[Vm-dev] Tracing a Spur Image from Smalltalk

[David T. Lewis]

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.

Dave

>
> 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.)
>
>
>
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>