mfbt/tests/TestThreadSafeWeakPtr.cpp

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #include "mozilla/RefPtr.h"
   8 #include "mozilla/ThreadSafeWeakPtr.h"
   9
  10 using mozilla::SupportsThreadSafeWeakPtr;
  11 using mozilla::ThreadSafeWeakPtr;
  12
  13 // To have a class C support weak pointers, inherit from
  14 // SupportsThreadSafeWeakPtr<C>.
  15 class C : public SupportsThreadSafeWeakPtr<C> {
  16  public:
  17   MOZ_DECLARE_THREADSAFEWEAKREFERENCE_TYPENAME(C)
  18   MOZ_DECLARE_REFCOUNTED_TYPENAME(C)
  19
  20   int mNum;
  21
  22   C() : mNum(0) {}
  23
  24   ~C() {
  25     // Setting mNum in the destructor allows us to test against use-after-free
  26     // below
  27     mNum = 0xDEAD;
  28   }
  29
  30   void act() {}
  31 };
  32
  33 int main() {
  34   RefPtr<C> c1 = new C;
  35   MOZ_RELEASE_ASSERT(c1->mNum == 0);
  36
  37   // Get weak pointers to c1. The first time,
  38   // a reference-counted ThreadSafeWeakReference object is created that
  39   // can live beyond the lifetime of 'c1'. The ThreadSafeWeakReference
  40   // object will be notified of 'c1's destruction.
  41   ThreadSafeWeakPtr<C> w1(c1);
  42   {
  43     RefPtr<C> s1(w1);
  44     // Test a weak pointer for validity before using it.
  45     MOZ_RELEASE_ASSERT(s1);
  46     MOZ_RELEASE_ASSERT(s1 == c1);
  47     s1->mNum = 1;
  48     s1->act();
  49   }
  50
  51   // Test taking another ThreadSafeWeakPtr<C> to c1
  52   ThreadSafeWeakPtr<C> w2(c1);
  53   {
  54     RefPtr<C> s2(w2);
  55     MOZ_RELEASE_ASSERT(s2);
  56     MOZ_RELEASE_ASSERT(s2 == c1);
  57     MOZ_RELEASE_ASSERT(w1 == s2);
  58     MOZ_RELEASE_ASSERT(s2->mNum == 1);
  59   }
  60
  61   // Test that when a ThreadSafeWeakPtr is destroyed, it does not destroy the
  62   // object that it points to, and it does not affect other ThreadSafeWeakPtrs
  63   // pointing to the same object (e.g. it does not destroy the
  64   // ThreadSafeWeakReference object).
  65   {
  66     ThreadSafeWeakPtr<C> w4local(c1);
  67     MOZ_RELEASE_ASSERT(w4local == c1);
  68   }
  69   // Now w4local has gone out of scope. If that had destroyed c1, then the
  70   // following would fail for sure (see C::~C()).
  71   MOZ_RELEASE_ASSERT(c1->mNum == 1);
  72   // Check that w4local going out of scope hasn't affected other
  73   // ThreadSafeWeakPtr's pointing to c1
  74   MOZ_RELEASE_ASSERT(w1 == c1);
  75   MOZ_RELEASE_ASSERT(w2 == c1);
  76
  77   // Now construct another C object and test changing what object a
  78   // ThreadSafeWeakPtr points to
  79   RefPtr<C> c2 = new C;
  80   c2->mNum = 2;
  81   {
  82     RefPtr<C> s2(w2);
  83     MOZ_RELEASE_ASSERT(s2->mNum == 1);  // w2 was pointing to c1
  84   }
  85   w2 = c2;
  86   {
  87     RefPtr<C> s2(w2);
  88     MOZ_RELEASE_ASSERT(s2);
  89     MOZ_RELEASE_ASSERT(s2 == c2);
  90     MOZ_RELEASE_ASSERT(s2 != c1);
  91     MOZ_RELEASE_ASSERT(w1 != s2);
  92     MOZ_RELEASE_ASSERT(s2->mNum == 2);
  93   }
  94
  95   // Destroying the underlying object clears weak pointers to it.
  96   // It should not affect pointers that are not currently pointing to it.
  97   c1 = nullptr;
  98   MOZ_RELEASE_ASSERT(
  99       !bool(w1), "Deleting an object should clear ThreadSafeWeakPtr's to it.");
 100   MOZ_RELEASE_ASSERT(bool(w2),
 101                      "Deleting an object should not clear ThreadSafeWeakPtr "
 102                      "that are not pointing to it.");
 103
 104   c2 = nullptr;
 105   MOZ_RELEASE_ASSERT(
 106       !bool(w2), "Deleting an object should clear ThreadSafeWeakPtr's to it.");
 107 }