title: Makefile: macros with default parameters
body: <p>Consider the following Makefile:</p>
  
  <pre><code>MAKEFLAGS += --warn-undefined-variables
  
  define foobar
  echo "$(1)"
  endef
  
  .PHONY: all
  all:
      $(foobar)
  </code></pre>
  
  <p>Is there a way to have macros with default parameters without producing undefined variable warnings?
  I mean: sometimes I call "foobar" with a parameter, but sometimes not. In the latter case I'd like to have a default value for $(1).</p>