<rdar://problem/10103468>

I started work on being able to add symbol files after a debug session
had started with a new "target symfile add" command and quickly ran into
problems with stale Address objects in breakpoint locations that had 
lldb_private::Section pointers into modules that had been removed or 
replaced. This also let to grabbing stale modules from those sections. 
So I needed to thread harded the Address, Section and related objects.

To do this I modified the ModuleChild class to now require a ModuleSP
on initialization so that a weak reference can created. I also changed
all places that were handing out "Section *" to have them hand out SectionSP.
All ObjectFile, SymbolFile and SymbolVendors were inheriting from ModuleChild
so all of the find plug-in, static creation function and constructors now
require ModuleSP references instead of Module *. 

Address objects now have weak references to their sections which can
safely go stale when a module gets destructed. 

This checkin doesn't complete the "target symfile add" command, but it
does get us a lot clioser to being able to do such things without a high
risk of crashing or memory corruption.

llvm-svn: 151336
diff --git a/lldb/source/Symbol/Variable.cpp b/lldb/source/Symbol/Variable.cpp
index 161d482..616eaa7 100644
--- a/lldb/source/Symbol/Variable.cpp
+++ b/lldb/source/Symbol/Variable.cpp
@@ -146,8 +146,9 @@
         ABI *abi = NULL;
         if (m_owner_scope)
         {
-            Module *module = m_owner_scope->CalculateSymbolContextModule();
-            abi = ABI::FindPlugin (module->GetArchitecture()).get();
+            ModuleSP module_sp (m_owner_scope->CalculateSymbolContextModule());
+            if (module_sp)
+                abi = ABI::FindPlugin (module_sp->GetArchitecture()).get();
         }
         m_location.GetDescription(s, lldb::eDescriptionLevelBrief, loclist_base_addr, abi);
     }
@@ -243,7 +244,7 @@
     {
         SymbolContext sc;
         CalculateSymbolContext(&sc);
-        if (sc.module_sp.get() == address.GetModulePtr())
+        if (sc.module_sp == address.GetModule())
         {
             // Is the variable is described by a single location?
             if (!m_location.IsLocationList())
@@ -480,13 +481,14 @@
     {
         SymbolContext sc;
         CalculateSymbolContext(&sc);
-        if (sc.module_sp.get() == address.GetModulePtr())
+        if (sc.module_sp == address.GetModule())
         {
             ABI *abi = NULL;
             if (m_owner_scope)
             {
-                Module *module = m_owner_scope->CalculateSymbolContextModule();
-                abi = ABI::FindPlugin (module->GetArchitecture()).get();
+                ModuleSP module_sp (m_owner_scope->CalculateSymbolContextModule());
+                if (module_sp)
+                    abi = ABI::FindPlugin (module_sp->GetArchitecture()).get();
             }
 
             const addr_t file_addr = address.GetFileAddress();