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- Subject: Re: Strange behaviour of addresses of lua_objects
- From: Roberto Ierusalimschy <roberto@...>
- Date: Tue, 09 Jun 1998 14:10:05 -0300
> My question: Is there something
> tricky to take into account when using pointers to lua_objects as
> userdata in tables ?
I haven't understood your point. "lua_objects" are no pointers, they are
integers, and should be handled as abstract data types in C (that is, the only
thing you can do with a lua_object is to give it back to Lua). If you have
pointers to lua_objects, they point to your own variables, since Lua never
gives you a lua_object address.
What is a little tricky is not about pointers to lua_objects, but about
Because Lua has automatic memory management and garbage collection,
a |lua_Object| has a limited scope,
and is only valid inside the block where it has been created.
A C function called from Lua is a block,
and its parameters are valid only until its end.
It is good programming practice to convert Lua objects to C values
as soon as they are available,
and never to store |lua_Object|s in C global variables.
If you need a "non-volatile" reference to a Lua object in C, you must use
references (see lua_ref).