Parallel builds and SUBDIRS

[Harlan Stenn <Harlan dot Stenn at pfcs dot com>]

First, I'm not saying this is a good idea.

I'm working on a project where Somebody decided it would be a feature to
hack the automake templates to permit subdirs to be built in parallel.

They implemented an additional level of locking to prevent, for example, a
library that is needed by multiple subdirs from being built simultaneously.

I'm wondering if there is benefit to allowing SUBDIRS to be build in
parallel by option (or default), and wondering if it's possible, reasonable,
and not too difficult to use dependency lines in the "parent" Makefile.am to
control serialization, ie:

 SUBDIRS = include lib bar baz foo

 lib: include
 bar baz foo: lib

so that in a parallel build situation, we'd build include first, then lib,
then bar, baz and foo in parallel.

Comments?

H