title: gcov: cannot open graph file
body: <p>I am trying to use gcov. I have this simple file a.c:</p>
  
  <pre><code>int main() {
     return 0;
  }
  </code></pre>
  
  <p>So I do</p>
  
  <pre><code>gcc -fprofile-arcs -ftest-coverage a.c -o a
  ./a
  gcov a.c
  </code></pre>
  
  <p>and I get</p>
  
  <pre><code>a.gcno:cannot open graph file
  </code></pre>
  
  <p>Am I doing something wrong? I'm under Mac OS X Lion.</p>