Re: Re: disposing of pointers

[walker@nova.rdd.lmsc.lockheed.com ( Scott Walker)]

	From info-mcl-request@cambridge.apple.com Thu Apr 25 10:39:47 1991
	To: eliot@clarity.princeton.edu
	Subject: Re: disposing of pointers
	Cc: info-mcl@cambridge.apple.com
	
	>Can someone tell me how to dispose of a pointer? I'm making 
	>bitmaps using make-bitmap in quickdraw.lisp and can't seem to be able to
	>get rid of them afterwords.
	 
	Here's example 
	of how to:
	 (setf tmp-bmap (make-bitmap 0 0 10 10))
	...
	 (dispose-record tmp-bmap :bitmap)
	 (setf tmp-bmap nil) ; important to nil lisp var holding  pointer 
	                     ; since ptr meaningless now & could lead to
	                     ;crashes during GC
	 
what if MACL decides to do a GC after the dispose-record but before 
the (setf tmp-bmap nil)?????  Can someone tell me WHY there is
no window of vulnerability here?

thank you,
scott