linux/scripts/Makefile.extrawarn
Arnd Bergmann 095fbca0a9 Makefile.extrawarn: move -Wcast-align to W=3
This warning behaves differently depending on the architecture
and compiler. Using x86 gcc, we get no output at all because
gcc knows the architecture can handle unaligned accesses.

Using x86 clang, or gcc on an architecture that needs to
manually deal with unaligned accesses, the build log is
completely flooded with these warnings, as they are commonly
invoked by inline functions of networking headers, e.g.

include/linux/skbuff.h:1426:26: warning: cast increases required alignment of target type [-Wcast-align]

The compiler is correct to point this out, as we are dealing
with undefined behavior that does cause problems in practice,
but there is also no good way to rewrite the code in commonly
included headers to a safer method.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2020-11-25 03:36:10 +09:00

96 lines
2.8 KiB
Makefile

# SPDX-License-Identifier: GPL-2.0
# ==========================================================================
# make W=... settings
#
# There are three warning groups enabled by W=1, W=2, W=3.
# They are independent, and can be combined like W=12 or W=123.
# ==========================================================================
KBUILD_CFLAGS += $(call cc-disable-warning, packed-not-aligned)
# backward compatibility
KBUILD_EXTRA_WARN ?= $(KBUILD_ENABLE_EXTRA_GCC_CHECKS)
ifeq ("$(origin W)", "command line")
KBUILD_EXTRA_WARN := $(W)
endif
export KBUILD_EXTRA_WARN
#
# W=1 - warnings which may be relevant and do not occur too often
#
ifneq ($(findstring 1, $(KBUILD_EXTRA_WARN)),)
KBUILD_CFLAGS += -Wextra -Wunused -Wno-unused-parameter
KBUILD_CFLAGS += -Wmissing-declarations
KBUILD_CFLAGS += -Wmissing-format-attribute
KBUILD_CFLAGS += -Wmissing-prototypes
KBUILD_CFLAGS += -Wold-style-definition
KBUILD_CFLAGS += -Wmissing-include-dirs
KBUILD_CFLAGS += $(call cc-option, -Wunused-but-set-variable)
KBUILD_CFLAGS += $(call cc-option, -Wunused-const-variable)
KBUILD_CFLAGS += $(call cc-option, -Wpacked-not-aligned)
KBUILD_CFLAGS += $(call cc-option, -Wstringop-truncation)
# The following turn off the warnings enabled by -Wextra
KBUILD_CFLAGS += -Wno-missing-field-initializers
KBUILD_CFLAGS += -Wno-sign-compare
KBUILD_CFLAGS += -Wno-type-limits
KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN1
else
# Some diagnostics enabled by default are noisy.
# Suppress them by using -Wno... except for W=1.
ifdef CONFIG_CC_IS_CLANG
KBUILD_CFLAGS += -Wno-initializer-overrides
KBUILD_CFLAGS += -Wno-format
KBUILD_CFLAGS += -Wno-sign-compare
KBUILD_CFLAGS += -Wno-format-zero-length
KBUILD_CFLAGS += $(call cc-disable-warning, pointer-to-enum-cast)
KBUILD_CFLAGS += -Wno-tautological-constant-out-of-range-compare
endif
endif
#
# W=2 - warnings which occur quite often but may still be relevant
#
ifneq ($(findstring 2, $(KBUILD_EXTRA_WARN)),)
KBUILD_CFLAGS += -Wdisabled-optimization
KBUILD_CFLAGS += -Wnested-externs
KBUILD_CFLAGS += -Wshadow
KBUILD_CFLAGS += $(call cc-option, -Wlogical-op)
KBUILD_CFLAGS += -Wmissing-field-initializers
KBUILD_CFLAGS += -Wtype-limits
KBUILD_CFLAGS += $(call cc-option, -Wmaybe-uninitialized)
KBUILD_CFLAGS += $(call cc-option, -Wunused-macros)
KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN2
endif
#
# W=3 - more obscure warnings, can most likely be ignored
#
ifneq ($(findstring 3, $(KBUILD_EXTRA_WARN)),)
KBUILD_CFLAGS += -Wbad-function-cast
KBUILD_CFLAGS += -Wcast-align
KBUILD_CFLAGS += -Wcast-qual
KBUILD_CFLAGS += -Wconversion
KBUILD_CFLAGS += -Wpacked
KBUILD_CFLAGS += -Wpadded
KBUILD_CFLAGS += -Wpointer-arith
KBUILD_CFLAGS += -Wredundant-decls
KBUILD_CFLAGS += -Wsign-compare
KBUILD_CFLAGS += -Wswitch-default
KBUILD_CFLAGS += $(call cc-option, -Wpacked-bitfield-compat)
KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN3
endif