> On Feb 27, 2024, at 10:32 AM, Kyle Huey <kh...@pernos.co> wrote: > > On Wed, Feb 21, 2024 at 9:12 AM Adrian Prantl <apra...@apple.com > <mailto:apra...@apple.com>> wrote: >> Can you clarify what kind of information you are interested in? Are you >> talking about representing variables inside of coroutines, function pointers >> to coroutines, linetables for coroutines, ...? >> >> LLDB's Swift plugin for example supports Swift async functions (which are >> effectively coroutines) but does so without adding any new extensions to >> DWARF. Here's a recent talk from last year's LLVM dev meeting on that topic: >> https://www.youtube.om/watch?v=g4fei6Vl7o8 >> <https://www.youtube.com/watch?v=g4fei6Vl7o8> > > The async control flow parts of this (backtraces and stepping) are what I am > particularly interested in. Variables seem straightforward since DWARF > location expressions are already generic enough to let you point to heap > allocated storage for variables that survive across yield points. Your talk > is a good demo of the behavior I'd like to achieve (for Rust specifically). A > few technical questions: > > How do you "identify" a particular chain of funclet invocations that go > together? I assume this is done based on the pointer identity of the > async_context.
Each async_context has a continuation pointer pointing to the next funclet that is going to be executed when the current coroutine returns. > And the logic to understand what the async_context is and where it's found at > function entry points is hardcoded into the Swift plugin? Yes, there is a Swift-specific unwinder plugin in LLDB that does this. There is also a custom stepping plan there. > > How do you handle pointer reuse on async_contexts? If I'm understanding the question correctly: there is a heap async_context object for every continuation that is on the schedule at any time. I don't think we can prevent a later continuation to be allocated in the same place as a previous one, but since they can never appear at the same time, this also isn't a problem. -- adrian > > - Kyle > >> -- adrian >> >> >> >> >> >> > On Feb 20, 2024, at 11:47 AM, Kyle Huey via Dwarf-discuss >> > <dwarf-discuss@lists.dwarfstd.org >> > <mailto:dwarf-discuss@lists.dwarfstd.org>> wrote: >> > >> > Has anyone proposed or discussed DWARF structures to represent coroutines >> > or similar constructs? I skimmed the open issues list and didn't see >> > anything relevant. >> > >> > - Kyle >>
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