+ return ret;
+end
+
+local function build_source_boundary_marker(last_source_desc)
+ local padding = string.rep("-", math.floor(((optimal_line_length - 6) - #last_source_desc)/2));
+ return getstring(styles.boundary_padding, "v"..padding).." "..getstring(styles.filename, last_source_desc).." "..getstring(styles.boundary_padding, padding..(#last_source_desc%2==0 and "-v" or "v "));
+end
+
+function _traceback(thread, message, level)
+
+ -- Lua manual says: debug.traceback ([thread,] [message [, level]])
+ -- I fathom this to mean one of:
+ -- ()
+ -- (thread)
+ -- (message, level)
+ -- (thread, message, level)
+
+ if thread == nil then -- Defaults
+ thread, message, level = coroutine.running(), message, level;
+ elseif type(thread) == "string" then
+ thread, message, level = coroutine.running(), thread, message;
+ elseif type(thread) ~= "thread" then
+ return nil; -- debug.traceback() does this