Re: pattern rule dependency question

[Paul D. Smith]

%% Der Herr Hofrat <address@hidden> writes:

  dhh> _%: $*

This rule doesn't mean anything.  The automatic variables, like $@, $*,
etc. are not set in prerequisite lists; they are ONLY available inside
command scripts.  So, $* is the global variable "*", which is almost
certainly not set, and this rule basically just says:

    _%:

Which is pretty meaningless.

Second, a pattern rule without a command script does not define
prerequisites as an explicit rule would; instead it deletes the pattern
rule.  Since there is no pattern for _%, this deletes something that
didn't exist and so doesn't do anything.

  dhh> And we then call make as make _video.mss which as I had expected
  dhh> then runs the %.mss rule.

Yes, because _video.mss matches that pattern, but $* here will be
"_video", not "video".

  dhh> but I could not find any note in the info pages stating that
  dhh> automatic variables can't be used in prerequisites

They can't be.

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