scripts/Makefile.extrawarn

   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
  10 KBUILD_CFLAGS += -Wall
  11 KBUILD_CFLAGS += -Wundef
  12 KBUILD_CFLAGS += -Werror=implicit-function-declaration
  13 KBUILD_CFLAGS += -Werror=implicit-int
  14 KBUILD_CFLAGS += -Werror=return-type
  15 KBUILD_CFLAGS += -Werror=strict-prototypes
  16 KBUILD_CFLAGS += -Wno-format-security
  17 KBUILD_CFLAGS += -Wno-trigraphs
  18 KBUILD_CFLAGS += $(call cc-disable-warning,frame-address,)
  19 KBUILD_CFLAGS += $(call cc-disable-warning, format-truncation)
  20 KBUILD_CFLAGS += $(call cc-disable-warning, format-overflow)
  21 KBUILD_CFLAGS += $(call cc-disable-warning, address-of-packed-member)
  22
  23 ifneq ($(CONFIG_FRAME_WARN),0)
  24 KBUILD_CFLAGS += -Wframe-larger-than=$(CONFIG_FRAME_WARN)
  25 endif
  26
  27 KBUILD_CPPFLAGS-$(CONFIG_WERROR) += -Werror
  28 KBUILD_CPPFLAGS += $(KBUILD_CPPFLAGS-y)
  29 KBUILD_CFLAGS-$(CONFIG_CC_NO_ARRAY_BOUNDS) += -Wno-array-bounds
  30
  31 ifdef CONFIG_CC_IS_CLANG
  32 # The kernel builds with '-std=gnu11' so use of GNU extensions is acceptable.
  33 KBUILD_CFLAGS += -Wno-gnu
  34 else
  35
  36 # gcc inanely warns about local variables called 'main'
  37 KBUILD_CFLAGS += -Wno-main
  38 endif
  39
  40 # These warnings generated too much noise in a regular build.
  41 # Use make W=1 to enable them (see scripts/Makefile.extrawarn)
  42 KBUILD_CFLAGS += $(call cc-disable-warning, unused-but-set-variable)
  43 KBUILD_CFLAGS += $(call cc-disable-warning, unused-const-variable)
  44
  45 # These result in bogus false positives
  46 KBUILD_CFLAGS += $(call cc-disable-warning, dangling-pointer)
  47
  48 # Variable Length Arrays (VLAs) should not be used anywhere in the kernel
  49 KBUILD_CFLAGS += -Wvla
  50
  51 # disable pointer signed / unsigned warnings in gcc 4.0
  52 KBUILD_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.
  57 KBUILD_CFLAGS += $(call cc-option, -Wcast-function-type)
  58
  59 # We'll want to enable this eventually, but it's not going away for 5.7 at least
  60 KBUILD_CFLAGS += $(call cc-disable-warning, stringop-overflow)
  61
  62 # Another good warning that we'll want to enable eventually
  63 KBUILD_CFLAGS += $(call cc-disable-warning, restrict)
  64
  65 # The allocators already balk at large sizes, so silence the compiler
  66 # warnings for bounds checks involving those possible values. While
  67 # -Wno-alloc-size-larger-than would normally be used here, earlier versions
  68 # of gcc (<9.1) weirdly don't handle the option correctly when _other_
  69 # warnings are produced (?!). Using -Walloc-size-larger-than=SIZE_MAX
  70 # doesn't work (as it is documented to), silently resolving to "0" prior to
  71 # version 9.1 (and producing an error more recently). Numeric values larger
  72 # than PTRDIFF_MAX also don't work prior to version 9.1, which are silently
  73 # ignored, continuing to default to PTRDIFF_MAX. So, left with no other
  74 # choice, we must perform a versioned check to disable this warning.
  75 # https://lore.kernel.org/lkml/20210824115859.187f272f@canb.auug.org.au
  76 KBUILD_CFLAGS-$(call gcc-min-version, 90100) += -Wno-alloc-size-larger-than
  77 KBUILD_CFLAGS += $(KBUILD_CFLAGS-y) $(CONFIG_CC_IMPLICIT_FALLTHROUGH)
  78
  79 # Prohibit date/time macros, which would make the build non-deterministic
  80 KBUILD_CFLAGS += -Werror=date-time
  81
  82 # enforce correct pointer usage
  83 KBUILD_CFLAGS += $(call cc-option,-Werror=incompatible-pointer-types)
  84
  85 # Require designated initializers for all marked structures
  86 KBUILD_CFLAGS += $(call cc-option,-Werror=designated-init)
  87
  88 # Warn if there is an enum types mismatch
  89 KBUILD_CFLAGS += $(call cc-option,-Wenum-conversion)
  90
  91 # backward compatibility
  92 KBUILD_EXTRA_WARN ?= $(KBUILD_ENABLE_EXTRA_GCC_CHECKS)
  93
  94 ifeq ("$(origin W)", "command line")
  95   KBUILD_EXTRA_WARN := $(W)
  96 endif
  97
  98 export KBUILD_EXTRA_WARN
  99
 100 #
 101 # W=1 - warnings which may be relevant and do not occur too often
 102 #
 103 ifneq ($(findstring 1, $(KBUILD_EXTRA_WARN)),)
 104
 105 KBUILD_CFLAGS += -Wextra -Wunused -Wno-unused-parameter
 106 KBUILD_CFLAGS += -Wmissing-declarations
 107 KBUILD_CFLAGS += -Wmissing-format-attribute
 108 KBUILD_CFLAGS += -Wmissing-prototypes
 109 KBUILD_CFLAGS += -Wold-style-definition
 110 KBUILD_CFLAGS += -Wmissing-include-dirs
 111 KBUILD_CFLAGS += $(call cc-option, -Wunused-but-set-variable)
 112 KBUILD_CFLAGS += $(call cc-option, -Wunused-const-variable)
 113 KBUILD_CFLAGS += $(call cc-option, -Wpacked-not-aligned)
 114 KBUILD_CFLAGS += $(call cc-option, -Wstringop-truncation)
 115
 116 KBUILD_CPPFLAGS += -Wundef
 117 KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN1
 118
 119 else
 120
 121 # Some diagnostics enabled by default are noisy.
