How can I use .NOTPARALLEL in makefile only on specific targets?

Question

I have 5 labels in Makefile:

all: label1 label2 label3 label4 last_label

I want last_label to be done last, and I want to use make -j. If I use .NOTPARALLEL, it will make all of them NOTPARALLEL, any suggestion on how to do that?

Solution 1

Create a target specifying the four targets that can be executed in parallel & include this and last_label in the all target:

intermediate: label1 label2 label3 label4

all:
        $(MAKE) intermediate
        $(MAKE) last_label

This would execute the targets specified within intermediate in parallel, but intermediate and last_label would be forced consecutively.

(Note that the leading space before $(MAKE) is a TAB character.)

Solution 2

If the reason last_label needs to run last is that it needs data from the other labels, the best approach would be to tell make about that dependency:

all: last_label

last_label: label1 label2 label3 label4

If there's not a true dependency (i.e., if you don't want last_label to be rebuilt if one of the others changes), and if you're using GNU Make, you can specify these as "order-only" dependencies--make will just make sure they exist before last_label is built:

all: last_label

last_label: | label1 label2 label3 label4

Comments

[Maxim Egorushkin]

It is called order-only dependency to be precise.

[Nitin4873]

this should solve the base requirement - hence the make even if it forks many processes it will have to ensure that order of completion of the targets even iff the non parallel option is not used !! , +1 @laindir

[devnull]

Yes. The solution would work in parallel, regardless of the number of simultaneous jobs.

[shd]

this will not work with -j7 , since it ignore everything i think

[laindir]

This will work with any number of jobs, since we have explicitly told make that last_label must not run before the other labels have finished.

[TrueY]

I assume the intermediate target should come after all, otherwise it would become the default target.