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 result in bogus false positives 41KBUILD_CFLAGS += $(call cc-disable-warning, dangling-pointer) 42 43# Variable Length Arrays (VLAs) should not be used anywhere in the kernel 44KBUILD_CFLAGS += -Wvla 45 46# disable pointer signed / unsigned warnings in gcc 4.0 47KBUILD_CFLAGS += -Wno-pointer-sign 48 49# In order to make sure new function cast mismatches are not introduced 50# in the kernel (to avoid tripping CFI checking), the kernel should be 51# globally built with -Wcast-function-type. 52KBUILD_CFLAGS += $(call cc-option, -Wcast-function-type) 53 54# The allocators already balk at large sizes, so silence the compiler 55# warnings for bounds checks involving those possible values. While 56# -Wno-alloc-size-larger-than would normally be used here, earlier versions 57# of gcc (<9.1) weirdly don't handle the option correctly when _other_ 58# warnings are produced (?!). Using -Walloc-size-larger-than=SIZE_MAX 59# doesn't work (as it is documented to), silently resolving to "0" prior to 60# version 9.1 (and producing an error more recently). Numeric values larger 61# than PTRDIFF_MAX also don't work prior to version 9.1, which are silently 62# ignored, continuing to default to PTRDIFF_MAX. So, left with no other 63# choice, we must perform a versioned check to disable this warning. 64# https://lore.kernel.org/lkml/20210824115859.187f272f@canb.auug.org.au 65KBUILD_CFLAGS-$(call gcc-min-version, 90100) += -Wno-alloc-size-larger-than 66KBUILD_CFLAGS += $(KBUILD_CFLAGS-y) $(CONFIG_CC_IMPLICIT_FALLTHROUGH) 67 68# Prohibit date/time macros, which would make the build non-deterministic 69KBUILD_CFLAGS += -Werror=date-time 70 71# enforce correct pointer usage 72KBUILD_CFLAGS += $(call cc-option,-Werror=incompatible-pointer-types) 73 74# Require designated initializers for all marked structures 75KBUILD_CFLAGS += $(call cc-option,-Werror=designated-init) 76 77# Warn if there is an enum types mismatch 78KBUILD_CFLAGS += $(call cc-option,-Wenum-conversion) 79 80# Explicitly clear padding bits during variable initialization 81KBUILD_CFLAGS += $(call cc-option,-fzero-init-padding-bits=all) 82 83KBUILD_CFLAGS += -Wextra 84KBUILD_CFLAGS += -Wunused 85 86# 87# W=1 - warnings which may be relevant and do not occur too often 88# 89ifneq ($(findstring 1, $(KBUILD_EXTRA_WARN)),) 90 91KBUILD_CFLAGS += -Wmissing-format-attribute 92KBUILD_CFLAGS += -Wmissing-include-dirs 93KBUILD_CFLAGS += $(call cc-option, -Wunused-const-variable) 94 95KBUILD_CPPFLAGS += -Wundef 96KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN1 97 98else 99 100# Some diagnostics enabled by default are noisy. 101# Suppress them by using -Wno... except for W=1. 102KBUILD_CFLAGS += $(call cc-disable-warning, unused-but-set-variable) 103KBUILD_CFLAGS += $(call cc-disable-warning, unused-const-variable) 104KBUILD_CFLAGS += $(call cc-disable-warning, packed-not-aligned) 105KBUILD_CFLAGS += $(call cc-disable-warning, format-overflow) 106ifdef CONFIG_CC_IS_GCC 107KBUILD_CFLAGS += $(call cc-disable-warning, format-truncation) 108else 109# Clang checks for overflow/truncation with '%p', while GCC does not: 110# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111219 111KBUILD_CFLAGS += $(call cc-disable-warning, format-overflow-non-kprintf) 112KBUILD_CFLAGS += $(call cc-disable-warning, format-truncation-non-kprintf) 113endif 114KBUILD_CFLAGS += $(call cc-disable-warning, stringop-truncation) 115 116KBUILD_CFLAGS += -Wno-override-init # alias for -Wno-initializer-overrides in clang 117 118ifdef CONFIG_CC_IS_CLANG 119# Clang before clang-16 would warn on default argument promotions. 120ifneq ($(call clang-min-version, 160000),y) 121# Disable -Wformat 122KBUILD_CFLAGS += -Wno-format 123# Then re-enable flags that were part of the -Wformat group that aren't 124# problematic. 125KBUILD_CFLAGS += -Wformat-extra-args -Wformat-invalid-specifier 126KBUILD_CFLAGS += -Wformat-zero-length -Wnonnull 127# Requires clang-12+. 128ifeq ($(call clang-min-version, 120000),y) 129KBUILD_CFLAGS += -Wformat-insufficient-args 130endif 131endif 132KBUILD_CFLAGS += $(call cc-disable-warning, pointer-to-enum-cast) 133KBUILD_CFLAGS += -Wno-tautological-constant-out-of-range-compare 134KBUILD_CFLAGS += $(call cc-disable-warning, unaligned-access) 135KBUILD_CFLAGS += -Wno-enum-compare-conditional 136KBUILD_CFLAGS += -Wno-enum-enum-conversion 137endif 138 139endif 140 141# 142# W=2 - warnings which occur quite often but may still be relevant 143# 144ifneq ($(findstring 2, $(KBUILD_EXTRA_WARN)),) 145 146KBUILD_CFLAGS += -Wdisabled-optimization 147KBUILD_CFLAGS += -Wshadow 148KBUILD_CFLAGS += $(call cc-option, -Wlogical-op) 149KBUILD_CFLAGS += $(call cc-option, -Wunused-macros) 150 151KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN2 152 153else 154 155# The following turn off the warnings enabled by -Wextra 156KBUILD_CFLAGS += -Wno-missing-field-initializers 157KBUILD_CFLAGS += -Wno-type-limits 158KBUILD_CFLAGS += -Wno-shift-negative-value 159 160ifdef CONFIG_CC_IS_GCC 161KBUILD_CFLAGS += -Wno-maybe-uninitialized 162endif 163 164endif 165 166# 167# W=3 - more obscure warnings, can most likely be ignored 168# 169ifneq ($(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