Character Substitution in makefile

[rpaskudniak]

Greetings.

My name is Rasputin and I'm a makefilic. (Obviously not successful as a comic! )

OK, right to the point (well, maybe not so fast - it needs a build-up):

Consider the following sequence of macros and dependencies, which I wish to refine:

M4_MODULES = first.m4 second.m4 third.m4 fourth.m4
C_MODULES  = first.c  second.c  third.c  fourth.c
O_MODULES  = first.o  second.o  third.o  fourth.o
my_program: $(O_MODULES) $(LIBRARIES)

(Yes, lots of steps skipped here; that's not the point of this post.) What's mainly wrong with this is that if I add a fifth module, I have to add fifth.m4, fifth.c, and fifth.o to the respective lines. In a complicated makefile that is error prone. So I came up with the following fix, which does work. (I've tested it.) Note the dot at the end of each module name:

MODULES = first. second. third. fourth.
M4_MODULES = ${MODULES:.=.m4}
C_MODULES  = ${MODULES:.=.c}
O_MODULES  =  ${MODULES:.=.o}

So if it works, what's my problem? Well, it seems the original module names have their own dependency issues. So it really is necessary to specify:

MODULES = first second third fourth

without the terminating dots. Thus, I need to substitute for the end of a string, something like:

M4_MODULES = ${MODULES:$=.m4}

and so on.

The problem is that the above substitution does not work. Neither does $$=.m4 nor does \$=.m4; I'm plumb out of guesses.

SO finally the obvious question:

Does anyone know of an syntax in a makefile macro that will perform end-of-string substitutions?

Thanks much for some assistance with this.

-- Rasputin Paskudniak

[anduril462]

Use the make function patsubst for pattern substitution, and possibly look into the wildcard function for grabbing all .m4 files as a starter:

M4_MODULES = $(wildcard *.m4)
C_MODULES = $(patsubst %.m4, %.c, $(M4_MODULES))
O_MODULES = $(patsubst %.c, %.o, $(C_MODULES))

Make has fantastic documentation with examples online at GNU `make'.

[rpaskudniak]

Use the make function patsubst for pattern substitution, and possibly look into the wildcard function for grabbing all .m4 files as a starter:

M4_MODULES = $(wildcard *.m4)
C_MODULES = $(patsubst %.m4, %.c, $(M4_MODULES))
O_MODULES = $(patsubst %.c, %.o, $(C_MODULES))

Make has fantastic documentation with examples online at GNU `make'.

Whoopie! That did it, with some slight difference WRT your sample code.

Thank you, Anduril! Here's the syntax I used:

MODULES = first second third fourth
M4_MODULES = $(patsubst %,%.m4,$(MODULES))

And it did exactly what I needed!

Yours Gratefully,
Rasputin