v8/test/mjsunit/harmony/weakrefs/cleanup.js

// Copyright 2018 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

// Flags: --expose-gc --noincremental-marking

let cleanup_called = 0;
let holdings_list = [];
let cleanup = function(holdings) {
  holdings_list.push(holdings);
  cleanup_called++;
}

let fg = new FinalizationRegistry(cleanup);
let o1 = {};
let o2 = {};

// Ignition holds references to objects in temporary registers. These will be
// released when the function exits. So only access o inside a function to
// prevent any references to objects in temporary registers when a gc is
(function() {
  fg.register(o1, 1);
  fg.register(o2, 2);
})();

gc();
assertEquals(cleanup_called, 0);

// Drop the last references to o1 and o2.
(function() {
  o1 = null;
  o2 = null;
})();

// GC will reclaim the target objects; the cleanup function will be called the
// next time we enter the event loop.
gc();
assertEquals(cleanup_called, 0);

let timeout_func = function() {
  assertEquals(cleanup_called, 2);
  assertEquals(holdings_list.length, 2);
  if (holdings_list[0] == 1) {
    assertEquals(holdings_list[1], 2);
  } else {
    assertEquals(holdings_list[0], 2);
    assertEquals(holdings_list[1], 1);
  }
}

setTimeout(timeout_func, 0);