Comment author: administrator

Full_Name: David Fox
Version: 3.02

let alarm = Gc.create_alarm (fun () -> print_endline "Hello"; flush stdout)
let _ = Gc.major ()

But I get nothing running 3.02 on a Linux machine.

You're right, I made a stupid bug in the implementation of GC alarms.
This is now fixed in the working version and a patch is included in this mail.

You'll have to call Gc.major twice before you start seeing the messages,
though. That's because alarms are based on finalised values, and the
alarm record is not unreachable on the first GC after its allocation.

Thanks for the report,

-- Damien

Index: stdlib/gc.ml

RCS file: /net/pauillac/caml/repository/csl/stdlib/gc.ml,v
retrieving revision 1.12
diff -c -r1.12 gc.ml
*** gc.ml 2001/02/05 14:59:23 1.12
--- gc.ml 2001/08/28 12:47:44

*** 75,93 ****
external finalise : ('a -> unit) -> 'a -> unit = "final_register";;

! type alarm = {mutable active : bool; f : unit -> unit};;

! let rec call_alarm a =
! if a.active then begin
! finalise call_alarm a;
! a.f ();
end;
;;

let create_alarm f =
! let a = { active = true; f = f } in
! finalise call_alarm a;
a
;;

! let delete_alarm a = a.active <- false;;
--- 75,96 ----
external finalise : ('a -> unit) -> 'a -> unit = "final_register";;

! type alarm_rec = {active : alarm; f : unit -> unit}
! and alarm = bool ref
! ;;

! let rec call_alarm arec =
! if !(arec.active) then begin
! finalise call_alarm arec;
! arec.f ();
end;
;;

let create_alarm f =
! let a = ref true in
! let arec = { active = ref true; f = f } in
! finalise call_alarm arec;
a
;;

! let delete_alarm a = a := false;;