[Lldb-commits] [PATCH] D132624: [LLDB] Devirtualize coroutine promise types for `std::coroutine_handle`

[Jim Ingham via lldb-commits]

> On Aug 26, 2022, at 7:05 AM, Adrian Vogelsgesang via Phabricator via lldb-commits <lldb-commits at lists.llvm.org> wrote:
> 
> avogelsgesang added a comment.
> 
>> I don't know much about coroutines, but it seems like your goal is to format them like a linked list
> 
> actually, my preferred goal would be to show them as a logical, user-level thread. Such that you can type
> 
>  thread backtrace cxxcoro:0x55555555b2a0
> 
> to get the backtrace of the logical coroutine thread routed at the coroutine at address `0x55555555b2a0`, or maybe even
> 
>  thread backtrace cxxcoro:hdl
> 
> where `hdl` is evaluated as an expression to identify the coroutine handle from where to dump the backtrace.
> 
> Also, it would be neat if those logical threads show up in `thread list`...
> 
> But it seems there is currently no infrastructure yet in LLDB for logical threads provided by `LanguageRuntime` plugins.
> 
> I guess at some point, I will write an RFC about that on discourse. But before that, I will first do some more exploration on how LLDB works and I will first grab the low-hanging fruits (like a data formatter for `std::coroutine_handle` and patching LLVM to emit the necessary debug info)

lldb has the notion of "extended backtrace threads" - backed by lldb's "History" threads - that it uses in a similar circumstance handling Darwin dispatch queues.  If you have a thread that is serving a Darwin "dispatch queue" SBThread.GetExtendedBacktraceThreads will return the backtrace of the thread that enqueued the work, at the point where the enqueuing is done.  I bet you could make the same setup work for these coroutines.

Jim


> 
> 
> Repository:
>  rG LLVM Github Monorepo
> 
> CHANGES SINCE LAST ACTION
>  https://reviews.llvm.org/D132624/new/
> 
> https://reviews.llvm.org/D132624
> 
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