CODEWITHSUNDEEP
makefile
PistoletPierre
PistoletPierre

Reputation: 131

make/Makefile: CLI option to "disable" a dependency from a target

I'm exploring a feature of some software that's used in a very mature Makefile to see if that feature can be incorporated into the flow. There is a target like the following:

my_target: dependency_1 dependency_2
        echo foo
        touch bar
        # etc...

In regular use, dependency_2 would always be called before my_target's commands were executed. But for my exploration purposes, I want to selectively call dependency_2 from its own make command. And then make my_target after, possibly several times, without re-doing dependency_2 each time.

For the time being I just copy/pasted my_target into my_target_2 and removed the dependency from my_target_2 (easy enough), but I'm wondering if there's a command-line option to disable a target's dependency without modifying the file.

EDIT: dependency_2 is a PHONY target

Upvotes: 1

Views: 768

Answers (2)

MadScientist
MadScientist

Reputation: 100836

There's no way to do this without editing the makefile, that I can think of.

You can put dependency_2 into a variable then use the variable in the prerequisite list of my_target:

dependency_2 = dependency_2

my_target : dependency_1 $(dependency_2)

then when you don't want to rebuild it, run make dependency_2= to reset the variable to empty.

Upvotes: 1

Matt
Matt

Reputation: 15091

But for my exploration purposes, I want to selectively call dependency_2 from its own make command

This is done as easy as make dependency_2

And then make my_target after, possibly several times, without re-doing dependency_2 each time

Normally, dependency_2 should be a file on the disk, so make would skip rebuilding it until its own prerequisites (source files) are changed.

But if dependency_2 is a .PHONY target ("fake file"), it will be rebuilt on each run. In this case you still can fool it like this:

echo "dependency_2:;@:" | make -f Makefile -f -

However, make will issue a warning about overriding a recipe for dependency_2.

Upvotes: 2

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