[Omake] Dependencies on generated tools

[Nathaniel Gray]

On Apr 8, 2007, at 3:52 PM, Jonathan Roewen wrote:

> Hi Again,
>
> Yes, I have two problems to be tackled today =)
>
> Well, more a question of best practice/style, etc.
>
> I have a dir: toolchain/ocaml, which builds a custom ocamlc.
>
> Now, I need my entire tree except that subdir to be built using that
> ocamlc. So I set OCAMLC to $(file $(ROOT)/toolchain/ocaml/ocamlc), and
> OCAMLLINK to that as well in my OMakeroot.
>
> Then, in toolchain/ocaml/OMakefile I redefine those to ocamlc.
>
> The problem: when it comes to building my tree, it doesn't know to
> build my custom ocamlc first. So I'm wondering how do I generate this
> dependency properly?
>
> Currently, I just add it as a dependency on the main rules in the root
> OMakefile, but I'm pretty sure that if I were in a subdir, trying to
> rebuild part of the tree, this trick would fail.
>
> So, is there a nice way to do this more smartly?

We've got a similar problem in one of our projects and here's how we  
tackled it.  There may be better ways, but this works and it's  
reasonably clean.  You can use LocalOCamlGeneratedFiles($(OCAMLC)) in  
every subdir *except* for the toolchain subdir.  This is pretty easy  
to do, since it's scoped -- you just declare it after you list the  
toolchain subdir so it doesn't apply there.

There's some discussion of this function going away in the future  
(some of its use-cases have been subsumed by OCAMLDEP_MODULES, but  
that doesn't yet work on all platforms).  I think there will be  
something to replace it, but it's a simple function so you can define  
it locally if necessary.  In fact, I think this would work just as  
well (though I haven't tested it and my omake-fu is not terribly  
strong):
	.SUBDIRS: toolchain
	. . .
	# After the toolchain subdir but before the others
	%.cmi: $(OCAMLC)
	%.cmx %.cmo: $(OCAMLC)

Cheers,
-n8

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