the mode I didn't know is : FILE_EXCLUSIVE

The file was opened with the "x" mode flag.

FILE_SET_CLOSE_ON_EXEC FILE_HAS_INTERNAL_REF FILE_NO_CLOSE_ON_DESTRUCT FILE_LOCK_FD FILE_NOT_OPENED

All of these are essentially internal and should be of no concern if you're only using Stdio.File. I think they should be removed from the documentation.