Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/18/84; site gumby.UUCP Path: utzoo!watmath!clyde!burl!ulysses!allegra!mit-eddie!godot!harvard!seismo!uwvax!gumby!g-frank From: g-frank@gumby.UUCP Newsgroups: net.lang,net.lang.mod2 Subject: nil pointer dereferencing Message-ID: <286@gumby.UUCP> Date: Tue, 12-Feb-85 09:01:57 EST Article-I.D.: gumby.286 Posted: Tue Feb 12 09:01:57 1985 Date-Received: Thu, 14-Feb-85 01:49:49 EST Distribution: net Organization: U of Wisconsin CS Dept Lines: 23 Xref: watmath net.lang:1424 net.lang.mod2:164 Since I don't remember what newsgroup this discussion was in, I'll try these two . . . The Logitech Modula-2/86 compiler for the 8086, as of version 1.1, has an address constant called NIL which produces the value FFFF:FFFF (segment:offset). Since this is not a very valid address on the processor (it wraps around into lower memory), no addressability is lost by this convention. Actually, this was in v1.0. What is new in 1.1 is that, by default, the compiler generates code to check for a NIL dereferencing operation before it takes place. This checking may be turned off by a compile- time switch. -- Dan Frank Q: What's the difference between an Apple MacIntosh and an Etch-A-Sketch? A: You don't have to shake the Mac to clear the screen.