__gc() isn't always called.

[Joe Gester <joe@...>]

Hi,

I have several full userdatas with metatables and a __gc metamethod 
implemented in C.  Storing the userdata in a global variable, I can 
access its members and call other metamethods like __index and 
__newindex as exoected.  If my script assigns nil to the global 
variable, the __gc method runs.  If I assign nil to the variable from C 
and use lua_gc to collect the garbage or call lua_close, the __gc method 
does not run.

Should __gc called when the references are broken from outside the 
script and/or when lua_close is run?  Is there something in particular I 
ought to be doing to get __gc to run?  I would expect it to just work 
since garbage is properly collected when the references are broken from 
within the script.

-- Joe Gester