xref: /linux/scripts/Makefile.extrawarn (revision c04022dccb2f9cf2b1cfe65807149500d1fc080a)
1b2441318SGreg Kroah-Hartman# SPDX-License-Identifier: GPL-2.0
2a86fe353SMasahiro Yamada# ==========================================================================
3a86fe353SMasahiro Yamada# make W=... settings
4a86fe353SMasahiro Yamada#
5c77d06e7SYann Droneaud# There are four warning groups enabled by W=1, W=2, W=3, and W=e
6c77d06e7SYann Droneaud# They are independent, and can be combined like W=12 or W=123e.
7a86fe353SMasahiro Yamada# ==========================================================================
8a86fe353SMasahiro Yamada
9e88ca243SArnd Bergmann# Default set of warnings, always enabled
10e88ca243SArnd BergmannKBUILD_CFLAGS += -Wall
114f79eaa2SNathan ChancellorKBUILD_CFLAGS += -Wextra
12e88ca243SArnd BergmannKBUILD_CFLAGS += -Wundef
13e88ca243SArnd BergmannKBUILD_CFLAGS += -Werror=implicit-function-declaration
14e88ca243SArnd BergmannKBUILD_CFLAGS += -Werror=implicit-int
15e88ca243SArnd BergmannKBUILD_CFLAGS += -Werror=return-type
16e88ca243SArnd BergmannKBUILD_CFLAGS += -Werror=strict-prototypes
17e88ca243SArnd BergmannKBUILD_CFLAGS += -Wno-format-security
18e88ca243SArnd BergmannKBUILD_CFLAGS += -Wno-trigraphs
19bad14b5dSLinus TorvaldsKBUILD_CFLAGS += $(call cc-option, -Wno-frame-address)
20bad14b5dSLinus TorvaldsKBUILD_CFLAGS += $(call cc-option, -Wno-address-of-packed-member)
210fcb7085SArnd BergmannKBUILD_CFLAGS += -Wmissing-declarations
220fcb7085SArnd BergmannKBUILD_CFLAGS += -Wmissing-prototypes
23e88ca243SArnd Bergmann
24e88ca243SArnd Bergmannifneq ($(CONFIG_FRAME_WARN),0)
25e88ca243SArnd BergmannKBUILD_CFLAGS += -Wframe-larger-than=$(CONFIG_FRAME_WARN)
26e88ca243SArnd Bergmannendif
27e88ca243SArnd Bergmann
28e88ca243SArnd BergmannKBUILD_CFLAGS-$(CONFIG_CC_NO_ARRAY_BOUNDS) += -Wno-array-bounds
29e88ca243SArnd Bergmann
30e88ca243SArnd Bergmannifdef CONFIG_CC_IS_CLANG
31e88ca243SArnd Bergmann# The kernel builds with '-std=gnu11' so use of GNU extensions is acceptable.
32e88ca243SArnd BergmannKBUILD_CFLAGS += -Wno-gnu
33738fc998SNathan Chancellor
34738fc998SNathan Chancellor# Clang checks for overflow/truncation with '%p', while GCC does not:
35738fc998SNathan Chancellor# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111219
36bad14b5dSLinus TorvaldsKBUILD_CFLAGS += $(call cc-option, -Wno-format-overflow-non-kprintf)
37bad14b5dSLinus TorvaldsKBUILD_CFLAGS += $(call cc-option, -Wno-format-truncation-non-kprintf)
38d0afcfebSNathan Chancellor
39d0afcfebSNathan Chancellor# Clang may emit a warning when a const variable, such as the dummy variables
40d0afcfebSNathan Chancellor# in typecheck(), or const member of an aggregate type are not initialized,
41d0afcfebSNathan Chancellor# which can result in unexpected behavior. However, in many audited cases of
42d0afcfebSNathan Chancellor# the "field" variant of the warning, this is intentional because the field is
43d0afcfebSNathan Chancellor# never used within a particular call path, the field is within a union with
44d0afcfebSNathan Chancellor# other non-const members, or the containing object is not const so the field
45d0afcfebSNathan Chancellor# can be modified via memcpy() / memset(). While the variable warning also gets
46d0afcfebSNathan Chancellor# disabled with this same switch, there should not be too much coverage lost
47d0afcfebSNathan Chancellor# because -Wuninitialized will still flag when an uninitialized const variable
48d0afcfebSNathan Chancellor# is used.
