Your code seems to be endless loop, your call sequence goes something like:

Qt Code: 
  1. :
  2. :
  3. -> runThread
  4. -> doWork
  5. -> run
  6. -> emits completed (connected to jobDone)
  7. -> jobDone
  8. -> runThread
  9. -> doWork
  10. :
  11. :
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Maybe because of this you reach some system resource limit (heap/stack) in this recursive function call sequence and that causes your code to crash at the point you mentioned.

I have 8GB RAM in Ubuntu and I reach ~9500 (runcount) after crash, at that point my function call "tree" is 66609 function deep!