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Commit27758d8c25("kbuild: enable -Werror for hostprogs") unconditionally enabled -Werror for the compiler, assembler, and linker when building the host programs, as the build footprint of the host programs is small (thus risk of build failures from warnings are low) and that stage of the build may not have Kconfig values (thus CONFIG_WERROR could not be used as a precondition). While turning warnings into errors unconditionally happens in a few places within the kernel, it can be disruptive to people who may be building with newer compilers, such as while doing a bisect. While it is possible to avoid this behavior by passing HOSTCFLAGS=-w or HOSTCFLAGS=-Wno-error, it may not be the most intuitive for regular users not intimately familiar with Kbuild. Avoid being disruptive to the entire build by depending on the explicit opt-in of CONFIG_WERROR or W=e to enable -Werror and the like while building the host programs. While this means there is a small portion of the build that does not have -Werror enabled (namely scripts/kconfig/* and scripts/basic/fixdep), it is better than not having it altogether. Fixes:27758d8c25("kbuild: enable -Werror for hostprogs") Acked-by: Miguel Ojeda <ojeda@kernel.org> Reported-by: Askar Safin <safinaskar@gmail.com> Closes: https://lore.kernel.org/20251005011100.1035272-1-safinaskar@gmail.com/ Reviewed-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de> Tested-by: Miguel Ojeda <ojeda@kernel.org> # Rust Link: https://patch.msgid.link/20251006-kbuild-hostprogs-werror-fix-v1-1-23cf1ffced5c@kernel.org Signed-off-by: Nathan Chancellor <nathan@kernel.org>
234 lines
8.4 KiB
Makefile
234 lines
8.4 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 += -Wextra
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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-option, -Wno-frame-address)
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KBUILD_CFLAGS += $(call cc-option, -Wno-address-of-packed-member)
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KBUILD_CFLAGS += -Wmissing-declarations
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KBUILD_CFLAGS += -Wmissing-prototypes
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ifneq ($(CONFIG_FRAME_WARN),0)
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KBUILD_CFLAGS += -Wframe-larger-than=$(CONFIG_FRAME_WARN)
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endif
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KBUILD_CFLAGS-$(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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# Clang checks for overflow/truncation with '%p', while GCC does not:
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# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111219
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KBUILD_CFLAGS += $(call cc-option, -Wno-format-overflow-non-kprintf)
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KBUILD_CFLAGS += $(call cc-option, -Wno-format-truncation-non-kprintf)
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# Clang may emit a warning when a const variable, such as the dummy variables
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# in typecheck(), or const member of an aggregate type are not initialized,
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# which can result in unexpected behavior. However, in many audited cases of
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# the "field" variant of the warning, this is intentional because the field is
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# never used within a particular call path, the field is within a union with
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# other non-const members, or the containing object is not const so the field
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# can be modified via memcpy() / memset(). While the variable warning also gets
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# disabled with this same switch, there should not be too much coverage lost
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# because -Wuninitialized will still flag when an uninitialized const variable
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# is used.
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KBUILD_CFLAGS += $(call cc-option, -Wno-default-const-init-unsafe)
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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 result in bogus false positives
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KBUILD_CFLAGS += $(call cc-option, -Wno-dangling-pointer)
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# Stack Variable Length Arrays (VLAs) must not be used in the kernel.
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# Function array parameters should, however, be usable, but -Wvla will
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# warn for those. Clang has no way yet to distinguish between the VLA
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# types, so depend on GCC for now to keep stack VLAs out of the tree.
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# https://github.com/llvm/llvm-project/issues/57098
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# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98217
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KBUILD_CFLAGS += $(call cc-option,-Wvla-larger-than=1)
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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 += $(call cc-option, -Wcast-function-type)
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# Currently, disable -Wstringop-overflow for GCC 11, globally.
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KBUILD_CFLAGS-$(CONFIG_CC_NO_STRINGOP_OVERFLOW) += $(call cc-option, -Wno-stringop-overflow)
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KBUILD_CFLAGS-$(CONFIG_CC_STRINGOP_OVERFLOW) += $(call cc-option, -Wstringop-overflow)
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# Currently, disable -Wunterminated-string-initialization as broken
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KBUILD_CFLAGS += $(call cc-option, -Wno-unterminated-string-initialization)
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# The allocators already balk at large sizes, so silence the compiler
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# warnings for bounds checks involving those possible values. While
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# -Wno-alloc-size-larger-than would normally be used here, earlier versions
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# of gcc (<9.1) weirdly don't handle the option correctly when _other_
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# warnings are produced (?!). Using -Walloc-size-larger-than=SIZE_MAX
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# doesn't work (as it is documented to), silently resolving to "0" prior to
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# version 9.1 (and producing an error more recently). Numeric values larger
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# than PTRDIFF_MAX also don't work prior to version 9.1, which are silently
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# ignored, continuing to default to PTRDIFF_MAX. So, left with no other
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# choice, we must perform a versioned check to disable this warning.