49bad14b5dSLinus TorvaldsKBUILD_CFLAGS += $(call cc-option, -Wno-default-const-init-unsafe)
50e88ca243SArnd Bergmannelse
51e88ca243SArnd Bergmann
52e88ca243SArnd Bergmann# gcc inanely warns about local variables called 'main'
53e88ca243SArnd BergmannKBUILD_CFLAGS += -Wno-main
54e88ca243SArnd Bergmannendif
55e88ca243SArnd Bergmann
56e88ca243SArnd Bergmann# These result in bogus false positives
57bad14b5dSLinus TorvaldsKBUILD_CFLAGS += $(call cc-option, -Wno-dangling-pointer)
58e88ca243SArnd Bergmann
595e88c48cSKees Cook# Stack Variable Length Arrays (VLAs) must not be used in the kernel.
605e88c48cSKees Cook# Function array parameters should, however, be usable, but -Wvla will
615e88c48cSKees Cook# warn for those. Clang has no way yet to distinguish between the VLA
625e88c48cSKees Cook# types, so depend on GCC for now to keep stack VLAs out of the tree.
635e88c48cSKees Cook# https://github.com/llvm/llvm-project/issues/57098
645e88c48cSKees Cook# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98217
655e88c48cSKees CookKBUILD_CFLAGS += $(call cc-option,-Wvla-larger-than=1)
66e88ca243SArnd Bergmann
67e88ca243SArnd Bergmann# disable pointer signed / unsigned warnings in gcc 4.0
68e88ca243SArnd BergmannKBUILD_CFLAGS += -Wno-pointer-sign
69e88ca243SArnd Bergmann
70e88ca243SArnd Bergmann# In order to make sure new function cast mismatches are not introduced
71e88ca243SArnd Bergmann# in the kernel (to avoid tripping CFI checking), the kernel should be
72e88ca243SArnd Bergmann# globally built with -Wcast-function-type.
73e88ca243SArnd BergmannKBUILD_CFLAGS += $(call cc-option, -Wcast-function-type)
74e88ca243SArnd Bergmann
754f79eaa2SNathan Chancellor# Currently, disable -Wstringop-overflow for GCC 11, globally.
76bad14b5dSLinus TorvaldsKBUILD_CFLAGS-$(CONFIG_CC_NO_STRINGOP_OVERFLOW) += $(call cc-option, -Wno-stringop-overflow)
774f79eaa2SNathan ChancellorKBUILD_CFLAGS-$(CONFIG_CC_STRINGOP_OVERFLOW) += $(call cc-option, -Wstringop-overflow)
784f79eaa2SNathan Chancellor
794f79eaa2SNathan Chancellor# Currently, disable -Wunterminated-string-initialization as broken
80bad14b5dSLinus TorvaldsKBUILD_CFLAGS += $(call cc-option, -Wno-unterminated-string-initialization)
814f79eaa2SNathan Chancellor
82e88ca243SArnd Bergmann# The allocators already balk at large sizes, so silence the compiler
83e88ca243SArnd Bergmann# warnings for bounds checks involving those possible values. While
84e88ca243SArnd Bergmann# -Wno-alloc-size-larger-than would normally be used here, earlier versions
85e88ca243SArnd Bergmann# of gcc (<9.1) weirdly don't handle the option correctly when _other_
86e88ca243SArnd Bergmann# warnings are produced (?!). Using -Walloc-size-larger-than=SIZE_MAX
87e88ca243SArnd Bergmann# doesn't work (as it is documented to), silently resolving to "0" prior to
88e88ca243SArnd Bergmann# version 9.1 (and producing an error more recently). Numeric values larger
89e88ca243SArnd Bergmann# than PTRDIFF_MAX also don't work prior to version 9.1, which are silently
90e88ca243SArnd Bergmann# ignored, continuing to default to PTRDIFF_MAX. So, left with no other
91e88ca243SArnd Bergmann# choice, we must perform a versioned check to disable this warning.
