Re: Problem with circular refrence and garbage collection

[Mark Hamburg <mark@...>]

Weak-keyed tables in Lua 5.1 will mark all of their values. So, the  
callback functions get marked which marks their upvalues which keeps  
col alive and conceivably button as well.

Lua 5.2 is supposed to address this, but a better solution is probably  
to use the fenv tables for userdata because this avoids the repeated  
marking and scanning cycles the Lua 5.2 solution needs to make as part  
of the atomic phase and because it's available and works now. (The Lua  
5.2 solution is far better than the situation in 5.1, but one still  
should probably look for other options where possible.)

Mark