rules.mak - qemu - Git at Google


 # These are used when we want to do substitutions without confusing Make
 NULL  :=
 SPACE := $(NULL) #
 COMMA := ,

 # Don't use implicit rules or variables
 # we have explicit rules for everything
 MAKEFLAGS += -rR

 # Files with this suffixes are final, don't try to generate them
 # using implicit rules
 %/trace-events:
 %.hx:
 %.py:
 %.objs:
 %.d:
 %.h:
 %.c:
 %.cc:
 %.cpp:
 %.m:
 %.mak:
 clean-target:

 # Flags for dependency generation
 QEMU_DGFLAGS += -MMD -MP -MT $@ -MF $(@D)/$(*F).d

 # Compiler searches the source file dir first, but in vpath builds
 # we need to make it search the build dir too, before any other
 # explicit search paths. There are two search locations in the build
 # dir, one absolute and the other relative to the compiler working
 # directory. These are the same for target-independent files, but
 # different for target-dependent ones.
 QEMU_LOCAL_INCLUDES = -iquote $(BUILD_DIR)/$(@D) -iquote $(@D)

 WL_U := -Wl,-u,
 find-symbols = $(if $1, $(sort $(shell $(NM) -P -g $1 | $2)))
 defined-symbols = $(call find-symbols,$1,awk '$$2!="U"{print $$1}')
 undefined-symbols = $(call find-symbols,$1,awk '$$2=="U"{print $$1}')

 # All the .mo objects in -m variables are also added into corresponding -y
 # variable in unnest-vars, but filtered out here, when LINK is called.
 #
 # The .mo objects are supposed to be linked as a DSO, for module build. So here
 # they are only used as a placeholders to generate those "archive undefined"
 # symbol options (-Wl,-u,$symbol_name), which are the archive functions
 # referenced by the code in the DSO.
 #
 # Also the presence in -y variables will also guarantee they are built before
 # linking executables that will load them. So we can look up symbol reference
 # in LINK.
 #
 # This is necessary because the exectuable itself may not use the function, in
 # which case the function would not be linked in. Then the DSO loading will
 # fail because of the missing symbol.
 process-archive-undefs = $(filter-out %.a %.mo,$1) \
                 $(addprefix $(WL_U), \
                      $(filter $(call defined-symbols,$(filter %.a, $1)), \
                               $(call undefined-symbols,$(filter %.mo,$1)))) \
                 $(filter %.a,$1)

 extract-libs = $(strip $(foreach o,$(filter-out %.mo,$1),$($o-libs)))
 expand-objs = $(strip $(sort $(filter %.o,$1)) \
                   $(foreach o,$(filter %.mo,$1),$($o-objs)) \
                   $(filter-out %.o %.mo,$1))

 %.o: %.c
 	$(call quiet-command,$(CC) $(QEMU_LOCAL_INCLUDES) $(QEMU_INCLUDES) \
 	       $(QEMU_CFLAGS) $(QEMU_DGFLAGS) $(CFLAGS) $($@-cflags) \
 	       -c -o $@ $<,"CC","$(TARGET_DIR)$@")
 %.o: %.rc
 	$(call quiet-command,$(WINDRES) -I. -o $@ $<,"RC","$(TARGET_DIR)$@")

 # If we have a CXX we might have some C++ objects, in which case we
 # must link with the C++ compiler, not the plain C compiler.
 LINKPROG = $(or $(CXX),$(CC))

 LINK = $(call quiet-command, $(LINKPROG) $(CFLAGS) $(QEMU_LDFLAGS) -o $@ \
        $(call process-archive-undefs, $1) \
        $(version-obj-y) $(call extract-libs,$1) $(LIBS),"LINK","$(TARGET_DIR)$@")

 %.o: %.S
 	$(call quiet-command,$(CCAS) $(QEMU_LOCAL_INCLUDES) $(QEMU_INCLUDES) \
 	       $(QEMU_CFLAGS) $(QEMU_DGFLAGS) $(CFLAGS) \
 	       -c -o $@ $<,"CCAS","$(TARGET_DIR)$@")

 %.o: %.cc
 	$(call quiet-command,$(CXX) $(QEMU_LOCAL_INCLUDES) $(QEMU_INCLUDES) \
 	       $(QEMU_CXXFLAGS) $(QEMU_DGFLAGS) $(CFLAGS) $($@-cflags) \
 	       -c -o $@ $<,"CXX","$(TARGET_DIR)$@")

 %.o: %.cpp
 	$(call quiet-command,$(CXX) $(QEMU_LOCAL_INCLUDES) $(QEMU_INCLUDES) \
 	       $(QEMU_CXXFLAGS) $(QEMU_DGFLAGS) $(CFLAGS) $($@-cflags) \
 	       -c -o $@ $<,"CXX","$(TARGET_DIR)$@")

