btrfs-progs/Makefile.extrawarn

# From linux.git/scripts/Kbuild.include
#
# try-run
# Usage: option = $(call try-run, $(CC)...-o "$$TMP",option-ok,otherwise)
# Exit code chooses option. "$$TMP" is can be used as temporary file and
# is automatically cleaned up.
try-run = $(shell set -e;               \
        TMP="$(TMPOUT).$$$$.tmp";       \
        TMPO="$(TMPOUT).$$$$.o";        \
        if ($(1)) >/dev/null 2>&1;      \
        then echo "$(2)";               \
        else echo "$(3)";               \
        fi;                             \
        rm -f "$$TMP" "$$TMPO")

 # cc-option
 # Usage: cflags-y += $(call cc-option,-march=winchip-c6,-march=i586)

 cc-option = $(call try-run,\
         $(CC) $(CFLAGS) $(1) -c -x c /dev/null -o "$$TMP",$(1),$(2))

# cc-disable-warning
# Usage: cflags-y += $(call cc-disable-warning,unused-but-set-variable)
cc-disable-warning = $(call try-run, \
	$(CC) -Werror $(CFLAGS) -W$(strip $(1)) -c -x c /dev/null -o "$$TMP",-Wno-$(strip $(1)))

# From linux.git/scripts/Makefile.extrawarn
# ==========================================================================
#
# make W=... settings
#
# W=1 - warnings that may be relevant and does not occur too often
# W=2 - warnings that occur quite often but may still be relevant
# W=3 - the more obscure warnings, can most likely be ignored
#
# $(call cc-option, -W...) handles gcc -W.. options which
# are not supported by all versions of the compiler
# ==========================================================================

ifeq ("$(origin W)", "command line")
  export BUILD_ENABLE_EXTRA_GCC_CHECKS := $(W)
endif

ifdef BUILD_ENABLE_EXTRA_GCC_CHECKS
warning-  := $(empty)

warning-1 := -Wextra -Wunused -Wno-unused-parameter
warning-1 += -Wmissing-declarations
warning-1 += -Wmissing-format-attribute
warning-1 += $(call cc-option, -Wmissing-prototypes)
warning-1 += -Wold-style-definition
warning-1 += $(call cc-option, -Wmissing-include-dirs)
warning-1 += $(call cc-option, -Wunused-but-set-variable)
warning-1 += $(call cc-disable-warning, missing-field-initializers)

warning-2 := -Waggregate-return
warning-2 += -Wcast-align
warning-2 += -Wdisabled-optimization
warning-2 += -Wnested-externs
warning-2 += -Wshadow
warning-2 += $(call cc-option, -Wlogical-op)
warning-2 += $(call cc-option, -Wmissing-field-initializers)

warning-3 := -Wbad-function-cast
warning-3 += -Wcast-qual
warning-3 += -Wconversion
warning-3 += -Wpacked
warning-3 += -Wpadded
warning-3 += -Wpointer-arith
warning-3 += -Wredundant-decls
warning-3 += -Wswitch-default
warning-3 += $(call cc-option, -Wpacked-bitfield-compat)
warning-3 += $(call cc-option, -Wvla)

warning := $(warning-$(findstring 1, $(BUILD_ENABLE_EXTRA_GCC_CHECKS)))
warning += $(warning-$(findstring 2, $(BUILD_ENABLE_EXTRA_GCC_CHECKS)))
warning += $(warning-$(findstring 3, $(BUILD_ENABLE_EXTRA_GCC_CHECKS)))

ifeq ("$(strip $(warning))","")
        $(error W=$(BUILD_ENABLE_EXTRA_GCC_CHECKS) is unknown)
endif

EXTRAWARN_CFLAGS += $(warning)
else

ifeq ($(COMPILER),clang)
EXTRAWARN_CFLAGS += $(call cc-disable-warning, initializer-overrides)
EXTRAWARN_CFLAGS += $(call cc-disable-warning, unused-value)
EXTRAWARN_CFLAGS += $(call cc-disable-warning, format)
EXTRAWARN_CFLAGS += $(call cc-disable-warning, unknown-warning-option)
EXTRAWARN_CFLAGS += $(call cc-disable-warning, sign-compare)
EXTRAWARN_CFLAGS += $(call cc-disable-warning, format-zero-length)
EXTRAWARN_CFLAGS += $(call cc-disable-warning, uninitialized)
endif
endif