Re: order-only dependency and transitivity

[Paul D. Smith]

%% Ross Boylan <address@hidden> writes:

  rb> Unfortunately, solving the toy problem in this case doesn't help with
  rb> the real one.  It would have a rule someting like this:
  rb> m.touch: m.web
  rb>    ftangle -F m.web
  rb>    touch m.touch

  rb> The product of ftangle is a lot of .cc and .h files, but because of
  rb> the -F option only some of them are updated.  So in terms of the
  rb> example, it's as if the m.touch rule might or might not touch x.cc

  rb> My current solution is something like this
  rb> $(SOURCES): m.web
  rb>       ftangle -F m.web

  rb> but this ends up running ftangle many times, once for each of the
  rb> $(SOURCES) that do not get updated.

You almost had it... you have to do something like this:

    $(SOURCES): m.touch

    m.touch: m.web
        ftangle -F m.web
        @touch $@

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