xref: /linux/scripts/Makefile.extrawarn (revision 019b383d1132e4051de0d2e43254454b86538cf4) 
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 += -Wundef
12KBUILD_CFLAGS += -Werror=implicit-function-declaration
13KBUILD_CFLAGS += -Werror=implicit-int
14KBUILD_CFLAGS += -Werror=return-type
15KBUILD_CFLAGS += -Werror=strict-prototypes
16KBUILD_CFLAGS += -Wno-format-security
17KBUILD_CFLAGS += -Wno-trigraphs
18KBUILD_CFLAGS += $(call cc-disable-warning,frame-address,)
19KBUILD_CFLAGS += $(call cc-disable-warning, address-of-packed-member)
20
21ifneq ($(CONFIG_FRAME_WARN),0)
22KBUILD_CFLAGS += -Wframe-larger-than=$(CONFIG_FRAME_WARN)
23endif
24
25KBUILD_CPPFLAGS-$(CONFIG_WERROR) += -Werror
26KBUILD_CPPFLAGS += $(KBUILD_CPPFLAGS-y)
27KBUILD_CFLAGS-$(CONFIG_CC_NO_ARRAY_BOUNDS) += -Wno-array-bounds
28
29ifdef CONFIG_CC_IS_CLANG
30# The kernel builds with '-std=gnu11' so use of GNU extensions is acceptable.
31KBUILD_CFLAGS += -Wno-gnu
32else
33
34# gcc inanely warns about local variables called 'main'
35KBUILD_CFLAGS += -Wno-main
36endif
37
38# These warnings generated too much noise in a regular build.
39# Use make W=1 to enable them (see scripts/Makefile.extrawarn)
40KBUILD_CFLAGS += $(call cc-disable-warning, unused-but-set-variable)
41KBUILD_CFLAGS += $(call cc-disable-warning, unused-const-variable)
42
43# These result in bogus false positives
44KBUILD_CFLAGS += $(call cc-disable-warning, dangling-pointer)
45
46# Variable Length Arrays (VLAs) should not be used anywhere in the kernel
47KBUILD_CFLAGS += -Wvla
48
49# disable pointer signed / unsigned warnings in gcc 4.0
50KBUILD_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.
55KBUILD_CFLAGS += $(call cc-option, -Wcast-function-type)
56
57# The allocators already balk at large sizes, so silence the compiler
58# warnings for bounds checks involving those possible values. While
59# -Wno-alloc-size-larger-than would normally be used here, earlier versions
60# of gcc (<9.1) weirdly don't handle the option correctly when _other_
61# warnings are produced (?!). Using -Walloc-size-larger-than=SIZE_MAX
62# doesn't work (as it is documented to), silently resolving to "0" prior to
63# version 9.1 (and producing an error more recently). Numeric values larger
64# than PTRDIFF_MAX also don't work prior to version 9.1, which are silently
65# ignored, continuing to default to PTRDIFF_MAX. So, left with no other
66# choice, we must perform a versioned check to disable this warning.
67# https://lore.kernel.org/lkml/20210824115859.187f272f@canb.auug.org.au
68KBUILD_CFLAGS-$(call gcc-min-version, 90100) += -Wno-alloc-size-larger-than
69KBUILD_CFLAGS += $(KBUILD_CFLAGS-y) $(CONFIG_CC_IMPLICIT_FALLTHROUGH)
70
71# Prohibit date/time macros, which would make the build non-deterministic
72KBUILD_CFLAGS += -Werror=date-time
73
74# enforce correct pointer usage
75KBUILD_CFLAGS += $(call cc-option,-Werror=incompatible-pointer-types)
76
77# Require designated initializers for all marked structures
78KBUILD_CFLAGS += $(call cc-option,-Werror=designated-init)
79
80# Warn if there is an enum types mismatch
81KBUILD_CFLAGS += $(call cc-option,-Wenum-conversion)
82
83# backward compatibility
84KBUILD_EXTRA_WARN ?= $(KBUILD_ENABLE_EXTRA_GCC_CHECKS)
85
86ifeq ("$(origin W)", "command line")
87  KBUILD_EXTRA_WARN := $(W)
88endif
89
90export KBUILD_EXTRA_WARN
91
92#
93# W=1 - warnings which may be relevant and do not occur too often
94#
95ifneq ($(findstring 1, $(KBUILD_EXTRA_WARN)),)
96
97KBUILD_CFLAGS += -Wextra -Wunused -Wno-unused-parameter
98KBUILD_CFLAGS += -Wmissing-declarations
99KBUILD_CFLAGS += $(call cc-option, -Wrestrict)
100KBUILD_CFLAGS += -Wmissing-format-attribute
101KBUILD_CFLAGS += -Wmissing-prototypes
102KBUILD_CFLAGS += -Wold-style-definition
103KBUILD_CFLAGS += -Wmissing-include-dirs
104KBUILD_CFLAGS += $(call cc-option, -Wunused-but-set-variable)
105KBUILD_CFLAGS += $(call cc-option, -Wunused-const-variable)
106KBUILD_CFLAGS += $(call cc-option, -Wpacked-not-aligned)
107KBUILD_CFLAGS += $(call cc-option, -Wformat-overflow)
108KBUILD_CFLAGS += $(call cc-option, -Wformat-truncation)
109KBUILD_CFLAGS += $(call cc-option, -Wstringop-overflow)
110KBUILD_CFLAGS += $(call cc-option, -Wstringop-truncation)
111
112KBUILD_CPPFLAGS += -Wundef
113KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN1
114
115else
116
117# Some diagnostics enabled by default are noisy.
