RE: basename function does nothing when it appears in prerequisites

[Paul D. Smith]

%% Matt Swift <address@hidden> writes:

  ms> I understand the explanation, but I do not understand why, if it
  ms> applies to the $(basename) function, it does not apply to the
  ms> $(addsuffix) function.  If addsuffix behaved like basename, then
  ms> the dependency list for the target foo.yy would be ".zz" instead
  ms> of "foo.yy.zz" (which it is by experiment -- that's why this was
  ms> in the test makefile).

Well, it's a little obscure I suppose.  Let's look:

  ms> foo.yy: %: $(addsuffix .zz, %)

In this case, what does the function expand to?  Well, it adds the .zz
suffix to its arguments, so you'll get:

  foo.yy: %: %.zz

OK, that works!  Because when make goes through to replace the "%"
characters with the proper values, it'll replace the "%" with "foo.yy"
and you'll get "foo.yy.zz" just as you want.

  ms> foo.xx: %: $(basename %)

In this case, what is basename of "%"?  Just "%" itself, so you end up
with this:

  foo.xx: %: %

This is not correct, because it's equivalent to "foo.xx: foo.xx", which
is never a good thing in a makefile :)

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