llvm-project

1aed87d2 - [lldb] Don't merge a frame provider's frames into the unwinder frame list (#216847)

[lldb] Don't merge a frame provider's frames into the unwinder frame list (#216847) `Thread::ClearStackFrames` keeps the previous public frame list as the predecessor of the next unwinder list. When a scripted frame provider is registered, that public list is a `SyntheticStackFrameList` holding `BorrowedStackFrames`, and the unwinder list's merge step reuses a predecessor frame whenever the stack IDs match, so it adopted frames belonging to the provider's list. `UpdatePreviousFrameFromCurrentFrame` refreshes `StackFrame::m_frame_index`, but `BorrowedStackFrame::GetFrameIndex()` returns its own `m_new_frame_index`, which supersedes it. The adopted frame keeps reporting its index from the previous stop, so once the stack grows the backtrace stops counting up: ``` frame #1: middle frame #1: main frame #2: start ``` Such a frame also delegates its stack ID, register context and symbol context to a frame from the previous stop that the merge never refreshes, so it could report stale state as well. In the backtrace above, main also lost its source location. When the merge finds a matching predecessor frame that is a `BorrowedStackFrame`, keep the freshly unwound frame instead of adopting it. Only providers create BorrowedStackFrames, so this never drops a frame the unwinder built itself. Signed-off-by: Med Ismail Bennani <ismail@bennani.ma>