Re: How does one find a loop in a gettable chain?

[Sean Conner <sean@...>]

It was thus said that the Great Dirk Laurie once stated:
> I'm getting the following error:
> 
>    gettable chain too long; possible loop
> 
> It's difficult to locate the error by my usual technique
> of sprinkling print statements around. This may be
> a case where the debug library is needed.
> 
> The traceback is of little use. It contains only the
> outermost call, which is almost the only statement
> in the main chunk.

  You could trying wrapping the topmost call with xpcall().  I do that at
work and use the following message handler:

function stackdump(...)
  local max = select('#',...)

  for i = 1 , max do
    syslog('debug',"Stack: %d %d %s",i,i-max-1,tostring(select(i,...)))
  end

  local stack = {}
  for i = 1 , 10 do
    local info = debug.getinfo(i,"Sl")
    if not info then break end
    table.insert(stack,string.format(" [%s(%d)]",info.source,info.currentline))
  end
  
  syslog('debug',"stack=%s",table.concat(stack))
  return ...
end

I use syslog() because I might not *have* a terminal, but it should be easy
enough to replace syslog() with print().

  -spc (I tend to log to syslog() as I have a real time view of it [1][2])

[1]	https://github.com/spc476/syslogintr

	It's a syslog daemon written in C and Lua.  

[2]	I have syslogintr  configured to forward logs to a multicast
	address.  I can then run other instances of syslogintr to listen on
	this address and the most common use I use of this is to view the
	logs in realtime (and color coded: https://github.com/spc476/syslogintr/blob/master/realtime.lua)