Re: [TUHS] Disassemblers

I saw this post and it reminded me of a meeting that Dennis and I had with Bill Wulf. At one point, Dennis decided to write an optimizer but gave up after a week or two because when he had coded the data structures he needed he had filled up the PDP-11 memory! It was a very strong part of the Unix meme that Unix and C would run on small computers since most of the universities couldn't afford bigger ones at the time. When PCC came along and started running on 32-bit machines, I started thinking about algorithms for optimization. A problem that I had no good solution for could be illustrated by a simple piece of code: x = *p; y = *q; q gets changed *q = z; The question is, do I need to reload x now because q might have been changed to point to the same place as p? At around this time, Al Aho was invited to go to CMU and give a talk, and he invited me to come with him. We spent about an hour and a half one-on-one with Bill Wulf -- I seem to remember a lot of mutual respect going on. But when I asked him about my problem, he really didn't have much to say about it. I finally got him to agree that his compiler had a bug. But he said there was a flag they could set on the compiler that would turn of optimization and if your program had mysterious bugs, you should use the flag. I recall that Al, always in search of better algorithms, was a bit disappointed -- I was a bit more pragmatic about it. On the whole, it was a good meeting, and the "Engineering ... Compiler" book was one of my favorites when it came out. Steve