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 += $(call cc-disable-warning, address-of-packed-member) 20 21ifneq ($(CONFIG_FRAME_WARN),0) 22KBUILD_CFLAGS += -Wframe-larger-than=$(CONFIG_FRAME_WARN) 23endif 24 25KBUILD_CPPFLAGS-$(CONFIG_WERROR) += -Werror 26KBUILD_CPPFLAGS += $(KBUILD_CPPFLAGS-y) 27KBUILD_CFLAGS-$(CONFIG_CC_NO_ARRAY_BOUNDS) += -Wno-array-bounds 28 29ifdef CONFIG_CC_IS_CLANG 30# The kernel builds with '-std=gnu11' so use of GNU extensions is acceptable. 31KBUILD_CFLAGS += -Wno-gnu 32else 33 34# gcc inanely warns about local variables called 'main' 35KBUILD_CFLAGS += -Wno-main 36endif 37 38# These warnings generated too much noise in a regular build. 39# Use make W=1 to enable them (see scripts/Makefile.extrawarn) 40KBUILD_CFLAGS += $(call cc-disable-warning, unused-but-set-variable) 41KBUILD_CFLAGS += $(call cc-disable-warning, unused-const-variable) 42 43# These result in bogus false positives 44KBUILD_CFLAGS += $(call cc-disable-warning, dangling-pointer) 45 46# Variable Length Arrays (VLAs) should not be used anywhere in the kernel 47KBUILD_CFLAGS += -Wvla 48 49# disable pointer signed / unsigned warnings in gcc 4.0 50KBUILD_CFLAGS += -Wno-pointer-sign 51 52# In order to make sure new function cast mismatches are not introduced 53# in the kernel (to avoid tripping CFI checking), the kernel should be 54# globally built with -Wcast-function-type. 55KBUILD_CFLAGS += $(call cc-option, -Wcast-function-type) 56 57# The allocators already balk at large sizes, so silence the compiler 58# warnings for bounds checks involving those possible values. While 59# -Wno-alloc-size-larger-than would normally be used here, earlier versions 60# of gcc (<9.1) weirdly don't handle the option correctly when _other_ 61# warnings are produced (?!). Using -Walloc-size-larger-than=SIZE_MAX 62# doesn't work (as it is documented to), silently resolving to "0" prior to 63# version 9.1 (and producing an error more recently). Numeric values larger 64# than PTRDIFF_MAX also don't work prior to version 9.1, which are silently 65# ignored, continuing to default to PTRDIFF_MAX. So, left with no other 66# choice, we must perform a versioned check to disable this warning. 67# https://lore.kernel.org/lkml/20210824115859.187f272f@canb.auug.org.au 68KBUILD_CFLAGS-$(call gcc-min-version, 90100) += -Wno-alloc-size-larger-than 69KBUILD_CFLAGS += $(KBUILD_CFLAGS-y) $(CONFIG_CC_IMPLICIT_FALLTHROUGH) 70 71# Prohibit date/time macros, which would make the build non-deterministic 72KBUILD_CFLAGS += -Werror=date-time 73 74# enforce correct pointer usage 75KBUILD_CFLAGS += $(call cc-option,-Werror=incompatible-pointer-types) 76 77# Require designated initializers for all marked structures 78KBUILD_CFLAGS += $(call cc-option,-Werror=designated-init) 79 80# Warn if there is an enum types mismatch 81KBUILD_CFLAGS += $(call cc-option,-Wenum-conversion) 82 83# backward compatibility 84KBUILD_EXTRA_WARN ?= $(KBUILD_ENABLE_EXTRA_GCC_CHECKS) 85 86ifeq ("$(origin W)", "command line") 87 KBUILD_EXTRA_WARN := $(W) 88endif 89 90export KBUILD_EXTRA_WARN 91 92# 93# W=1 - warnings which may be relevant and do not occur too often 94# 95ifneq ($(findstring 1, $(KBUILD_EXTRA_WARN)),) 96 97KBUILD_CFLAGS += -Wextra -Wunused -Wno-unused-parameter 98KBUILD_CFLAGS += -Wmissing-declarations 99KBUILD_CFLAGS += $(call cc-option, -Wrestrict) 100KBUILD_CFLAGS += -Wmissing-format-attribute 101KBUILD_CFLAGS += -Wmissing-prototypes 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 += $(call cc-disable-warning, cast-function-type-strict) 146KBUILD_CFLAGS += -Wno-enum-compare-conditional 147KBUILD_CFLAGS += -Wno-enum-enum-conversion 148endif 149 150endif 151 152# 153# W=2 - warnings which occur quite often but may still be relevant 154# 155ifneq ($(findstring 2, $(KBUILD_EXTRA_WARN)),) 156 157KBUILD_CFLAGS += -Wdisabled-optimization 158KBUILD_CFLAGS += -Wshadow 159KBUILD_CFLAGS += $(call cc-option, -Wlogical-op) 160KBUILD_CFLAGS += -Wmissing-field-initializers 161KBUILD_CFLAGS += -Wtype-limits 162KBUILD_CFLAGS += $(call cc-option, -Wmaybe-uninitialized) 163KBUILD_CFLAGS += $(call cc-option, -Wunused-macros) 164 165ifdef CONFIG_CC_IS_CLANG 166KBUILD_CFLAGS += -Winitializer-overrides 167endif 168 169KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN2 170 171else 172 173# The following turn off the warnings enabled by -Wextra 174KBUILD_CFLAGS += -Wno-missing-field-initializers 175KBUILD_CFLAGS += -Wno-type-limits 176KBUILD_CFLAGS += -Wno-shift-negative-value 177 178ifdef CONFIG_CC_IS_CLANG 179KBUILD_CFLAGS += -Wno-initializer-overrides 180else 181KBUILD_CFLAGS += -Wno-maybe-uninitialized 182endif 183 184endif 185 186# 187# W=3 - more obscure warnings, can most likely be ignored 188# 189ifneq ($(findstring 3, $(KBUILD_EXTRA_WARN)),) 190 191KBUILD_CFLAGS += -Wbad-function-cast 192KBUILD_CFLAGS += -Wcast-align 193KBUILD_CFLAGS += -Wcast-qual 194KBUILD_CFLAGS += -Wconversion 195KBUILD_CFLAGS += -Wpacked 196KBUILD_CFLAGS += -Wpadded 197KBUILD_CFLAGS += -Wpointer-arith 198KBUILD_CFLAGS += -Wredundant-decls 199KBUILD_CFLAGS += -Wsign-compare 200KBUILD_CFLAGS += -Wswitch-default 201KBUILD_CFLAGS += $(call cc-option, -Wpacked-bitfield-compat) 202 203KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN3 204 205else 206 207# The following turn off the warnings enabled by -Wextra 208KBUILD_CFLAGS += -Wno-sign-compare 209 210endif 211 212# 213# W=e - error out on warnings 214# 215ifneq ($(findstring e, $(KBUILD_EXTRA_WARN)),) 216 217KBUILD_CFLAGS += -Werror 218 219endif 220