Re: GC of external resources

[Rici Lake <lua@...>]

On 1-Dec-06, at 11:16 PM, Diego Nehab wrote:

> Hi,
>
> I don't claim to understand what is going on with the new
> garbage collector. :) What I want to know is if there is a
> simple way to cause the garbage collector notice the
> difference between a simple boxed pointer, and a boxed
> pointer that represents a big chunk of memory. Creating a
> bunch of small userdata with no references to them is fine,
> as long as there is not a lot of external memory associated
> to them. In the later case, it would be nice if the GC could
> be made more reactive.

I guess the hackish way to do that would be to invade the userdata 
object once it's been created and add to its size the amount of memory 
actually being used. You'd have to update Lua's record of how much 
memory has been allocated by the amount you added.

Although seriously impolite to the internals of Lua, that should be 
safe provided you never refer to lua_objlen of the userdata or replace 
the standard memory allocation function with something that actually 
uses the allocation length.

It would be interesting to know if that actually makes a difference to 
program behaviour, anyway.