[Lldb-commits] [lldb] [lldb][Target] Clear selected frame index after a StopInfo::PerformAction (PR #133078)

[Michael Buch via lldb-commits]

https://github.com/Michael137 created https://github.com/llvm/llvm-project/pull/133078

The motivation for this patch is that `StopInfo::GetSuggestedStackFrameIndex` would not take effect for `InstrumentationRuntimeStopInfo` (which we plan to implement in TBD). This was happening because the instrumentation runtime plugins would run utility expressions as part of the stop that would set the `m_selected_frame_idx`. This means `SelectMostRelevantFrame` was never called, and we would not be able to report the selected frame via the `StopInfo` object.

This patch makes sure we clear the `m_selected_frame_idx` to allow `GetSuggestedStackFrameIndex` to take effect, regardless of what the frame recognizers choose to do.

>From 91110b85aab9ddf41d1b52b9fc23d68883966b93 Mon Sep 17 00:00:00 2001
From: Michael Buch <michaelbuch12 at gmail.com>
Date: Wed, 26 Mar 2025 13:20:24 +0000
Subject: [PATCH] [lldb][Target] Clear selected frame index after a
 StopInfo::PerformAction

---
 lldb/include/lldb/Target/StackFrameList.h | 3 +++
 lldb/include/lldb/Target/Thread.h         | 5 +++++
 lldb/source/Target/Process.cpp            | 2 ++
 lldb/source/Target/StackFrameList.cpp     | 4 ++++
 4 files changed, 14 insertions(+)

diff --git a/lldb/include/lldb/Target/StackFrameList.h b/lldb/include/lldb/Target/StackFrameList.h
index 8a66296346f2d..d805b644b0b31 100644
--- a/lldb/include/lldb/Target/StackFrameList.h
+++ b/lldb/include/lldb/Target/StackFrameList.h
@@ -46,6 +46,9 @@ class StackFrameList {
   /// Mark a stack frame as the currently selected frame and return its index.
   uint32_t SetSelectedFrame(lldb_private::StackFrame *frame);
 
+  /// Resets the selected frame index of this object.
+  void ClearSelectedFrameIndex();
+
   /// Get the currently selected frame index.
   /// We should only call SelectMostRelevantFrame if (a) the user hasn't already
   /// selected a frame, and (b) if this really is a user facing
diff --git a/lldb/include/lldb/Target/Thread.h b/lldb/include/lldb/Target/Thread.h
index 1d1e3dcfc1dc6..9eb9cda983c4a 100644
--- a/lldb/include/lldb/Target/Thread.h
+++ b/lldb/include/lldb/Target/Thread.h
@@ -480,6 +480,11 @@ class Thread : public std::enable_shared_from_this<Thread>,
   bool SetSelectedFrameByIndexNoisily(uint32_t frame_idx,
                                       Stream &output_stream);
 
+  /// Resets the selected frame index of this object.
+  void ClearSelectedFrameIndex() {
+    return GetStackFrameList()->ClearSelectedFrameIndex();
+  }
+
   void SetDefaultFileAndLineToSelectedFrame() {
     GetStackFrameList()->SetDefaultFileAndLineToSelectedFrame();
   }
diff --git a/lldb/source/Target/Process.cpp b/lldb/source/Target/Process.cpp
index f2f5598f0ab53..6843d5b220742 100644
--- a/lldb/source/Target/Process.cpp
+++ b/lldb/source/Target/Process.cpp
@@ -4257,6 +4257,8 @@ bool Process::ProcessEventData::ShouldStop(Event *event_ptr,
         // appropriately. We also need to stop processing actions, since they
         // aren't expecting the target to be running.
 
+        thread_sp->ClearSelectedFrameIndex();
+
         // FIXME: we might have run.
         if (stop_info_sp->HasTargetRunSinceMe()) {
           SetRestarted(true);
diff --git a/lldb/source/Target/StackFrameList.cpp b/lldb/source/Target/StackFrameList.cpp
index 9c6208e9e0a65..3592c3c03db74 100644
--- a/lldb/source/Target/StackFrameList.cpp
+++ b/lldb/source/Target/StackFrameList.cpp
@@ -936,3 +936,7 @@ size_t StackFrameList::GetStatus(Stream &strm, uint32_t first_frame,
   strm.IndentLess();
   return num_frames_displayed;
 }
+
+void StackFrameList::ClearSelectedFrameIndex() {
+  m_selected_frame_idx.reset();
+}