[polyml] Using a finalizer with multiple arguments

Thanks for the example - it was a useful to see how to use the Thread structure. And to see how easy it was. That's a nice library.

Attached is a first stab at implementing the FINALIZABLE signature shown below, which is identical to MLTON_FINALIZABLE. The code is based on the MLton implementation but with a number of differences. As mentioned in the other email, there seems to be an issue with finalizers not being run when exiting via OS.Process.exit.

Phil

signature FINALIZABLE = sig type 'a t val new : 'a -> 'a t val addFinalizer : 'a t * ('a -> unit) -> unit val finalizeBefore : 'a t * 'b t -> unit val touch : 'a t -> unit val withValue : 'a t * ('a -> 'b) -> 'b end

16/09/15 11:56, David Matthews wrote:

On 15/09/2015 23:06, Phil Clayton wrote:

...

In MLton, creating a finalizable value from the pointer and size is simple. Roughly as follows:

fun fromNewPtr p n = let val array = Finalizable.new p in Finalizable.addFinalizer (t, fn p => free_ (p, n)); array end

where free_ is the C free function. If Poly/ML can use the same or similar code, that would be much easier!

This is my quick attempt to create something similar. As long as the result of the call to makeFinal is reachable the finalisation function will not be called. Once it becomes unreachable the finalisation function will be called soon after the GC. I've only tested it with explicit calls to PolyML.fullGC but it should work equally when the GC is activated automatically. However it does require a full GC and that can occur relatively infrequently. David

local open Weak val finals = ref []

 fun threadFn () =
 let
     val () = Thread.Mutex.lock weakLock
     fun doFilter (ref (SOME _), _) = true
     |   doFilter (ref NONE, f) = (f(); false)
 in
     while true do
     (
         finals := List.filter doFilter (!finals);
         Thread.ConditionVar.wait(weakSignal, weakLock)
     )
 end

 val _ = Thread.Thread.fork(threadFn, [])

in fun makeFinal (f : unit -> unit) = let val r = ref () val () = ThreadLib.protect weakLock (fn () => finals := (weak(SOME r), f) :: ! finals) () in r end end; _______________________________________________ polyml mailing list polyml at inf.ed.ac.uk http://lists.inf.ed.ac.uk/mailman/listinfo/polyml