projects/linux·blob v7.2-rc2 · refs

219 lines · 7.7 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 += -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# Clang checks for overflow/truncation with '%p', while GCC does not:
32# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111219
33KBUILD_CFLAGS += $(call cc-option, -Wno-format-overflow-non-kprintf)
34KBUILD_CFLAGS += $(call cc-option, -Wno-format-truncation-non-kprintf)
35
36# Clang may emit a warning when a const variable, such as the dummy variables
37# in typecheck(), or const member of an aggregate type are not initialized,
38# which can result in unexpected behavior. However, in many audited cases of
39# the "field" variant of the warning, this is intentional because the field is
40# never used within a particular call path, the field is within a union with
41# other non-const members, or the containing object is not const so the field
42# can be modified via memcpy() / memset(). While the variable warning also gets
43# disabled with this same switch, there should not be too much coverage lost
44# because -Wuninitialized will still flag when an uninitialized const variable
45# is used.
46KBUILD_CFLAGS += $(call cc-option, -Wno-default-const-init-unsafe)
47else
48
49# gcc inanely warns about local variables called 'main'
50KBUILD_CFLAGS += -Wno-main
51endif
52
53# Too noisy on range checks and in macros handling both signed and unsigned.
54KBUILD_CFLAGS += -Wno-type-limits
55
56# These result in bogus false positives
57KBUILD_CFLAGS += $(call cc-option, -Wno-dangling-pointer)
58
59# Stack Variable Length Arrays (VLAs) must not be used in the kernel.
60# Function array parameters should, however, be usable, but -Wvla will
61# warn for those. Clang has no way yet to distinguish between the VLA
62# types, so depend on GCC for now to keep stack VLAs out of the tree.
63# https://github.com/llvm/llvm-project/issues/57098
64# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98217
65KBUILD_CFLAGS += $(call cc-option,-Wvla-larger-than=1)
66
67# disable pointer signed / unsigned warnings in gcc 4.0
68KBUILD_CFLAGS += -Wno-pointer-sign
69
70# In order to make sure new function cast mismatches are not introduced
71# in the kernel (to avoid tripping CFI checking), the kernel should be
72# globally built with -Wcast-function-type.
73KBUILD_CFLAGS += -Wcast-function-type
74
75# Currently, disable -Wstringop-overflow for GCC 11, globally.
76KBUILD_CFLAGS-$(CONFIG_CC_NO_STRINGOP_OVERFLOW) += $(call cc-option, -Wno-stringop-overflow)
77KBUILD_CFLAGS-$(CONFIG_CC_STRINGOP_OVERFLOW) += $(call cc-option, -Wstringop-overflow)
78
79# Currently, disable -Wunterminated-string-initialization as broken
80KBUILD_CFLAGS += $(call cc-option, -Wno-unterminated-string-initialization)
81
82# The allocators already balk at large sizes, so silence the compiler
83# warnings for bounds checks involving those possible values. While
84# -Wno-alloc-size-larger-than would normally be used here, earlier versions
85# of gcc (<9.1) weirdly don't handle the option correctly when _other_
86# warnings are produced (?!). Using -Walloc-size-larger-than=SIZE_MAX
87# doesn't work (as it is documented to), silently resolving to "0" prior to
88# version 9.1 (and producing an error more recently). Numeric values larger
89# than PTRDIFF_MAX also don't work prior to version 9.1, which are silently
90# ignored, continuing to default to PTRDIFF_MAX. So, left with no other
91# choice, we must perform a versioned check to disable this warning.
92# https://lore.kernel.org/lkml/[email protected]
93KBUILD_CFLAGS-$(call gcc-min-version, 90100) += -Wno-alloc-size-larger-than
94KBUILD_CFLAGS += $(KBUILD_CFLAGS-y) $(CONFIG_CC_IMPLICIT_FALLTHROUGH)
95
96# Prohibit date/time macros, which would make the build non-deterministic
97KBUILD_CFLAGS += -Werror=date-time
98
99# enforce correct pointer usage
100KBUILD_CFLAGS += -Werror=incompatible-pointer-types
101
102# Require designated initializers for all marked structures
103KBUILD_CFLAGS += $(call cc-option,-Werror=designated-init)
104
105# Warn if there is an enum types mismatch
106KBUILD_CFLAGS += $(call cc-option,-Wenum-conversion)
107
108KBUILD_CFLAGS += -Wunused
109
110#
111# W=1 - warnings which may be relevant and do not occur too often
112#
113ifneq ($(findstring 1, $(KBUILD_EXTRA_WARN)),)
114
115KBUILD_CFLAGS += -Wmissing-format-attribute
116KBUILD_CFLAGS += -Wmissing-include-dirs
117KBUILD_CFLAGS += -Wunused-const-variable
118
119KBUILD_CPPFLAGS += -Wundef
120KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN1
121
122else
123
124# Some diagnostics enabled by default are noisy.
