dedupeTenuredBase.js

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function str(c) {

  let s = c;

  for (let i = 0; i < 30; i++) {

    s += c;

  ensureLinearString(s);

  return s;

function f() {

  // Create some slots to write into.

  const o = { owner: "short1", s: "short2" };

  // Make a tenured rope.

  const r1 = str("a") + str("b");

  gc();

  // Write the first instance of our duplicate string into one of the slots

  // (`owner`). This will be scanned first, and entered into deDupSet when

  // tenured.

  o.owner = ensureLinearString(str("a") + str("b") + str("c"));

  // Make another rope with identical contents, with a tenured subtree.

  const r2 = r1 + str("c");

  // Linearize the new rope, creating a new extensible string and a bunch of

  // dependent strings replacing the rest of the rope nodes.

  ensureLinearString(r2);

  // Write the new rope into a slot, so that it will be scanned next during the

  // minor GC during traceSlots().

  o.s = r2;

  // Do a nursery collection. o.owner will be tenured and inserted into

  // deDupSet. Then o.s aka r2 will be tenured. If things work correctly, r2

  // will be marked non-deduplicatable because it is the base of a tenured

  // string r1. If not, it will be deduplicated to o.owner.

  minorgc();

  // Extract out that r1 child node. If its base was deduplicated, this will

  // assert because its chars have been freed.

  const s1 = r1.substr(0, 31);

f();