TestWeakPtr.cpp - mozsearch

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/* -*- 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/WeakPtr.h"

using mozilla::SupportsWeakPtr;

using mozilla::WeakPtr;

static char IamB[] = "B";

static char IamC[] = "C";

static char IamD[] = "D";

class B : public SupportsWeakPtr {

 public:

  char const* whoAmI() const { return IamB; }

};

// To have a class C support weak pointers, inherit from SupportsWeakPtr.

class C : public SupportsWeakPtr {

 public:

  int mNum;

  C() : mNum(0) {}

  ~C() {

    // Setting mNum in the destructor allows us to test against use-after-free

    // below

    mNum = 0xDEAD;

  char const* whoAmI() const { return IamC; }

  void act() {}

  bool isConst() { return false; }

  bool isConst() const { return true; }

};

// Derived from a class that supports weakptr, but doesn't implement itself

// To check upcast works as expected

class D : public B {

 public:

  char const* whoAmI() const { return IamD; }

};

bool isConst(C*) { return false; }

bool isConst(const C*) { return true; }

int main() {

  C* c1 = new C;

  MOZ_RELEASE_ASSERT(c1->mNum == 0);

  // Get weak pointers to c1. The first time,

  // a reference-counted WeakReference object is created that

  // can live beyond the lifetime of 'c1'. The WeakReference

  // object will be notified of 'c1's destruction.

  WeakPtr<C> w1 = c1;

  // Test a weak pointer for validity before using it.

  MOZ_RELEASE_ASSERT(w1);

  MOZ_RELEASE_ASSERT(w1 == c1);

  w1->mNum = 1;

  w1->act();

  // Test taking another WeakPtr<C> to c1

  WeakPtr<C> w2 = c1;

  MOZ_RELEASE_ASSERT(w2);

  MOZ_RELEASE_ASSERT(w2 == c1);

  MOZ_RELEASE_ASSERT(w2 == w1);

  MOZ_RELEASE_ASSERT(w2->mNum == 1);

  // Test a WeakPtr<const C>

  WeakPtr<const C> w3const = c1;

  MOZ_RELEASE_ASSERT(w3const);

  MOZ_RELEASE_ASSERT(w3const == c1);

  MOZ_RELEASE_ASSERT(w3const == w1);

  MOZ_RELEASE_ASSERT(w3const == w2);

  MOZ_RELEASE_ASSERT(w3const->mNum == 1);

  // Test const-correctness of operator-> and operator T*

  MOZ_RELEASE_ASSERT(!w1->isConst());

  MOZ_RELEASE_ASSERT(w3const->isConst());

  MOZ_RELEASE_ASSERT(!isConst(w1));

  MOZ_RELEASE_ASSERT(isConst(w3const));

  // Test that when a WeakPtr is destroyed, it does not destroy the object that

  // it points to, and it does not affect other WeakPtrs pointing to the same

  // object (e.g. it does not destroy the WeakReference object).

    WeakPtr<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 WeakPtr'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 WeakPtr

  // points to

  C* c2 = new C;

  c2->mNum = 2;

  MOZ_RELEASE_ASSERT(w2->mNum == 1);  // w2 was pointing to c1

  w2 = c2;

  MOZ_RELEASE_ASSERT(w2);

  MOZ_RELEASE_ASSERT(w2 == c2);

  MOZ_RELEASE_ASSERT(w2 != c1);

  MOZ_RELEASE_ASSERT(w2 != w1);

  MOZ_RELEASE_ASSERT(w2->mNum == 2);

  // Destroying the underlying object clears weak pointers to it.

  // It should not affect pointers that are not currently pointing to it.

  delete c1;

  MOZ_RELEASE_ASSERT(!w1, "Deleting an object should clear WeakPtr's to it.");

  MOZ_RELEASE_ASSERT(!w3const,

                     "Deleting an object should clear WeakPtr's to it.");

  MOZ_RELEASE_ASSERT(w2,

                     "Deleting an object should not clear WeakPtr that are not "

                     "pointing to it.");

  delete c2;

  MOZ_RELEASE_ASSERT(!w2, "Deleting an object should clear WeakPtr's to it.");

  // Check that we correctly upcast to the base class supporting weakptr

  D* d = new D;

  WeakPtr<B> db = d;

  // You should be able to use WeakPtr<D> even if it's a base class which

  // implements SupportsWeakPtr.

  WeakPtr<D> weakd = d;

  MOZ_RELEASE_ASSERT(db->whoAmI() == IamB);

  MOZ_RELEASE_ASSERT(weakd.get() == db.get());

  delete d;

  MOZ_RELEASE_ASSERT(!db);

  MOZ_RELEASE_ASSERT(!weakd);