125# Suppress them by using -Wno... except for W=1.
126KBUILD_CFLAGS += -Wno-unused-but-set-variable
127KBUILD_CFLAGS += -Wno-unused-const-variable
128KBUILD_CFLAGS += $(call cc-option, -Wno-packed-not-aligned)
129KBUILD_CFLAGS += $(call cc-option, -Wno-format-overflow)
130ifdef CONFIG_CC_IS_GCC
131KBUILD_CFLAGS += -Wno-format-truncation
132endif
133KBUILD_CFLAGS += $(call cc-option, -Wno-stringop-truncation)
134
135KBUILD_CFLAGS += -Wno-override-init # alias for -Wno-initializer-overrides in clang
136
137ifdef CONFIG_CC_IS_CLANG
138KBUILD_CFLAGS += -Wno-pointer-to-enum-cast
139KBUILD_CFLAGS += -Wno-tautological-constant-out-of-range-compare
140KBUILD_CFLAGS += -Wno-unaligned-access
141KBUILD_CFLAGS += -Wno-enum-compare-conditional
142endif
143
144endif
145
146#
147# W=2 - warnings which occur quite often but may still be relevant
148#
149ifneq ($(findstring 2, $(KBUILD_EXTRA_WARN)),)
150
151KBUILD_CFLAGS += -Wdisabled-optimization
152KBUILD_CFLAGS += -Wshadow
153KBUILD_CFLAGS += $(call cc-option, -Wlogical-op)
154KBUILD_CFLAGS += -Wunused-macros
155
156KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN2
157
158else
159
160# The following turn off the warnings enabled by -Wextra
161KBUILD_CFLAGS += -Wno-missing-field-initializers
162KBUILD_CFLAGS += -Wno-shift-negative-value
163
164ifdef CONFIG_CC_IS_CLANG
165KBUILD_CFLAGS += -Wno-enum-enum-conversion
166endif
167
168ifdef CONFIG_CC_IS_GCC
169KBUILD_CFLAGS += -Wno-maybe-uninitialized
170endif
171
172endif
173
174#
175# W=3 - more obscure warnings, can most likely be ignored
176#
177ifneq ($(findstring 3, $(KBUILD_EXTRA_WARN)),)
178
179KBUILD_CFLAGS += -Wbad-function-cast
180KBUILD_CFLAGS += -Wcast-align
181KBUILD_CFLAGS += -Wcast-qual
182KBUILD_CFLAGS += -Wconversion
183KBUILD_CFLAGS += -Wpacked
184KBUILD_CFLAGS += -Wpadded
185KBUILD_CFLAGS += -Wpointer-arith
186KBUILD_CFLAGS += -Wredundant-decls
187KBUILD_CFLAGS += -Wsign-compare
188KBUILD_CFLAGS += -Wswitch-default
189
190KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN3
191
192else
193
194# The following turn off the warnings enabled by -Wextra
195KBUILD_CFLAGS += -Wno-sign-compare
196KBUILD_CFLAGS += -Wno-unused-parameter
197
198endif
199
200#
201# W=e and CONFIG_WERROR - error out on warnings
202#
203ifneq ($(findstring e, $(KBUILD_EXTRA_WARN))$(CONFIG_WERROR),)
204
205KBUILD_CPPFLAGS += -Werror
206KBUILD_AFLAGS += -Wa,--fatal-warnings
207KBUILD_LDFLAGS += --fatal-warnings
208KBUILD_USERCFLAGS += -Werror
209KBUILD_USERLDFLAGS += -Wl,--fatal-warnings
210KBUILD_RUSTFLAGS += -Dwarnings
211
212# While hostprog flags are used during build bootstrapping (thus should not
213# depend on CONFIG_ symbols), -Werror is disruptive and should be opted into.
214# Only apply -Werror to hostprogs built after the initial Kconfig stage.
215KBUILD_HOSTCFLAGS += -Werror
216KBUILD_HOSTLDFLAGS += -Wl,--fatal-warnings
217KBUILD_HOSTRUSTFLAGS += -Dwarnings
218
219endif