[lldb] Fix stepping out if the return address is not allowed to stop at (#161982)

When a thread reaches a breakpoint at the return address set by
`ThreadPlanStepOut`, `ThreadPlanStepOut::ShouldStop()` calls
`ThreadPlanShouldStopHere::InvokeShouldStopHereCallback()`, and if it
returns `false`, `ThreadPlanShouldStopHere::QueueStepOutFromHerePlan()`
is called to queue a new plan to skip the corresponding range. Once the
new plan finishes, `ThreadPlanStepOut::ShouldStop()` should recheck the
stop condition; however, there is no code path in the method that sets
`done` to `true`. Before #126838, if `done` was `false`, the method checked
if a suitable frame had been reached. After the patch, the check is only
performed at a breakpoint; thus, the execution continues.

This patch causes `ThreadPlanStepOut::ShouldStop()` to recheck the stop
condition when `m_step_out_further_plan_sp` completes.

Author: igorkudrin

lldb/source/Target/ThreadPlanStepOut.cpp

@@ -397,9 +397,10 @@ bool ThreadPlanStepOut::ShouldStop(Event *event_ptr) {
     else
       return m_step_through_inline_plan_sp->ShouldStop(event_ptr);
   } else if (m_step_out_further_plan_sp) {
-    if (m_step_out_further_plan_sp->MischiefManaged())
+    if (m_step_out_further_plan_sp->MischiefManaged()) {
       m_step_out_further_plan_sp.reset();
-    else
+      done = true;
+    } else
       return m_step_out_further_plan_sp->ShouldStop(event_ptr);
   }
 

lldb/test/API/functionalities/thread/step_out_line0/Makefile

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

lldb/test/API/functionalities/thread/step_out_line0/TestThreadStepOutLine0.py

@@ -0,0 +1,35 @@
+"""
+Test stepping out of a function when the return location is an unsuitable
+stopping point.
+"""
+
+
+import lldb
+from lldbsuite.test.decorators import *
+from lldbsuite.test.lldbtest import *
+from lldbsuite.test import lldbutil
+
+
+class ThreadStepOutLine0TestCase(TestBase):
+    def test(self):
+        self.build()
+        target, process, thread, _ = lldbutil.run_to_source_breakpoint(
+            self, "// Set breakpoint here", lldb.SBFileSpec("main.c")
+        )
+        correct_stepped_out_line = line_number("main.c", "// Should stop here")
+        return_statement_line = line_number("main.c", "// Ran too far")
+        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())
+
+        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/step_out_line0/main.c

@@ -0,0 +1,11 @@
+int step_out_of_here(int a) {
+  return a + 5; // Set breakpoint here
+}
+
+int main() {
+#line 0
+  int v = step_out_of_here(3) + 7;
+#line 9
+  v += 11;  // Should stop here
+  return v; // Ran too far
+}