Makefile set if variable is empty

Question

I want to set a variable if it is empty. I tried in this way:

....
TEST := $(something)
...
TEST ?= $(something else)

The first $(somethi

Answer 1

In case you need to distinguish if a variable is undefined or just has an empty value, use $(origin VARNAME) function:

ifeq ($(origin VARNAME),undefined)
VARNAME := "now it's finally defined"
endif

Note that VARNAME is not surrounded by $() - you literally give the name of the variable.