1# SPDX-License-Identifier: GPL-2.0 2# ========================================================================== 3# make W=... settings 4# 5# There are four warning groups enabled by W=1, W=2, W=3, and W=e 6# They are independent, and can be combined like W=12 or W=123e. 7# ========================================================================== 8 9# Default set of warnings, always enabled 10KBUILD_CFLAGS += -Wall 11KBUILD_CFLAGS += -Wundef 12KBUILD_CFLAGS += -Werror=implicit-function-declaration 13KBUILD_CFLAGS += -Werror=implicit-int 14KBUILD_CFLAGS += -Werror=return-type 15KBUILD_CFLAGS += -Werror=strict-prototypes 16KBUILD_CFLAGS += -Wno-format-security 17KBUILD_CFLAGS += -Wno-trigraphs 18KBUILD_CFLAGS += $(call cc-disable-warning,frame-address,) 19KBUILD_CFLAGS += $(call cc-disable-warning, address-of-packed-member) 20KBUILD_CFLAGS += -Wmissing-declarations 21KBUILD_CFLAGS += -Wmissing-prototypes 22 23ifneq ($(CONFIG_FRAME_WARN),0) 24KBUILD_CFLAGS += -Wframe-larger-than=$(CONFIG_FRAME_WARN) 25endif 26 27KBUILD_CPPFLAGS-$(CONFIG_WERROR) += -Werror 28KBUILD_CPPFLAGS += $(KBUILD_CPPFLAGS-y) 29KBUILD_CFLAGS-$(CONFIG_CC_NO_ARRAY_BOUNDS) += -Wno-array-bounds 30 31ifdef CONFIG_CC_IS_CLANG 32# The kernel builds with '-std=gnu11' so use of GNU extensions is acceptable. 33KBUILD_CFLAGS += -Wno-gnu 34else 35 36# gcc inanely warns about local variables called 'main' 37KBUILD_CFLAGS += -Wno-main 38endif 39 40# These warnings generated too much noise in a regular build. 41# Use make W=1 to enable them (see scripts/Makefile.extrawarn) 42KBUILD_CFLAGS += $(call cc-disable-warning, unused-but-set-variable) 43KBUILD_CFLAGS += $(call cc-disable-warning, unused-const-variable) 44 45# These result in bogus false positives 46KBUILD_CFLAGS += $(call cc-disable-warning, dangling-pointer) 47 48# Variable Length Arrays (VLAs) should not be used anywhere in the kernel 49KBUILD_CFLAGS += -Wvla 50 51# disable pointer signed / unsigned warnings in gcc 4.0 52KBUILD_CFLAGS += -Wno-pointer-sign 53 54# In order to make sure new function cast mismatches are not introduced 55# in the kernel (to avoid tripping CFI checking), the kernel should be 56# globally built with -Wcast-function-type. 57KBUILD_CFLAGS += $(call cc-option, -Wcast-function-type) 58 59# The allocators already balk at large sizes, so silence the compiler 60# warnings for bounds checks involving those possible values. While 61# -Wno-alloc-size-larger-than would normally be used here, earlier versions 62# of gcc (<9.1) weirdly don't handle the option correctly when _other_ 63# warnings are produced (?!). Using -Walloc-size-larger-than=SIZE_MAX 64# doesn't work (as it is documented to), silently resolving to "0" prior to 65# version 9.1 (and producing an error more recently). Numeric values larger 66# than PTRDIFF_MAX also don't work prior to version 9.1, which are silently 67# ignored, continuing to default to PTRDIFF_MAX. So, left with no other 68# choice, we must perform a versioned check to disable this warning. 69# https://lore.kernel.org/lkml/[email protected] 70KBUILD_CFLAGS-$(call gcc-min-version, 90100) += -Wno-alloc-size-larger-than 71KBUILD_CFLAGS += $(KBUILD_CFLAGS-y) $(CONFIG_CC_IMPLICIT_FALLTHROUGH) 72 73# Prohibit date/time macros, which would make the build non-deterministic 74KBUILD_CFLAGS += -Werror=date-time 75 76# enforce correct pointer usage 77KBUILD_CFLAGS += $(call cc-option,-Werror=incompatible-pointer-types) 78 79# Require designated initializers for all marked structures 80KBUILD_CFLAGS += $(call cc-option,-Werror=designated-init) 81 82# Warn if there is an enum types mismatch 83KBUILD_CFLAGS += $(call cc-option,-Wenum-conversion) 84 85# backward compatibility 86KBUILD_EXTRA_WARN ?