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 += $(call cc-disable-warning, address-of-packed-member)
  20
  21 ifneq ($(CONFIG_FRAME_WARN),0)
  22 KBUILD_CFLAGS += -Wframe-larger-than=$(CONFIG_FRAME_WARN)
  23 endif
  24
  25 KBUILD_CPPFLAGS-$(CONFIG_WERROR) += -Werror
  26 KBUILD_CPPFLAGS += $(KBUILD_CPPFLAGS-y)
  27 KBUILD_CFLAGS-$(CONFIG_CC_NO_ARRAY_BOUNDS) += -Wno-array-bounds
  28
  29 ifdef CONFIG_CC_IS_CLANG
  30 # The kernel builds with '-std=gnu11' so use of GNU extensions is acceptable.
  31 KBUILD_CFLAGS += -Wno-gnu
  32 else
  33
  34 # gcc inanely warns about local variables called 'main'
  35 KBUILD_CFLAGS += -Wno-main
  36 endif
  37
  38 # These warnings generated too much noise in a regular build.
  39 # Use make W=1 to enable them (see scripts/Makefile.extrawarn)
  40 KBUILD_CFLAGS += $(call cc-disable-warning, unused-but-set-variable)
  41 KBUILD_CFLAGS += $(call cc-disable-warning, unused-const-variable)
  42
  43 # These result in bogus false positives
  44 KBUILD_CFLAGS += $(call cc-disable-warning, dangling-pointer)
  45
  46 # Variable Length Arrays (VLAs) should not be used anywhere in the kernel
  47 KBUILD_CFLAGS += -Wvla
  48
  49 # disable pointer signed / unsigned warnings in gcc 4.0
  50 KBUILD_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.
  55 KBUILD_CFLAGS += $(call cc-option, -Wcast-function-type)
  56
  57 # Another good warning that we'll want to enable eventually
  58 KBUILD_CFLAGS += $(call cc-disable-warning, restrict)
  59
  60 # The allocators already balk at large sizes, so silence the compiler
  61 # warnings for bounds checks involving those possible values. While
  62 # -Wno-alloc-size-larger-than would normally be used here, earlier versions
  63 # of gcc (<9.1) weirdly don't handle the option correctly when _other_
  64 # warnings are produced (?!). Using -Walloc-size-larger-than=SIZE_MAX
  65 # doesn't work (as it is documented to), silently resolving to "0" prior to
  66 # version 9.1 (and producing an error more recently). Numeric values larger
  67 # than PTRDIFF_MAX also don't work prior to version 9.1, which are silently
  68 # ignored, continuing to default to PTRDIFF_MAX. So, left with no other
  69 # choice, we must perform a versioned check to disable this warning.
  70 # https://lore.kernel.org/lkml/20210824115859.187f272f@canb.auug.org.au
  71 KBUILD_CFLAGS-$(call gcc-min-version, 90100) += -Wno-alloc-size-larger-than
  72 KBUILD_CFLAGS += $(KBUILD_CFLAGS-y) $(CONFIG_CC_IMPLICIT_FALLTHROUGH)
  73
  74 # Prohibit date/time macros, which would make the build non-deterministic
  75 KBUILD_CFLAGS += -Werror=date-time
  76
  77 # enforce correct pointer usage
  78 KBUILD_CFLAGS += $(call cc-option,-Werror=incompatible-pointer-types)
  79
  80 # Require designated initializers for all marked structures
  81 KBUILD_CFLAGS += $(call cc-option,-Werror=designated-init)
  82
  83 # Warn if there is an enum types mismatch
  84 KBUILD_CFLAGS += $(call cc-option,-Wenum-conversion)
  85
  86 # backward compatibility
  87 KBUILD_EXTRA_WARN ?= $(KBUILD_ENABLE_EXTRA_GCC_CHECKS)
  88
  89 ifeq ("$(origin W)", "command line")
  90   KBUILD_EXTRA_WARN := $(W)
  91 endif
  92
  93 export KBUILD_EXTRA_WARN
  94
  95 #
  96 # W=1 - warnings which may be relevant and do not occur too often
  97 #
  98 ifneq ($(findstring 1, $(KBUILD_EXTRA_WARN)),)
  99
 100 KBUILD_CFLAGS += -Wextra -Wunused -Wno-unused-parameter
 101 KBUILD_CFLAGS += -Wmissing-declarations
 102 KBUILD_CFLAGS += -Wmissing-format-attribute
 103 KBUILD_CFLAGS += -Wmissing-prototypes
 104 KBUILD_CFLAGS += -Wold-style-definition
 105 KBUILD_CFLAGS += -Wmissing-include-dirs
 106 KBUILD_CFLAGS += $(call cc-option, -Wunused-but-set-variable)
 107 KBUILD_CFLAGS += $(call cc-option, -Wunused-const-variable)
 108 KBUILD_CFLAGS += $(call cc-option, -Wpacked-not-aligned)
 109 KBUILD_CFLAGS += $(call cc-option, -Wformat-overflow)
 110 KBUILD_CFLAGS += $(call cc-option, -Wformat-truncation)
 111 KBUILD_CFLAGS += $(call cc-option, -Wstringop-overflow)
 112 KBUILD_CFLAGS += $(call cc-option, -Wstringop-truncation)
 113
 114 KBUILD_CPPFLAGS += -Wundef
 115 KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN1
 116
 117 else
 118
 119 # Some diagnostics enabled by default are noisy.
