holmes@dalcs.UUCP (Ray Holmes) (01/14/84)
[] I used to show people (CDC hackers) a short routine (about eight lines) and ask what was in the registers after it stopped. No one ever got the right answer as it consisted of a self modifying loop that depended on this "bug" to actually loop almost twice as many times as the code sugested. This caused several interactive debugging programs to get the same (incorrect) answers as people did. R
saj@iuvax.UUCP (02/15/84)
#R:azure:-248800:iuvax:11800010:000:472 iuvax!apratt Jan 12 20:59:00 1984 You better believe there were some COMPASS hacks (CDC assembly code) who took advantage of the "bug" you mention -- once a word is in cache, you can modify it. It would be just like one fellow I know to do that. His loops always (well, almost always) fit in 15 words (I think that was the number), and he never wasted the 15 bits which a jump instruction at the beginning of a word wastes. Talk about slick, tight code! -- Allan Pratt ...ihnp4!inuxc!iuvax!apratt