[Vm-dev] Tracing a Spur Image from Smalltalk

David T. Lewis lewis at mail.msen.com
Fri Feb 26 19:27:56 UTC 2016

That is very good news! The Cuis folks will be happy to hear about this
also, as there has been recent discussion on the Cuis list about how to do
a transition to Spur format.

If I recall right, the issue with tracing and resuming on Cog had to do
with resuming in the middle of a method of a jitted method. I don't think
that I ever positively confirmed that theory, but things worked fine under
an interpreter and it was a trivial step to re-save from Cog.


> I've updated the SystemTracer package to trace a Spur-format image.
> This works as far as I can tell, producing a header that looks just like
> the
> header produced by the VM and the objects written also look good. I can
> also
> open the image in RSqueak, but not on Spur. It crashes immediately and
> produces a Smalltalk backtrace that looks like it never manages to return
> from the image-saving method (but the names in the Stack-trace all look
> ok,
> leading me to believe that enough objects got written ok to figure out
> classes, method names, find the right Process to run and so forth).
> Curiously, the old SystemTracer2 class that writes Cog-format images also
> produces images that cannot be opened by Cog VMs, only Interpreter VMs. So
> I
> assume there are other assumptions that maybe the JIT makes when starting
> up.
> So my question is, what assumptions could there be, and where could I
> start
> looking.
> Cheers,
> Tim
> (If you're wondering why I'm using the Smalltalk-level tracing at all - in
> our quest to create (with RSqueakVM) a Squeak VM that runs Squeak code
> fast
> enough that we no longer have to rely on C code from plugins or optional
> primitives, we're trying to see how far we can push this, and e.g. write
> the
> image from within itself, too.)
> --
> View this message in context:
> http://forum.world.st/Tracing-a-Spur-Image-from-Smalltalk-tp4881224.html
> Sent from the Squeak VM mailing list archive at Nabble.com.

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