Project

General

Profile

Actions

Feature #5494

closed

Proposal: Improved Finalizer Semantics

Added by kstephens (Kurt Stephens) over 12 years ago. Updated over 12 years ago.

Status:
Rejected
Assignee:
-
Target version:
[ruby-core:40474]

Description

Proposal: Improved Finalizer Semantics:

ObjectSpace.define_finalizer(object, proc):
** proc should have a single parameter, the object to be finalized, not its id.

When an object with a finalizer is no longer referenced (sweepable):

  • The object is reconsidered to be REFERENCED until next GC.
  • It's finalizer proc(s) are called, only once, with the object as the sole argument.
  • Subsequently, the finalizer procs are removed from the object.
  • The object's memory will NOT be reclaimed yet, nor will its C free_proc be called,
    since calling the finalizer proc effectively creates new (temporary) references to the object.
  • If the finalizer did NOT create any additonal, long-term references to the object,
    the object's memory and low-level C resources will be reclaimed in the next GC.

This is a simpler protocol:

  • It removes the need for _id2ref in the finalizer procs.
  • Prevents other complications: such as GC being reinvoked within a finalizer.
  • Finalizers are invoked with the same "urgency" as before.

The downside:

  • Objects with finalizers actually live for more than one GC cycle, if they are unreferenced.
  • This is probably acceptable since the resources the finalizers "clean-up"
    (eg.: file descriptors in a File object) are generally more scarce than the objects holding them.
Actions

Also available in: Atom PDF

Like0
Like0Like0Like0Like0