Question

For example, I have a variable $(modules), and this variable contains a list (string separated by spaces) of objects, like “Modules = obj1 obj2…” so on.

Each of the obj in the modules also contains a list, let’s say “obj1 = obj1a obj1b…” so on.

Now, I want to make a variable to contain all these lowest level variables (e.g. obj1a), for example, “$(variable) = obj1a obj1b…obj2a obj2b…”

I tried $($(modules))… it obviously didn’t work…

Answer 1

Use foreach function:

MODULES := foo bar baz

foo := a b c
bar := i j k
baz := x y z

FLAT_MODULES := $(foreach m,$(MODULES),$($m))
# FLAT_MODULES is now 'a b c i j k x y z'