title: Can multiple threads join the same boost::thread?
body: <p><a href="http://man7.org/linux/man-pages/man3/pthread_join.3.html" rel="nofollow"><code>pthreads</code></a> has undefined behavior if multiple threads try to join the same thread:</p>
  
  <blockquote>
    <p>If multiple threads simultaneously try to join with the same thread,
           the results are undefined.</p>
  </blockquote>
  
  <p>Is the same true for <a href="http://www.boost.org/doc/libs/1_60_0/doc/html/thread/thread_management.html" rel="nofollow"><code>boost::thread</code></a>s? The documentation does not appears to specify this.</p>
  
  <p>If it is undefined, then what would be a clean way for multiple threads to wait on one thread completing?</p>