test_DominatorTree_06.js

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/* Any copyright is dedicated to the Public Domain.

   http://creativecommons.org/publicdomain/zero/1.0/ */

"use strict";

// Test that the retained size of a node is the sum of its children retained

// sizes plus its shallow size.

// Note that we don't assert directly, only if we get an unexpected

// value. There are just way too many nodes in the heap graph to assert for

// every one. This test would constantly time out and assertion messages would

// overflow the log size.

function fastAssert(cond, msg) {

  if (!cond) {

    ok(false, msg);

const COUNT = { by: "count", count: false, bytes: true };

function run_test() {

  const path = saveNewHeapSnapshot();

  const snapshot = ChromeUtils.readHeapSnapshot(path);

  const dominatorTree = snapshot.computeDominatorTree();

  // Do a traversal of the dominator tree and assert the relationship between

  // retained size, shallow size, and children's retained sizes.

  const root = dominatorTree.root;

  const stack = [root];

  while (stack.length) {

    const top = stack.pop();

    const children = dominatorTree.getImmediatelyDominated(top);

    const topRetainedSize = dominatorTree.getRetainedSize(top);

    const topShallowSize = snapshot.describeNode(COUNT, top).bytes;

    fastAssert(

      topShallowSize <= topRetainedSize,

      "The shallow size should be less than or equal to the " + "retained size"

);

    let sumOfChildrensRetainedSizes = 0;

    for (let i = 0; i < children.length; i++) {

      sumOfChildrensRetainedSizes += dominatorTree.getRetainedSize(children[i]);

      stack.push(children[i]);

    fastAssert(

      sumOfChildrensRetainedSizes <= topRetainedSize,

      "The sum of the children's retained sizes should be less than " +

        "or equal to the retained size"

);

    fastAssert(

      sumOfChildrensRetainedSizes + topShallowSize === topRetainedSize,

      "The sum of the children's retained sizes plus the shallow " +

        "size should be equal to the retained size"

);

  ok(true, "Successfully walked the tree");

  do_test_finished();