92e88ca243SArnd Bergmann# https://lore.kernel.org/lkml/20210824115859.187f272f@canb.auug.org.au
93e88ca243SArnd BergmannKBUILD_CFLAGS-$(call gcc-min-version, 90100) += -Wno-alloc-size-larger-than
94e88ca243SArnd BergmannKBUILD_CFLAGS += $(KBUILD_CFLAGS-y) $(CONFIG_CC_IMPLICIT_FALLTHROUGH)
95e88ca243SArnd Bergmann
96e88ca243SArnd Bergmann# Prohibit date/time macros, which would make the build non-deterministic
97e88ca243SArnd BergmannKBUILD_CFLAGS += -Werror=date-time
98e88ca243SArnd Bergmann
99e88ca243SArnd Bergmann# enforce correct pointer usage
100e88ca243SArnd BergmannKBUILD_CFLAGS += $(call cc-option,-Werror=incompatible-pointer-types)
101e88ca243SArnd Bergmann
102e88ca243SArnd Bergmann# Require designated initializers for all marked structures
103e88ca243SArnd BergmannKBUILD_CFLAGS += $(call cc-option,-Werror=designated-init)
104e88ca243SArnd Bergmann
105e88ca243SArnd Bergmann# Warn if there is an enum types mismatch
106e88ca243SArnd BergmannKBUILD_CFLAGS += $(call cc-option,-Wenum-conversion)
107e88ca243SArnd Bergmann
108f5982cceSArnd BergmannKBUILD_CFLAGS += -Wunused
109f5982cceSArnd Bergmann
11064a91907SMasahiro Yamada#
11164a91907SMasahiro Yamada# W=1 - warnings which may be relevant and do not occur too often
11264a91907SMasahiro Yamada#
113e27128dbSMasahiro Yamadaifneq ($(findstring 1, $(KBUILD_EXTRA_WARN)),)
114a86fe353SMasahiro Yamada
11564a91907SMasahiro YamadaKBUILD_CFLAGS += -Wmissing-format-attribute
11664a91907SMasahiro YamadaKBUILD_CFLAGS += -Wmissing-include-dirs
11764a91907SMasahiro YamadaKBUILD_CFLAGS += $(call cc-option, -Wunused-const-variable)
118a86fe353SMasahiro Yamada
11980b6093bSMasahiro YamadaKBUILD_CPPFLAGS += -Wundef
1206863f564SMasahiro YamadaKBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN1
1216863f564SMasahiro Yamada
12226ea6bb1SBehan Websterelse
12326ea6bb1SBehan Webster
12464a91907SMasahiro Yamada# Some diagnostics enabled by default are noisy.
12564a91907SMasahiro Yamada# Suppress them by using -Wno... except for W=1.
126bad14b5dSLinus TorvaldsKBUILD_CFLAGS += $(call cc-option, -Wno-unused-but-set-variable)
127bad14b5dSLinus TorvaldsKBUILD_CFLAGS += $(call cc-option, -Wno-unused-const-variable)
128bad14b5dSLinus TorvaldsKBUILD_CFLAGS += $(call cc-option, -Wno-packed-not-aligned)
129bad14b5dSLinus TorvaldsKBUILD_CFLAGS += $(call cc-option, -Wno-format-overflow)
130908dd508SArnd Bergmannifdef CONFIG_CC_IS_GCC
131bad14b5dSLinus TorvaldsKBUILD_CFLAGS += $(call cc-option, -Wno-format-truncation)
132908dd508SArnd Bergmannendif
133bad14b5dSLinus TorvaldsKBUILD_CFLAGS += $(call cc-option, -Wno-stringop-truncation)
13464a91907SMasahiro Yamada
135c40845e3SArnd BergmannKBUILD_CFLAGS += -Wno-override-init # alias for -Wno-initializer-overrides in clang
136c40845e3SArnd Bergmann
137076f421dSMasahiro Yamadaifdef CONFIG_CC_IS_CLANG
138b0839b28SNick Desaulniers# Clang before clang-16 would warn on default argument promotions.
