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##
# A set of makefile rules loosely based on kbuild.

all: compile

ifndef build

toplevelrun:=yes

##
# Disable default rules and make output pretty.

MAKEFLAGS += -rR --no-print-directory

Makefile: ;

ifdef V
  ifeq ("$(origin V)", "command line")
    VERBOSE = $(V)
  endif
endif
ifndef VERBOSE
  VERBOSE = 0
endif

ifeq ($(VERBOSE),1)
  quiet =
  Q =
else
  quiet=quiet_
  Q = @
endif

ifneq ($(findstring s,$(MAKEFLAGS)),)
  quiet=silent_
endif

export quiet Q VERBOSE

##
# Recursion helpers.
srctree		:= $(CURDIR)
objtree		:= $(CURDIR)

export srctree objtree

##
# Consult SCM for better version string.

GIT_REV := $(shell test -d .git && git describe || echo exported)
ifneq ($(GIT_REV), exported)
FULL_VERSION	:= $(patsubst $(TAGPREFIX)%,%,$(GIT_REV))
else
FULL_VERSION	:= $(VERSION)
endif

RCS_FIND_IGNORE := \( -name SCCS -o -name BitKeeper -o -name .svn -o -name CVS -o -name .pc -o -name .hg -o -name .git \) -prune -o

export FULL_VERSION RCS_FIND_IGNORE

##
# Utilities and default flags for them.

CROSS_COMPILE	?=
CC		:= $(CROSS_COMPILE)gcc
LD		:= $(CROSS_COMPILE)ld
INSTALL		:= install
INSTALLDIR	:= $(INSTALL) -d

CFLAGS		?= -g -O2
CFLAGS_ALL	:= -Werror -Wall -Wstrict-prototypes -D_GNU_SOURCE -std=gnu99
CFLAGS_ALL	+= $(CFLAGS)

LDFLAGS		?= -g
LDFLAGS_ALL	+= $(LDFLAGS)

export CC LD INSTALL INSTALLDIR CFLAGS_ALL LDFLAGS_ALL

build		:=

endif

##
# Reset all variables.
ifneq ($(origin targets),file)
targets		:=
endif

src		:=
obj		:=

src		+= $(build)
obj		:= $(build)

##
# Include directory specific stuff

ifneq ($(build),)
$(build)/Makefile: ;
include $(build)/Makefile
endif

##
# Rules and helpers

PHONY += all compile install clean FORCE

# Convinient variables
comma   := ,
squote  := '
empty   :=
space   := $(empty) $(empty)

# The temporary file to save gcc -MD generated dependencies must not
# contain a comma
depfile = $(subst $(comma),_,$(@D)/.$(@F).d)

build-dir  = $(patsubst %/,%,$(dir $@))
target-dir = $(dir $@)

##
# Build rules

ifneq ($(NOCMDDEP),1)
# Check if both arguments has same arguments. Result in empty string if equal
# User may override this check using make NOCMDDEP=1
# Check if both arguments has same arguments. Result is empty string if equal.
# User may override this check using make KBUILD_NOCMDDEP=1
arg-check = $(strip $(filter-out $(cmd_$(1)), $(cmd_$@)) \
                    $(filter-out $(cmd_$@),   $(cmd_$(1))) )
endif

# echo command.
# Short version is used, if $(quiet) equals `quiet_', otherwise full one.
echo-cmd = $(if $($(quiet)cmd_$(1)),\
	echo '  $(call escsq,$($(quiet)cmd_$(1)))$(echo-why)';)

make-cmd = $(subst \#,\\\#,$(subst $$,$$$$,$(call escsq,$(cmd_$(1)))))

# printing commands
cmd = @$(echo-cmd) $(cmd_$(1))

# Name of target with a '.' as filename prefix. foo/bar.o => foo/.bar.o
dot-target = $(dir $@).$(notdir $@)

# The temporary file to save gcc -MD generated dependencies must not
# contain a comma
depfile = $(subst $(comma),_,$(dot-target).d)

# Escape single quote for use in echo statements
escsq = $(subst $(squote),'\$(squote)',$1)

# Find any prerequisites that is newer than target or that does not exist.
# PHONY targets skipped in both cases.
any-prereq = $(filter-out $(PHONY),$?) $(filter-out $(PHONY) $(wildcard $^),$^)

# Execute command if command has changed or prerequisite(s) are updated.
#
if_changed = $(if $(strip $(any-prereq) $(arg-check)),                       \
	@set -e;                                                             \
	$(echo-cmd) $(cmd_$(1));                                             \
	echo 'cmd_$@ := $(make-cmd)' > $(dot-target).cmd)

