ifneq ($(O),)ifeq ($(origin O), command line)	dummy := $(if $(shell test -d $(O) || echo $(O)),$(error O=$(O) does not exist),)	ABSOLUTE_O := $(shell cd $(O) ; pwd)	OUTPUT := $(ABSOLUTE_O)/$(if $(subdir),$(subdir)/)	COMMAND_O := O=$(ABSOLUTE_O)ifeq ($(objtree),)	objtree := $(O)endifendifendif # check that the output directory actually existsifneq ($(OUTPUT),)OUTDIR := $(shell cd $(OUTPUT) && /bin/pwd)$(if $(OUTDIR),, $(error output directory "$(OUTPUT)" does not exist))endif ## Include saner warnings here, which can catch bugs:#EXTRA_WARNINGS := -Wbad-function-castEXTRA_WARNINGS += -Wdeclaration-after-statementEXTRA_WARNINGS += -Wformat-securityEXTRA_WARNINGS += -Wformat-y2kEXTRA_WARNINGS += -Winit-selfEXTRA_WARNINGS += -Wmissing-declarationsEXTRA_WARNINGS += -Wmissing-prototypesEXTRA_WARNINGS += -Wnested-externsEXTRA_WARNINGS += -Wno-system-headersEXTRA_WARNINGS += -Wold-style-definitionEXTRA_WARNINGS += -WpackedEXTRA_WARNINGS += -Wredundant-declsEXTRA_WARNINGS += -WshadowEXTRA_WARNINGS += -Wstrict-aliasing=3EXTRA_WARNINGS += -Wstrict-prototypesEXTRA_WARNINGS += -Wswitch-defaultEXTRA_WARNINGS += -Wswitch-enumEXTRA_WARNINGS += -WundefEXTRA_WARNINGS += -Wwrite-stringsEXTRA_WARNINGS += -Wformat ifneq ($(findstring $(MAKEFLAGS), w),w)PRINT_DIR = --no-print-directoryelseNO_SUBDIR = :endif ## Define a callable command for descending to a new directory## Call by doing: $(call descend,directory[,target])#descend = \	+mkdir -p $(OUTPUT)$(1) && \	$(MAKE) $(COMMAND_O) subdir=$(if $(subdir),$(subdir)/$(1),$(1)) $(PRINT_DIR) -C $(1) $(2) QUIET_SUBDIR0  = +$(MAKE) $(COMMAND_O) -C # space to separate -C and subdirQUIET_SUBDIR1  = ifneq ($(findstring $(MAKEFLAGS),s),s)  ifneq ($(V),1)	QUIET_CC       = @echo '  CC       '$@;	QUIET_CC_FPIC  = @echo '  CC FPIC  '$@;	QUIET_AR       = @echo '  AR       '$@;	QUIET_LINK     = @echo '  LINK     '$@;	QUIET_MKDIR    = @echo '  MKDIR    '$@;	QUIET_GEN      = @echo '  GEN      '$@;	QUIET_SUBDIR0  = +@subdir=	QUIET_SUBDIR1  = ;$(NO_SUBDIR) \			  echo '  SUBDIR   '$$subdir; \			 $(MAKE) $(PRINT_DIR) -C $$subdir	QUIET_FLEX     = @echo '  FLEX     '$@;	QUIET_BISON    = @echo '  BISON    '$@; 	descend = \		+@echo	       '  DESCEND  '$(1); \		mkdir -p $(OUTPUT)$(1) && \		$(MAKE) $(COMMAND_O) subdir=$(if $(subdir),$(subdir)/$(1),$(1)) $(PRINT_DIR) -C $(1) $(2) 	QUIET_CLEAN    = @printf '  CLEAN    %s\n' $1;	QUIET_INSTALL  = @printf '  INSTALL  %s\n' $1;  endifendif