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 # disable stringop warnings in gcc 8+
  60 KBUILD_CFLAGS += $(call cc-disable-warning, stringop-truncation)
  61
  62 # We'll want to enable this eventually, but it's not going away for 5.7 at least
  63 KBUILD_CFLAGS += $(call cc-disable-warning, stringop-overflow)
  64
  65 # Another good warning that we'll want to enable eventually
  66 KBUILD_CFLAGS += $(call cc-disable-warning, restrict)
  67
  68 # Enabled with W=2, disabled by default as noisy
  69 ifdef CONFIG_CC_IS_GCC
  70 KBUILD_CFLAGS += -Wno-maybe-uninitialized
  71 endif
  72
  73 # The allocators already balk at large sizes, so silence the compiler
  74 # warnings for bounds checks involving those possible values. While
  75 # -Wno-alloc-size-larger-than would normally be used here, earlier versions
  76 # of gcc (<9.1) weirdly don't handle the option correctly when _other_
  77 # warnings are produced (?!). Using -Walloc-size-larger-than=SIZE_MAX
  78 # doesn't work (as it is documented to), silently resolving to "0" prior to
  79 # version 9.1 (and producing an error more recently). Numeric values larger
  80 # than PTRDIFF_MAX also don't work prior to version 9.1, which are silently
  81 # ignored, continuing to default to PTRDIFF_MAX. So, left with no other
  82 # choice, we must perform a versioned check to disable this warning.
  83 # https://lore.kernel.org/lkml/20210824115859.187f272f@canb.auug.org.au
  84 KBUILD_CFLAGS-$(call gcc-min-version, 90100) += -Wno-alloc-size-larger-than
  85 KBUILD_CFLAGS += $(KBUILD_CFLAGS-y) $(CONFIG_CC_IMPLICIT_FALLTHROUGH)
  86
  87 # Prohibit date/time macros, which would make the build non-deterministic
  88 KBUILD_CFLAGS += -Werror=date-time
  89
  90 # enforce correct pointer usage
  91 KBUILD_CFLAGS += $(call cc-option,-Werror=incompatible-pointer-types)
  92
  93 # Require designated initializers for all marked structures
  94 KBUILD_CFLAGS += $(call cc-option,-Werror=designated-init)
  95
  96 # Warn if there is an enum types mismatch
  97 KBUILD_CFLAGS += $(call cc-option,-Wenum-conversion)
  98
  99 KBUILD_CFLAGS += $(call cc-disable-warning, packed-not-aligned)
 100
 101 # backward compatibility
 102 KBUILD_EXTRA_WARN ?= $(KBUILD_ENABLE_EXTRA_GCC_CHECKS)
 103
 104 ifeq ("$(origin W)", "command line")
 105   KBUILD_EXTRA_WARN := $(W)
 106 endif
 107
 108 export KBUILD_EXTRA_WARN
 109
 110 #
 111 # W=1 - warnings which may be relevant and do not occur too often
 112 #
 113 ifneq ($(findstring 1, $(KBUILD_EXTRA_WARN)),)
 114
 115 KBUILD_CFLAGS += -Wextra -Wunused -Wno-unused-parameter
 116 KBUILD_CFLAGS += -Wmissing-declarations
 117 KBUILD_CFLAGS += -Wmissing-format-attribute
 118 KBUILD_CFLAGS += -Wmissing-prototypes
 119 KBUILD_CFLAGS += -Wold-style-definition
 120 KBUILD_CFLAGS += -Wmissing-include-dirs
 121 KBUILD_CFLAGS += $(call cc-option, -Wunused-but-set-variable)
 122 KBUILD_CFLAGS += $(call cc-option, -Wunused-const-variable)
 123 KBUILD_CFLAGS += $(call cc-option, -Wpacked-not-aligned)
 124 KBUILD_CFLAGS += $(call cc-option, -Wstringop-truncation)
 125 # The following turn off the warnings enabled by -Wextra
 126 KBUILD_CFLAGS += -Wno-missing-field-initializers
 127 KBUILD_CFLAGS += -Wno-sign-compare
 128 KBUILD_CFLAGS += -Wno-type-limits
 129 KBUILD_CFLAGS += -Wno-shift-negative-value
 130
 131 KBUILD_CPPFLAGS += -Wundef
 132 KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN1
 133
 134 else
 135
 136 # Some diagnostics enabled by default are noisy.
