VC6 doesn't seem to want to accept default parameter value for templated functions like this. Poor solution: just put in the default in the actual function call.

stepmania/src/LuaFunctions.h

@@ -71,7 +71,7 @@ int LuaFunc_##func( lua_State *L ) { \
 	REQ_ARGS( #func, 1 ); \
 	REQ_ARG( #func, 1, string ); \
 	CString str; \
-	LuaHelpers::PopStack( str ); \
+	LuaHelpers::PopStack( str, NULL ); \
 	LUA_RETURN( call, L ); \
 } \
 LuaFunction( func ); /* register it */
@@ -83,8 +83,8 @@ int LuaFunc_##func( lua_State *L ) { \
 	REQ_ARG( #func, 2, string ); \
 	CString str1; \
 	CString str2; \
-	LuaHelpers::PopStack( str2 ); \
-	LuaHelpers::PopStack( str1 ); \
+	LuaHelpers::PopStack( str2, NULL ); \
+	LuaHelpers::PopStack( str1, NULL ); \
 	LUA_RETURN( call, L ); \
 } \
 LuaFunction( func ); /* register it */

stepmania/src/LuaManager.cpp

@@ -141,7 +141,7 @@ void LuaManager::SetGlobal( const CString &sName )
 static int LuaPanic( lua_State *L )
 {
 	CString sErr;
-	LuaHelpers::PopStack( sErr );
+	LuaHelpers::PopStack( sErr, NULL );
 
 	RageException::Throw( "%s", sErr.c_str() );
 }
@@ -270,7 +270,7 @@ bool LuaManager::RunScript( const CString &sScript, const CString &sName, CStrin
 
 		if( ret )
 		{
-			LuaHelpers::PopStack( sError );
+			LuaHelpers::PopStack( sError, NULL );
 			return false;
 		}
 	}
@@ -280,7 +280,7 @@ bool LuaManager::RunScript( const CString &sScript, const CString &sName, CStrin
 		int ret = lua_pcall( L, 0, iReturnValues, 0 );
 		if( ret )
 		{
-			LuaHelpers::PopStack( sError );
+			LuaHelpers::PopStack( sError, NULL );
 			return false;
 		}
 	}

stepmania/src/PrefsManager.cpp

@@ -861,7 +861,7 @@ int LuaFunc_GetPreference( lua_State *L )
 	REQ_ARG( "GetPreference", 1, string );
 
 	CString sName;
-	LuaHelpers::PopStack( sName );
+	LuaHelpers::PopStack( sName, NULL );
 
 	IPreference *pPref = PREFSMAN->GetPreferenceByName( sName );
 	if( pPref == NULL )