name : Makefile.extrawarn # 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 warnings generated too much noise in a regular build. # Use make W=1 to enable them (see scripts/Makefile.extrawarn) KBUILD_CFLAGS += $(call cc-disable-warning, unused-but-set-variable) KBUILD_CFLAGS += $(call cc-disable-warning, unused-const-variable) # 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 += $(call cc-option,-Wenum-conversion) # # W=1 - warnings which may be relevant and do not occur too often # ifneq ($(findstring 1, $(KBUILD_EXTRA_WARN)),) KBUILD_CFLAGS += -Wextra -Wunused -Wno-unused-parameter KBUILD_CFLAGS += $(call cc-option, -Wrestrict) KBUILD_CFLAGS += -Wmissing-format-attribute 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, -Wformat-overflow) KBUILD_CFLAGS += $(call cc-option, -Wformat-truncation) KBUILD_CFLAGS += $(call cc-option, -Wstringop-truncation) 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, restrict) KBUILD_CFLAGS += $(call cc-disable-warning, packed-not-aligned) KBUILD_CFLAGS += $(call cc-disable-warning, format-overflow) KBUILD_CFLAGS += $(call cc-disable-warning, format-truncation) KBUILD_CFLAGS += $(call cc-disable-warning, stringop-truncation) ifdef CONFIG_CC_IS_CLANG # Clang before clang-16 would warn on default argument promotions. ifneq ($(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 += $(call cc-disable-warning, cast-function-type-strict) KBUILD_CFLAGS += -Wno-enum-compare-conditional KBUILD_CFLAGS += -Wno-enum-enum-conversion endif endif # # W=2 - warnings which occur quite often but may still be relevant # ifneq ($(findstring 2, $(KBUILD_EXTRA_WARN)),) KBUILD_CFLAGS += -Wdisabled-optimization KBUILD_CFLAGS += -Wshadow KBUILD_CFLAGS += $(call cc-option, -Wlogical-op) KBUILD_CFLAGS += -Wmissing-field-initializers KBUILD_CFLAGS += -Wtype-limits KBUILD_CFLAGS += $(call cc-option, -Wmaybe-uninitialized) KBUILD_CFLAGS += $(call cc-option, -Wunused-macros) ifdef CONFIG_CC_IS_CLANG KBUILD_CFLAGS += -Winitializer-overrides endif KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN2 else # The following turn off the warnings enabled by -Wextra KBUILD_CFLAGS += -Wno-missing-field-initializers KBUILD_CFLAGS += -Wno-type-limits KBUILD_CFLAGS += -Wno-shift-negative-value ifdef CONFIG_CC_IS_CLANG KBUILD_CFLAGS += -Wno-initializer-overrides else KBUILD_CFLAGS += -Wno-maybe-uninitialized endif endif # # W=3 - more obscure warnings, can most likely be ignored # ifneq ($(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_CFLAGS += $(call cc-option, -Wpacked-bitfield-compat) KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN3 else # The following turn off the warnings enabled by -Wextra KBUILD_CFLAGS += -Wno-sign-compare endif # # W=e - error out on warnings # ifneq ($(findstring e, $(KBUILD_EXTRA_WARN)),) KBUILD_CFLAGS += -Werror endif