Variables defined *and* undefined

Question

I guess this makes sense somehow, but I can't grasp why: In the following code, I get both warnings (note that the original code was indented with tabs):

define variable-definition
    ifndef $1
        $(warning $1 is undefined)
    else
        $(warning $1 is defined)
    endif
endef

PS: I want to check whether the variable with the name passed as $1 exists, not whether $1 was passed.

PPS: Dedenting the entire thing doesn't help.

Answer 1

Beta's analysis of the root cause is correct, you're not escaping your $ on the $(warning) calls. Here's how I'd fix it:

define variable-def
  ifndef $1
    $$(warning $1 is undefined)
  else
    $$(warning $1 is defined)
  endif
endef
FOO=bar
$(eval $(call variable-def,FOO))

Note that I am indenting with spaces, not tabs. If you indent with tabs, you get this error: *** commands commence before first target. Stop.

This uses GNUisms, but so does your sample (I think).