* The caller should be responsible for cleaning up file descriptors
* If a caller safely creates a file descriptor (via
native::io::file::open) the returned structure (FileDesc) will try to
clean up the file, failing in the process and writing error messages
to the screen.
* This should not happen as the caller has no public interface for
telling the FileDesc structure to NOT free the underlying fd.
* Alternatively, if another file is opened under the same fd held by
the FileDesc structure returned by native::io::file::open, it will
close the wrong file upon destruction.
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