Hi, I'm implementing file AIO in asio for windows. I've tried to use as much as possible from asio. The problem is that when reading bigger files (more than one megabyte), the queue returns an error: code 997, that is converted to "Overlapped I/O operation is in progress." When that happens, the asio deletes the handler, but the operation is still happening, so GetQueuedCompletionStatus returns one more time for the same overlapped with the completed IO, but the handler is already deleted. This happens in: handler_operation::do_completion_impl (win_iocp_demuxer_service:169) It holds a std::auto_ptr to the handler, but has no access to the error code. So I cant see how to correct this. I think that socket AIO could return this too (specially in ConnectEx, I've seen this in my own "raw AIO" code). I havent finished the file aio yet, when it gets a little better I'll publish here (probably this weekend). Thanks, -- Felipe Magno de Almeida