title: Why PTHREAD_COND_INITIALIZER may be used to initialize a condition variable only when it is declared?
body: <blockquote>
    <p>Since the PTHREAD_COND_INITIALIZER is actually a structure initializer, it may be used to initialize a condition variable only when it is declared.</p>
  </blockquote>
  
  <p><strong>From</strong>: Multi-Threaded Programming With POSIX Threads</p>
  
  <p><strong>Question</strong>: Couldn't understand the above quote.<br>
  It is just a macro, <strong>why</strong> can't I use it to initialize the condition variable on run time?<br>
  What has its being a <em>structure initializer</em> to do with anything?</p>