5.7.3 Communicating Options to a Sub-make!(2)

[ali hagigat]

The ‘-j’ option is a special case (see Section 5.4 [Parallel
Execution], page 47). If you set
it to some numeric value ‘N’ and your operating system supports it
(most any UNIX system
will; others typically won’t), the parent make and all the sub-makes
will communicate to
ensure that there are only ‘N’ jobs running at the same time between them all.
Note that any job that is marked recursive (see Section 9.3 [Instead
of Executing Recipes], page 95)
doesn’t count against the total jobs (otherwise we could get ‘N’
sub-makes running and have
no slots left over for any real work!)
------------------------------------------------------------------
I wonder if you can write an example of the above situation. Why we
could get ‘N’ sub-makes running?
Makefile23
e12:
      make -f makefile23
make -f makefile23
Is the above an example of recursive jobs?