GNU Makefile: multiple outputs from single rule + preventing intermediate files from being deleted
- by makesaurus
This is sort of a continuation of question from link text. The problem is that there is a rule generating multiple outputs from a single input, and the command is time-consuming so we would prefer to avoid recomputation. Now there is an additional twist, that we want to keep files from being deleted as intermediate files, and rules involve wildcards to allow for parameters.
The solution suggested was that we set up the following rule:
file-a.out: program file.in
./program file.in file-a.out file-b.out file-c.out
file-b.out: file-a.out
@
file-c.out: file-b.out
@
Then, calling make file-c.out creates both and we avoid issues with running make in parallel with -j switch. All fine so far.
The problem is the following. Because the above solution sets up a chain in the DAG, make considers it differently; the files file-a.out and file-b.out are treated as intermediate files, and they by default get deleted as unnecessary as soon as file-c.out is ready.
A way of avoiding that was mentioned somewhere here, and consists of adding file-a.out and file-b.out as dependencies of a target .SECONDARY, which keeps them from being deleted. Unfortunately, this does not solve my case because my rules use wildcard patters; specifically, my rules look more like this:
file-a-%.out: program file.in
./program $* file.in file-a-$*.out file-b-$*.out file-c-$*.out
file-b-%.out: file-a-%.out
@
file-c-%.out: file-b-%.out
@
so that one can pass a parameter that gets included in the file name, for example by running
make file-c-12.out
The solution that make documentation suggests is to add these as implicit rules to the list of dependencies of .PRECIOUS, thus keeping these files from being deleted.
The solution with .PRECIOUS works, but it also prevents these files from being deleted when a rule fails and files are incomplete. Is there any other way to make this work?
