title: Variables defined *and* undefined
body: <p>I guess this makes sense somehow, but I can't grasp why: In the following code, I get <strong>both</strong> warnings (note that the original code was indented with tabs):</p>
  
  <pre><code>define variable-definition
      ifndef $1
          $(warning $1 is undefined)
      else
          $(warning $1 is defined)
      endif
  endef
  </code></pre>
  
  <p>PS: I want to check whether the variable with the name passed as <code>$1</code> exists, not whether <code>$1</code> was passed.</p>
  
  <p>PPS: Dedenting the entire thing doesn't help.</p>