= $(KBUILD_ENABLE_EXTRA_GCC_CHECKS) 87 88ifeq ("$(origin W)", "command line") 89 KBUILD_EXTRA_WARN := $(W) 90endif 91 92export KBUILD_EXTRA_WARN 93 94# 95# W=1 - warnings which may be relevant and do not occur too often 96# 97ifneq ($(findstring 1, $(KBUILD_EXTRA_WARN)),) 98 99KBUILD_CFLAGS += -Wextra -Wunused -Wno-unused-parameter 100KBUILD_CFLAGS += $(call cc-option, -Wrestrict) 101KBUILD_CFLAGS += -Wmissing-format-attribute 102KBUILD_CFLAGS += -Wold-style-definition 103KBUILD_CFLAGS += -Wmissing-include-dirs 104KBUILD_CFLAGS += $(call cc-option, -Wunused-but-set-variable) 105KBUILD_CFLAGS += $(call cc-option, -Wunused-const-variable) 106KBUILD_CFLAGS += $(call cc-option, -Wpacked-not-aligned) 107KBUILD_CFLAGS += $(call cc-option, -Wformat-overflow) 108KBUILD_CFLAGS += $(call cc-option, -Wformat-truncation) 109KBUILD_CFLAGS += $(call cc-option, -Wstringop-overflow) 110KBUILD_CFLAGS += $(call cc-option, -Wstringop-truncation) 111 112KBUILD_CPPFLAGS += -Wundef 113KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN1 114 115else 116 117# Some diagnostics enabled by default are noisy. 118# Suppress them by using -Wno... except for W=1. 119KBUILD_CFLAGS += $(call cc-disable-warning, unused-but-set-variable) 120KBUILD_CFLAGS += $(call cc-disable-warning, unused-const-variable) 121KBUILD_CFLAGS += $(call cc-disable-warning, restrict) 122KBUILD_CFLAGS += $(call cc-disable-warning, packed-not-aligned) 123KBUILD_CFLAGS += $(call cc-disable-warning, format-overflow) 124KBUILD_CFLAGS += $(call cc-disable-warning, format-truncation) 125KBUILD_CFLAGS += $(call cc-disable-warning, stringop-overflow) 126KBUILD_CFLAGS += $(call cc-disable-warning, stringop-truncation) 127 128ifdef CONFIG_CC_IS_CLANG 129# Clang before clang-16 would warn on default argument promotions. 130ifneq ($(call clang-min-version, 160000),y) 131# Disable -Wformat 132KBUILD_CFLAGS += -Wno-format 133# Then re-enable flags that were part of the -Wformat group that aren't 134# problematic. 135KBUILD_CFLAGS += -Wformat-extra-args -Wformat-invalid-specifier 136KBUILD_CFLAGS += -Wformat-zero-length -Wnonnull 137# Requires clang-12+. 138ifeq ($(call clang-min-version, 120000),y) 139KBUILD_CFLAGS += -Wformat-insufficient-args 140endif 141endif 142KBUILD_CFLAGS += $(call cc-disable-warning, pointer-to-enum-cast) 143KBUILD_CFLAGS += -Wno-tautological-constant-out-of-range-compare 144KBUILD_CFLAGS += $(call cc-disable-warning, unaligned-access) 145KBUILD_CFLAGS += $(call cc-disable-warning, cast-function-type-strict) 146endif 147 148endif 149 150# 151# W=2 - warnings which occur quite often but may still be relevant 152# 153ifneq ($(findstring 2, $(KBUILD_EXTRA_WARN)),) 154 155KBUILD_CFLAGS += -Wdisabled-optimization 156KBUILD_CFLAGS += -Wshadow 157KBUILD_CFLAGS += $(call cc-option, -Wlogical-op) 158KBUILD_CFLAGS += -Wmissing-field-initializers 159KBUILD_CFLAGS += -Wtype-limits 160KBUILD_CFLAGS += $(call cc-option, -Wmaybe-uninitialized) 161KBUILD_CFLAGS += $(call cc-option, -Wunused-macros) 162 163ifdef CONFIG_CC_IS_CLANG 164KBUILD_CFLAGS += -Winitializer-overrides 165endif 166 167KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN2 168 169else 170 171# The following turn off the warnings enabled by -Wextra 172KBUILD_CFLAGS += -Wno-missing-field-initializers 173KBUILD_CFLAGS += -Wno-type-limits 174KBUILD_CFLAGS += -Wno-shift-negative-value 175 176ifdef CONFIG_CC_IS_CLANG 177KBUILD_CFLAGS += -Wno-initializer-overrides 178else 179KBUILD_CFLAGS += -Wno-maybe-uninitialized 180endif 181 182endif 183 184# 185# W=3 - more obscure warnings, can most likely be ignored 186# 187ifneq ($(findstring 3, $(KBUILD_EXTRA_WARN)),) 188 189KBUILD_CFLAGS += -Wbad-function-cast 190KBUILD_CFLAGS += -Wcast-align 191KBUILD_CFLAGS += -Wcast-qual 192KBUILD_CFLAGS += -Wconversion 193KBUILD_CFLAGS += -Wpacked 194KBUILD_CFLAGS += -Wpadded 195KBUILD_CFLAGS += -Wpointer-arith 196KBUILD_CFLAGS += -Wredundant-decls 197KBUILD_CFLAGS += -Wsign-compare 198KBUILD_CFLAGS += -Wswitch-default 199KBUILD_CFLAGS += $(call cc-option, -Wpacked-bitfield-compat) 200 201KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN3 202 203else 204 205# The following turn off the warnings enabled by -Wextra 206KBUILD_CFLAGS += -Wno-sign-compare 207 208endif 209 210# 211# W=e - error out on warnings 212# 213ifneq ($(findstring e, $(KBUILD_EXTRA_WARN)),) 214 215KBUILD_CFLAGS += -Werror 216 217endif 218