Re: Q: what is the best praxis to express dependency-only-prerequisites ?

[Paul D. Smith]

%% "Markus F.X.J. Oberhumer" <address@hidden> writes:

  mfxjo> I'm sorry of this is an obvious question, but I somehow cannot
  mfxjo> find a way to nicely express dependency-only-prerequisites.

  mfxjo> What is the best praxis for the two scenarios outlined below ?

(FYI, I think you mean "practice" here...)

  mfxjo> # This Makefile contains a typo, and I would like to get
  mfxjo> #   make: *** No rule to make target `tmp/b', needed by `all'.  Stop.
  mfxjo> #
  mfxjo> # But the order-only-prerequiste below also seems to provide
  mfxjo> # an (empty) recipe. So the quesion is: how do you best express
  mfxjo> # a dependency-only-preqrequisite ?

Unfortunately, I don't know of any way.

Your comments above slightly mischaracterize the situation.  It's not
quite true that "order-only-prerequisites provide an empty recipe".  In
a makefile, just defining a target is enough to keep make from
complaining about no rule to make a target.  The manual says:

> If a rule has no prerequisites or commands, and the target of the rule
> is a nonexistent file, then `make' imagines this target to have been
> updated whenever its rule is run.

I guess the result is the same so it's a distinction without a difference.

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