projects/linux·blob v6.19 · refs

235 lines · 8.5 KiB

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 += -Wextra
12KBUILD_CFLAGS += -Wundef
13KBUILD_CFLAGS += -Werror=implicit-function-declaration
14KBUILD_CFLAGS += -Werror=implicit-int
15KBUILD_CFLAGS += -Werror=return-type
16KBUILD_CFLAGS += -Werror=strict-prototypes
17KBUILD_CFLAGS += -Wno-format-security
18KBUILD_CFLAGS += -Wno-trigraphs
19KBUILD_CFLAGS += $(call cc-option, -Wno-frame-address)
20KBUILD_CFLAGS += $(call cc-option, -Wno-address-of-packed-member)
21KBUILD_CFLAGS += -Wmissing-declarations
22KBUILD_CFLAGS += -Wmissing-prototypes
23
24ifneq ($(CONFIG_FRAME_WARN),0)
25KBUILD_CFLAGS += -Wframe-larger-than=$(CONFIG_FRAME_WARN)
26endif
27
28KBUILD_CFLAGS-$(CONFIG_CC_NO_ARRAY_BOUNDS) += -Wno-array-bounds
29
30ifdef CONFIG_CC_IS_CLANG
31# The kernel builds with '-std=gnu11' and '-fms-extensions' so use of GNU and
32# Microsoft extensions is acceptable.
33KBUILD_CFLAGS += -Wno-gnu
34KBUILD_CFLAGS += -Wno-microsoft-anon-tag
35
36# Clang checks for overflow/truncation with '%p', while GCC does not:
37# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111219
38KBUILD_CFLAGS += $(call cc-option, -Wno-format-overflow-non-kprintf)
39KBUILD_CFLAGS += $(call cc-option, -Wno-format-truncation-non-kprintf)
40
41# Clang may emit a warning when a const variable, such as the dummy variables
42# in typecheck(), or const member of an aggregate type are not initialized,
43# which can result in unexpected behavior. However, in many audited cases of
44# the "field" variant of the warning, this is intentional because the field is
45# never used within a particular call path, the field is within a union with
46# other non-const members, or the containing object is not const so the field
47# can be modified via memcpy() / memset(). While the variable warning also gets
48# disabled with this same switch, there should not be too much coverage lost
49# because -Wuninitialized will still flag when an uninitialized const variable
50# is used.
51KBUILD_CFLAGS += $(call cc-option, -Wno-default-const-init-unsafe)
52else
53
54# gcc inanely warns about local variables called 'main'
55KBUILD_CFLAGS += -Wno-main
56endif
57
58# These result in bogus false positives
59KBUILD_CFLAGS += $(call cc-option, -Wno-dangling-pointer)
60
61# Stack Variable Length Arrays (VLAs) must not be used in the kernel.
62# Function array parameters should, however, be usable, but -Wvla will
63# warn for those. Clang has no way yet to distinguish between the VLA
64# types, so depend on GCC for now to keep stack VLAs out of the tree.
65# https://github.com/llvm/llvm-project/issues/57098
66# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98217
67KBUILD_CFLAGS += $(call cc-option,-Wvla-larger-than=1)
68
69# disable pointer signed / unsigned warnings in gcc 4.0
70KBUILD_CFLAGS += -Wno-pointer-sign
71
72# In order to make sure new function cast mismatches are not introduced
73# in the kernel (to avoid tripping CFI checking), the kernel should be
74# globally built with -Wcast-function-type.
75KBUILD_CFLAGS += $(call cc-option, -Wcast-function-type)
76
77# Currently, disable -Wstringop-overflow for GCC 11, globally.
78KBUILD_CFLAGS-$(CONFIG_CC_NO_STRINGOP_OVERFLOW) += $(call cc-option, -Wno-stringop-overflow)
79KBUILD_CFLAGS-$(CONFIG_CC_STRINGOP_OVERFLOW) += $(call cc-option, -Wstringop-overflow)
80
81# Currently, disable -Wunterminated-string-initialization as broken
82KBUILD_CFLAGS += $(call cc-option, -Wno-unterminated-string-initialization)
83
84# The allocators already balk at large sizes, so silence the compiler
85# warnings for bounds checks involving those possible values. While
86# -Wno-alloc-size-larger-than would normally be used here, earlier versions
87# of gcc (<9.1) weirdly don't handle the option correctly when _other_
88# warnings are produced (?!). Using -Walloc-size-larger-than=SIZE_MAX
89# doesn't work (as it is documented to), silently resolving to "0" prior to
90# version 9.1 (and producing an error more recently). Numeric values larger
91# than PTRDIFF_MAX also don't work prior to version 9.1, which are silently
92# ignored, continuing to default to PTRDIFF_MAX. So, left with no other
93# choice, we must perform a versioned check to disable this warning.
94# https://lore.kernel.org/lkml/[email protected]
95KBUILD_CFLAGS-$(call gcc-min-version, 90100) += -Wno-alloc-size-larger-than
96KBUILD_CFLAGS += $(KBUILD_CFLAGS-y) $(CONFIG_CC_IMPLICIT_FALLTHROUGH)
97
98# Prohibit date/time macros, which would make the build non-deterministic
99KBUILD_CFLAGS += -Werror=date-time
100
101# enforce correct pointer usage
102KBUILD_CFLAGS += $(call cc-option,-Werror=incompatible-pointer-types)
103
104# Require designated initializers for all marked structures
105KBUILD_CFLAGS += $(call cc-option,-Werror=designated-init)
106
107# Warn if there is an enum types mismatch
108KBUILD_CFLAGS += $(call cc-option,-Wenum-conversion)
109
110KBUILD_CFLAGS += -Wunused
111
112#
113# W=1 - warnings which may be relevant and do not occur too often
114#
115ifneq ($(findstring 1, $(KBUILD_EXTRA_WARN)),)
116
117KBUILD_CFLAGS += -Wmissing-format-attribute
118KBUILD_CFLAGS += -Wmissing-include-dirs
119KBUILD_CFLAGS += $(call cc-option, -Wunused-const-variable)
120
121KBUILD_CPPFLAGS += -Wundef
122KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN1
123
124else
125
126# Some diagnostics enabled by default are noisy.
