Re: [NSE] Getting a backtrace?

["Patrick Donnelly" <batrick.donnelly () gmail com>]

On Fri, Oct 24, 2008 at 8:47 AM, Ron <ron () skullsecurity net> wrote:
> Hello,
>
> When trying to troubleshoot problems with my scripts, I often get errors
> such as this:
> SCRIPT ENGINE: /usr/share/nmap/nselib/msrpc.lua:139: bad argument #1 to
> 'char' (number expected, got nil)
>
> The problem is, the error is happening inside a function that's being called
> from 100+ places. Is there some way to get more information when there's a
> failure (the most important being, the backtrace/call stack/whatever)?
>
> Thanks!
>
> Ron

As of right now NSE does not print out a backtrace (it could easily if
there is a general desire for this). You can get the information when
debugging by hooking your action function (emphasis on "when
debugging") like so:

function action (host, port)
 -- your script does stuff
end

-- ... other stuff in file

local real_action = action;

function action (...)
  local t = {n = select("#", ...), ...};
  local status, ret = xpcall(function() return real_action(unpack(t,
1, t.n)) end,
      debug.traceback)
  if not status then error(ret) end
  return ret
end

Cheers,

-- 
-Patrick Donnelly

"One of the lessons of history is that nothing is often a good thing
to do and always a clever thing to say."

-Will Durant

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