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 += $(call cc-disable-warning, address-of-packed-member)
  20 KBUILD_CFLAGS += -Wmissing-declarations
  21 KBUILD_CFLAGS += -Wmissing-prototypes
  22
  23 ifneq ($(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
  35 # Clang checks for overflow/truncation with '%p', while GCC does not:
  36 # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111219
  37 KBUILD_CFLAGS += $(call cc-disable-warning, format-overflow-non-kprintf)
  38 KBUILD_CFLAGS += $(call cc-disable-warning, format-truncation-non-kprintf)
  39 else
  40
  41 # gcc inanely warns about local variables called 'main'
  42 KBUILD_CFLAGS += -Wno-main
  43 endif
  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 += $(call cc-option, -Wcast-function-type)
  58
  59 # The allocators already balk at large sizes, so silence the compiler
  60 # warnings for bounds checks involving those possible values. While
  61 # -Wno-alloc-size-larger-than would normally be used here, earlier versions
  62 # of gcc (<9.1) weirdly don't handle the option correctly when _other_
  63 # warnings are produced (?!). Using -Walloc-size-larger-than=SIZE_MAX
  64 # doesn't work (as it is documented to), silently resolving to "0" prior to
  65 # version 9.1 (and producing an error more recently). Numeric values larger
  66 # than PTRDIFF_MAX also don't work prior to version 9.1, which are silently
  67 # ignored, continuing to default to PTRDIFF_MAX. So, left with no other
  68 # choice, we must perform a versioned check to disable this warning.
  69 # https://lore.kernel.org/lkml/[email protected]
  70 KBUILD_CFLAGS-$(call gcc-min-version, 90100) += -Wno-alloc-size-larger-than
  71 KBUILD_CFLAGS += $(KBUILD_CFLAGS-y) $(CONFIG_CC_IMPLICIT_FALLTHROUGH)
  72
  73 # Prohibit date/time macros, which would make the build non-deterministic
  74 KBUILD_CFLAGS += -Werror=date-time
  75
  76 # enforce correct pointer usage
  77 KBUILD_CFLAGS += $(call cc-option,-Werror=incompatible-pointer-types)
  78
  79 # Require designated initializers for all marked structures
  80 KBUILD_CFLAGS += $(call cc-option,-Werror=designated-init)
  81
  82 # Warn if there is an enum types mismatch
  83 KBUILD_CFLAGS += $(call cc-option,-Wenum-conversion)
  84
  85 # Explicitly clear padding bits during variable initialization
  86 KBUILD_CFLAGS += $(call cc-option,-fzero-init-padding-bits=all)
  87
  88 KBUILD_CFLAGS += -Wextra
  89 KBUILD_CFLAGS += -Wunused
  90
  91 #
  92 # W=1 - warnings which may be relevant and do not occur too often
  93 #
  94 ifneq ($(findstring 1, $(KBUILD_EXTRA_WARN)),)
  95
  96 KBUILD_CFLAGS += -Wmissing-format-attribute
  97 KBUILD_CFLAGS += -Wmissing-include-dirs
  98 KBUILD_CFLAGS += $(call cc-option, -Wunused-const-variable)
  99
 100 KBUILD_CPPFLAGS += -Wundef
 101 KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN1
 102
 103 else
 104
 105 # Some diagnostics enabled by default are noisy.
 106 # Suppress them by using -Wno... except for W=1.
 107 KBUILD_CFLAGS += $(call cc-disable-warning, unused-but-set-variable)
 108 KBUILD_CFLAGS += $(call cc-disable-warning, unused-const-variable)
 109 KBUILD_CFLAGS += $(call cc-disable-warning, packed-not-aligned)
 110 KBUILD_CFLAGS += $(call cc-disable-warning, format-overflow)
 111 ifdef CONFIG_CC_IS_GCC
 112 KBUILD_CFLAGS += $(call cc-disable-warning, format-truncation)
 113 endif
 114 KBUILD_CFLAGS += $(call cc-disable-warning, stringop-truncation)
 115
 116 KBUILD_CFLAGS += -Wno-override-init # alias for -Wno-initializer-overrides in clang
 117
 118 ifdef CONFIG_CC_IS_CLANG
 119 # Clang before clang-16 would warn on default argument promotions.
