[Squeak-VMdev] Re: SystemTracer2

[Dan I. <Da...@Sq...>]

Hi, Anthony -

>Here is the latest SystemTracer2, a merge of my past changes with
>Stephen Pair's.  SystemTracer2 works successfully on 3.7, but
>RehashingSystemTracer produces a corrupt image (bad hash tables?).  It
>shouldn't be too hard to inspect the code and figure it out (the
>Rehashing code is relatively small), otherwise you will have to run the
>InterpreterSimulator on the corrupt image in the debugger to see where
>it's getting stuck.  Stephen, hopefully you can figure this out.
>
>Dan, I hope you find the SystemTracer2 easy to work with.  Read the
>enclosed Readme and the SystemTracer2 class comment.

Many thanks for this.  It's going to be great to have all the tools up to date.  Right now, I'm hacking what I need to get started, but we will soon need the real tracer, including rehashing ability.

I'll hold off a bit more in hopes that Stephen can get the rehasher working, but I'm not stuck waiting on it yet.

	- Dan

PS:  A bit of history that might interest you .  In the "old days" before we put rehashing into the tracer, we would start up the new image, and "just hope" that enough would run so we could execute #rehashBadSets, which rehashed all sets in the system.  But, of course, this would not work if we changed the hashing of method dictionaries.  What did we do then?  We produced an interim VM that did linear search in all the message dictionaries.  Then we could run that one, fix the image, and save.  After that we could go back to a normal VM and everything worked.