Automatically Handling Tools that Produce Many Outputs

[Olly Betts]

I've read (and use the recipes from) the automake manual section
"Handling Tools that Produce Many Outputs".  However, these recipes
require a lot of boilerplate code which annoyingly obscures the actual
rule they are protecting - a two line rule is swamped by a dozen lines of
boilerplate.

It's just struck me that automake is good at inserting lots of
boilerplate code into makefiles!  Has anyone considered adding some
sort of support to automake to allow such rules to get rewritten
automatically?

I don't have a concrete proposal, but it seems that this would need
to be controllable rather than automatically adjusting any rule with
multiple targets, if only to avoid messing with rules which are already
protected.

Two initial ideas - either a new automake option, or special handling
for a rule which is written with some other token instead of a ":"
(or perhaps both?).

GNU make support "::" rules, but ":::" could be used perhaps.  The multiple
colons are mnemonic for multiple outputs.

So this in Makefile.am would mean "automatically protect this rule for me":

    data.c data.h::: data.foo
            foo data.foo

The main difficulty I see is what to name the auxiliary files (witnesses,
locks, etc) so as avoid clashing with user files.  Perhaps creating a
subdirectory for them would be best - it would make it easy to ignore
them in a VCS.

Thoughts?

Cheers,
    Olly