Re: Collected objects still in table?

[Philipp Janda <siffiejoe@...>]

Am 21.03.2014 01:54 schröbte Rena:
> I've just noticed a strange issue with garbage collection in my Lua code.
> The code is quite large, would be difficult to create a test case, but the
> basics are:
>
> 1) Create a userdata object
> 2) Store it as a key in a table in the registry
> 3) Create more objects
> 4) Close the Lua state
> 5) The object created in step 1 is collected and its __gc is called
> 6) Other objects' __gc look in the table in the registry, and that object
> is still there!
>
> How can __gc be called and the object not be removed from the table?

Lua's GC only modifies weak tables. If a non-weak table contains a 
reference to a value that is about to be garbage-collected, then the 
table must be garbage as well, so there is no need to update the table 
because it will soon be collected anyway.

The obvious exception is `__gc` metamethods. If your finalizers rely on 
the fact that a table only contains non-finalized objects, then
remove the objects from the table yourself during `__gc`.


Philipp