title: Using sinf() without a header on OSX
body: <p>I've been reading a lot of old C lately, and one common idiom is simply forward-declaring standard libraries instead of including the header file.  I wanted to try it, so instead of <code>#include &lt;math.h&gt;</code> I just declared</p>
  
  <pre><code>float sinf(float);
  </code></pre>
  
  <p>at the top of the file.  To my surprise, I got a link error!  I even tried manually including the math library like so:</p>
  
  <pre><code>clang++ -lm test.c
  </code></pre>
  
  <p>But alas, this gives me a linker error as well.  What gives?</p>
  
  <p><strong>EDIT</strong></p>
  
  <p>I was not enclosing the forward declaration in <code>extern "C"</code>...</p>