Re: .PHONY targets and prerequisite checking

[Paul D. Smith]

%% Anoneironaut <address@hidden> writes:

  a> toplevel: main.o $(MODULES) $(MODULE_LIBS) 

  a> .PHONY: $(MODULES) 

  a> how can I avoid setting "foo" and "bar" to be phony?

Assuming "foo" and "bar" are directories, then you can't do this.  Even
if you avoid having them phony it won't work correctly since directory
timestamps are updated when files are added, removed, or renamed.

There are various ways to solve this.  One is to use order-only
prerequisites, like this:

  toplevel: main.o $(MODULE_LIBS) | $(MODULES)

This ensures that the $(MODULES) targets are built before "toplevel",
but that toplevel won't be rebuilt because of them.


See the GNU make manual for more info.

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