Re: custom "mark" function for userdata?

["Alex Davies" <alex.mania@...>]

I had the same problem when I was just starting out, as it isn't obvious in 
the documentation but Lua allows a table to be associated with a userdata 
and marks it appropriately.  So all circularly references are handled 
correctly, something that's hard to do via the registry.

Quick example:
lua_newuserdata(L, 0);
lua_newtable(L);
lua_pushvalue(L, -1);
lua_setfenv(L, -3);

After this script the table at the top of the stack is associated with the 
userdata below it (and can be retrieved by lua_getfenv).

Hope this helps :)

- Alex