title: Conflicting specifiers in declaration c++
body: <p>I use a data structure <code>bimap</code></p>
  
  <pre><code>typedef boost::bimap&lt; std::string, int &gt; hash_bimap;
  typedef hash_bimap::value_type position;
  hash_bimap perm;
  </code></pre>
  
  <p>and it works fine in main file. However, i am interested to use it in header file to make it accessible in any other <code>.cpp</code> file.</p>
  
  <p>when I try to make it <code>extern</code> in <code>my.h</code> like </p>
  
  <pre><code>extern typedef boost::bimap&lt; std::string, int &gt; hash_bimap;
  extern typedef hash_bimap::value_type position;
  extern hash_bimap perm;
  </code></pre>
  
  <blockquote>
    <p>conflicting specifiers in declaration of ‘hash_bimap’
     extern typedef boost::bimap&lt; std::string, int > hash_bimap;</p>
  </blockquote>