Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/18/84; site peora.UUCP Path: utzoo!watmath!clyde!burl!ulysses!mhuxr!mhuxn!ihnp4!houxm!vax135!petsd!peora!jer From: jer@peora.UUCP (J. Eric Roskos) Newsgroups: net.arch Subject: Re: Re: Where to do stack checking, etc. Message-ID: <1684@peora.UUCP> Date: Fri, 27-Sep-85 08:10:43 EDT Article-I.D.: peora.1684 Posted: Fri Sep 27 08:10:43 1985 Date-Received: Sun, 29-Sep-85 08:31:06 EDT References: <796@kuling.UUCP> <1713@orca.UUCP> <1599@peora.UUCP> Organization: Perkin-Elmer SDC, Orlando, Fl. Lines: 27 Keywords: parity error, uninitialized data Joe Orost writes: > What about an uninitialized array of bytes. Say you want to set the first > byte = 0. So, you execute a store byte instruction. Now, most processors > that I know of do a store byte by doing a load fullword, inserting the byte, > and doing a store fullword. BANGO!* a parity error! > > No wonder Ada doesn't require unitialized variable checking! There's another problem related to arrays, also. Suppose you have an array, some of whose elements are uninitialized. Then should the whole array be treated as uninitialized, or not? Either way you can find cases where you need it to be the other way. The above example relates to a more general problem of implementing tagged architectures, viz., do you put tags on bytes, or words, or what? If you put the tags on bytes, then when you have a data type that is, say, a word, you have that problem with how to handle arrays with some uninitialized and some initialized elements, again... (if you allow someone to access the word as bytes sometimes too, at least). -- Shyy-Anzr: J. Eric Roskos UUCP: Ofc: ..!{decvax,ucbvax,ihnp4}!vax135!petsd!peora!jer Home: ..!{decvax,ucbvax,ihnp4}!vax135!petsd!peora!jerpc!jer US Mail: MS 795; Perkin-Elmer SDC; 2486 Sand Lake Road, Orlando, FL 32809-7642 *"But, I want one what goes `WANGO'!" -- From a 1950s Pogo comic strip Brought to you by Super Global Mega Corp .com