####
  # kbuild: Generic definitions

  # Convenient variables

  comma   := ,

  quote   := "

  squote  := '

  empty   :=
  space   := $(empty) $(empty)
  
  ###

  # 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)

  
  ###

  # filename of target with directory and extension stripped
  basetarget = $(basename $(notdir $@))
  
  ###

  # filename of first prerequisite with directory and extension stripped
  baseprereq = $(basename $(notdir $<))
  
  ###

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

  # Easy method for doing a status message
         kecho := :
   quiet_kecho := echo
  silent_kecho := :
  kecho := $($(quiet)kecho)
  
  ###

  # filechk is used to check if the content of a generated file is updated.
  # Sample usage:
  # define filechk_sample
  #	echo $KERNELRELEASE
  # endef
  # version.h : Makefile
  #	$(call filechk,sample)
  # The rule defined shall write to stdout the content of the new file.
  # The existing file will be compared with the new one.
  # - If no file exist it is created
  # - If the content differ the new file is used
  # - If they are equal no change, and no timestamp update
  # - stdin is piped in from the first prerequisite ($<) so one has
  #   to specify a valid file as first prerequisite (often the kbuild file)
  define filechk
  	$(Q)set -e;				\

  	$(kecho) '  CHK     $@';		\

  	mkdir -p $(dir $@);			\
  	$(filechk_$(1)) < $< > $@.tmp;		\
  	if [ -r $@ ] && cmp -s $@ $@.tmp; then	\
  		rm -f $@.tmp;			\
  	else					\

  		$(kecho) '  UPD     $@';	\

  		mv -f $@.tmp $@;		\
  	fi
  endef

  ######

  # gcc support functions

  # See documentation in Documentation/kbuild/makefiles.txt

  # cc-cross-prefix
  # Usage: CROSS_COMPILE := $(call cc-cross-prefix, m68k-linux-gnu- m68k-linux-)
  # Return first prefix where a prefix$(CC) is found in PATH.
  # If no $(CC) found in PATH with listed prefixes return nothing
  cc-cross-prefix =  \
  	$(word 1, $(foreach c,$(1),                                   \
  		$(shell set -e;                                       \
  		if (which $(strip $(c))$(CC)) > /dev/null 2>&1 ; then \
  			echo $(c);                                    \
  		fi)))

  # output directory for tests below
  TMPOUT := $(if $(KBUILD_EXTMOD),$(firstword $(KBUILD_EXTMOD))/)
  
  # 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")

  # as-option

  # Usage: cflags-y += $(call as-option,-Wa$(comma)-isa=foo,)

  
  as-option = $(call try-run,\

  	$(CC) $(KBUILD_CFLAGS) $(1) -c -x assembler /dev/null -o "$$TMP",$(1),$(2))

  # as-instr

  # Usage: cflags-y += $(call as-instr,instr,option1,option2)

  
  as-instr = $(call try-run,\

  	printf "%b
  " "$(1)" | $(CC) $(KBUILD_AFLAGS) -c -x assembler -o "$$TMP" -,$(2),$(3))

  # cc-option

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

  
  cc-option = $(call try-run,\

  	$(CC) $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS) $(1) -c -x c /dev/null -o "$$TMP",$(1),$(2))

  
  # cc-option-yn

  # Usage: flag := $(call cc-option-yn,-march=winchip-c6)

  cc-option-yn = $(call try-run,\

  	$(CC) $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS) $(1) -c -x c /dev/null -o "$$TMP",y,n)

  
  # cc-option-align
  # Prefix align with either -falign or -malign
  cc-option-align = $(subst -functions=0,,\

  	$(call cc-option,-falign-functions=0,-malign-functions=0))

  # cc-disable-warning
  # Usage: cflags-y += $(call cc-disable-warning,unused-but-set-variable)
  cc-disable-warning = $(call try-run,\

  	$(CC) $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS) -W$(strip $(1)) -c -x c /dev/null -o "$$TMP",-Wno-$(strip $(1)))

  # cc-version

  # Usage gcc-ver := $(call cc-version)

  cc-version = $(shell $(CONFIG_SHELL) $(srctree)/scripts/gcc-version.sh $(CC))

  # cc-fullversion
  # Usage gcc-ver := $(call cc-fullversion)
  cc-fullversion = $(shell $(CONFIG_SHELL) \
  	$(srctree)/scripts/gcc-version.sh -p $(CC))

  # cc-ifversion
  # Usage:  EXTRA_CFLAGS += $(call cc-ifversion, -lt, 0402, -O1)

  cc-ifversion = $(shell [ $(call cc-version, $(CC)) $(1) $(2) ] && echo $(3))

