Info Catalog make: Phony Targets make: Rules make: Empty Targets

make: Force Targets

 
 4.7 Rules without Recipes or Prerequisites
 ==========================================
 
 If a rule has no prerequisites or recipe, and the target of the rule is
 a nonexistent file, then 'make' imagines this target to have been
 updated whenever its rule is run.  This implies that all targets
 depending on this one will always have their recipe run.
 
    An example will illustrate this:
 
      clean: FORCE
              rm $(objects)
      FORCE:
 
    Here the target 'FORCE' satisfies the special conditions, so the
 target 'clean' that depends on it is forced to run its recipe.  There is
 nothing special about the name 'FORCE', but that is one name commonly
 used this way.
 
    As you can see, using 'FORCE' this way has the same results as using
 '.PHONY: clean'.
 
    Using '.PHONY' is more explicit and more efficient.  However, other
 versions of 'make' do not support '.PHONY'; thus 'FORCE' appears in many
 makefiles.  Phony Targets.
 

Info Catalog make: Phony Targets make: Rules make: Empty Targets