127# Suppress them by using -Wno... except for W=1.
128KBUILD_CFLAGS += $(call cc-option, -Wno-unused-but-set-variable)
129KBUILD_CFLAGS += $(call cc-option, -Wno-unused-const-variable)
130KBUILD_CFLAGS += $(call cc-option, -Wno-packed-not-aligned)
131KBUILD_CFLAGS += $(call cc-option, -Wno-format-overflow)
132ifdef CONFIG_CC_IS_GCC
133KBUILD_CFLAGS += $(call cc-option, -Wno-format-truncation)
134endif
135KBUILD_CFLAGS += $(call cc-option, -Wno-stringop-truncation)
136
137KBUILD_CFLAGS += -Wno-override-init # alias for -Wno-initializer-overrides in clang
138
139ifdef CONFIG_CC_IS_CLANG
140# Clang before clang-16 would warn on default argument promotions.
141ifneq ($(call clang-min-version, 160000),y)
142# Disable -Wformat
143KBUILD_CFLAGS += -Wno-format
144# Then re-enable flags that were part of the -Wformat group that aren't
145# problematic.
146KBUILD_CFLAGS += -Wformat-extra-args -Wformat-invalid-specifier
147KBUILD_CFLAGS += -Wformat-zero-length -Wnonnull
148# Requires clang-12+.
149ifeq ($(call clang-min-version, 120000),y)
150KBUILD_CFLAGS += -Wformat-insufficient-args
151endif
152endif
153KBUILD_CFLAGS += $(call cc-option, -Wno-pointer-to-enum-cast)
154KBUILD_CFLAGS += -Wno-tautological-constant-out-of-range-compare
155KBUILD_CFLAGS += $(call cc-option, -Wno-unaligned-access)
156KBUILD_CFLAGS += -Wno-enum-compare-conditional
157endif
158
159endif
160
161#
162# W=2 - warnings which occur quite often but may still be relevant
163#
164ifneq ($(findstring 2, $(KBUILD_EXTRA_WARN)),)
165
166KBUILD_CFLAGS += -Wdisabled-optimization
167KBUILD_CFLAGS += -Wshadow
168KBUILD_CFLAGS += $(call cc-option, -Wlogical-op)
169KBUILD_CFLAGS += $(call cc-option, -Wunused-macros)
170
171KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN2
172
173else
174
175# The following turn off the warnings enabled by -Wextra
176KBUILD_CFLAGS += -Wno-missing-field-initializers
177KBUILD_CFLAGS += -Wno-type-limits
178KBUILD_CFLAGS += -Wno-shift-negative-value
179
180ifdef CONFIG_CC_IS_CLANG
181KBUILD_CFLAGS += -Wno-enum-enum-conversion
182endif
183
184ifdef CONFIG_CC_IS_GCC
185KBUILD_CFLAGS += -Wno-maybe-uninitialized
186endif
187
188endif
189
190#
191# W=3 - more obscure warnings, can most likely be ignored
192#
193ifneq ($(findstring 3, $(KBUILD_EXTRA_WARN)),)
194
195KBUILD_CFLAGS += -Wbad-function-cast
196KBUILD_CFLAGS += -Wcast-align
197KBUILD_CFLAGS += -Wcast-qual
198KBUILD_CFLAGS += -Wconversion
199KBUILD_CFLAGS += -Wpacked
200KBUILD_CFLAGS += -Wpadded
201KBUILD_CFLAGS += -Wpointer-arith
202KBUILD_CFLAGS += -Wredundant-decls
203KBUILD_CFLAGS += -Wsign-compare
204KBUILD_CFLAGS += -Wswitch-default
205
206KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN3
207
208else
209
210# The following turn off the warnings enabled by -Wextra
211KBUILD_CFLAGS += -Wno-sign-compare
212KBUILD_CFLAGS += -Wno-unused-parameter
213
214endif
215
216#
217# W=e and CONFIG_WERROR - error out on warnings
218#
219ifneq ($(findstring e, $(KBUILD_EXTRA_WARN))$(CONFIG_WERROR),)
220
221KBUILD_CPPFLAGS += -Werror
222KBUILD_AFLAGS += -Wa,--fatal-warnings
223KBUILD_LDFLAGS += --fatal-warnings
224KBUILD_USERCFLAGS += -Werror
225KBUILD_USERLDFLAGS += -Wl,--fatal-warnings
226KBUILD_RUSTFLAGS += -Dwarnings
227
228# While hostprog flags are used during build bootstrapping (thus should not
229# depend on CONFIG_ symbols), -Werror is disruptive and should be opted into.
230# Only apply -Werror to hostprogs built after the initial Kconfig stage.
231KBUILD_HOSTCFLAGS += -Werror
232KBUILD_HOSTLDFLAGS += -Wl,--fatal-warnings
233KBUILD_HOSTRUSTFLAGS += -Dwarnings
234
235endif