I haven't looked closely at your example but the problem reminds me of one for which I have a different solution. See attached Makefile and run "make help" to get started. My solution assumes Linux or at least the presence of an equivalent command-line interface to file locking.
David B On Fri, Jul 31, 2020 at 6:35 AM David Deutsch <sk...@valanx.org> wrote: > Hey everybody, > > I've been looking through the mailing list trying to come up with an > answer to how I could do .NOT_PARALLEL for some targets but not others. > > There hasn't been a solution thus far and it has been mentioned that > implementing it in make itself might be highly non-trivial. I think that > I've come up with a solution for my case that I wanted to share with > you. Perhaps it could inform a more generalized solution. > > So in my case, I want to create linux user accounts as a target like so: > > > /home/[newUserName]/: > adduser [newUserName] > > > If you run this in parallel with other targets like it (just replacing > [newUserName], of course), it fails because you get user ID conflicts > (it tries to use the same user ID for all of the accounts, because they > all iterate on the same base number, which creates a lot of issues) > > > My solution looks like this: > > > ifeq ($(origin NOTPARALLEL),undefined) > NOTPARALLEL := > endif > > /home/[newUserName]/: | $(NOTPARALLEL) > adduser [newUserName] > > NOTPARALLEL += /home/[newUserName]/ > > > so that no matter how many times or where I use this snippet, all of the > targets are lined up sequentially. > > > This got me wondering though: Perhaps this kind of "grouped > non-parallel" approach could actually work out and be cheap to implement? > > As in - If you write: > > .NOTPARALLEL: target_a target_b target_c > > target_a: > myCmd > > target_b: > myCmd > > target_c: > myCmd > > > That gets interpreted as: > > ifeq ($(origin NOTPARALLEL),undefined) > NOTPARALLEL := > endif > > target_a: | $(NOTPARALLEL) > myCmd > > NOTPARALLEL += target_a > > target_b: | $(NOTPARALLEL) > myCmd > > NOTPARALLEL += target_b > > target_c: | $(NOTPARALLEL) > myCmd > > NOTPARALLEL += target_c > > > I know that it's not a perfect solution (and it would be hard to make > this work with pattern rules), but perhaps it's good enough to at least > cover most of the cases where people expect ".NOTPARALLEL: x y z" to > work this way? > > The other caveat of this is that an order-only-prerequisite only means > that this would work for newly generated files, not for updating them. > For that you'd need regular prerequisites, but then you'd interfere with > recipes that depend on a clean $^ variable. > > > best regards, > David > > >
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