13988b61e3bSNick Desaulniersifneq ($(call clang-min-version, 160000),y)
140b0839b28SNick Desaulniers# Disable -Wformat
14121f9c8a1SLinus TorvaldsKBUILD_CFLAGS += -Wno-format
142b0839b28SNick Desaulniers# Then re-enable flags that were part of the -Wformat group that aren't
143b0839b28SNick Desaulniers# problematic.
144b0839b28SNick DesaulniersKBUILD_CFLAGS += -Wformat-extra-args -Wformat-invalid-specifier
145b0839b28SNick DesaulniersKBUILD_CFLAGS += -Wformat-zero-length -Wnonnull
146b0839b28SNick Desaulniers# Requires clang-12+.
14788b61e3bSNick Desaulniersifeq ($(call clang-min-version, 120000),y)
148b0839b28SNick DesaulniersKBUILD_CFLAGS += -Wformat-insufficient-args
149b0839b28SNick Desaulniersendif
150b0839b28SNick Desaulniersendif
151bad14b5dSLinus TorvaldsKBUILD_CFLAGS += $(call cc-option, -Wno-pointer-to-enum-cast)
152afe956c5SNathan ChancellorKBUILD_CFLAGS += -Wno-tautological-constant-out-of-range-compare
153bad14b5dSLinus TorvaldsKBUILD_CFLAGS += $(call cc-option, -Wno-unaligned-access)
15475b5ab13SNathan ChancellorKBUILD_CFLAGS += -Wno-enum-compare-conditional
15526ea6bb1SBehan Websterendif
15664a91907SMasahiro Yamada
15764a91907SMasahiro Yamadaendif
15864a91907SMasahiro Yamada
15964a91907SMasahiro Yamada#
16064a91907SMasahiro Yamada# W=2 - warnings which occur quite often but may still be relevant
16164a91907SMasahiro Yamada#
162e27128dbSMasahiro Yamadaifneq ($(findstring 2, $(KBUILD_EXTRA_WARN)),)
16364a91907SMasahiro Yamada
16464a91907SMasahiro YamadaKBUILD_CFLAGS += -Wdisabled-optimization
16564a91907SMasahiro YamadaKBUILD_CFLAGS += -Wshadow
16664a91907SMasahiro YamadaKBUILD_CFLAGS += $(call cc-option, -Wlogical-op)
16764a91907SMasahiro YamadaKBUILD_CFLAGS += $(call cc-option, -Wunused-macros)
16864a91907SMasahiro Yamada
1696863f564SMasahiro YamadaKBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN2
1706863f564SMasahiro Yamada
1712cd3271bSArnd Bergmannelse
1722cd3271bSArnd Bergmann
1732cd3271bSArnd Bergmann# The following turn off the warnings enabled by -Wextra
1742cd3271bSArnd BergmannKBUILD_CFLAGS += -Wno-missing-field-initializers
1752cd3271bSArnd BergmannKBUILD_CFLAGS += -Wno-type-limits
1762cd3271bSArnd BergmannKBUILD_CFLAGS += -Wno-shift-negative-value
1772cd3271bSArnd Bergmann
1788f6629c0SNathan Chancellorifdef CONFIG_CC_IS_CLANG
1798f6629c0SNathan ChancellorKBUILD_CFLAGS += -Wno-enum-enum-conversion
1808f6629c0SNathan Chancellorendif
1818f6629c0SNathan Chancellor
182c40845e3SArnd Bergmannifdef CONFIG_CC_IS_GCC
1832cd3271bSArnd BergmannKBUILD_CFLAGS += -Wno-maybe-uninitialized
1842cd3271bSArnd Bergmannendif
1852cd3271bSArnd Bergmann
