title: When is curl_global_init() necessary at all?
body: <p>Though its document says this function is MUST, but I saw two examples, one has it, the other doesn't.</p>
  
  <p><a href="http://curl.haxx.se/libcurl/c/persistant.html" rel="noreferrer">http://curl.haxx.se/libcurl/c/persistant.html</a></p>
  
  <p><a href="http://curl.haxx.se/libcurl/c/multi-app.html" rel="noreferrer">http://curl.haxx.se/libcurl/c/multi-app.html</a></p>
  
  <p>Is this function necessary at all?</p>