  # cc-ldoption
  # Usage: ldflags += $(call cc-ldoption, -Wl$(comma)--hash-style=both)
  cc-ldoption = $(call try-run,\

  	$(CC) $(1) -nostdlib -x c /dev/null -o "$$TMP",$(1),$(2))

  # ld-option
  # Usage: LDFLAGS += $(call ld-option, -X)
  ld-option = $(call try-run,\

  	$(CC) -x c /dev/null -c -o "$$TMPO" ; $(LD) $(1) "$$TMPO" -o "$$TMP",$(1),$(2))

  # ar-option
  # Usage: KBUILD_ARFLAGS := $(call ar-option,D)
  # Important: no spaces around options
  ar-option = $(call try-run, $(AR) rc$(1) "$$TMP",$(1),$(2))

  # ld-version
  # Usage: $(call ld-version)
  # Note this is mainly for HJ Lu's 3 number binutil versions
  ld-version = $(shell $(LD) --version | $(srctree)/scripts/ld-version.sh)
  
  # ld-ifversion
  # Usage:  $(call ld-ifversion, -ge, 22252, y)
  ld-ifversion = $(shell [ $(call ld-version) $(1) $(2) ] && echo $(3))

  ######

  ###

  # Shorthand for $(Q)$(MAKE) -f scripts/Makefile.build obj=
  # Usage:
  # $(Q)$(MAKE) $(build)=dir

  build := -f $(srctree)/scripts/Makefile.build obj

  ###
  # Shorthand for $(Q)$(MAKE) -f scripts/Makefile.modbuiltin obj=
  # Usage:
  # $(Q)$(MAKE) $(modbuiltin)=dir

  modbuiltin := -f $(srctree)/scripts/Makefile.modbuiltin obj

  # Prefix -I with $(srctree) if it is not an absolute path.

  # skip if -I has no parameter
  addtree = $(if $(patsubst -I%,%,$(1)), \
  $(if $(filter-out -I/%,$(1)),$(patsubst -I%,-I$(srctree)/%,$(1))) $(1))

  # Find all -I options and call addtree

  flags = $(foreach o,$($(1)),$(if $(filter -I%,$(o)),$(call addtree,$(o)),$(o)))

  # 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)';)
  
  # printing commands

  cmd = @$(echo-cmd) $(cmd_$(1))

  # Add $(obj)/ for paths that are not absolute

  objectify = $(foreach o,$(1),$(if $(filter /%,$(o)),$(o),$(obj)/$(o)))

  ###

  # if_changed      - execute command if any prerequisite is newer than

  #                   target, or command line has changed
  # if_changed_dep  - as if_changed, but uses fixdep to reveal dependencies
  #                   including used config symbols
  # if_changed_rule - as if_changed but execute rule instead
  # See Documentation/kbuild/makefiles.txt for more info
  
  ifneq ($(KBUILD_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))) )

  else
  arg-check = $(if $(strip $(cmd_$@)),,1)

  endif

  # Replace >$< with >$$< to preserve $ when reloading the .cmd file
  # (needed for make)
  # Replace >#< with >\#< to avoid starting a comment in the .cmd file
  # (needed for make)
  # Replace >'< with >'\''< to be able to enclose the whole string in '...'
  # (needed for the shell)
  make-cmd = $(call escsq,$(subst \#,\\\#,$(subst $$,$$$$,$(cmd_$(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));                                             \

  	printf '%s
  ' 'cmd_$@ := $(make-cmd)' > $(dot-target).cmd)

  # Execute the command and also postprocess generated .d dependencies file.

  if_changed_dep = $(if $(strip $(any-prereq) $(arg-check) ),                  \
  	@set -e;                                                             \
  	$(echo-cmd) $(cmd_$(1));                                             \
  	scripts/basic/fixdep $(depfile) $@ '$(make-cmd)' > $(dot-target).tmp;\
  	rm -f $(depfile);                                                    \
  	mv -f $(dot-target).tmp $(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)))

  ###
  # why - tell why a a target got build
  #       enabled by make V=2
  #       Output (listed in the order they are checked):
  #          (1) - due to target is PHONY
  #          (2) - due to target missing
  #          (3) - due to: file1.h file2.h
  #          (4) - due to command line change
  #          (5) - due to missing .cmd file
  #          (6) - due to target not in $(targets)
  # (1) PHONY targets are always build
  # (2) No target, so we better build it
  # (3) Prerequisite is newer than target
  # (4) The command line stored in the file named dir/.target.cmd
  #     differed from actual command line. This happens when compiler
  #     options changes
  # (5) No dir/.target.cmd file (used to store command line)
  # (6) No dir/.target.cmd file and target not listed in $(targets)
  #     This is a good hint that there is a bug in the kbuild file
  ifeq ($(KBUILD_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,             \
                          $(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