118# Suppress them by using -Wno... except for W=1.
119KBUILD_CFLAGS += $(call cc-disable-warning, unused-but-set-variable)
120KBUILD_CFLAGS += $(call cc-disable-warning, unused-const-variable)
121KBUILD_CFLAGS += $(call cc-disable-warning, restrict)
122KBUILD_CFLAGS += $(call cc-disable-warning, packed-not-aligned)
123KBUILD_CFLAGS += $(call cc-disable-warning, format-overflow)
124KBUILD_CFLAGS += $(call cc-disable-warning, format-truncation)
125KBUILD_CFLAGS += $(call cc-disable-warning, stringop-overflow)
126KBUILD_CFLAGS += $(call cc-disable-warning, stringop-truncation)
127
128ifdef CONFIG_CC_IS_CLANG
129# Clang before clang-16 would warn on default argument promotions.
130ifneq ($(call clang-min-version, 160000),y)
131# Disable -Wformat
132KBUILD_CFLAGS += -Wno-format
133# Then re-enable flags that were part of the -Wformat group that aren't
134# problematic.
135KBUILD_CFLAGS += -Wformat-extra-args -Wformat-invalid-specifier
136KBUILD_CFLAGS += -Wformat-zero-length -Wnonnull
137# Requires clang-12+.
138ifeq ($(call clang-min-version, 120000),y)
139KBUILD_CFLAGS += -Wformat-insufficient-args
140endif
141endif
142KBUILD_CFLAGS += $(call cc-disable-warning, pointer-to-enum-cast)
143KBUILD_CFLAGS += -Wno-tautological-constant-out-of-range-compare
144KBUILD_CFLAGS += $(call cc-disable-warning, unaligned-access)
145KBUILD_CFLAGS += $(call cc-disable-warning, cast-function-type-strict)
146endif
147
148endif
149
150#
151# W=2 - warnings which occur quite often but may still be relevant
152#
153ifneq ($(findstring 2, $(KBUILD_EXTRA_WARN)),)
154
155KBUILD_CFLAGS += -Wdisabled-optimization
156KBUILD_CFLAGS += -Wshadow
157KBUILD_CFLAGS += $(call cc-option, -Wlogical-op)
158KBUILD_CFLAGS += -Wmissing-field-initializers
159KBUILD_CFLAGS += -Wtype-limits
160KBUILD_CFLAGS += $(call cc-option, -Wmaybe-uninitialized)
161KBUILD_CFLAGS += $(call cc-option, -Wunused-macros)
162
163ifdef CONFIG_CC_IS_CLANG
164KBUILD_CFLAGS += -Winitializer-overrides
165endif
166
167KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN2
168
169else
170
171# The following turn off the warnings enabled by -Wextra
172KBUILD_CFLAGS += -Wno-missing-field-initializers
173KBUILD_CFLAGS += -Wno-type-limits
174KBUILD_CFLAGS += -Wno-shift-negative-value
175
176ifdef CONFIG_CC_IS_CLANG
177KBUILD_CFLAGS += -Wno-initializer-overrides
178else
179KBUILD_CFLAGS += -Wno-maybe-uninitialized
180endif
181
182endif
183
184#
185# W=3 - more obscure warnings, can most likely be ignored
186#
187ifneq ($(findstring 3, $(KBUILD_EXTRA_WARN)),)
188
189KBUILD_CFLAGS += -Wbad-function-cast
190KBUILD_CFLAGS += -Wcast-align
191KBUILD_CFLAGS += -Wcast-qual
192KBUILD_CFLAGS += -Wconversion
193KBUILD_CFLAGS += -Wpacked
194KBUILD_CFLAGS += -Wpadded
195KBUILD_CFLAGS += -Wpointer-arith
196KBUILD_CFLAGS += -Wredundant-decls
197KBUILD_CFLAGS += -Wsign-compare
198KBUILD_CFLAGS += -Wswitch-default
199KBUILD_CFLAGS += $(call cc-option, -Wpacked-bitfield-compat)
200
201KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN3
202
203else
204
205# The following turn off the warnings enabled by -Wextra
206KBUILD_CFLAGS += -Wno-sign-compare
207
208endif
209
210#
211# W=e - error out on warnings
212#
213ifneq ($(findstring e, $(KBUILD_EXTRA_WARN)),)
214
215KBUILD_CFLAGS += -Werror
216
217endif
218