makefile - Parallel Make - Sub-Projects called multiple times -

the question answered on file-level. have bigger project has quite lot of inter-project-dependencies (caused dbus headers, generated dynamically).

i ve created following example (example files zip - real project more complex).

the top-level makefile following:

sub-%:     $(make) -c $(patsubst sub-%,%,$@)  default:     $(make) -j12 sub-p1 sub-p2 sub-p3 

the makefile of sub-project (p1, p2 , p3):

all: p1  ../lib/lib.a:     $(make) -c ../lib lib.a  p1: ../lib/lib.a     cp -f ../lib/lib.a p1 

and makefile of lib looks this:

lib.a:     sleep 2     date > $@     echo done building $@ 

the problem: library built each p*-project separately in parallel - in example it's not problem, in our case causes unsolvable problems.

when call make on top-level, following output:

$ make make -j12 sub-p1 sub-p2 sub-p3 make[1]: entering directory '/home/kkr/tmp/parallelmake' make -c p1 make -c p2 make -c p3 make[2]: entering directory '/home/kkr/tmp/parallelmake/p1' make -c ../lib lib.a make[2]: entering directory '/home/kkr/tmp/parallelmake/p2' make -c ../lib lib.a make[2]: entering directory '/home/kkr/tmp/parallelmake/p3' make -c ../lib lib.a make[3]: entering directory '/home/kkr/tmp/parallelmake/lib' make[3]: entering directory '/home/kkr/tmp/parallelmake/lib' make[3]: entering directory '/home/kkr/tmp/parallelmake/lib' sleep 2 sleep 2 sleep 2 date > lib.a date > lib.a date > lib.a make[3]: leaving directory '/home/kkr/tmp/parallelmake/lib' make[3]: leaving directory '/home/kkr/tmp/parallelmake/lib' make[3]: leaving directory '/home/kkr/tmp/parallelmake/lib' cp -f ../lib/lib.a p3 cp -f ../lib/lib.a p1 cp -f ../lib/lib.a p2 make[2]: leaving directory '/home/kkr/tmp/parallelmake/p3' make[2]: leaving directory '/home/kkr/tmp/parallelmake/p1' make[2]: leaving directory '/home/kkr/tmp/parallelmake/p2' make[1]: leaving directory '/home/kkr/tmp/parallelmake' 

question: possible synchronize sub-projects somehow automatically?

since real project has 13 sub-projects - of them having inter-project-dependencies - manual synchronization quite difficult.

there no way recursive make system "automatically" synchronize this; separate processes , have no way tell each other running given target.

you have 2 choices. first, best may lot of work, rework build system it's non-recursive. if have single make invocation builds entire system there 1 instance of make, , globally coordinate creation of targets. won't need $(make) -c ../lib lib.a rules @ all.

if that's not feasible, need rewrite top-level makefile enforce ordering such never start making 2 directories depend on same external target, @ same time. example instead of top-level makefile show above, write this:

default: p1 p2 p3  p%: ; $(make) -c $@  .phony: default p1 p2 p3 

now suppose want ensure p1 runs before p2 , p3 because want p1 build shared targets; you'd add rule top-level makefile:

p2 p3: p1 

and can add other orderings needed.