Stop printall(df.global) from breaking if there are unknown addresses.

LUA_API.rst

@@ -68,6 +68,11 @@ All typed objects have the following built-in features:
   and values. Fields are enumerated in memory order. Methods and
   lua wrapper properties are not included in the iteration.
 
+  **WARNING**: a few of the data structures (like ui_look_list)
+  contain unions with pointers to different types with vtables.
+  Using pairs on such structs is an almost sure way to crash with
+  an access violation.
+
 * ``ref._kind``
 
   Returns one of: ``primitive``, ``struct``, ``container``,

Lua API.html

@@ -395,6 +395,10 @@ Every structured field access produces a new userdata instance.</p>
 <p>Returns an iterator for the sequence of actual C++ field names
 and values. Fields are enumerated in memory order. Methods and
 lua wrapper properties are not included in the iteration.</p>
+<p><strong>WARNING</strong>: a few of the data structures (like ui_look_list)
+contain unions with pointers to different types with vtables.
+Using pairs on such structs is an almost sure way to crash with
+an access violation.</p>
 </li>
 <li><p class="first"><tt class="docutils literal">ref._kind</tt></p>
 <p>Returns one of: <tt class="docutils literal">primitive</tt>, <tt class="docutils literal">struct</tt>, <tt class="docutils literal">container</tt>,

library/LuaTypes.cpp

@@ -1072,10 +1072,10 @@ void LuaWrapper::SetFunctionWrappers(lua_State *state, const FunctionReg *reg)
 /**
  * Add fields in the array to the UPVAL_FIELDTABLE candidates on the stack.
  */
-static void IndexFields(lua_State *state, int base, struct_identity *pstruct)
+static void IndexFields(lua_State *state, int base, struct_identity *pstruct, bool globals)
 {
     if (pstruct->getParent())
-        IndexFields(state, base, pstruct->getParent());
+        IndexFields(state, base, pstruct->getParent(), globals);
 
     auto fields = pstruct->getFields();
     if (!fields)
@@ -1105,7 +1105,10 @@ static void IndexFields(lua_State *state, int base, struct_identity *pstruct)
             break;
 
         default:
-            AssociateId(state, base+3, ++cnt, name.c_str());
+            // Do not add invalid globals to the enumeration order
+            if (!globals || *(void**)fields[i].offset)
+                AssociateId(state, base+3, ++cnt, name.c_str());
+
             lua_pushlightuserdata(state, (void*)&fields[i]);
             lua_setfield(state, base+2, name.c_str());
             break;
@@ -1143,7 +1146,7 @@ void LuaWrapper::IndexStatics(lua_State *state, int meta_idx, int ftable_idx, st
  * Make a struct-style object metatable.
  */
 static void MakeFieldMetatable(lua_State *state, struct_identity *pstruct,
-                               lua_CFunction reader, lua_CFunction writer)
+                               lua_CFunction reader, lua_CFunction writer, bool globals = false)
 {
     int base = lua_gettop(state);
 
@@ -1152,7 +1155,7 @@ static void MakeFieldMetatable(lua_State *state, struct_identity *pstruct,
     // Index the fields
     lua_newtable(state);
 
-    IndexFields(state, base, pstruct);
+    IndexFields(state, base, pstruct, globals);
 
     // Add the iteration metamethods
     PushStructMethod(state, base+1, base+3, meta_struct_next);
@@ -1304,7 +1307,7 @@ void struct_identity::build_metatable(lua_State *state)
 
 void global_identity::build_metatable(lua_State *state)
 {
-    MakeFieldMetatable(state, this, meta_global_index, meta_global_newindex);
+    MakeFieldMetatable(state, this, meta_global_index, meta_global_newindex, true);
 }
 
 /**