On Tue, Jan 10, 2017 at 3:13 PM, David T. Lewis <lewis@mail.msen.com> wrote:

Thanks Bert. It appears to be something related to MethodContext. Since it
is VM related, I initially guessed that it might be something related to
the method cache, but I was able to disable that in the VM and the symptoms
did not change. I'm thinking now that it might be a failure in primitive 61
when trying to copy a MethodContext, this based on the debugger stack
(although I cannot actually display anything useful in the debugger).

I'll report back if I end up figuring it out, meanwhile any and all historical
clues are appreciated :-)

Ah, slowly all the hacks I had to put in are coming back to me ;)

Some early images fill the context stack before advancing its stack pointer. I have a flag to allow that, it's pretty certainly used in primitive 61. Normally the VM does not allow access beyond the SP because there is garbage there (stack pops do not nil out the context slot):


But since the regular VM does not allow it, no image (except the really old ones) ever does it, so I just leave the flag enabled whenever "oldPrims" is in effect ;) Would be better if we could come up with a better way to identify these images.

- Bert -