With the bytecode interpreter, I've been able to make ocaml segfault by using Graphics. I don't know how reproductible this is but iirc, I had to Graphics.open_graph "" then close the window with the cross on the window and last reuse Graphics.open_graph "" (has maybe to be done twice with a Graphics.close_graph() between). I encountered this on ocaml-3.10.0 under linux. I did not try to reproduce it as it wasn't my goal and right now I don't have ocaml available. Anyway, this or something very similar would raise a fatal I/O error which surprinsigly was sometimes fatal to the bytecode interpreter but not always. Morality : use close_graph() ;) --- Adrien Nader