[lldb][swift] Mark async unwinding plans as SourcedFromCompiler #9820
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LLDB always attempts to check other unwinding plans when an unwind plan produces a CFA == 0. It does so because it doesn't distinguish the case where the plan truly produced the end of the stack versus the case where the plan was faulty. We need a mechanism to disable this for swift async plans: if the language runtime constructs such a plan, then that plan will correctly identify the bottom of the stack. Checking other plans is harmless in non-async settings (they would just produce the same backtrace), but it is harmful for async virtual backtraces, as a "regular" unwind plan would produce a real backtrace if it were asked to start from the top of the stack (which would happen in short backtraces). Until such mechanism exists, we can work around the issue by claiming swift async plans are "sourced from compiler", which seem to disable the fallback mechanism because plans sourced from the compiler are considered the most reliable plans. rdar://142683622
adrian-prantl
approved these changes
Jan 13, 2025
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@swift-ci test |
jasonmolenda
approved these changes
Jan 13, 2025
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LLDB always attempts to check other unwinding plans when an unwind plan produces a CFA == 0. It does so because it doesn't distinguish the case where the plan truly produced the end of the stack versus the case where the plan was faulty.
We need a mechanism to disable this for swift async plans: if the language runtime constructs such a plan, then that plan will correctly identify the bottom of the stack. Checking other plans is harmless in non-async settings (they would just produce the same backtrace), but it is harmful for async virtual backtraces, as a "regular" unwind plan would produce a real backtrace if it were asked to start from the top of the stack (which would happen in short backtraces).
Until such mechanism exists, we can work around the issue by claiming swift async plans are "sourced from compiler", which seem to disable the fallback mechanism because plans sourced from the compiler are considered the most reliable plans.
rdar://142683622