disposing of bitmaps

[Eliot Handelman <eliot@clarity.Princeton.EDU>]

And now for the summary:

The way to dispose of a bitmap is (_Disposptr :a0 your-bitmap). This
was Bill's answer. I haven't had any success with the other methods,
which I don't understand, anyway. Why is 

(LET ((X (MAKE-BITMAP ..)))
  (DISPOSE-RECORD X)
  (SETQ X NIL))

any different from 


(LET ((X (MAKE-BITMAP ..)))
  (DISPOSE-RECORD X))

In both cases the previous value of X is restored, so if it is
unbound it points to nothing on exit from the LET.

And surely the "area of danger" should be enclosed by a 
WITHOUT-INTERRUPTS -- I don't see how UNWIND-PROTECT will
protect against a GC.

--eliot