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# https://lore.kernel.org/lkml/20210824115859.187f272f@canb.auug.org.au
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KBUILD_CFLAGS-$(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 += $(call cc-option,-Wenum-conversion)
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KBUILD_CFLAGS += -Wunused
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#
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# W=1 - warnings which may be relevant and do not occur too often
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#
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ifneq ($(findstring 1, $(KBUILD_EXTRA_WARN)),)
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KBUILD_CFLAGS += -Wmissing-format-attribute
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KBUILD_CFLAGS += -Wmissing-include-dirs
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KBUILD_CFLAGS += $(call cc-option, -Wunused-const-variable)
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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-option, -Wno-unused-but-set-variable)
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KBUILD_CFLAGS += $(call cc-option, -Wno-unused-const-variable)
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KBUILD_CFLAGS += $(call cc-option, -Wno-packed-not-aligned)
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KBUILD_CFLAGS += $(call cc-option, -Wno-format-overflow)
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ifdef CONFIG_CC_IS_GCC
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KBUILD_CFLAGS += $(call cc-option, -Wno-format-truncation)
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endif
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KBUILD_CFLAGS += $(call cc-option, -Wno-stringop-truncation)
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KBUILD_CFLAGS += -Wno-override-init # alias for -Wno-initializer-overrides in clang
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ifdef CONFIG_CC_IS_CLANG
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# Clang before clang-16 would warn on default argument promotions.
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ifneq ($(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-option, -Wno-pointer-to-enum-cast)
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KBUILD_CFLAGS += -Wno-tautological-constant-out-of-range-compare
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KBUILD_CFLAGS += $(call cc-option, -Wno-unaligned-access)
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KBUILD_CFLAGS += -Wno-enum-compare-conditional
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endif
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endif
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#
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# W=2 - warnings which occur quite often but may still be relevant
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#
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ifneq ($(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 += $(call cc-option, -Wunused-macros)
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KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN2
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else
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# The following turn off the warnings enabled by -Wextra
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KBUILD_CFLAGS += -Wno-missing-field-initializers
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KBUILD_CFLAGS += -Wno-type-limits
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KBUILD_CFLAGS += -Wno-shift-negative-value
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ifdef CONFIG_CC_IS_CLANG
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KBUILD_CFLAGS += -Wno-enum-enum-conversion
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endif
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ifdef CONFIG_CC_IS_GCC
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KBUILD_CFLAGS += -Wno-maybe-uninitialized
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endif
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endif
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#
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# W=3 - more obscure warnings, can most likely be ignored
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#
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ifneq ($(findstring 3, $(KBUILD_EXTRA_WARN)),)
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KBUILD_CFLAGS += -Wbad-function-cast
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KBUILD_CFLAGS += -Wcast-align
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KBUILD_CFLAGS += -Wcast-qual
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KBUILD_CFLAGS += -Wconversion
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KBUILD_CFLAGS += -Wpacked
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KBUILD_CFLAGS += -Wpadded
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KBUILD_CFLAGS += -Wpointer-arith
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KBUILD_CFLAGS += -Wredundant-decls
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KBUILD_CFLAGS += -Wsign-compare
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KBUILD_CFLAGS += -Wswitch-default
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KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN3
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else
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# The following turn off the warnings enabled by -Wextra
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KBUILD_CFLAGS += -Wno-sign-compare
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KBUILD_CFLAGS += -Wno-unused-parameter
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endif
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#
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# W=e and CONFIG_WERROR - error out on warnings
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#
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ifneq ($(findstring e, $(KBUILD_EXTRA_WARN))$(CONFIG_WERROR),)
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KBUILD_CPPFLAGS += -Werror
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KBUILD_AFLAGS += -Wa,--fatal-warnings
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KBUILD_LDFLAGS += --fatal-warnings
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KBUILD_USERCFLAGS += -Werror
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KBUILD_USERLDFLAGS += -Wl,--fatal-warnings
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KBUILD_RUSTFLAGS += -Dwarnings
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# While hostprog flags are used during build bootstrapping (thus should not
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# depend on CONFIG_ symbols), -Werror is disruptive and should be opted into.
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# Only apply -Werror to hostprogs built after the initial Kconfig stage.
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KBUILD_HOSTCFLAGS += -Werror
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KBUILD_HOSTLDFLAGS += -Wl,--fatal-warnings
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KBUILD_HOSTRUSTFLAGS += -Dwarnings
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endif
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