 %.o: %.m
 	$(call quiet-command,$(OBJCC) $(QEMU_LOCAL_INCLUDES) $(QEMU_INCLUDES) \
 	       $(QEMU_CFLAGS) $(QEMU_DGFLAGS) $(CFLAGS) $($@-cflags) \
 	       -c -o $@ $<,"OBJC","$(TARGET_DIR)$@")

 %.o: %.dtrace
 	$(call quiet-command,dtrace -o $@ -G -s $<,"GEN","$(TARGET_DIR)$@")

 DSO_OBJ_CFLAGS := -fPIC -DBUILD_DSO
 module-common.o: CFLAGS += $(DSO_OBJ_CFLAGS)
 %$(DSOSUF): QEMU_LDFLAGS += $(LDFLAGS_SHARED)
 %$(DSOSUF): %.mo
 	$(call LINK,$^)
 	@# Copy to build root so modules can be loaded when program started without install
 	$(if $(findstring /,$@),$(call quiet-command,cp $@ $(subst /,-,$@),"CP","$(subst /,-,$@)"))


 LD_REL := $(CC) -nostdlib $(LD_REL_FLAGS)

 %.mo:
 	$(call quiet-command,$(LD_REL) -o $@ $^,"LD","$(TARGET_DIR)$@")

 .PHONY: modules
 modules:

 %$(EXESUF): %.o
 	$(call LINK,$(filter %.o %.a %.mo, $^))

 %.a:
 	$(call quiet-command,rm -f $@ && $(AR) rcs $@ $^,"AR","$(TARGET_DIR)$@")

 # Usage: $(call quiet-command,command and args,"NAME","args to print")
 # This will run "command and args", and either:
 #  if V=1 just print the whole command and args
 #  otherwise print the 'quiet' output in the format "  NAME     args to print"
 # NAME should be a short name of the command, 7 letters or fewer.
 # If called with only a single argument, will print nothing in quiet mode.
 quiet-command-run = $(if $(V),,$(if $2,printf "  %-7s %s\n" $2 $3 && ))$1
 quiet-@ = $(if $(V),,@)
 quiet-command = $(quiet-@)$(call quiet-command-run,$1,$2,$3)

 # cc-option
 # Usage: CFLAGS+=$(call cc-option, -falign-functions=0, -malign-functions=0)

 cc-option = $(if $(shell $(CC) $1 $2 -S -o /dev/null -xc /dev/null \
               >/dev/null 2>&1 && echo OK), $2, $3)
 cc-c-option = $(if $(shell $(CC) $1 $2 -c -o /dev/null -xc /dev/null \
                 >/dev/null 2>&1 && echo OK), $2, $3)

 VPATH_SUFFIXES = %.c %.h %.S %.cc %.cpp %.m %.mak %.texi %.sh %.rc Kconfig% %.json.in
 set-vpath = $(if $1,$(foreach PATTERN,$(VPATH_SUFFIXES),$(eval vpath $(PATTERN) $1)))

 # install-prog list, dir
 define install-prog
 	$(INSTALL_DIR) "$2"
 	$(INSTALL_PROG) $1 "$2"
 	$(if $(STRIP),$(STRIP) $(foreach T,$1,"$2/$(notdir $T)"),)
 endef

 # find-in-path
 # Usage: $(call find-in-path, prog)
 # Looks in the PATH if the argument contains no slash, else only considers one
 # specific directory.  Returns an # empty string if the program doesn't exist
 # there.
 find-in-path = $(if $(findstring /, $1), \
         $(wildcard $1), \
         $(wildcard $(patsubst %, %/$1, $(subst :, ,$(PATH)))))

 # Logical functions (for operating on y/n values like CONFIG_FOO vars)
 # Inputs to these must be either "y" (true) or "n" or "" (both false)
 # Output is always either "y" or "n".
 # Usage: $(call land,$(CONFIG_FOO),$(CONFIG_BAR))
 # Logical NOT
 lnot = $(if $(subst n,,$1),n,y)
 # Logical AND
 land = $(if $(findstring yy,$1$2),y,n)
 # Logical OR
 lor = $(if $(findstring y,$1$2),y,n)
 # Logical XOR (note that this is the inverse of leqv)
 lxor = $(if $(filter $(call lnot,$1),$(call lnot,$2)),n,y)
 # Logical equivalence (note that leqv "","n" is true)
 leqv = $(if $(filter $(call lnot,$1),$(call lnot,$2)),y,n)
 # Logical if: like make's $(if) but with an leqv-like test
 lif = $(if $(subst n,,$1),$2,$3)

