# Initiate a garbage collection
fun force_garbage_collection is intern
end
+
+# An object needing finalization
+#
+# Sub-classes of `Finalizable` must no have cycles, or else they will not be
+# liberated. For this reason, it is recommended to sub-class `Finalizable`
+# only on simple objects directly managing a limited resource. This use case
+# is common when wrapping an extern instance with a standard object.
+class Finalizable
+
+ # Liberate any resources held by `self` before the memory holding `self` is freed
+ #
+ # This method is invoked by the GC during a garbage collection when `self`
+ # is no longer referenced. It can also be called by the user. Its implementation
+ # must be planned accordingly and ensure that it may be invoked more than once.
+ #
+ # The object are finialized in a topological order, it is safe for this method
+ # to use attributes of this instances.
+ fun finalize do end
+end
+
+# An object to be finalized only once
+#
+# This is an utility sub-class to `Finalizable` which ensures that `finalized_once`
+# is called only once per instance. User classes implementing `FinalizableOnce`
+# shoud specialize `finalize_once` and _not_ `finalize`. When manipulating the user
+# class, only `finalize` should be called as it protects `finalize_once`.
+class FinalizableOnce
+ super Finalizable
+
+ # Has `self` been finalized? (either by the GC or an explicit call to `finalize`)
+ var finalized = false
+
+ redef fun finalize
+ do
+ if finalized then return
+
+ finalize_once
+ finalized = true
+ end
+
+ # Real finalization method of `FinalizableOnce`, will be called only once
+ #
+ # See: `Finalizable::finalize` for restrictions on finalizer methods.
+ protected fun finalize_once do end
+end