# Usage: $(call if_changed_rule,foo)
# Will check if $(cmd_foo) or any of the prerequisites changed,
# and if so will execute $(rule_foo).
if_changed_rule = $(if $(strip $(any-prereq) $(arg-check) ),                 \
	@set -e;                                                             \
	$(rule_$(1)))

#####
# Handle options to gcc.

c_flags		= -Wp,-MD,$(depfile),-MT,$@ $(CFLAGS_ALL) $(CFLAGS_EXTRA) \
		  $(CFLAGS_$(notdir $@))
ld_flags	= $(LDFLAGS_ALL) $(LDFLAGS_EXTRA) $(LDFLAGS_$(notdir $@))

#####
# Compile c-files.
quiet_cmd_cc_o_c = CC      $@

cmd_cc_o_c = $(CC) $(c_flags) -c -o $@ $<

define rule_cc_o_c
	$(call echo-cmd,cc_o_c) $(cmd_cc_o_c);		\
	(echo 'cmd_$@ := $(call make-cmd,cc_o_c)'; echo; cat $(depfile)) \
		> $(dot-target).cmd ; \
	rm $(depfile)
endef

$(obj)/%.o: $(src)/%.c FORCE
	$(call if_changed_rule,cc_o_c)

#####
# Link programs

# Link an executable based on list of .o files, all plain c
# host-cmulti -> executable
__progs	:= $(addprefix $(obj)/,$(sort $(progs-y)))
cobjs	:= $(addprefix $(obj)/,$(sort $(foreach m,$(progs-y),$($(m)-objs))))

quiet_cmd_ld	= LD      $@
      cmd_ld	= $(CC) $(ld_flags) -o $@ \
			  $(addprefix $(obj)/,$($(@F)-objs)) \
			  $(LIBS) $(LIBS_$(@F))

$(__progs): $(obj)/%: $(cobjs) FORCE
	$(call if_changed,ld)

targets += $(__progs) $(cobjs)

###
# why - tell why a a target got build
ifeq ($(VERBOSE),2)
why =                                                                        \
    $(if $(filter $@, $(PHONY)),- due to target is PHONY,                    \
        $(if $(wildcard $@),                                                 \
            $(if $(strip $(any-prereq)),- due to: $(any-prereq),             \
                $(if $(arg-check),                                           \
                    $(if $(cmd_$@),- due to command line change: $(arg-check),             \
                        $(if $(filter $@, $(targets)),                       \
                            - due to missing .cmd file,                      \
                            - due to $(notdir $@) not in $$(targets)         \
                         )                                                   \
                     )                                                       \
                 )                                                           \
             ),                                                              \
             - due to target missing                                         \
         )                                                                   \
     )

echo-why = $(call escsq, $(strip $(why)))
endif

##
# Top level rules.

%/: FORCE
	$(Q)$(MAKE) -f Make.rules build=$(build-dir) $(MAKECMDGOALS)

compile: $(targets)
	@:

install: $(targets) FORCE

clean: $(filter %/,$(targets))
ifeq ($(toplevelrun),yes)
	$(Q)find . $(RCS_FIND_IGNORE) \
		\( -name '*.[oas]' -o -name '.*.cmd' -o -name '.*.d' \) \
		-type f -print | xargs rm -f
endif
	$(Q)rm -rf $(addprefix $(obj)/,$(sort $(progs-y) $(progs-n) $(progs-)))

ifeq ($(origin VERSION),command line)
DIST_VERSION=$(VERSION)
else
DIST_VERSION=$(FULL_VERSION)
endif

dist:
	git archive --format tar --prefix=$(PACKAGE)-$(DIST_VERSION)/ \
		$(TAGPREFIX)$(DIST_VERSION) \
		| bzip2 -9 > $(PACKAGE)-$(DIST_VERSION).tar.bz2

FORCE:

# Read all saved command lines and dependencies for the $(targets) we
# may be building above, using $(if_changed{,_dep}). As an
# optimization, we don't need to read them if the target does not
# exist, we will rebuild anyway in that case.

targets := $(wildcard $(sort $(targets)))
cmd_files := $(wildcard $(foreach f,$(targets),$(dir $(f)).$(notdir $(f)).cmd))

ifneq ($(cmd_files),)
  include $(cmd_files)
endif

# Declare the contents of the .PHONY variable as phony.  We keep that
# information in a variable se we can use it in if_changed and friends.

.PHONY: $(PHONY)