 # String testing functions: inputs to these can be any string;
 # the output is always either "y" or "n". Leading and trailing whitespace
 # is ignored when comparing strings.
 # String equality
 eq = $(if $(subst $2,,$1)$(subst $1,,$2),n,y)
 # String inequality
 ne = $(if $(subst $2,,$1)$(subst $1,,$2),y,n)
 # Emptiness/non-emptiness tests:
 isempty = $(if $1,n,y)
 notempty = $(if $1,y,n)

 # Generate files with tracetool
 TRACETOOL=$(PYTHON) $(SRC_PATH)/scripts/tracetool.py

 # Generate timestamp files for .h include files

 config-%.h: config-%.h-timestamp
 	@cmp $< $@ >/dev/null 2>&1 || cp $< $@

 config-%.h-timestamp: config-%.mak $(SRC_PATH)/scripts/create_config
 	$(call quiet-command, sh $(SRC_PATH)/scripts/create_config < $< > $@,"GEN","$(TARGET_DIR)config-$*.h")

 .PHONY: clean-timestamp
 clean-timestamp:
 	rm -f *.timestamp
 clean: clean-timestamp

 # will delete the target of a rule if commands exit with a nonzero exit status
 .DELETE_ON_ERROR:

 # save-vars
 # Usage: $(call save-vars, vars)
 # Save each variable $v in $vars as save-vars-$v, save their object's
 # variables, then clear $v.  saved-vars-$v contains the variables that
 # where saved for the objects, in order to speedup load-vars.
 define save-vars
     $(foreach v,$1,
         $(eval save-vars-$v := $(value $v))
         $(eval saved-vars-$v := $(foreach o,$($v), \
             $(if $($o-cflags), $o-cflags $(eval save-vars-$o-cflags := $($o-cflags))$(eval $o-cflags := )) \
             $(if $($o-libs), $o-libs $(eval save-vars-$o-libs := $($o-libs))$(eval $o-libs := )) \
             $(if $($o-objs), $o-objs $(eval save-vars-$o-objs := $($o-objs))$(eval $o-objs := ))))
         $(eval $v := ))
 endef

 # load-vars
 # Usage: $(call load-vars, vars, add_var)
 # Load the saved value for each variable in @vars, and the per object
 # variables.
 # Append @add_var's current value to the loaded value.
 define load-vars
     $(eval $2-new-value := $(value $2))
     $(foreach v,$1,
         $(eval $v := $(value save-vars-$v))
         $(foreach o,$(saved-vars-$v),
             $(eval $o := $(save-vars-$o)) $(eval save-vars-$o := ))
         $(eval save-vars-$v := )
         $(eval saved-vars-$v := ))
     $(eval $2 := $(value $2) $($2-new-value))
 endef

 # fix-paths
 # Usage: $(call fix-paths, obj_path, src_path, vars)
 # Add prefix @obj_path to all objects in @vars, and add prefix @src_path to all
 # directories in @vars.
 define fix-paths
     $(foreach v,$3,
         $(foreach o,$($v),
             $(if $($o-libs),
                 $(eval $1$o-libs := $($o-libs)))
             $(if $($o-cflags),
                 $(eval $1$o-cflags := $($o-cflags)))
             $(if $($o-objs),
                 $(eval $1$o-objs := $(addprefix $1,$($o-objs)))))
         $(eval $v := $(addprefix $1,$(filter-out %/,$($v))) \
                      $(addprefix $2,$(filter %/,$($v)))))
 endef

 # unnest-var-recursive
 # Usage: $(call unnest-var-recursive, obj_prefix, vars, var)
 #
 # Unnest @var by including subdir Makefile.objs, while protect others in @vars
 # unchanged.
 #
 # @obj_prefix is the starting point of object path prefix.
 #
 define unnest-var-recursive
     $(eval dirs := $(sort $(filter %/,$($3))))
     $(eval $3 := $(filter-out %/,$($3)))
     $(foreach d,$(dirs:%/=%),
             $(call save-vars,$2)
             $(eval obj := $(if $1,$1/)$d)
             $(eval -include $(SRC_PATH)/$d/Makefile.objs)
             $(call fix-paths,$(if $1,$1/)$d/,$d/,$2)
             $(call load-vars,$2,$3)
             $(call unnest-var-recursive,$1,$2,$3))
 endef

