sig
  type stat = {
    minor_words : float;
    promoted_words : float;
    major_words : float;
    minor_collections : int;
    major_collections : int;
    heap_words : int;
    heap_chunks : int;
    live_words : int;
    live_blocks : int;
    free_words : int;
    free_blocks : int;
    largest_free : int;
    fragments : int;
    compactions : int;
  } 
  and control = {
    mutable minor_heap_size : int;
    mutable major_heap_increment : int;
    mutable space_overhead : int;
    mutable verbose : int;
    mutable max_overhead : int;
    mutable stack_limit : int;
  } 
  external stat : unit -> Gc.stat = "gc_stat"
  external counters : unit -> float * float * float = "gc_counters"
  external get : unit -> Gc.control = "gc_get"
  external set : Gc.control -> unit = "gc_set"
  external minor : unit -> unit = "gc_minor"
  external major : unit -> unit = "gc_major"
  external full_major : unit -> unit = "gc_full_major"
  external compact : unit -> unit = "gc_compaction"
  val print_stat : Pervasives.out_channel -> unit
  val allocated_bytes : unit -> float
  val finalise : ('a -> unit) -> 'a -> unit
  type alarm
  val create_alarm : (unit -> unit) -> Gc.alarm
  val delete_alarm : Gc.alarm -> unit
end