGS += -Wshadow
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KBUILD_CFLAGS += $(call cc-option, -Wlogical-op)
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KBUILD_CFLAGS += -Wmissing-field-initializers
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KBUILD_CFLAGS += -Wtype-limits
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KBUILD_CFLAGS += $(call cc-option, -Wmaybe-uninitialized)
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KBUILD_CFLAGS += $(call cc-option, -Wunused-macros)
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ifdef CONFIG_CC_IS_CLANG
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KBUILD_CFLAGS += -Winitializer-overrides
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endif
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KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN2
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else
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# The following turn off the warnings enabled by -Wextra
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KBUILD_CFLAGS += -Wno-missing-field-initializers
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KBUILD_CFLAGS += -Wno-type-limits
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KBUILD_CFLAGS += -Wno-shift-negative-value
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ifdef CONFIG_CC_IS_CLANG
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KBUILD_CFLAGS += -Wno-initializer-overrides
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else
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KBUILD_CFLAGS += -Wno-maybe-uninitialized
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endif
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endif
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#
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# W=3 - more obscure warnings, can most likely be ignored
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#
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ifneq ($(findstring 3, $(KBUILD_EXTRA_WARN)),)
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KBUILD_CFLAGS += -Wbad-function-cast
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KBUILD_CFLAGS += -Wcast-align
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KBUILD_CFLAGS += -Wcast-qual
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KBUILD_CFLAGS += -Wconversion
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KBUILD_CFLAGS += -Wpacked
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KBUILD_CFLAGS += -Wpadded
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KBUILD_CFLAGS += -Wpointer-arith
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KBUILD_CFLAGS += -Wredundant-decls
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KBUILD_CFLAGS += -Wsign-compare
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KBUILD_CFLAGS += -Wswitch-default
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KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN3
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else
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# The following turn off the warnings enabled by -Wextra
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KBUILD_CFLAGS += -Wno-sign-compare
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endif
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#
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# W=e - error out on warnings
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#
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ifneq ($(findstring e, $(KBUILD_EXTRA_WARN)),)
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KBUILD_CFLAGS += -Werror
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endif
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