 # unnest-vars
 # Usage: $(call unnest-vars, obj_prefix, vars)
 #
 # @obj_prefix: object path prefix, can be empty, or '..', etc. Don't include
 # ending '/'.
 #
 # @vars: the list of variable names to unnest.
 #
 # This macro will scan subdirectories's Makefile.objs, include them, to build
 # up each variable listed in @vars.
 #
 # Per object and per module cflags and libs are saved with relative path fixed
 # as well, those variables include -libs, -cflags and -objs. Items in -objs are
 # also fixed to relative path against SRC_PATH plus the prefix @obj_prefix.
 #
 # All nested variables postfixed by -m in names are treated as DSO variables,
 # and will be built as modules, if enabled.
 #
 # A simple example of the unnest:
 #
 #     obj_prefix = ..
 #     vars = hot cold
 #     hot  = fire.o sun.o season/
 #     cold = snow.o water/ season/
 #
 # Unnest through a faked source directory structure:
 #
 #     SRC_PATH
 #        ├── water
 #        │   └── Makefile.objs──────────────────┐
 #        │       │ hot += steam.o               │
 #        │       │ cold += ice.mo               │
 #        │       │ ice.mo-libs := -licemaker    │
 #        │       │ ice.mo-objs := ice1.o ice2.o │
 #        │       └──────────────────────────────┘
 #        │
 #        └── season
 #            └── Makefile.objs──────┐
 #                │ hot += summer.o  │
 #                │ cold += winter.o │
 #                └──────────────────┘
 #
 # In the end, the result will be:
 #
 #     hot  = ../fire.o ../sun.o ../season/summer.o
 #     cold = ../snow.o ../water/ice.mo ../season/winter.o
 #     ../water/ice.mo-libs = -licemaker
 #     ../water/ice.mo-objs = ../water/ice1.o ../water/ice2.o
 #
 # Note that 'hot' didn't include 'water/' in the input, so 'steam.o' is not
 # included.
 #
 define unnest-vars
     # In the case of target build (i.e. $1 == ..), fix path for top level
     # Makefile.objs objects
     $(if $1,$(call fix-paths,$1/,,$2))

     # Descend and include every subdir Makefile.objs
     $(foreach v, $2,
         $(call unnest-var-recursive,$1,$2,$v)
         # Pass the .mo-cflags and .mo-libs along to its member objects
         $(foreach o, $(filter %.mo,$($v)),
             $(foreach p,$($o-objs),
                 $(if $($o-cflags), $(eval $p-cflags += $($o-cflags)))
                 $(if $($o-libs), $(eval $p-libs += $($o-libs))))))

     # For all %.mo objects that are directly added into -y, just expand them
     $(foreach v,$(filter %-y,$2),
         $(eval $v := $(foreach o,$($v),$(if $($o-objs),$($o-objs),$o))))

     $(foreach v,$(filter %-m,$2),
         # All .o found in *-m variables are single object modules, create .mo
         # for them
         $(foreach o,$(filter %.o,$($v)),
             $(eval $(o:%.o=%.mo)-objs := $o))
         # Now unify .o in -m variable to .mo
         $(eval $v := $($v:%.o=%.mo))
         $(eval modules-m += $($v))

         # For module build, build shared libraries during "make modules"
         # For non-module build, add -m to -y
         $(if $(CONFIG_MODULES),
              $(foreach o,$($v),
                    $(eval $($o-objs): CFLAGS += $(DSO_OBJ_CFLAGS))
                    $(eval $o: $($o-objs)))
              $(eval $(patsubst %-m,%-y,$v) += $($v))
              $(eval modules: $($v:%.mo=%$(DSOSUF))),
              $(eval $(patsubst %-m,%-y,$v) += $(call expand-objs, $($v)))))

     # Post-process all the unnested vars
     $(foreach v,$2,
         $(foreach o, $(filter %.mo,$($v)),
             # Find all the .mo objects in variables and add dependency rules
             # according to .mo-objs. Report error if not set
             $(if $($o-objs),
                 $(eval $(o:%.mo=%$(DSOSUF)): module-common.o $($o-objs)),
                 $(error $o added in $v but $o-objs is not set)))
         $(shell mkdir -p ./ $(sort $(dir $($v))))
         # Include all the .d files
         $(eval -include $(patsubst %.o,%.d,$(patsubst %.mo,%.d,$($v))))
         $(eval $v := $(filter-out %/,$($v))))
 endef

 TEXI2MAN = $(call quiet-command, \
 	perl -Ww -- $(SRC_PATH)/scripts/texi2pod.pl $(TEXI2PODFLAGS) $< $@.pod && \
 	$(POD2MAN) --section=$(subst .,,$(suffix $@)) --center=" " --release=" " $@.pod > $@, \
 	"GEN","$@")

 %.1:
 	$(call TEXI2MAN)
 %.7:
 	$(call TEXI2MAN)
 %.8:
 	$(call TEXI2MAN)

 GEN_SUBST = $(call quiet-command, \
 	sed -e "s!@libexecdir@!$(libexecdir)!g" < $< > $@, \
 	"GEN","$@")

