[Sunrisepeak]

The construction openkal-linux#53 reports is this implementation's too: kal_net_close, kal_net_close_listener and kal_datagram_close closed the descriptor and then retired the handle, so a file or a connection another context opened between the two took the number with the old generation and was left with a stale handle; its stream was answered as zero, standard input.

• Every release is okm::release, which retires and then closes (src/handle.h).
• The generation is advanced by a compare-and-exchange from the value the handle carries: one release closes, a second closes nothing. It is read through the atomic operations.
• kal_fs_stream and kal_net_stream answer a handle that names no live descriptor with a word no descriptor has; a transfer upon it reports kal_err_invalid.
• tests/a_released_handle_is_stale_before_its_number_is_free.cpp: one context accepts and closes connections, one connects and closes, one opens, reads and closes a file; every read returns the file. On openkal-linux the same test finds 94 stale files in 3.4 million opens without the change, none with it.