18664a91907SMasahiro Yamadaendif
18764a91907SMasahiro Yamada
18864a91907SMasahiro Yamada#
18964a91907SMasahiro Yamada# W=3 - more obscure warnings, can most likely be ignored
19064a91907SMasahiro Yamada#
191e27128dbSMasahiro Yamadaifneq ($(findstring 3, $(KBUILD_EXTRA_WARN)),)
19264a91907SMasahiro Yamada
19364a91907SMasahiro YamadaKBUILD_CFLAGS += -Wbad-function-cast
194095fbca0SArnd BergmannKBUILD_CFLAGS += -Wcast-align
19564a91907SMasahiro YamadaKBUILD_CFLAGS += -Wcast-qual
19664a91907SMasahiro YamadaKBUILD_CFLAGS += -Wconversion
19764a91907SMasahiro YamadaKBUILD_CFLAGS += -Wpacked
19864a91907SMasahiro YamadaKBUILD_CFLAGS += -Wpadded
19964a91907SMasahiro YamadaKBUILD_CFLAGS += -Wpointer-arith
20064a91907SMasahiro YamadaKBUILD_CFLAGS += -Wredundant-decls
201a97ea93eSJoe PerchesKBUILD_CFLAGS += -Wsign-compare
20264a91907SMasahiro YamadaKBUILD_CFLAGS += -Wswitch-default
20364a91907SMasahiro Yamada
2046863f564SMasahiro YamadaKBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN3
2056863f564SMasahiro Yamada
2062cd3271bSArnd Bergmannelse
2072cd3271bSArnd Bergmann
2082cd3271bSArnd Bergmann# The following turn off the warnings enabled by -Wextra
2092cd3271bSArnd BergmannKBUILD_CFLAGS += -Wno-sign-compare
210f5982cceSArnd BergmannKBUILD_CFLAGS += -Wno-unused-parameter
2112cd3271bSArnd Bergmann
212a86fe353SMasahiro Yamadaendif
213c77d06e7SYann Droneaud
214c77d06e7SYann Droneaud#
215e7a10929SThomas Weißschuh# W=e and CONFIG_WERROR - error out on warnings
216c77d06e7SYann Droneaud#
217e7a10929SThomas Weißschuhifneq ($(findstring e, $(KBUILD_EXTRA_WARN))$(CONFIG_WERROR),)
218c77d06e7SYann Droneaud
219f852ce05SThomas WeißschuhKBUILD_CPPFLAGS		+= -Werror
220ec4a3992SThomas WeißschuhKBUILD_AFLAGS		+= -Wa,--fatal-warnings
221ec4a3992SThomas WeißschuhKBUILD_LDFLAGS		+= --fatal-warnings
2223f0ff4ccSThomas WeißschuhKBUILD_USERCFLAGS	+= -Werror
2233f0ff4ccSThomas WeißschuhKBUILD_USERLDFLAGS	+= -Wl,--fatal-warnings
224592b571fSMiguel OjedaKBUILD_RUSTFLAGS	+= -Dwarnings
225c77d06e7SYann Droneaud
226*7ded7d37SNathan Chancellor# While hostprog flags are used during build bootstrapping (thus should not
227*7ded7d37SNathan Chancellor# depend on CONFIG_ symbols), -Werror is disruptive and should be opted into.
228*7ded7d37SNathan Chancellor# Only apply -Werror to hostprogs built after the initial Kconfig stage.
22927758d8cSThomas WeißschuhKBUILD_HOSTCFLAGS	+= -Werror
23027758d8cSThomas WeißschuhKBUILD_HOSTLDFLAGS	+= -Wl,--fatal-warnings
23127758d8cSThomas WeißschuhKBUILD_HOSTRUSTFLAGS	+= -Dwarnings
232*7ded7d37SNathan Chancellor
233*7ded7d37SNathan Chancellorendif
234