 %.json: %.json.in
 	$(call GEN_SUBST)

	# These are used when we want to do substitutions without confusing Make
	NULL :=
	SPACE := $(NULL) #
	COMMA := ,

	# Don't use implicit rules or variables
	# we have explicit rules for everything
	MAKEFLAGS += -rR

	# Files with this suffixes are final, don't try to generate them
	# using implicit rules
	%/trace-events:
	%.hx:
	%.py:
	%.objs:
	%.d:
	%.h:
	%.c:
	%.cc:
	%.cpp:
	%.m:
	%.mak:
	clean-target:

	# Flags for dependency generation
	QEMU_DGFLAGS += -MMD -MP -MT $@ -MF $(@D)/$(*F).d

	# Compiler searches the source file dir first, but in vpath builds
	# we need to make it search the build dir too, before any other
	# explicit search paths. There are two search locations in the build
	# dir, one absolute and the other relative to the compiler working
	# directory. These are the same for target-independent files, but
	# different for target-dependent ones.
	QEMU_LOCAL_INCLUDES = -iquote $(BUILD_DIR)/$(@D) -iquote $(@D)

	WL_U := -Wl,-u,
	find-symbols = $(if $1, $(sort $(shell $(NM) -P -g $1 \| $2)))
	defined-symbols = $(call find-symbols,$1,awk '$$2!="U"{print $$1}')
	undefined-symbols = $(call find-symbols,$1,awk '$$2=="U"{print $$1}')

	# All the .mo objects in -m variables are also added into corresponding -y
	# variable in unnest-vars, but filtered out here, when LINK is called.
	#
	# The .mo objects are supposed to be linked as a DSO, for module build. So here
	# they are only used as a placeholders to generate those "archive undefined"
	# symbol options (-Wl,-u,$symbol_name), which are the archive functions
	# referenced by the code in the DSO.
	#
	# Also the presence in -y variables will also guarantee they are built before
	# linking executables that will load them. So we can look up symbol reference
	# in LINK.
	#
	# This is necessary because the exectuable itself may not use the function, in
	# which case the function would not be linked in. Then the DSO loading will
	# fail because of the missing symbol.
	process-archive-undefs = $(filter-out %.a %.mo,$1) \
	$(addprefix $(WL_U), \
	$(filter $(call defined-symbols,$(filter %.a, $1)), \
	$(call undefined-symbols,$(filter %.mo,$1)))) \
	$(filter %.a,$1)

	extract-libs = $(strip $(foreach o,$(filter-out %.mo,$1),$($o-libs)))
	expand-objs = $(strip $(sort $(filter %.o,$1)) \
	$(foreach o,$(filter %.mo,$1),$($o-objs)) \
	$(filter-out %.o %.mo,$1))

	%.o: %.c
	$(call quiet-command,$(CC) $(QEMU_LOCAL_INCLUDES) $(QEMU_INCLUDES) \
	$(QEMU_CFLAGS) $(QEMU_DGFLAGS) $(CFLAGS) $($@-cflags) \
	-c -o $@ $<,"CC","$(TARGET_DIR)$@")
	%.o: %.rc
	$(call quiet-command,$(WINDRES) -I. -o $@ $<,"RC","$(TARGET_DIR)$@")

	# If we have a CXX we might have some C++ objects, in which case we
	# must link with the C++ compiler, not the plain C compiler.
	LINKPROG = $(or $(CXX),$(CC))

	LINK = $(call quiet-command, $(LINKPROG) $(CFLAGS) $(QEMU_LDFLAGS) -o $@ \
	$(call process-archive-undefs, $1) \
	$(version-obj-y) $(call extract-libs,$1) $(LIBS),"LINK","$(TARGET_DIR)$@")

	%.o: %.S
	$(call quiet-command,$(CCAS) $(QEMU_LOCAL_INCLUDES) $(QEMU_INCLUDES) \
	$(QEMU_CFLAGS) $(QEMU_DGFLAGS) $(CFLAGS) \
	-c -o $@ $<,"CCAS","$(TARGET_DIR)$@")

	%.o: %.cc
	$(call quiet-command,$(CXX) $(QEMU_LOCAL_INCLUDES) $(QEMU_INCLUDES) \
	$(QEMU_CXXFLAGS) $(QEMU_DGFLAGS) $(CFLAGS) $($@-cflags) \
	-c -o $@ $<,"CXX","$(TARGET_DIR)$@")

	%.o: %.cpp
	$(call quiet-command,$(CXX) $(QEMU_LOCAL_INCLUDES) $(QEMU_INCLUDES) \
	$(QEMU_CXXFLAGS) $(QEMU_DGFLAGS) $(CFLAGS) $($@-cflags) \
	-c -o $@ $<,"CXX","$(TARGET_DIR)$@")

