title: What does gcc without multilib mean?
body: <p>I was trying to use the <code>omh.h</code> header file and I realized it was missing. I tried reinstalling gcc on my mac using brew. This is the message I got at the end of the installation.</p>
  
  <pre><code>..
  GCC has been built with multilib support. Notably, OpenMP may not work:
    https://gcc.gnu.org/bugzilla/show_bug.cgi?id=60670
  If you need OpenMP support you may want to
    brew reinstall gcc --without-multilib
  ==&gt; Summary
    /usr/local/Cellar/gcc/4.9.2_1: 1156 files, 203M
  </code></pre>
  
  <p>It suggests that if I need OpenMP support I need to install <code>brew reinstall gcc --without-multilib</code>. I am not able to understand the meaning of <code>--without-multilib</code>. How is it different from simply installing gcc?</p>
  
  <p>And apparently <code>brew reinstall gcc --without-multilib</code> takes forever to run and <code>brew uninstall gcc &amp;&amp; brew install gcc</code> was lightning fast.</p>