 122 # Suppress them by using -Wno... except for W=1.
 123 KBUILD_CFLAGS += $(call cc-disable-warning, unused-but-set-variable)
 124 KBUILD_CFLAGS += $(call cc-disable-warning, unused-const-variable)
 125 KBUILD_CFLAGS += $(call cc-disable-warning, packed-not-aligned)
 126 KBUILD_CFLAGS += $(call cc-disable-warning, stringop-truncation)
 127
 128 ifdef CONFIG_CC_IS_CLANG
 129 # Clang before clang-16 would warn on default argument promotions.
 130 ifneq ($(call clang-min-version, 160000),y)
 131 # Disable -Wformat
 132 KBUILD_CFLAGS += -Wno-format
 133 # Then re-enable flags that were part of the -Wformat group that aren't
 134 # problematic.
 135 KBUILD_CFLAGS += -Wformat-extra-args -Wformat-invalid-specifier
 136 KBUILD_CFLAGS += -Wformat-zero-length -Wnonnull
 137 # Requires clang-12+.
 138 ifeq ($(call clang-min-version, 120000),y)
 139 KBUILD_CFLAGS += -Wformat-insufficient-args
 140 endif
 141 endif
 142 KBUILD_CFLAGS += $(call cc-disable-warning, pointer-to-enum-cast)
 143 KBUILD_CFLAGS += -Wno-tautological-constant-out-of-range-compare
 144 KBUILD_CFLAGS += $(call cc-disable-warning, unaligned-access)
 145 KBUILD_CFLAGS += $(call cc-disable-warning, cast-function-type-strict)
 146 endif
 147
 148 endif
 149
 150 #
 151 # W=2 - warnings which occur quite often but may still be relevant
 152 #
 153 ifneq ($(findstring 2, $(KBUILD_EXTRA_WARN)),)
 154
 155 KBUILD_CFLAGS += -Wdisabled-optimization
 156 KBUILD_CFLAGS += -Wshadow
 157 KBUILD_CFLAGS += $(call cc-option, -Wlogical-op)
 158 KBUILD_CFLAGS += -Wmissing-field-initializers
 159 KBUILD_CFLAGS += -Wtype-limits
 160 KBUILD_CFLAGS += $(call cc-option, -Wmaybe-uninitialized)
 161 KBUILD_CFLAGS += $(call cc-option, -Wunused-macros)
 162
 163 ifdef CONFIG_CC_IS_CLANG
 164 KBUILD_CFLAGS += -Winitializer-overrides
 165 endif
 166
 167 KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN2
 168
 169 else
 170
 171 # The following turn off the warnings enabled by -Wextra
 172 KBUILD_CFLAGS += -Wno-missing-field-initializers
 173 KBUILD_CFLAGS += -Wno-type-limits
 174 KBUILD_CFLAGS += -Wno-shift-negative-value
 175
 176 ifdef CONFIG_CC_IS_CLANG
 177 KBUILD_CFLAGS += -Wno-initializer-overrides
 178 else
 179 KBUILD_CFLAGS += -Wno-maybe-uninitialized
 180 endif
 181
 182 endif
 183
 184 #
 185 # W=3 - more obscure warnings, can most likely be ignored
 186 #
 187 ifneq ($(findstring 3, $(KBUILD_EXTRA_WARN)),)
 188
 189 KBUILD_CFLAGS += -Wbad-function-cast
 190 KBUILD_CFLAGS += -Wcast-align
 191 KBUILD_CFLAGS += -Wcast-qual
 192 KBUILD_CFLAGS += -Wconversion
 193 KBUILD_CFLAGS += -Wpacked
 194 KBUILD_CFLAGS += -Wpadded
 195 KBUILD_CFLAGS += -Wpointer-arith
 196 KBUILD_CFLAGS += -Wredundant-decls
 197 KBUILD_CFLAGS += -Wsign-compare
 198 KBUILD_CFLAGS += -Wswitch-default
 199 KBUILD_CFLAGS += $(call cc-option, -Wpacked-bitfield-compat)
 200
 201 KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN3
 202
 203 else
 204
 205 # The following turn off the warnings enabled by -Wextra
 206 KBUILD_CFLAGS += -Wno-sign-compare
 207
 208 endif
 209
 210 #
 211 # W=e - error out on warnings
 212 #
 213 ifneq ($(findstring e, $(KBUILD_EXTRA_WARN)),)
 214
 215 KBUILD_CFLAGS += -Werror
 216
 217 endif