title: Swift 1.2 crashes in release mode
body: <p>When an app is built with -O (fastest) setting , crashes occur very quickly at seemingly random places.</p>
  
  <p>Occurs in latest beta as well as final.</p>
  
  <p>How would one track those down? </p>
  
  <p>Tried allocations instrument with NSZombie detection enabled. 
  Tried crashlytics and/or device crash reports but they are similarliy cryptic to me.
  Started to put debug messages in the code, trying to find out where it sometimes hits.</p>
  
  <p>I read here and on the apple dev formus that it could be related to core data fetches, to upper/lower case String operations, Array conversions from/to NSArray, etc.</p>
  
  <p>All I am getting currently is:</p>
  
  <pre><code>malloc: *** error for object 0x174e3439c: Invalid pointer dequeued from free list
  
  *** set a breakpoint in malloc_error_break to debug
  </code></pre>
  
  <p>Turning off optimizations in release mode with -Onone seems to fix the problem(s) I am experiencing with my code.</p>
  
  <p>Any pointers would be highly appreciated.</p>