title: Valgrind reporting a segment overflow
body: <p>When running my program with valgrind / callgrind I get the following message a lot:</p>
  
  <p><code>==21734== brk segment overflow in thread #1: can't grow to 0x4a39000</code>
  (with different addresses)</p>
  
  <p>Note that it is not preceded by a stack overflow message.</p>
  
  <p>I can't find any documentation on this message and I have no idea what is overflowing exactly.</p>
  
  <p>Can anybody help me figure out what the problem is? Is this a problem of valgrind, or of my program?</p>