Thread Plans pushed by a scripted plan should be private plans.

If a plan is not private, "thread plan discard" can discard it.  It would
not be hard to write reliable scripted plan if its subplans could get
removed out from under it.

Author: jimingham

lldb/source/API/SBThreadPlan.cpp

@@ -237,7 +237,9 @@ SBThreadPlan SBThreadPlan::QueueThreadPlanForStepOverRange(
 
     if (plan_status.Fail())
       error.SetErrorString(plan_status.AsCString());
-
+    else
+      plan.m_opaque_sp->SetPrivate(true);
+    
     return LLDB_RECORD_RESULT(plan);
   } else {
     return LLDB_RECORD_RESULT(SBThreadPlan());
@@ -281,6 +283,8 @@ SBThreadPlan::QueueThreadPlanForStepInRange(SBAddress &sb_start_address,
 
     if (plan_status.Fail())
       error.SetErrorString(plan_status.AsCString());
+    else
+      plan.m_opaque_sp->SetPrivate(true);
 
     return LLDB_RECORD_RESULT(plan);
   } else {
@@ -321,6 +325,8 @@ SBThreadPlan::QueueThreadPlanForStepOut(uint32_t frame_idx_to_step_to,
 
     if (plan_status.Fail())
       error.SetErrorString(plan_status.AsCString());
+    else
+      plan.m_opaque_sp->SetPrivate(true);
 
     return LLDB_RECORD_RESULT(plan);
   } else {
@@ -356,6 +362,8 @@ SBThreadPlan SBThreadPlan::QueueThreadPlanForRunToAddress(SBAddress sb_address,
 
     if (plan_status.Fail())
       error.SetErrorString(plan_status.AsCString());
+    else
+      plan.m_opaque_sp->SetPrivate(true);
 
     return LLDB_RECORD_RESULT(plan);
   } else {
@@ -390,6 +398,8 @@ SBThreadPlan::QueueThreadPlanForStepScripted(const char *script_class_name,
 
     if (plan_status.Fail())
       error.SetErrorString(plan_status.AsCString());
+    else
+      plan.m_opaque_sp->SetPrivate(true);
 
     return LLDB_RECORD_RESULT(plan);
   } else {
@@ -415,6 +425,8 @@ SBThreadPlan::QueueThreadPlanForStepScripted(const char *script_class_name,
 
     if (plan_status.Fail())
       error.SetErrorString(plan_status.AsCString());
+    else
+      plan.m_opaque_sp->SetPrivate(true);
 
     return LLDB_RECORD_RESULT(plan);
   } else {