	%.o: %.m
	$(call quiet-command,$(OBJCC) $(QEMU_LOCAL_INCLUDES) $(QEMU_INCLUDES) \
	$(QEMU_CFLAGS) $(QEMU_DGFLAGS) $(CFLAGS) $($@-cflags) \
	-c -o $@ $<,"OBJC","$(TARGET_DIR)$@")

	%.o: %.dtrace
	$(call quiet-command,dtrace -o $@ -G -s $<,"GEN","$(TARGET_DIR)$@")

	DSO_OBJ_CFLAGS := -fPIC -DBUILD_DSO
	module-common.o: CFLAGS += $(DSO_OBJ_CFLAGS)
	%$(DSOSUF): QEMU_LDFLAGS += $(LDFLAGS_SHARED)
	%$(DSOSUF): %.mo
	$(call LINK,$^)
	@# Copy to build root so modules can be loaded when program started without install
	$(if $(findstring /,$@),$(call quiet-command,cp $@ $(subst /,-,$@),"CP","$(subst /,-,$@)"))


	LD_REL := $(CC) -nostdlib $(LD_REL_FLAGS)

	%.mo:
	$(call quiet-command,$(LD_REL) -o $@ $^,"LD","$(TARGET_DIR)$@")

	.PHONY: modules
	modules:

	%$(EXESUF): %.o
	$(call LINK,$(filter %.o %.a %.mo, $^))

	%.a:
	$(call quiet-command,rm -f $@ && $(AR) rcs $@ $^,"AR","$(TARGET_DIR)$@")

	# Usage: $(call quiet-command,command and args,"NAME","args to print")
	# This will run "command and args", and either:
	# if V=1 just print the whole command and args
	# otherwise print the 'quiet' output in the format " NAME args to print"
	# NAME should be a short name of the command, 7 letters or fewer.
	# If called with only a single argument, will print nothing in quiet mode.
	quiet-command-run = $(if $(V),,$(if $2,printf " %-7s %s\n" $2 $3 && ))$1
	quiet-@ = $(if $(V),,@)
	quiet-command = $(quiet-@)$(call quiet-command-run,$1,$2,$3)

	# cc-option
	# Usage: CFLAGS+=$(call cc-option, -falign-functions=0, -malign-functions=0)

	cc-option = $(if $(shell $(CC) $1 $2 -S -o /dev/null -xc /dev/null \
	>/dev/null 2>&1 && echo OK), $2, $3)
	cc-c-option = $(if $(shell $(CC) $1 $2 -c -o /dev/null -xc /dev/null \
	>/dev/null 2>&1 && echo OK), $2, $3)

	VPATH_SUFFIXES = %.c %.h %.S %.cc %.cpp %.m %.mak %.texi %.sh %.rc Kconfig% %.json.in
	set-vpath = $(if $1,$(foreach PATTERN,$(VPATH_SUFFIXES),$(eval vpath $(PATTERN) $1)))

	# install-prog list, dir
	define install-prog
	$(INSTALL_DIR) "$2"
	$(INSTALL_PROG) $1 "$2"
	$(if $(STRIP),$(STRIP) $(foreach T,$1,"$2/$(notdir $T)"),)
	endef

	# find-in-path
	# Usage: $(call find-in-path, prog)
	# Looks in the PATH if the argument contains no slash, else only considers one
	# specific directory. Returns an # empty string if the program doesn't exist
	# there.
	find-in-path = $(if $(findstring /, $1), \
	$(wildcard $1), \
	$(wildcard $(patsubst %, %/$1, $(subst :, ,$(PATH)))))

	# Logical functions (for operating on y/n values like CONFIG_FOO vars)
	# Inputs to these must be either "y" (true) or "n" or "" (both false)
	# Output is always either "y" or "n".
	# Usage: $(call land,$(CONFIG_FOO),$(CONFIG_BAR))
	# Logical NOT
	lnot = $(if $(subst n,,$1),n,y)
	# Logical AND
	land = $(if $(findstring yy,$1$2),y,n)
	# Logical OR
	lor = $(if $(findstring y,$1$2),y,n)
	# Logical XOR (note that this is the inverse of leqv)
	lxor = $(if $(filter $(call lnot,$1),$(call lnot,$2)),n,y)
	# Logical equivalence (note that leqv "","n" is true)
	leqv = $(if $(filter $(call lnot,$1),$(call lnot,$2)),y,n)
	# Logical if: like make's $(if) but with an leqv-like test
	lif = $(if $(subst n,,$1),$2,$3)

