>> Sure, but here the loop is explicit in the looping program, so it
 >> could prevent the infloop.
 >
 > Indeed, I thought a loop like this would work without changing the documented behaviour as far as I can see:
 >
 > ,----
 > | (let ((current-frame (selected-frame))
 > |       prev-frame
 > |       frame)
 > |   (while (and
 > |           (not (eq frame current-frame))
 > |           (not (eq frame prev-frame)))
 > |     (setq
 > |      prev-frame frame
 > |      frame (next-frame frame 0))))
 > `----

Whatever we do here we won't fix the principal problem with next_frame
namely that

(progn
   (set-frame-parameter nil 'no-other-frame t)
   (next-frame nil 0))

can loop forever.  I attach a patch that should fix the problems with
'make-frame-names-alist' and 'delete-other-frames' using 'frame-list' as
base.

martin