Re: userdata and the gc

[roberto@... (Roberto Ierusalimschy)]

> >The current garbage collector is non-compacting, so no GCed objects
> >ever move around. IIRC, the authors have cautioned that this may not
> >always be the case, though a lot of current code I've seen relies on
> >unmoving userdata.

The caution is about strings, not about userdata (although we actually
did not say that explicitly in the manual). We have no intention of
allowing userdata addresses to change during GC. Unlike strings, which
are an internal data in Lua, the only purpose of userdata is to be used
by C code, which prefer that things stay where they are :)


> If that is the case, I'm confused about how the gc can shrink the pool 
> without invalidating userdata. Using sockets for userdata :

The gc can shrink the pool as much as malloc/free can. In fact, Lua
has no notion of "pool". It only manipulates memory through
malloc/free/realloc.

-- Roberto