+# must come rather early
+.SECONDEXPANSION:
+
+$(obj)/config.h:
+ $(MAKE) oldconfig
+
+# Add a new class of source/object files to the build system
+add-class= \
+ $(eval $(1)-srcs:=) \
+ $(eval $(1)-objs:=) \
+ $(eval classes+=$(1))
+
+# Special classes are managed types with special behaviour
+# On parse time, for each entry in variable $(1)-y
+# a handler $(1)-handler is executed with the arguments:
+# * $(1): directory the parser is in
+# * $(2): current entry
+add-special-class= \
+ $(eval $(1):=) \
+ $(eval special-classes+=$(1))
+
+# Clean -y variables, include Makefile.inc
+# Add paths to files in X-y to X-srcs
+# Add subdirs-y to subdirs
+includemakefiles= \
+ $(foreach class,classes subdirs $(classes) $(special-classes), $(eval $(class)-y:=)) \
+ $(eval -include $(1)) \
+ $(foreach class,$(classes-y), $(call add-class,$(class))) \
+ $(foreach class,$(classes), \
+ $(eval $(class)-srcs+= \
+ $$(subst $(top)/,, \
+ $$(abspath $$(addprefix $(dir $(1)),$$($(class)-y)))))) \
+ $(foreach special,$(special-classes), \
+ $(foreach item,$($(special)-y), $(call $(special)-handler,$(dir $(1)),$(item)))) \
+ $(eval subdirs+=$$(subst $(CURDIR)/,,$$(abspath $$(addprefix $(dir $(1)),$$(subdirs-y)))))
+
+# For each path in $(subdirs) call includemakefiles
+# Repeat until subdirs is empty
+evaluate_subdirs= \
+ $(eval cursubdirs:=$(subdirs)) \
+ $(eval subdirs:=) \
+ $(foreach dir,$(cursubdirs), \
+ $(eval $(call includemakefiles,$(dir)/Makefile.inc))) \
+ $(if $(subdirs),$(eval $(call evaluate_subdirs)))
+
+# collect all object files eligible for building
+subdirs:=$(TOPLEVEL)
+$(eval $(call evaluate_subdirs))
+
+src-to-obj=$(addsuffix .$(1).o, $(basename $(addprefix $(obj)/, $($(1)-srcs))))
+$(foreach class,$(classes),$(eval $(class)-objs:=$(call src-to-obj,$(class))))
+
+allsrcs:=$(foreach var, $(addsuffix -srcs,$(classes)), $($(var)))
+allobjs:=$(foreach var, $(addsuffix -objs,$(classes)), $($(var)))
+alldirs:=$(sort $(abspath $(dir $(allobjs))))
+
+# macro to define template macros that are used by use_template macro
+define create_cc_template
+# $1 obj class
+# $2 source suffix (c, S)
+# $3 additional compiler flags
+# $4 additional dependencies
+ifn$(EMPTY)def $(1)-objs_$(2)_template
+de$(EMPTY)fine $(1)-objs_$(2)_template
+$(obj)/$$(1).$(1).o: $$(1).$(2) $(obj)/config.h $(4)
+ @printf " CC $$$$(subst $$$$(obj)/,,$$$$(@))\n"
+ $(CC) $(3) -MMD $$$$(CFLAGS) -c -o $$$$@ $$$$<
+en$(EMPTY)def
+end$(EMPTY)if
+endef
+
+filetypes-of-class=$(subst .,,$(sort $(suffix $($(1)-srcs))))
+$(foreach class,$(classes), \
+ $(foreach type,$(call filetypes-of-class,$(class)), \
+ $(eval $(call create_cc_template,$(class),$(type),$($(class)-$(type)-ccopts),$($(class)-$(type)-deps)))))
+
+foreach-src=$(foreach file,$($(1)-srcs),$(eval $(call $(1)-objs_$(subst .,,$(suffix $(file)))_template,$(basename $(file)))))
+$(eval $(foreach class,$(classes),$(call foreach-src,$(class))))
+
+DEPENDENCIES = $(allobjs:.o=.d)
+-include $(DEPENDENCIES)
+
+printall:
+ @$(foreach class,$(classes),echo $(class)-objs:=$($(class)-objs); )
+ @echo alldirs:=$(alldirs)
+ @echo allsrcs=$(allsrcs)
+ @echo DEPENDENCIES=$(DEPENDENCIES)
+ @echo LIBGCC_FILE_NAME=$(LIBGCC_FILE_NAME)
+ @$(foreach class,$(special-classes),echo $(class):='$($(class))'; )