title: Why would an app crash with _objc_msgSend_uncached
body: <p>Is a document or a place to find information information on what would cause _objc_msgSend_uncached in a crash report?</p>
  
  <p>more info on the crash</p>
  
  <pre><code>libobjc.A.dylib 0x37e623cc  _objc_inform
  4   libobjc.A.dylib 0x37e616f2  _ZN7cache_t9bad_cacheEP11objc_objectP13objc_selectorP10objc_class
  5   libobjc.A.dylib 0x37e61730  _ZN7cache_t4findEm
  6   libobjc.A.dylib 0x37e617da  cache_fill
  7   libobjc.A.dylib 0x37e65890  lookUpImpOrForward
  8   libobjc.A.dylib 0x37e5e02a  _class_lookupMethodAndLoadCache3
  9   libobjc.A.dylib 0x37e5ddf8  _objc_msgSend_uncached
  10  MyApp   0x00253f5c  -[AEEngine scanKeyframes:currentFrame:] in AEEngine.m on Line 256
  11  MyApp   0x00256148  -[AEEngine doFrame] in AEEngine.m on Line 664
  12  MyApp   0x00255f28  __31-[AEEngine doFrameInBackground]_block_invoke in AEEngine.m on Line 642
  </code></pre>
  
  <p>Got another similar crash that looks like this and ends in cache_t::bad_cache</p>
  
  <pre><code>  0   libobjc.A.dylib                   0x37b44368 _objc_trap() + 0
    1   libobjc.A.dylib                   0x37b443c8 _objc_fatal + 68
    2   libobjc.A.dylib                   0x37b436ee cache_t::bad_cache(objc_object*, objc_selector*, objc_class*) + 202
    3   libobjc.A.dylib                   0x37b4372c cache_t::find(unsigned long) + 48
    4   libobjc.A.dylib                   0x37b437d6 cache_fill + 122
    5   libobjc.A.dylib                   0x37b4788c lookUpImpOrForward + 320
    6   libobjc.A.dylib                   0x37b40026 _class_lookupMethodAndLoadCache3 + 30
    7   libobjc.A.dylib                   0x37b3fdf6 _objc_msgSend_uncached + 22
    8   MyApp                         0x0033811c -[MyCellCell configureCell:] (MyCellCell.m:81)
  </code></pre>