Re: Appending to builtin Automake variables from an included file

[Jeroen N. Witmond [Bahco]]

Allan Caffee wrote:
> Thank you both for your speedy responses.
>
> On Wed, Feb 25, 2009 at 7:04 PM, Jan Engelhardt <address@hidden>
> wrote:
>> In one project I use -- though not a "header + main makefile" but
>> a "main makefile + subordinates" layout --:
>>
>> # Makefile.am (http://tinyurl.com/dhxfwf)
>> bin_PROGRAMS =
>> include bar/Automakefile
>> include foo/Automakefile
>>
>> # bar/Automakefile
>> bin_PROGRAMS += bar
>>
>> # foo/Automakefile
>> bin_PROGRAMS += foo
>>
>> that is, setting all variables ever used to "" before appending to them.
>
> That is certainly one possibility.  Unfortunately though that means that
> in the Makefile.am files you _must_ use += since Automake will error out
> if you assign more than one value to a variable (within the same
> Automake conditional block).  But I was hoping for away that wouldn't
> require the author of Makefile.am to change their syntax.  I want to
> "sneak" some additional files onto the clean list.
>
> Hopes and dreams aside that is much cleaner for the case I provided.  I
> think I'll use this instead if I can't turn up a more encapsulated
> approach.  Thanks!

I'm not an expert on automake, but perhaps you've chosen the wrong
solution to your problem: maintainer-cleaning some additional files. I
would have thought target maintainer-clean-local was invented for this
purpose! :) (However, I have never needed to use it.)

See for instance
http://www.gnu.org/software/automake/manual/html_node/Clean.html#index-maintainer_002dclean_002dlocal-751

>
>
> On Wed, Feb 25, 2009 at 7:36 PM, Bob Friesenhahn
> <address@hidden> wrote:
>> Modern automake supports += syntax.
>
> Modern Automake does support appending.  But only appending to a
> variable that has already been set.  My understanding is that Automake
> handles appending in a way very similar to that shown above, using temp
> variables which depending on the Automake conditionals defined, may or
> may not be empty.  This allows it to sidestep implementations of Make
> which don't allow +=.  Perhaps we could just drop the error about
> appending to an undefined variable and treat it as setting the variable
> if not already set.  I don't know how this would effect the reporting of
> "multiply defined" variables though.
>
> The real reason I think it would be nice to have this flexibility is for
> macro authors to be able to add files to be cleaned up/distributed
> without requiring the users to manually add anything to their setup.  So
> assuming anything I just said was actually correct, how difficult would
> it be to safely allow this?
>
> ~Allan

Jeroen.