 120 # Suppress them by using -Wno... except for W=1.
 121 KBUILD_CFLAGS += $(call cc-disable-warning, unused-but-set-variable)
 122 KBUILD_CFLAGS += $(call cc-disable-warning, unused-const-variable)
 123 KBUILD_CFLAGS += $(call cc-disable-warning, packed-not-aligned)
 124 KBUILD_CFLAGS += $(call cc-disable-warning, format-overflow)
 125 KBUILD_CFLAGS += $(call cc-disable-warning, format-truncation)
 126 KBUILD_CFLAGS += $(call cc-disable-warning, stringop-overflow)
 127 KBUILD_CFLAGS += $(call cc-disable-warning, stringop-truncation)
 128
 129 ifdef CONFIG_CC_IS_CLANG
 130 # Clang before clang-16 would warn on default argument promotions.
 131 ifneq ($(call clang-min-version, 160000),y)
 132 # Disable -Wformat
 133 KBUILD_CFLAGS += -Wno-format
 134 # Then re-enable flags that were part of the -Wformat group that aren't
 135 # problematic.
 136 KBUILD_CFLAGS += -Wformat-extra-args -Wformat-invalid-specifier
 137 KBUILD_CFLAGS += -Wformat-zero-length -Wnonnull
 138 # Requires clang-12+.
 139 ifeq ($(call clang-min-version, 120000),y)
 140 KBUILD_CFLAGS += -Wformat-insufficient-args
 141 endif
 142 endif
 143 KBUILD_CFLAGS += $(call cc-disable-warning, pointer-to-enum-cast)
 144 KBUILD_CFLAGS += -Wno-tautological-constant-out-of-range-compare
 145 KBUILD_CFLAGS += $(call cc-disable-warning, unaligned-access)
 146 KBUILD_CFLAGS += $(call cc-disable-warning, cast-function-type-strict)
 147 endif
 148
 149 endif
 150
 151 #
 152 # W=2 - warnings which occur quite often but may still be relevant
 153 #
 154 ifneq ($(findstring 2, $(KBUILD_EXTRA_WARN)),)
 155
 156 KBUILD_CFLAGS += -Wdisabled-optimization
 157 KBUILD_CFLAGS += -Wshadow
 158 KBUILD_CFLAGS += $(call cc-option, -Wlogical-op)
 159 KBUILD_CFLAGS += -Wmissing-field-initializers
 160 KBUILD_CFLAGS += -Wtype-limits
 161 KBUILD_CFLAGS += $(call cc-option, -Wmaybe-uninitialized)
 162 KBUILD_CFLAGS += $(call cc-option, -Wunused-macros)
 163
 164 ifdef CONFIG_CC_IS_CLANG
 165 KBUILD_CFLAGS += -Winitializer-overrides
 166 endif
 167
 168 KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN2
 169
 170 else
 171
 172 # The following turn off the warnings enabled by -Wextra
 173 KBUILD_CFLAGS += -Wno-missing-field-initializers
 174 KBUILD_CFLAGS += -Wno-type-limits
 175 KBUILD_CFLAGS += -Wno-shift-negative-value
 176
 177 ifdef CONFIG_CC_IS_CLANG
 178 KBUILD_CFLAGS += -Wno-initializer-overrides
 179 else
 180 KBUILD_CFLAGS += -Wno-maybe-uninitialized
 181 endif
 182
 183 endif
 184
 185 #
 186 # W=3 - more obscure warnings, can most likely be ignored
 187 #
 188 ifneq ($(findstring 3, $(KBUILD_EXTRA_WARN)),)
 189
 190 KBUILD_CFLAGS += -Wbad-function-cast
 191 KBUILD_CFLAGS += -Wcast-align
 192 KBUILD_CFLAGS += -Wcast-qual
 193 KBUILD_CFLAGS += -Wconversion
 194 KBUILD_CFLAGS += -Wpacked
 195 KBUILD_CFLAGS += -Wpadded
 196 KBUILD_CFLAGS += -Wpointer-arith
 197 KBUILD_CFLAGS += -Wredundant-decls
 198 KBUILD_CFLAGS += -Wsign-compare
 199 KBUILD_CFLAGS += -Wswitch-default
 200 KBUILD_CFLAGS += $(call cc-option, -Wpacked-bitfield-compat)
 201
 202 KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN3
 203
 204 else
 205
 206 # The following turn off the warnings enabled by -Wextra
 207 KBUILD_CFLAGS += -Wno-sign-compare
 208
 209 endif
 210
 211 #
 212 # W=e - error out on warnings
 213 #
 214 ifneq ($(findstring e, $(KBUILD_EXTRA_WARN)),)
 215
 216 KBUILD_CFLAGS += -Werror
 217
 218 endif