fix interface api in lua5.2

src/lua/LuaCompat.c

@@ -1,11 +1,19 @@
 #include "LuaCompat.h"
 
 #if LUA_VERSION_NUM >= 502
-//implement missing luaL_typerror function
+// Implement missing luaL_typerror function
 int luaL_typerror (lua_State *L, int narg, const char *tname)
 {
 	const char *msg = lua_pushfstring(L, "%s expected, got %s", tname, luaL_typename(L, narg));
 	return luaL_argerror(L, narg, msg);
 }
 
+#else
+
+// Implement function added in lua 5.2 that we now use
+void lua_pushglobaltable(lua_State *L)
+{
+	lua_pushvalue(L, LUA_GLOBALSINDEX);
+}
+
 #endif

src/lua/LuaCompat.h

@@ -26,9 +26,10 @@ extern "C"
 
 #if LUA_VERSION_NUM >= 502
 #define luaL_getn(L,i)		lua_rawlen(L, (i))
-#define LUA_GLOBALSINDEX	LUA_RIDX_GLOBALS
 
 LUALIB_API int (luaL_typerror) (lua_State *L, int narg, const char *tname);
+#else
+LUALIB_API void (lua_pushglobaltable) (lua_State *L);
 #endif
 
 #ifdef __cplusplus

src/lua/LuaLuna.h

@@ -15,14 +15,17 @@ template <typename T> class Luna
 		lua_newtable(L);
 		int methods = lua_gettop(L);
 
+		// push global table to the stack, so we can add the component APIs to it
+		lua_pushglobaltable(L);
+
 		luaL_newmetatable(L, T::className);
 		int metatable = lua_gettop(L);
 
 		// store method table in globals so that
 		// scripts can add functions written in Lua.
 		lua_pushstring(L, T::className);
 		lua_pushvalue(L, methods);
-		lua_settable(L, LUA_GLOBALSINDEX);
+		lua_settable(L, -4);
 
 		lua_pushliteral(L, "__metatable");
 		lua_pushvalue(L, methods);
@@ -60,7 +63,7 @@ template <typename T> class Luna
 			lua_settable(L, methods);
 		}
 
-		lua_pop(L, 2);  // drop metatable and method table
+		lua_pop(L, 3);  // pop global table, metatable, and method table
 	}
 
 	// get userdata from Lua stack and return pointer to T object