mfbt/tests/TestThreadSafeWeakPtr.cpp
author Brian Hackett <bhackett1024@gmail.com>
Wed, 14 Nov 2018 16:09:58 -1000
changeset 446931 1c7fc8389e012c987347efefca6b35f3948b742a
parent 387006 efd9a7070a08bdcf2077f3b9cf230f6462ce671a
child 450554 09c71a7cf75aeaf2963050e315276fb9a866fd62
permissions -rw-r--r--
Bug 1507359 Part 2 - Bindings and internal changes to allow ReplayDebugger to control child pausing/resuming, r=mccr8.

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "mozilla/RefPtr.h"
#include "mozilla/ThreadSafeWeakPtr.h"

using mozilla::SupportsThreadSafeWeakPtr;
using mozilla::ThreadSafeWeakPtr;

// To have a class C support weak pointers, inherit from SupportsThreadSafeWeakPtr<C>.
class C : public SupportsThreadSafeWeakPtr<C>
{
public:
  MOZ_DECLARE_THREADSAFEWEAKREFERENCE_TYPENAME(C)
  MOZ_DECLARE_REFCOUNTED_TYPENAME(C)

  int mNum;

  C()
    : mNum(0)
  {}

  ~C()
  {
    // Setting mNum in the destructor allows us to test against use-after-free below
    mNum = 0xDEAD;
  }

  void act() {}
};

int
main()
{
  RefPtr<C> c1 = new C;
  MOZ_RELEASE_ASSERT(c1->mNum == 0);

  // Get weak pointers to c1. The first time,
  // a reference-counted ThreadSafeWeakReference object is created that
  // can live beyond the lifetime of 'c1'. The ThreadSafeWeakReference
  // object will be notified of 'c1's destruction.
  ThreadSafeWeakPtr<C> w1(c1);
  {
    RefPtr<C> s1(w1);
    // Test a weak pointer for validity before using it.
    MOZ_RELEASE_ASSERT(s1);
    MOZ_RELEASE_ASSERT(s1 == c1);
    s1->mNum = 1;
    s1->act();
  }

  // Test taking another ThreadSafeWeakPtr<C> to c1
  ThreadSafeWeakPtr<C> w2(c1);
  {
    RefPtr<C> s2(w2);
    MOZ_RELEASE_ASSERT(s2);
    MOZ_RELEASE_ASSERT(s2 == c1);
    MOZ_RELEASE_ASSERT(w1 == s2);
    MOZ_RELEASE_ASSERT(s2->mNum == 1);
  }

  // Test that when a ThreadSafeWeakPtr is destroyed, it does not destroy the object that it points to,
  // and it does not affect other ThreadSafeWeakPtrs pointing to the same object (e.g. it does not
  // destroy the ThreadSafeWeakReference object).
  {
    ThreadSafeWeakPtr<C> w4local(c1);
    MOZ_RELEASE_ASSERT(w4local == c1);
  }
  // Now w4local has gone out of scope. If that had destroyed c1, then the following would fail
  // for sure (see C::~C()).
  MOZ_RELEASE_ASSERT(c1->mNum == 1);
  // Check that w4local going out of scope hasn't affected other ThreadSafeWeakPtr's pointing to c1
  MOZ_RELEASE_ASSERT(w1 == c1);
  MOZ_RELEASE_ASSERT(w2 == c1);

  // Now construct another C object and test changing what object a ThreadSafeWeakPtr points to
  RefPtr<C> c2 = new C;
  c2->mNum = 2;
  {
    RefPtr<C> s2(w2);
    MOZ_RELEASE_ASSERT(s2->mNum == 1); // w2 was pointing to c1
  }
  w2 = c2;
  {
    RefPtr<C> s2(w2);
    MOZ_RELEASE_ASSERT(s2);
    MOZ_RELEASE_ASSERT(s2 == c2);
    MOZ_RELEASE_ASSERT(s2 != c1);
    MOZ_RELEASE_ASSERT(w1 != s2);
    MOZ_RELEASE_ASSERT(s2->mNum == 2);
  }

  // Destroying the underlying object clears weak pointers to it.
  // It should not affect pointers that are not currently pointing to it.
  c1 = nullptr;
  MOZ_RELEASE_ASSERT(!bool(w1), "Deleting an object should clear ThreadSafeWeakPtr's to it.");
  MOZ_RELEASE_ASSERT(bool(w2), "Deleting an object should not clear ThreadSafeWeakPtr that are not pointing to it.");

  c2 = nullptr;
  MOZ_RELEASE_ASSERT(!bool(w2), "Deleting an object should clear ThreadSafeWeakPtr's to it.");
}