Re: use functions to create rules

[Paul Smith]

On Mon, 2012-06-11 at 23:53 -0400, ogronom wrote:
> # --------BEGIN
> tests_SRC=1.c 2.c
> tests=$(tests_SRC:.c=.out))
> 
> define out_template =
> $(DEST_DIR)/$$($(1):.c=.out) : $(1)
>       echo $$@ $(1)
> endef
> 
> $(eval $(call $(out_template 1.c)))
> $(eval $(call $(out_template 2.c)))
> 
> all: $(tests)
> 
> check: $(tests)
>       for f in $(tests) ; do ./$$f ; done
> #---------END

First, you should put "all" closer to the top.  It should be the first
target defined.

> make: *** No rule to make target `1.out', needed by `all'.  Stop.

Your invocation of the $(call ...) function is wrong, first of all.  It
should be:

    $(eval $(call out_template,1.c))
    $(eval $(call out_template,2.c))

The first argument to the call function is expanded and the expansion is
treated as the name of a variable to be used as the user-defined
function.  The remaining arguments are used to replace $1, $2, etc.

In your case, where you write $(call $(out_template 1.c)), make
evaluates the reference $(out_template 1.c); since there's no variable
by that name it evaluates to empty, which means you're invoking $(eval )
(on the empty string) and nothing is being defined.

If you replace $(eval ...) with $(info ...) you'll see what make is
evaluating; that can be a useful debugging tool.  Running make with
--warn-undefined-variables would have also helped, but note that gives a
lot of false positives as well.