	# String testing functions: inputs to these can be any string;
	# the output is always either "y" or "n". Leading and trailing whitespace
	# is ignored when comparing strings.
	# String equality
	eq = $(if $(subst $2,,$1)$(subst $1,,$2),n,y)
	# String inequality
	ne = $(if $(subst $2,,$1)$(subst $1,,$2),y,n)
	# Emptiness/non-emptiness tests:
	isempty = $(if $1,n,y)
	notempty = $(if $1,y,n)

	# Generate files with tracetool
	TRACETOOL=$(PYTHON) $(SRC_PATH)/scripts/tracetool.py

	# Generate timestamp files for .h include files

	config-%.h: config-%.h-timestamp
	@cmp $< $@ >/dev/null 2>&1 \|\| cp $< $@

	config-%.h-timestamp: config-%.mak $(SRC_PATH)/scripts/create_config
	$(call quiet-command, sh $(SRC_PATH)/scripts/create_config < $< > $@,"GEN","$(TARGET_DIR)config-$*.h")

	.PHONY: clean-timestamp
	clean-timestamp:
	rm -f *.timestamp
	clean: clean-timestamp

	# will delete the target of a rule if commands exit with a nonzero exit status
	.DELETE_ON_ERROR:

	# save-vars
	# Usage: $(call save-vars, vars)
	# Save each variable $v in $vars as save-vars-$v, save their object's
	# variables, then clear $v. saved-vars-$v contains the variables that
	# where saved for the objects, in order to speedup load-vars.
	define save-vars
	$(foreach v,$1,
	$(eval save-vars-$v := $(value $v))
	$(eval saved-vars-$v := $(foreach o,$($v), \
	$(if $($o-cflags), $o-cflags $(eval save-vars-$o-cflags := $($o-cflags))$(eval $o-cflags := )) \
	$(if $($o-libs), $o-libs $(eval save-vars-$o-libs := $($o-libs))$(eval $o-libs := )) \
	$(if $($o-objs), $o-objs $(eval save-vars-$o-objs := $($o-objs))$(eval $o-objs := ))))
	$(eval $v := ))
	endef

	# load-vars
	# Usage: $(call load-vars, vars, add_var)
	# Load the saved value for each variable in @vars, and the per object
	# variables.
	# Append @add_var's current value to the loaded value.
	define load-vars
	$(eval $2-new-value := $(value $2))
	$(foreach v,$1,
	$(eval $v := $(value save-vars-$v))
	$(foreach o,$(saved-vars-$v),
	$(eval $o := $(save-vars-$o)) $(eval save-vars-$o := ))
	$(eval save-vars-$v := )
	$(eval saved-vars-$v := ))
	$(eval $2 := $(value $2) $($2-new-value))
	endef

	# fix-paths
	# Usage: $(call fix-paths, obj_path, src_path, vars)
	# Add prefix @obj_path to all objects in @vars, and add prefix @src_path to all
	# directories in @vars.
	define fix-paths
	$(foreach v,$3,
	$(foreach o,$($v),
	$(if $($o-libs),
	$(eval $1$o-libs := $($o-libs)))
	$(if $($o-cflags),
	$(eval $1$o-cflags := $($o-cflags)))
	$(if $($o-objs),
	$(eval $1$o-objs := $(addprefix $1,$($o-objs)))))
	$(eval $v := $(addprefix $1,$(filter-out %/,$($v))) \
	$(addprefix $2,$(filter %/,$($v)))))
	endef

	# unnest-var-recursive
	# Usage: $(call unnest-var-recursive, obj_prefix, vars, var)
	#
	# Unnest @var by including subdir Makefile.objs, while protect others in @vars
	# unchanged.
	#
	# @obj_prefix is the starting point of object path prefix.
	#
	define unnest-var-recursive
	$(eval dirs := $(sort $(filter %/,$($3))))
	$(eval $3 := $(filter-out %/,$($3)))
	$(foreach d,$(dirs:%/=%),
	$(call save-vars,$2)
	$(eval obj := $(if $1,$1/)$d)
	$(eval -include $(SRC_PATH)/$d/Makefile.objs)
	$(call fix-paths,$(if $1,$1/)$d/,$d/,$2)
	$(call load-vars,$2,$3)
	$(call unnest-var-recursive,$1,$2,$3))
	endef

