Jason Orendorff [:jorendorff] Assignee
	Description • 6 years ago

All the state needed to recreate an actual stack frame is present in a suspended generator, so it should be possible to query a suspended generator frame like any other frame.

Wait, wait-- I'm getting a signal from ... THE FUTURE

It's me! I'm saying that... querying the suspended frame turns out to be embarrassingly easy, to the point of not even being interesting... while getting the bookkeeping right involves fixing an apparently endless long tail of assertions.

Hmm.

I'm going to try to get someone else to take this bug.

	Jason Orendorff [:jorendorff] Assignee
	Comment 1 • 6 years ago

jimb refuses to take, claiming the resulting time-travel paradox would destroy the universe :-P

	Jason Orendorff [:jorendorff] Assignee
	Comment 2 • 6 years ago

DebuggerFrame::RESERVED_SLOTS is inaccurate and fortunately unused.

	Jason Orendorff [:jorendorff] Assignee
	Comment 3 • 6 years ago

For compartment correctness, the reference is via a Debugger.Object whose
referent is the actual GeneratorObject.

	Jason Orendorff [:jorendorff] Assignee
	Comment 4 • 6 years ago

The slot won't be accessed again once the Frame is inactive, because all
operations on the Frame throw. So the sole effect of these changes is that
inactive Frame objects no longer keep the generator unnecessarily GC-alive.

	Jason Orendorff [:jorendorff] Assignee
	Comment 5 • 6 years ago

There's also a little bit of code motion in this patch--not much. Still no
observable change in behavior.

	Jason Orendorff [:jorendorff] Assignee
	Comment 6 • 6 years ago

Code motion only.

	Jason Orendorff [:jorendorff] Assignee
	Comment 7 • 6 years ago

This is an AbstractFramePtr lookalike that can also handle suspended
generators, answering many of the same questions the debugger might ask of any
on-stack frame.

In this patch the type is implemented but not used.

TODO: See if it could just be a Variant.
TODO: Implement js::GetThisValueForDebuggerMaybeOptimizedOutGenerator.

	Jason Orendorff [:jorendorff] Assignee
	Comment 8 • 6 years ago

With this change, suspended Debugger.Frame objects are now `.live`.

	Jason Orendorff [:jorendorff] Assignee
	Comment 9 • 6 years ago

DebuggerFrame::RESERVED_SLOTS is inaccurate and fortunately unused.

Depends on D6990

	Jason Orendorff [:jorendorff] Assignee
	Comment 10 • 6 years ago

For compartment correctness, the reference is via a Debugger.Object whose
referent is the actual GeneratorObject.

Depends on D7012

	Jason Orendorff [:jorendorff] Assignee
	Comment 11 • 6 years ago

The slot won't be accessed again once the Frame is inactive, because all
operations on the Frame throw. So the sole effect of these changes is that
inactive Frame objects no longer keep the generator unnecessarily GC-alive.

Depends on D7015

	Jason Orendorff [:jorendorff] Assignee
	Comment 12 • 6 years ago

There's also a little bit of code motion in this patch--not much. Still no
observable change in behavior.

Depends on D7016

	Jason Orendorff [:jorendorff] Assignee
	Comment 13 • 6 years ago

Code motion only.

Depends on D7018

	Jason Orendorff [:jorendorff] Assignee
	Comment 14 • 6 years ago

https://treeherder.mozilla.org/#/jobs?repo=try&revision=5c77276d344c407ce94baf1f86cc2bfd90714409

	Jason Orendorff [:jorendorff] Assignee
	Comment 15 • 6 years ago

This is an AbstractFramePtr lookalike that can also handle suspended
generators, answering many of the same questions the debugger might ask of any
on-stack frame.

In this patch the type is implemented but not used.

TODO: Implement js::GetThisValueForDebuggerMaybeOptimizedOutGenerator.

Depends on D7019

	Jason Orendorff [:jorendorff] Assignee
	Comment 16 • 6 years ago

With this change, suspended Debugger.Frame objects are now `.live`.

Depends on D10386