My name is Andrew, I'm PhD student at Voronezh State University, Russia. I was trying to play with your library PyOpenCL and found that it crashes whatever example I ran. To investigate this problem I compiled debug version of PyOpenCL (see attached siteconf.py) and run it under debugger. After running examples/demo.py under debugger, there was exception 'vector iterator not dereferencable' at the line 2237, wrap_cl.hpp. It seems that we cannot use constructions like &event_wait_list.front() for empty vector due to the fact that vector::front method dereference a begin iterator, which was invalid in my case. To fix this problem I change all such constructions to following: event_wait_list.empty( ) ? NULL : &event_wait_list.front(). After this change, all samples started to work perfectly. Can you integrate this fix into future release of PyOpenCL? It can safe a lot of time for all people which will face with same problem. I attached modified wrap_cl.hpp.