inconsistency of 'emptiness'?

[gk]

I have noticed inconsistent behavior when a variable contains a single space:
* If the variable comes from the command-line, make thinks it is empty
* If the variable is set in the makefile, make knows it is not empty

# Makefile
.PHONY: test
i:=
ifdef internal
FOO:=$i #
endif

list:=hi there

# if not empty, we clear the list
ifneq ($(FOO),)
list:=
endif

test:
        @echo $(list)
        @echo FOO: origin=$(origin FOO)
#eof

address@hidden junk]$ make
hi there
FOO: origin=undefined
address@hidden junk]$ make FOO=' '
hi there
FOO: origin=command line
address@hidden junk]$ make internal=1

FOO: origin=file
address@hidden junk]$

Does this make sense? Is it documented? Is it a bug?

- Greg Keraunen
http://www.xmake.org
http://www.xmlmake.com