Re: using light userdata to keep full userdata alive?
[
Date Prev][
Date Next][
Thread Prev][
Thread Next]
[
Date Index]
[
Thread Index]
- Subject: Re: using light userdata to keep full userdata alive?
- From: Norman Ramsey <nr@...>
- Date: 2008年1月08日 20:33:58 -0500
> Norman Ramsey wrote:
> > The only way I can think of to do this is to use a weak table in
> > which both keys and values are weak and the light userdata is the
> > key, the heavy userdata is the value. Is this the correct approach?
> > Are there other possible approaches?
>
> I think that won't work. Light userdata are simple values like numbers
> and booleans, they are stored directly in tables, not by reference. Thus
> the light userdata as a weak key will make the value associated (the
> full userdata) immediately collectable.
Ouch! Roberto, have I mentioned recently how useful it would be to
have a formal semantics for parts of Lua?
> AFAIK the only way to handle your situation is to pass around the full
> big userdata (which is handle by reference, so it's just a pointer
> passed around), or eventually a smaller (but still full) userdata which
> contains only the array pointer. In that case you have to link the big
> and small (full) userdatas in some way (with a weak table or the
> metatable/environment mechanisms).
Urgh. Well, sometimes that's the way the cookie crumbles.
Norman