Re: Named parameters in make?

[Philip Guenther]

On Fri, Jun 10, 2011 at 6:09 AM, Lane Schwartz <address@hidden> wrote:
> A major reason why the resulting code looks cryptic is because of the $1,
> $2, $3... variable names for parameters. If there were some way to name
> these parameters, the resulting code would be better documented and more
> readable.
...
> Here's a (slightly simplified) use case that comes from one of my Makefiles:
>
> TMs:=$(wildcard tm-*)
> LMs:=$(wildcard lm-*)
> DEVs:=$(wildcard dev-*)
>
> define OPTIMIZE
>
> $1.$2.$3/optimize.cfg: $1/fragment.cfg $2/fragment.cfg $3/fragment.cfg | 
> $1.$2.$3
>      cat $$^ > $$@
>
> $1.$2.$3:
>      mkdir -p $$@
>
> endef
>
> # Dynamically construct new targets
> $(foreach TM,${TMs},\
>   $(foreach LM,${LMs},\
>      $(foreach DEV,${DEVs},\
>         $(eval $(call OPTIMIZE,${TM},${LM},${DEV}))\
>      )\
>   )\
> )
>
>
> Named parameters would in this case mean that I could use names like ${TM}
> instead of $1, ${LM} instead of $2, and ${DEV} instead of $3, making the
> define block more readable.

You *can* use those names, Right Now!  You're setting TM, LM, and DEV
right now to exactly the value you want.  You don't *have* to use $1,
$2, and $3.  Indeed, if you don't then you don't need to use $(call)
here at all; that's (almost) all that $(call) does, compared to simply
expanding the named variable.  Compare:

-----
TMs:=$(wildcard tm-*)
LMs:=$(wildcard lm-*)
DEVs:=$(wildcard dev-*)

define OPTIMIZE

all: ${TM}.${LM}.${DEV}/optimize.cfg
${TM}.${LM}.${DEV}/optimize.cfg: ${TM}/fragment.cfg ${LM}/fragment.cfg \
                        ${DEV}/fragment.cfg | ${TM}.${LM}.${DEV}
        cat $$^ > $$@

${TM}.${LM}.${DEV}:
        mkdir -p $$@

endef

# Dynamically construct new targets
$(foreach TM,${TMs},\
  $(foreach LM,${LMs},\
     $(foreach DEV,${DEVs},\
        $(eval ${OPTIMIZE})\
     )\
  )\
)
----


Philip Guenther