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b0839b281c
-Wformat was recently re-enabled for builds with clang, then quickly re-disabled, due to concerns stemming from the frequency of default argument promotion related warning instances. commit258fafcd06("Makefile.extrawarn: re-enable -Wformat for clang") commit21f9c8a13b("Revert "Makefile.extrawarn: re-enable -Wformat for clang"") ISO WG14 has ratified N2562 to address default argument promotion explicitly for printf, as part of the upcoming ISO C2X standard. The behavior of clang was changed in clang-16 to not warn for the cited cases in all language modes. Add a version check, so that users of clang-16 now get the full effect of -Wformat. For older clang versions, re-enable flags under the -Wformat group that way users still get some useful checks related to format strings, without noisy default argument promotion warnings. I intentionally omitted -Wformat-y2k and -Wformat-security from being re-enabled, which are also part of -Wformat in clang-16. Link: https://github.com/ClangBuiltLinux/linux/issues/378 Link: https://github.com/llvm/llvm-project/issues/57102 Link: https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2562.pdf Suggested-by: Justin Stitt <jstitt007@gmail.com> Suggested-by: Nathan Chancellor <nathan@kernel.org> Suggested-by: Youngmin Nam <youngmin.nam@samsung.com> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> Reviewed-by: Masahiro Yamada <masahiroy@kernel.org> Reviewed-by: Nathan Chancellor <nathan@kernel.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
117 lines
3.4 KiB
Makefile
117 lines
3.4 KiB
Makefile
# SPDX-License-Identifier: GPL-2.0
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# ==========================================================================
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# make W=... settings
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#
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# There are four warning groups enabled by W=1, W=2, W=3, and W=e
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# They are independent, and can be combined like W=12 or W=123e.
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# ==========================================================================
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KBUILD_CFLAGS += $(call cc-disable-warning, packed-not-aligned)
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# backward compatibility
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KBUILD_EXTRA_WARN ?= $(KBUILD_ENABLE_EXTRA_GCC_CHECKS)
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ifeq ("$(origin W)", "command line")
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KBUILD_EXTRA_WARN := $(W)
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endif
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export KBUILD_EXTRA_WARN
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#
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# W=1 - warnings which may be relevant and do not occur too often
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#
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ifneq ($(findstring 1, $(KBUILD_EXTRA_WARN)),)
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KBUILD_CFLAGS += -Wextra -Wunused -Wno-unused-parameter
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KBUILD_CFLAGS += -Wmissing-declarations
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KBUILD_CFLAGS += -Wmissing-format-attribute
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KBUILD_CFLAGS += -Wmissing-prototypes
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KBUILD_CFLAGS += -Wold-style-definition
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KBUILD_CFLAGS += -Wmissing-include-dirs
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KBUILD_CFLAGS += $(call cc-option, -Wunused-but-set-variable)
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KBUILD_CFLAGS += $(call cc-option, -Wunused-const-variable)
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KBUILD_CFLAGS += $(call cc-option, -Wpacked-not-aligned)
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KBUILD_CFLAGS += $(call cc-option, -Wstringop-truncation)
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# The following turn off the warnings enabled by -Wextra
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KBUILD_CFLAGS += -Wno-missing-field-initializers
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KBUILD_CFLAGS += -Wno-sign-compare
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KBUILD_CFLAGS += -Wno-type-limits
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KBUILD_CFLAGS += -Wno-shift-negative-value
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KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN1
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else
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# Some diagnostics enabled by default are noisy.
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# Suppress them by using -Wno... except for W=1.
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ifdef CONFIG_CC_IS_CLANG
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KBUILD_CFLAGS += -Wno-initializer-overrides
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# Clang before clang-16 would warn on default argument promotions.
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ifeq ($(shell [ $(CONFIG_CLANG_VERSION) -lt 160000 ] && echo y),y)
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# Disable -Wformat
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KBUILD_CFLAGS += -Wno-format
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# Then re-enable flags that were part of the -Wformat group that aren't
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# problematic.
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KBUILD_CFLAGS += -Wformat-extra-args -Wformat-invalid-specifier
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KBUILD_CFLAGS += -Wformat-zero-length -Wnonnull
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# Requires clang-12+.
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ifeq ($(shell [ $(CONFIG_CLANG_VERSION) -ge 120000 ] && echo y),y)
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KBUILD_CFLAGS += -Wformat-insufficient-args
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endif
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endif
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KBUILD_CFLAGS += -Wno-sign-compare
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KBUILD_CFLAGS += $(call cc-disable-warning, pointer-to-enum-cast)
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KBUILD_CFLAGS += -Wno-tautological-constant-out-of-range-compare
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KBUILD_CFLAGS += $(call cc-disable-warning, unaligned-access)
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endif
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endif
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#
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# W=2 - warnings which occur quite often but may still be relevant
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#
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ifneq ($(findstring 2, $(KBUILD_EXTRA_WARN)),)
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KBUILD_CFLAGS += -Wdisabled-optimization
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KBUILD_CFLAGS += -Wshadow
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KBUILD_CFLAGS += $(call cc-option, -Wlogical-op)
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KBUILD_CFLAGS += -Wmissing-field-initializers
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KBUILD_CFLAGS += -Wtype-limits
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KBUILD_CFLAGS += $(call cc-option, -Wmaybe-uninitialized)
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KBUILD_CFLAGS += $(call cc-option, -Wunused-macros)
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KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN2
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endif
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#
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# W=3 - more obscure warnings, can most likely be ignored
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#
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ifneq ($(findstring 3, $(KBUILD_EXTRA_WARN)),)
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KBUILD_CFLAGS += -Wbad-function-cast
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KBUILD_CFLAGS += -Wcast-align
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KBUILD_CFLAGS += -Wcast-qual
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KBUILD_CFLAGS += -Wconversion
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KBUILD_CFLAGS += -Wpacked
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KBUILD_CFLAGS += -Wpadded
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KBUILD_CFLAGS += -Wpointer-arith
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KBUILD_CFLAGS += -Wredundant-decls
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KBUILD_CFLAGS += -Wsign-compare
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KBUILD_CFLAGS += -Wswitch-default
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KBUILD_CFLAGS += $(call cc-option, -Wpacked-bitfield-compat)
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KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN3
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endif
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#
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# W=e - error out on warnings
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#
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ifneq ($(findstring e, $(KBUILD_EXTRA_WARN)),)
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KBUILD_CFLAGS += -Werror
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endif
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