RE: Lunar, C++, and premature object destruction

["Sean Riley" <sean@...>]

Looking briefly at the Lunar code, I don't see anything that tries to
handle the case of the object being deleted from the C++ side.  The only
cleanup appears to be when the object's associated userdata is garbage
collected from the lua side.

Maybe you could always delete the ship from the lua code? This would
require a wrapper function that calls into lua to nil out the reference
to the shup in script, causing it to be garbage collected.

> -----Original Message-----
> From: lua-bounces@bazar2.conectiva.com.br [mailto:lua-
> bounces@bazar2.conectiva.com.br] On Behalf Of Watusimoto
> Sent: Thursday, July 02, 2009 1:04 AM
> To: lua@bazar2.conectiva.com.br
> Subject: Lunar, C++, and premature object destruction
> 
> 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