	# unnest-vars
	# Usage: $(call unnest-vars, obj_prefix, vars)
	#
	# @obj_prefix: object path prefix, can be empty, or '..', etc. Don't include
	# ending '/'.
	#
	# @vars: the list of variable names to unnest.
	#
	# This macro will scan subdirectories's Makefile.objs, include them, to build
	# up each variable listed in @vars.
	#
	# Per object and per module cflags and libs are saved with relative path fixed
	# as well, those variables include -libs, -cflags and -objs. Items in -objs are
	# also fixed to relative path against SRC_PATH plus the prefix @obj_prefix.
	#
	# All nested variables postfixed by -m in names are treated as DSO variables,
	# and will be built as modules, if enabled.
	#
	# A simple example of the unnest:
	#
	# obj_prefix = ..
	# vars = hot cold
	# hot = fire.o sun.o season/
	# cold = snow.o water/ season/
	#
	# Unnest through a faked source directory structure:
	#
	# SRC_PATH
	# ├── water
	# │ └── Makefile.objs──────────────────┐
	# │ │ hot += steam.o │
	# │ │ cold += ice.mo │
	# │ │ ice.mo-libs := -licemaker │
	# │ │ ice.mo-objs := ice1.o ice2.o │
	# │ └──────────────────────────────┘
	# │
	# └── season
	# └── Makefile.objs──────┐
	# │ hot += summer.o │
	# │ cold += winter.o │
	# └──────────────────┘
	#
	# In the end, the result will be:
	#
	# hot = ../fire.o ../sun.o ../season/summer.o
	# cold = ../snow.o ../water/ice.mo ../season/winter.o
	# ../water/ice.mo-libs = -licemaker
	# ../water/ice.mo-objs = ../water/ice1.o ../water/ice2.o
	#
	# Note that 'hot' didn't include 'water/' in the input, so 'steam.o' is not
	# included.
	#
	define unnest-vars
	# In the case of target build (i.e. $1 == ..), fix path for top level
	# Makefile.objs objects
	$(if $1,$(call fix-paths,$1/,,$2))

	# Descend and include every subdir Makefile.objs
	$(foreach v, $2,
	$(call unnest-var-recursive,$1,$2,$v)
	# Pass the .mo-cflags and .mo-libs along to its member objects
	$(foreach o, $(filter %.mo,$($v)),
	$(foreach p,$($o-objs),
	$(if $($o-cflags), $(eval $p-cflags += $($o-cflags)))
	$(if $($o-libs), $(eval $p-libs += $($o-libs))))))

	# For all %.mo objects that are directly added into -y, just expand them
	$(foreach v,$(filter %-y,$2),
	$(eval $v := $(foreach o,$($v),$(if $($o-objs),$($o-objs),$o))))

	$(foreach v,$(filter %-m,$2),
	# All .o found in *-m variables are single object modules, create .mo
	# for them
	$(foreach o,$(filter %.o,$($v)),
	$(eval $(o:%.o=%.mo)-objs := $o))
	# Now unify .o in -m variable to .mo
	$(eval $v := $($v:%.o=%.mo))
	$(eval modules-m += $($v))

	# For module build, build shared libraries during "make modules"
	# For non-module build, add -m to -y
	$(if $(CONFIG_MODULES),
	$(foreach o,$($v),
	$(eval $($o-objs): CFLAGS += $(DSO_OBJ_CFLAGS))
	$(eval $o: $($o-objs)))
	$(eval $(patsubst %-m,%-y,$v) += $($v))
	$(eval modules: $($v:%.mo=%$(DSOSUF))),
	$(eval $(patsubst %-m,%-y,$v) += $(call expand-objs, $($v)))))

	# Post-process all the unnested vars
	$(foreach v,$2,
	$(foreach o, $(filter %.mo,$($v)),
	# Find all the .mo objects in variables and add dependency rules
	# according to .mo-objs. Report error if not set
	$(if $($o-objs),
	$(eval $(o:%.mo=%$(DSOSUF)): module-common.o $($o-objs)),
	$(error $o added in $v but $o-objs is not set)))
	$(shell mkdir -p ./ $(sort $(dir $($v))))
	# Include all the .d files
	$(eval -include $(patsubst %.o,%.d,$(patsubst %.mo,%.d,$($v))))
	$(eval $v := $(filter-out %/,$($v))))
	endef

	TEXI2MAN = $(call quiet-command, \
	perl -Ww -- $(SRC_PATH)/scripts/texi2pod.pl $(TEXI2PODFLAGS) $< $@.pod && \
	$(POD2MAN) --section=$(subst .,,$(suffix $@)) --center=" " --release=" " $@.pod > $@, \
	"GEN","$@")

	%.1:
	$(call TEXI2MAN)
	%.7:
	$(call TEXI2MAN)
	%.8:
	$(call TEXI2MAN)

	GEN_SUBST = $(call quiet-command, \
	sed -e "s!@libexecdir@!$(libexecdir)!g" < $< > $@, \
	"GEN","$@")

	%.json: %.json.in
	$(call GEN_SUBST)