feature_dir := $(srctree)/tools/build/feature

  ifneq ($(OUTPUT),)

    OUTPUT_FEATURES = $(OUTPUT)feature/

    $(shell mkdir -p $(OUTPUT_FEATURES))
  endif
  
  feature_check = $(eval $(feature_check_code))
  define feature_check_code

    feature-$(1) := $(shell $(MAKE) OUTPUT=$(OUTPUT_FEATURES) CFLAGS="$(EXTRA_CFLAGS) $(FEATURE_CHECK_CFLAGS-$(1))" LDFLAGS="$(LDFLAGS) $(FEATURE_CHECK_LDFLAGS-$(1))" -C $(feature_dir) test-$1.bin >/dev/null 2>/dev/null && echo 1 || echo 0)

  endef
  
  feature_set = $(eval $(feature_set_code))
  define feature_set_code
    feature-$(1) := 1
  endef
  
  #
  # Build the feature check binaries in parallel, ignore errors, ignore return value and suppress output:
  #
  
  #
  # Note that this is not a complete list of all feature tests, just
  # those that are typically built on a fully configured system.
  #
  # [ Feature tests not mentioned here have to be built explicitly in
  #   the rule that uses them - an example for that is the 'bionic'
  #   feature check. ]
  #
  FEATURE_TESTS =			\
  	backtrace			\
  	dwarf				\
  	fortify-source			\
  	sync-compare-and-swap		\
  	glibc				\
  	gtk2				\
  	gtk2-infobar			\
  	libaudit			\
  	libbfd				\
  	libelf				\
  	libelf-getphdrnum		\
  	libelf-mmap			\
  	libnuma				\
  	libperl				\
  	libpython			\
  	libpython-version		\
  	libslang			\
  	libunwind			\
  	pthread-attr-setaffinity-np	\
  	stackprotector-all		\
  	timerfd				\
  	libdw-dwarf-unwind		\

  	zlib				\
  	lzma

  
  FEATURE_DISPLAY =			\
  	dwarf				\
  	glibc				\
  	gtk2				\
  	libaudit			\
  	libbfd				\
  	libelf				\
  	libnuma				\
  	libperl				\
  	libpython			\
  	libslang			\
  	libunwind			\
  	libdw-dwarf-unwind		\

  	zlib				\
  	lzma

  
  # Set FEATURE_CHECK_(C|LD)FLAGS-all for all FEATURE_TESTS features.
  # If in the future we need per-feature checks/flags for features not
  # mentioned in this list we need to refactor this ;-).
  set_test_all_flags = $(eval $(set_test_all_flags_code))
  define set_test_all_flags_code
    FEATURE_CHECK_CFLAGS-all  += $(FEATURE_CHECK_CFLAGS-$(1))
    FEATURE_CHECK_LDFLAGS-all += $(FEATURE_CHECK_LDFLAGS-$(1))
  endef
  
  $(foreach feat,$(FEATURE_TESTS),$(call set_test_all_flags,$(feat)))
  
  #
  # Special fast-path for the 'all features are available' case:
  #
  $(call feature_check,all,$(MSG))
  
  #
  # Just in case the build freshly failed, make sure we print the
  # feature matrix:
  #
  ifeq ($(feature-all), 1)
    #
    # test-all.c passed - just set all the core feature flags to 1:
    #
    $(foreach feat,$(FEATURE_TESTS),$(call feature_set,$(feat)))
  else

    $(shell $(MAKE) OUTPUT=$(OUTPUT_FEATURES) CFLAGS="$(EXTRA_CFLAGS)" LDFLAGS=$(LDFLAGS) -i -j -C $(feature_dir) $(addsuffix .bin,$(FEATURE_TESTS)) >/dev/null 2>&1)

    $(foreach feat,$(FEATURE_TESTS),$(call feature_check,$(feat)))
  endif
  
  #
  # Print the result of the feature test:
  #
  feature_print_status = $(eval $(feature_print_status_code)) $(info $(MSG))
  
  define feature_print_status_code
    ifeq ($(feature-$(1)), 1)
      MSG = $(shell printf '...%30s: [ \033[32mon\033[m  ]' $(1))
    else
      MSG = $(shell printf '...%30s: [ \033[31mOFF\033[m ]' $(1))
    endif
  endef
  
  feature_print_text = $(eval $(feature_print_text_code)) $(info $(MSG))
  define feature_print_text_code
      MSG = $(shell printf '...%30s: %s' $(1) $(2))
  endef
  
  FEATURE_DUMP := $(foreach feat,$(FEATURE_DISPLAY),feature-$(feat)($(feature-$(feat))))
  FEATURE_DUMP_FILE := $(shell touch $(OUTPUT)FEATURE-DUMP; cat $(OUTPUT)FEATURE-DUMP)
  
  ifeq ($(dwarf-post-unwind),1)
    FEATURE_DUMP += dwarf-post-unwind($(dwarf-post-unwind-text))
  endif
  
  # The $(feature_display) controls the default detection message
  # output. It's set if:
  # - detected features differes from stored features from
  #   last build (in FEATURE-DUMP file)
  # - one of the $(FEATURE_DISPLAY) is not detected
  # - VF is enabled
  
  ifneq ("$(FEATURE_DUMP)","$(FEATURE_DUMP_FILE)")
    $(shell echo "$(FEATURE_DUMP)" > $(OUTPUT)FEATURE-DUMP)
    feature_display := 1
  endif
  
  feature_display_check = $(eval $(feature_check_code))
  define feature_display_check_code
    ifneq ($(feature-$(1)), 1)
      feature_display := 1
    endif
  endef
  
  $(foreach feat,$(FEATURE_DISPLAY),$(call feature_display_check,$(feat)))
  
  ifeq ($(VF),1)
    feature_display := 1
    feature_verbose := 1
  endif
  
  ifeq ($(feature_display),1)
    $(info )
    $(info Auto-detecting system features:)
    $(foreach feat,$(FEATURE_DISPLAY),$(call feature_print_status,$(feat),))
  
    ifeq ($(dwarf-post-unwind),1)
      $(call feature_print_text,"DWARF post unwind library", $(dwarf-post-unwind-text))
    endif
  
    ifneq ($(feature_verbose),1)
      $(info )
    endif
  endif
  
  ifeq ($(feature_verbose),1)
    TMP := $(filter-out $(FEATURE_DISPLAY),$(FEATURE_TESTS))
    $(foreach feat,$(TMP),$(call feature_print_status,$(feat),))
    $(info )
  endif