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Re: [RFA] JVMTI Stack Tracing
Andrew Haley wrote:
David Daney writes:
> Andrew Haley wrote:
> > Kyle Galloway writes:
> >
> > Aha! That makes sense, thanks. You didn't say that, so I was very
> > confused.
> >
> > As far as I know, you're right. There doesn't seem to be any way to
> > use gcc's unwinder machinery to trace the stack of anything othe than
> > the current thread.
> >
> It shouldn't be too difficult though. All the unwinder does is load up
> a framestate structure with values taken from the current thread and run
> its state machine.
No, it's not as easy as that. The unwinder data is not always valid:
we only emit unwinder information at places where we believe an
exception might be thrown. A thread that has been pre-empted might
not have unwinder data for the current PC.
I knew that. It was just temporarily forgotten.
However I think that if DWARF .eh_frame data is used many target
architectures will always have sufficient information to generate a
stack trace. Actually being able to do the unwinding and discover
values for all variables would be problematical.
David Daney