empty:=
space:= $(empty) $(empty)
+comma:=,
merge=$(subst $(space),,$(1))
confvar=$(call merge,$(foreach v,$(1),$(if $($(v)),y,n)))
strip_last=$(patsubst %.$(lastword $(subst .,$(space),$(1))),%,$(1))
endef
define shexport
-$(call shvar,$(1))=$$(call $(1))
-export $(call shvar,$(1))
+export $(call shvar,$(1))=$$(call $(1))
endef
define include_mk