Q:

GNU Make: how to join list and separate it with separator?

I have this:
FOO = foo1 foo2 ... fooN

and want to get join all these string and separate it with, for instance, colong:
foo1:foo2:foo3:...:fooN

How to do this in GNU Make, without using external UNIX tools?

A:

See the code below.
# A literal space.
space :=
space +=

# Joins elements of the list in arg 2 with the given separator.
#   1. Element separator.
#   2. The list.
join-with = $(subst $(space),$1,$(strip $2))

Usage:
FOO = foo1 foo2 ... fooN

COLON_SEPARATED_FOO := $(call join-with,:,$(FOO))

A:

You can simply replace spaces with colon:
EMPTY :=
SPACE := $(EMPTY) $(EMPTY)
FOO = foo1 foo2 ... fooN
FOO_LIST = $(subst $(SPACE),:,$(FOO))

FOO_LIST is foo1:foo2:...:fooN.

