Question

I have this

SRC = file1.c file2.c file3.c

How do I make it into

file1.c + file2.c + file3.c

The closest I can get is (note the ‘+’ sign at the end)

file1.c + file2.c + file3.c +

using

SRC2 := $(SRC:.c=.c +)

Answer 1

Here’s one way to do it:

SRC=abc def ghi
SRC2=$(word 1,$(SRC))$(foreach f,$(wordlist 2,99999,$(SRC)), + $(f))
all:
        @echo $(SRC2)

That is, peel off the first word, then unconditionally add each additional word with the “+” prefix.

Here’s another, only works if you’re sure you have exactly one space between each word in SRC.

EMPTY=
SPACE=$(EMPTY) $(EMPTY)
SRC=abc def ghi
SRC2=$(subst $(SPACE), $(SPACE)+$(SPACE),$(SRC))
all:
        @echo $(SRC2)

This time the idea is to replace a single space character with the sequence space-plus-space. Make sure you don’t have a space between the comma and $(SRC)!