[lldb] Update ThreadPlanStepOut to handle new breakpoint behavior

lldb/source/Target/ThreadPlanStepOut.cpp

@@ -364,8 +364,11 @@ bool ThreadPlanStepOut::ShouldStop(Event *event_ptr) {
   }
 
   if (!done) {
-    StackID frame_zero_id = GetThread().GetStackFrameAtIndex(0)->GetStackID();
-    done = !(frame_zero_id < m_step_out_to_id);
+    StopInfoSP stop_info_sp = GetPrivateStopInfo();
+    if (stop_info && stop_info_sp->GetStopReason() == eStopReasonBreakpoint) {
+      StackID frame_zero_id = GetThread().GetStackFrameAtIndex(0)->GetStackID();
+      done = !(frame_zero_id < m_step_out_to_id);
+    }
   }
 
   // The normal step out computations think we are done, so all we need to do

lldb/test/API/functionalities/thread/finish-from-empty-func/Makefile

@@ -0,0 +1,3 @@
+C_SOURCES := main.c
+
+include Makefile.rules

lldb/test/API/functionalities/thread/finish-from-empty-func/TestEmptyFuncThreadStepOut.py

@@ -0,0 +1,43 @@
+"""
+Test finish out of an empty function (may be one-instruction long)
+"""
+
+import lldb
+from lldbsuite.test.decorators import *
+from lldbsuite.test.lldbtest import *
+from lldbsuite.test import lldbutil
+
+
+class FinishFromEmptyFunctionTestCase(TestBase):
+    NO_DEBUG_INFO_TESTCASE = True
+
+    def test_finish_from_empty_function(self):
+        """Test that when stopped at a breakpoint in an empty function, finish leaves it correctly."""
+        self.build()
+        exe = self.getBuildArtifact("a.out")
+        target, process, thread, _ = lldbutil.run_to_name_breakpoint(
+            self, "done", exe_name=exe
+        )
+        if self.TraceOn():
+            self.runCmd("bt")
+
+        correct_stepped_out_line = line_number("main.c", "leaving main")
+        return_statement_line = line_number("main.c", "return 0")
+        safety_bp = target.BreakpointCreateByLocation(
+            lldb.SBFileSpec("main.c"), return_statement_line
+        )
+        self.assertTrue(safety_bp.IsValid())
+
+        error = lldb.SBError()
+        thread.StepOut(error)
+        self.assertTrue(error.Success())
+
+        if self.TraceOn():
+            self.runCmd("bt")
+
+        frame = thread.GetSelectedFrame()
+        self.assertEqual(
+            frame.line_entry.GetLine(),
+            correct_stepped_out_line,
+            "Step-out lost control of execution, ran too far",
+        )

lldb/test/API/functionalities/thread/finish-from-empty-func/main.c

@@ -0,0 +1,8 @@
+#include <stdio.h>
+void done() {}
+int main() {
+  puts("in main");
+  done();
+  puts("leaving main");
+  return 0;
+}