 120 ifneq ($(call clang-min-version, 160000),y)
 121 # Disable -Wformat
 122 KBUILD_CFLAGS += -Wno-format
 123 # Then re-enable flags that were part of the -Wformat group that aren't
 124 # problematic.
 125 KBUILD_CFLAGS += -Wformat-extra-args -Wformat-invalid-specifier
 126 KBUILD_CFLAGS += -Wformat-zero-length -Wnonnull
 127 # Requires clang-12+.
 128 ifeq ($(call clang-min-version, 120000),y)
 129 KBUILD_CFLAGS += -Wformat-insufficient-args
 130 endif
 131 endif
 132 KBUILD_CFLAGS += $(call cc-disable-warning, pointer-to-enum-cast)
 133 KBUILD_CFLAGS += -Wno-tautological-constant-out-of-range-compare
 134 KBUILD_CFLAGS += $(call cc-disable-warning, unaligned-access)
 135 KBUILD_CFLAGS += -Wno-enum-compare-conditional
 136 endif
 137
 138 endif
 139
 140 #
 141 # W=2 - warnings which occur quite often but may still be relevant
 142 #
 143 ifneq ($(findstring 2, $(KBUILD_EXTRA_WARN)),)
 144
 145 KBUILD_CFLAGS += -Wdisabled-optimization
 146 KBUILD_CFLAGS += -Wshadow
 147 KBUILD_CFLAGS += $(call cc-option, -Wlogical-op)
 148 KBUILD_CFLAGS += $(call cc-option, -Wunused-macros)
 149
 150 KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN2
 151
 152 else
 153
 154 # The following turn off the warnings enabled by -Wextra
 155 KBUILD_CFLAGS += -Wno-missing-field-initializers
 156 KBUILD_CFLAGS += -Wno-type-limits
 157 KBUILD_CFLAGS += -Wno-shift-negative-value
 158
 159 ifdef CONFIG_CC_IS_CLANG
 160 KBUILD_CFLAGS += -Wno-enum-enum-conversion
 161 endif
 162
 163 ifdef CONFIG_CC_IS_GCC
 164 KBUILD_CFLAGS += -Wno-maybe-uninitialized
 165 endif
 166
 167 endif
 168
 169 #
 170 # W=3 - more obscure warnings, can most likely be ignored
 171 #
 172 ifneq ($(findstring 3, $(KBUILD_EXTRA_WARN)),)
 173
 174 KBUILD_CFLAGS += -Wbad-function-cast
 175 KBUILD_CFLAGS += -Wcast-align
 176 KBUILD_CFLAGS += -Wcast-qual
 177 KBUILD_CFLAGS += -Wconversion
 178 KBUILD_CFLAGS += -Wpacked
 179 KBUILD_CFLAGS += -Wpadded
 180 KBUILD_CFLAGS += -Wpointer-arith
 181 KBUILD_CFLAGS += -Wredundant-decls
 182 KBUILD_CFLAGS += -Wsign-compare
 183 KBUILD_CFLAGS += -Wswitch-default
 184
 185 KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN3
 186
 187 else
 188
 189 # The following turn off the warnings enabled by -Wextra
 190 KBUILD_CFLAGS += -Wno-sign-compare
 191 KBUILD_CFLAGS += -Wno-unused-parameter
 192
 193 endif
 194
 195 #
 196 # W=e - error out on warnings
 197 #
 198 ifneq ($(findstring e, $(KBUILD_EXTRA_WARN)),)
 199
 200 KBUILD_CFLAGS += -Werror
 201
 202 endif