title: Is optimisation level -O3 dangerous in g++?
body: <p>I have heard from various sources (though mostly from a colleague of mine), that compiling with an optimisation level of <code>-O3</code> in g++ is somehow 'dangerous', and should be avoided in general unless proven to be necessary.</p>
  
  <p>Is this true, and if so, why? Should I just be sticking to <code>-O2</code>?</p>