Or your printf changes: - the timing of execution so nothing works => hello USB driver! - the scheduling of your threads - the memory layout => a memory over

Or your printf changes: - the timing of execution so nothing works => hello USB driver! - the scheduling of your threads - the memory layout => a memory overflow won't crash your program the same way or not at all I feel lucky I've enough hairs to pull them out on this kind of bugs. Fun time indeed.