Path: utzoo!utgpu!attcan!uunet!husc6!lloyd!kent From: kent@lloyd.camex.uucp (Kent Borg) Newsgroups: comp.sys.mac.programmer Subject: Re: Register saving conventions Message-ID: <130@lloyd.camex.uucp> Date: 10 Aug 88 20:09:29 GMT References: <664@iraun1.ira.uka.de> <1133@lzsc.ATT.COM> <15055@santra.UUCP> <6600@umn-cs.cs.umn.edu> <25556@ucbvax.BERKELEY.EDU> <20078@cornell.UUCP> Reply-To: kent@lloyd.UUCP (Kent Borg) Organization: Camex, Inc., Boston, Mass USA Lines: 22 >From: schoaff@gefion.cs.cornell.edu (Peter Schoaff) >Excuse this basic question, but could someone explain to me what is >meant by a tail patch on a trap. If you want to change the behavior of one the routines in the Macintosh ROM, you can install your own routine that gets called first. You work your special custom magic and then possibly jump back to the original routine to do what it does. Because you jumped to the original routine, when it returns it will return back to the original calling code, not to your patch. If, on the misbehaving other hand, you arrange to have the original routine return control to your patch, you have installed a tail patch. I can't remember why tail patches are bad (I've never patched the Macintosh), but I think it has to do with interference between multiple patches (and Apple's tail patches?). Kent Borg kent@lloyd.uucp or hscfvax!lloyd!kent