 137 # Suppress them by using -Wno... except for W=1.
 138
 139 ifdef CONFIG_CC_IS_CLANG
 140 KBUILD_CFLAGS += -Wno-initializer-overrides
 141 # Clang before clang-16 would warn on default argument promotions.
 142 ifneq ($(call clang-min-version, 160000),y)
 143 # Disable -Wformat
 144 KBUILD_CFLAGS += -Wno-format
 145 # Then re-enable flags that were part of the -Wformat group that aren't
 146 # problematic.
 147 KBUILD_CFLAGS += -Wformat-extra-args -Wformat-invalid-specifier
 148 KBUILD_CFLAGS += -Wformat-zero-length -Wnonnull
 149 # Requires clang-12+.
 150 ifeq ($(call clang-min-version, 120000),y)
 151 KBUILD_CFLAGS += -Wformat-insufficient-args
 152 endif
 153 endif
 154 KBUILD_CFLAGS += -Wno-sign-compare
 155 KBUILD_CFLAGS += $(call cc-disable-warning, pointer-to-enum-cast)
 156 KBUILD_CFLAGS += -Wno-tautological-constant-out-of-range-compare
 157 KBUILD_CFLAGS += $(call cc-disable-warning, unaligned-access)
 158 KBUILD_CFLAGS += $(call cc-disable-warning, cast-function-type-strict)
 159 endif
 160
 161 endif
 162
 163 #
 164 # W=2 - warnings which occur quite often but may still be relevant
 165 #
 166 ifneq ($(findstring 2, $(KBUILD_EXTRA_WARN)),)
 167
 168 KBUILD_CFLAGS += -Wdisabled-optimization
 169 KBUILD_CFLAGS += -Wshadow
 170 KBUILD_CFLAGS += $(call cc-option, -Wlogical-op)
 171 KBUILD_CFLAGS += -Wmissing-field-initializers
 172 KBUILD_CFLAGS += -Wtype-limits
 173 KBUILD_CFLAGS += $(call cc-option, -Wmaybe-uninitialized)
 174 KBUILD_CFLAGS += $(call cc-option, -Wunused-macros)
 175
 176 KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN2
 177
 178 endif
 179
 180 #
 181 # W=3 - more obscure warnings, can most likely be ignored
 182 #
 183 ifneq ($(findstring 3, $(KBUILD_EXTRA_WARN)),)
 184
 185 KBUILD_CFLAGS += -Wbad-function-cast
 186 KBUILD_CFLAGS += -Wcast-align
 187 KBUILD_CFLAGS += -Wcast-qual
 188 KBUILD_CFLAGS += -Wconversion
 189 KBUILD_CFLAGS += -Wpacked
 190 KBUILD_CFLAGS += -Wpadded
 191 KBUILD_CFLAGS += -Wpointer-arith
 192 KBUILD_CFLAGS += -Wredundant-decls
 193 KBUILD_CFLAGS += -Wsign-compare
 194 KBUILD_CFLAGS += -Wswitch-default
 195 KBUILD_CFLAGS += $(call cc-option, -Wpacked-bitfield-compat)
 196
 197 KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN3
 198
 199 endif
 200
 201 #
 202 # W=e - error out on warnings
 203 #
 204 ifneq ($(findstring e, $(KBUILD_EXTRA_WARN)),)
 205
 206 KBUILD_CFLAGS += -Werror
 207
 208 endif