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 34 35# Clang checks for overflow/truncation with '%p', while GCC does not: 36# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111219 37KBUILD_CFLAGS += $(call cc-disable-warning, format-overflow-non-kprintf) 38KBUILD_CFLAGS += $(call cc-disable-warning, format-truncation-non-kprintf) 39else 40 41# gcc inanely warns about local variables called 'main' 42KBUILD_CFLAGS += -Wno-main 43endif 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 += $(call cc-option, -Wcast-function-type) 58 59# The allocators already balk at large sizes, so silence the compiler 60# warnings for bounds checks involving those possible values. While 61# -Wno-alloc-size-larger-than would normally be used here, earlier versions 62# of gcc (<9.1) weirdly don't handle the option correctly when _other_ 63# warnings are produced (?!). Using -Walloc-size-larger-than=SIZE_MAX 64# doesn't work (as it is documented to), silently resolving to "0" prior to 65# version 9.1 (and producing an error more recently). Numeric values larger 66# than PTRDIFF_MAX also don't work prior to version 9.1, which are silently 67# ignored, continuing to default to PTRDIFF_MAX. So, left with no other 68# choice, we must perform a versioned check to disable this warning. 69# https://lore.kernel.org/lkml/20210824115859.187f272f@canb.auug.org.au 70KBUILD_CFLAGS-$(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 += $(call cc-option,-Wenum-conversion) 84 85KBUILD_CFLAGS += -Wextra 86KBUILD_CFLAGS += -Wunused 87 88# 89# W=1 - warnings which may be relevant and do not occur too often 90# 91ifneq ($(findstring 1, $(KBUILD_EXTRA_WARN)),) 92 93KBUILD_CFLAGS += -Wmissing-format-attribute 94KBUILD_CFLAGS += -Wmissing-include-dirs 95KBUILD_CFLAGS += $(call cc-option, -Wunused-const-variable) 96 97KBUILD_CPPFLAGS += -Wundef 98KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN1 99 100else 101 102# Some diagnostics enabled by default are noisy. 103# Suppress them by using -Wno... except for W=1. 104KBUILD_CFLAGS += $(call cc-disable-warning, unused-but-set-variable) 105KBUILD_CFLAGS += $(call cc-disable-warning, unused-const-variable) 106KBUILD_CFLAGS += $(call cc-disable-warning, packed-not-aligned) 107KBUILD_CFLAGS += $(call cc-disable-warning, format-overflow) 108ifdef CONFIG_CC_IS_GCC 109KBUILD_CFLAGS += $(call cc-disable-warning, format-truncation) 110endif 111KBUILD_CFLAGS += $(call cc-disable-warning, stringop-truncation) 112 113KBUILD_CFLAGS += -Wno-override-init # alias for -Wno-initializer-overrides in clang 114 115ifdef CONFIG_CC_IS_CLANG 116# Clang before clang-16 would warn on default argument promotions. 117ifneq ($(call clang-min-version, 160000),y) 118# Disable -Wformat 119KBUILD_CFLAGS += -Wno-format 120# Then re-enable flags that were part of the -Wformat group that aren't 121# problematic. 122KBUILD_CFLAGS += -Wformat-extra-args -Wformat-invalid-specifier 123KBUILD_CFLAGS += -Wformat-zero-length -Wnonnull 124# Requires clang-12+. 125ifeq ($(call clang-min-version, 120000),y) 126KBUILD_CFLAGS += -Wformat-insufficient-args 127endif 128endif 129KBUILD_CFLAGS += $(call cc-disable-warning, pointer-to-enum-cast) 130KBUILD_CFLAGS += -Wno-tautological-constant-out-of-range-compare 131KBUILD_CFLAGS += $(call cc-disable-warning, unaligned-access) 132KBUILD_CFLAGS += -Wno-enum-compare-conditional 133endif 134 135endif 136 137# 138# W=2 - warnings which occur quite often but may still be relevant 139# 140ifneq ($(findstring 2, $(KBUILD_EXTRA_WARN)),) 141 142KBUILD_CFLAGS += -Wdisabled-optimization 143KBUILD_CFLAGS += -Wshadow 144KBUILD_CFLAGS += $(call cc-option, -Wlogical-op) 145KBUILD_CFLAGS += $(call cc-option, -Wunused-macros) 146 147KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN2 148 149else 150 151# The following turn off the warnings enabled by -Wextra 152KBUILD_CFLAGS += -Wno-missing-field-initializers 153KBUILD_CFLAGS += -Wno-type-limits 154KBUILD_CFLAGS += -Wno-shift-negative-value 155 156ifdef CONFIG_CC_IS_CLANG 157KBUILD_CFLAGS += -Wno-enum-enum-conversion 158endif 159 160ifdef CONFIG_CC_IS_GCC 161KBUILD_CFLAGS += -Wno-maybe-uninitialized 162endif 163 164endif 165 166# 167# W=3 - more obscure warnings, can most likely be ignored 168# 169ifneq ($(findstring 3, $(KBUILD_EXTRA_WARN)),) 170 171KBUILD_CFLAGS += -Wbad-function-cast 172KBUILD_CFLAGS += -Wcast-align 173KBUILD_CFLAGS += -Wcast-qual 174KBUILD_CFLAGS += -Wconversion 175KBUILD_CFLAGS += -Wpacked 176KBUILD_CFLAGS += -Wpadded 177KBUILD_CFLAGS += -Wpointer-arith 178KBUILD_CFLAGS += -Wredundant-decls 179KBUILD_CFLAGS += -Wsign-compare 180KBUILD_CFLAGS += -Wswitch-default 181 182KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN3 183 184else 185 186# The following turn off the warnings enabled by -Wextra 187KBUILD_CFLAGS += -Wno-sign-compare 188KBUILD_CFLAGS += -Wno-unused-parameter 189 190endif 191 192# 193# W=e - error out on warnings 194# 195ifneq ($(findstring e, $(KBUILD_EXTRA_WARN)),) 196 197KBUILD_CFLAGS += -Werror 198 199endif 200