CODEWITHSUNDEEP
makefilegnu-make
Chris
Chris

Reputation: 31186

Make: execute rule dynamically

Using GNU-Make,

Suppose I write the following:

.PHONY: foo bar

foo:
    $(eval foo:=1)
    @echo foo

bar:
ifneq (${foo},)
    @echo bar
endif

Then I make the following commands: 

$: make foo
foo

$: make bar
bar

$: make bar foo
bar
foo

$: make foo bar
foo
bar

However, I am trying to make the following result occur for the last two commands, preferably without dropping into shell code:

$: make foo bar
foo

$: make bar foo
bar
foo

How do I cause the if guard to dynamically inhibit the bar rule?

Upvotes: 0

Views: 34

Answers (1)

Matt
Matt

Reputation: 15081

First, you misuse ifneq --- it's always processed on the first pass, i.e. before any recipe-related stuff. So it's not an option.

Second, it's a bad design to behave differently on make foo bar and make bar foo, as it breaks parallel processing with -jN option. You should revise your logic: either foo must depend on bar, or bar on foo, or they must be fully independent on each other.

Upvotes: 2

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