// making it invalid; see runtime.SetFinalizer for more information on when
// a finalizer might be run. On Unix systems this will cause the SetDeadline
// methods to stop working.
+// Because file descriptors can be reused, the returned file descriptor may
+// only be closed through the Close method of f, or by its finalizer during
+// garbage collection. Otherwise, during garbage collection the finalizer
+// may close an unrelated file descriptor with the same (reused) number.
//
// As an alternative, see the f.SyscallConn method.
func (f *File) Fd() uintptr {
// descriptor. On Unix systems, if the file descriptor is in
// non-blocking mode, NewFile will attempt to return a pollable File
// (one for which the SetDeadline methods work).
+//
+// After passing it to NewFile, fd may become invalid under the same
+// conditions described in the comments of the Fd method, and the same
+// constraints apply.
func NewFile(fd uintptr, name string) *File {
kind := kindNewFile
if nb, err := unix.IsNonblock(int(fd)); err == nil && nb {