Lunar, C++, and premature object destruction

[Watusimoto <watusimoto@...>]

I'm working on a game that uses Lua to control robot players, written in 
C++, and bound with Lunar, and am having problems controlling the 
lifespan of objects created in C++ and referenced in Lua.  (It's at 
http://bitfighter.org, if you are curious, and the linked wiki contains 
examples of some robot scripts.)

My primary object is a Ship.  The lifetime of the Ship object is 
completely controlled by C++.  I also have a proxy object, called 
LuaShip, that contains a pointer to the Ship, and handles all the 
requests for information about the Ship from the Lua script.  The goal 
is that when the Ship is destroyed, the pointer on the LuaShip will be 
set to NULL, and any future requests to the LuaShip can be intelligently 
handled (probably by generating an error of some sort).  The LuaShip is 
exposed to Lua via Lunar if the robot script requests it (using a 
getShip() method or somesuch).

The Ship object also contains a pointer to its LuaShip proxy.  My 
problem is that when the Ship object is destroyed, C++ seems to think 
that all pointers to the LuaShip are gone, and it is OK to destroy the 
LuaShip as well.  It does not seem to recognize when a Lua instance is 
also referring to the LuaShip.  The result is that the LuaShip is 
destroyed, and the Lua script is now left holding a reference to 
nothing.  When the script acts on it (thinking it's still valid), the 
app crashes.

My questions are 1) Is this an appropriate architecture for managing Lua 
instances that can have persistent references to C++ objects (Ship in 
this case) that can be deleted without warning, and 2) are there any 
good examples of code that uses Lunar in this manner that I can examine 
to see where my problem might be?

Thank you,

Chris