Thread hardening part 3. Now lldb_private::Thread objects have std::weak_ptr
objects for the backlink to the lldb_private::Process. The issues we were
running into before was someone was holding onto a shared pointer to a 
lldb_private::Thread for too long, and the lldb_private::Process parent object
would get destroyed and the lldb_private::Thread had a "Process &m_process"
member which would just treat whatever memory that used to be a Process as a
valid Process. This was mostly happening for lldb_private::StackFrame objects
that had a member like "Thread &m_thread". So this completes the internal
strong/weak changes.

Documented the ExecutionContext and ExecutionContextRef classes so that our
LLDB developers can understand when and where to use ExecutionContext and 
ExecutionContextRef objects.



git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@151009 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/source/Interpreter/ScriptInterpreterPython.cpp b/source/Interpreter/ScriptInterpreterPython.cpp
index 0aefdaa..1d64e87 100644
--- a/source/Interpreter/ScriptInterpreterPython.cpp
+++ b/source/Interpreter/ScriptInterpreterPython.cpp
@@ -1496,7 +1496,8 @@
     if (!context)
         return true;
         
-    Target *target = context->exe_ctx.GetTargetPtr();
+    ExecutionContext exe_ctx (context->exe_ctx_ref);
+    Target *target = exe_ctx.GetTargetPtr();
     
     if (!target)
         return true;
@@ -1511,7 +1512,7 @@
     if (python_function_name != NULL 
         && python_function_name[0] != '\0')
     {
-        const StackFrameSP stop_frame_sp (context->exe_ctx.GetFrameSP());
+        const StackFrameSP stop_frame_sp (exe_ctx.GetFrameSP());
         BreakpointSP breakpoint_sp = target->GetBreakpointByID (break_id);
         if (breakpoint_sp)
         {