Returns a string with a traceback of the stack call. An optional message string is prepended to the beginning of the traceback message.
function f ()
function g ()
print (debug.traceback ("traceback in g"))
end -- g
g ()
end -- f
f ()
-->
traceback in g
stack traceback:
stdin:3: in function `g'
stdin:6: in function `f'
stdin:1: in main chunk
[C]: ?