Re: Serialization dependencies muck up configure-on-demand

[Daniel Jacobowitz <drow@mvista.com>]

On Mon, Dec 23, 2002 at 01:33:04PM -0500, DJ Delorie wrote:
> 
> > Do we need the serialization dependencies?
> 
> We need to make sure that no two configures run at the same time.  If
> you can figure out a better way to do that, please do.
> 
> > While we support all sorts of versions of Make, do we actually
> > support parallel make on anything that doesn't recognize
> > .NOTPARALLEL?
> 
> We want to run the toplevel makefile in parallel, because we want to
> do the builds and tests in parallel.  So, we want to get rid of
> .NOTPARALLEL, not depend on it.

Well, I'm not sure how useful of a goal that is; I suppose it would
speed up re-making when most directories don't need to be updated or
updated substantially.  I don't see a better way without being truly
gross about it... no, even having a combinatorial number of
serialization dependencies won't work since they have to be on real
files.

However, GNU make has the answer.  We'd probably have to autoconf for
this feature, it's quite new:
    * A new feature exists: order-only prerequisites.  These prerequisites
      affect the order in which targets are built, but they do not impact
      the rebuild/no-rebuild decision of their dependents.  That is to say,
      they allow you to require target B be built before target A, without
      requiring that target A will always be rebuilt if target B is updated.
      Patch for this feature provided by Greg McGary <greg@mcgary.org>.

The syntax is:
TARGETS : NORMAL-PREREQUISITES | ORDER-ONLY-PREREQUISITES

So if that works in a test at autoconf time, we could use it.

-- 
Daniel Jacobowitz
MontaVista Software                         Debian GNU/Linux Developer