title: Is std::vector or boost::vector thread safe?
body: <p>I have multiple threads simultaneously calling <code>push_back()</code> on a shared object of <code>std::vector</code>. Is <code>std::vector</code> thread safe? Or do I need to implement the mechanism myself to make it thread safe?<br>
  I want to avoid doing extra <em>"locking and freeing"</em> work because I'm a library user rather than a library designer. I hope to look for existing thread-safe solutions for vector. How about <code>boost::vector</code>, which was newly introduced from boost <em>1.48.0</em> onward. Is it thread safe?</p>