Googletest export

Remove linked_ptr and use std::shared_ptr instead

PiperOrigin-RevId: 218618184

googlemock/include/gmock/gmock-actions.h

@@ -42,7 +42,6 @@
 #endif
 
 #include <algorithm>
-#include <memory>
 #include <string>
 #include <utility>
 
@@ -347,7 +346,9 @@ class ActionInterface {
 // An Action<F> is a copyable and IMMUTABLE (except by assignment)
 // object that represents an action to be taken when a mock function
 // of type F is called.  The implementation of Action<T> is just a
-// std::shared_ptr to const ActionInterface<T>. Don't inherit from Action!
+// linked_ptr to const ActionInterface<T>, so copying is fairly cheap.
+// Don't inherit from Action!
+//
 // You can view an object implementing ActionInterface<F> as a
 // concrete action (including its current state), and an Action<F>
 // object as a handle to it.
@@ -424,7 +425,7 @@ class Action {
 #if GTEST_LANG_CXX11
   ::std::function<F> fun_;
 #endif
-  std::shared_ptr<ActionInterface<F>> impl_;
+  internal::linked_ptr<ActionInterface<F> > impl_;
 };
 
 // The PolymorphicAction class template makes it easy to implement a
@@ -518,7 +519,7 @@ class ActionAdaptor : public ActionInterface<F1> {
   }
 
  private:
-  const std::shared_ptr<ActionInterface<F2>> impl_;
+  const internal::linked_ptr<ActionInterface<F2> > impl_;
 
   GTEST_DISALLOW_ASSIGN_(ActionAdaptor);
 };
@@ -600,7 +601,7 @@ class ReturnAction {
     // Result to call.  ImplicitCast_ forces the compiler to convert R to
     // Result without considering explicit constructors, thus resolving the
     // ambiguity. value_ is then initialized using its copy constructor.
-    explicit Impl(const std::shared_ptr<R>& value)
+    explicit Impl(const linked_ptr<R>& value)
         : value_before_cast_(*value),
           value_(ImplicitCast_<Result>(value_before_cast_)) {}
 
@@ -625,7 +626,7 @@ class ReturnAction {
     typedef typename Function<F>::Result Result;
     typedef typename Function<F>::ArgumentTuple ArgumentTuple;
 
-    explicit Impl(const std::shared_ptr<R>& wrapper)
+    explicit Impl(const linked_ptr<R>& wrapper)
         : performed_(false), wrapper_(wrapper) {}
 
     virtual Result Perform(const ArgumentTuple&) {
@@ -637,12 +638,12 @@ class ReturnAction {
 
    private:
     bool performed_;
-    const std::shared_ptr<R> wrapper_;
+    const linked_ptr<R> wrapper_;
 
     GTEST_DISALLOW_ASSIGN_(Impl);
   };
 
-  const std::shared_ptr<R> value_;
+  const linked_ptr<R> value_;
 
   GTEST_DISALLOW_ASSIGN_(ReturnAction);
 };
@@ -865,7 +866,7 @@ class SetArgumentPointeeAction<N, Proto, true> {
   }
 
  private:
-  const std::shared_ptr<Proto> proto_;
+  const internal::linked_ptr<Proto> proto_;
 
   GTEST_DISALLOW_ASSIGN_(SetArgumentPointeeAction);
 };
@@ -930,7 +931,7 @@ class InvokeCallbackWithoutArgsAction {
   Result Perform(const ArgumentTuple&) const { return callback_->Run(); }
 
  private:
-  const std::shared_ptr<CallbackType> callback_;
+  const internal::linked_ptr<CallbackType> callback_;
 
   GTEST_DISALLOW_ASSIGN_(InvokeCallbackWithoutArgsAction);
 };

googlemock/include/gmock/gmock-cardinalities.h

@@ -40,7 +40,6 @@
 #define GMOCK_INCLUDE_GMOCK_GMOCK_CARDINALITIES_H_
 
 #include <limits.h>
-#include <memory>
 #include <ostream>  // NOLINT
 #include "gmock/internal/gmock-port.h"
 #include "gtest/gtest.h"
@@ -82,8 +81,9 @@ class CardinalityInterface {
 
 // A Cardinality is a copyable and IMMUTABLE (except by assignment)
 // object that specifies how many times a mock function is expected to
-// be called.  The implementation of Cardinality is just a std::shared_ptr
-// to const CardinalityInterface. Don't inherit from Cardinality!
+// be called.  The implementation of Cardinality is just a linked_ptr
+// to const CardinalityInterface, so copying is fairly cheap.
+// Don't inherit from Cardinality!
 class GTEST_API_ Cardinality {
  public:
   // Constructs a null cardinality.  Needed for storing Cardinality
@@ -123,7 +123,7 @@ class GTEST_API_ Cardinality {
                                         ::std::ostream* os);
 
  private:
-  std::shared_ptr<const CardinalityInterface> impl_;
+  internal::linked_ptr<const CardinalityInterface> impl_;
 };
 
 // Creates a cardinality that allows at least n calls.

googlemock/include/gmock/gmock-generated-actions.h

@@ -41,7 +41,6 @@
 #ifndef GMOCK_INCLUDE_GMOCK_GMOCK_GENERATED_ACTIONS_H_
 #define GMOCK_INCLUDE_GMOCK_GMOCK_GENERATED_ACTIONS_H_
 
-#include <memory>
 #include <utility>
 
 #include "gmock/gmock-actions.h"
@@ -349,7 +348,7 @@ class InvokeCallbackAction {
         callback_.get(), args);
   }
  private:
-  const std::shared_ptr<CallbackType> callback_;
+  const linked_ptr<CallbackType> callback_;
 };
 
 // An INTERNAL macro for extracting the type of a tuple field.  It's

googlemock/include/gmock/gmock-generated-actions.h.pump

@@ -43,7 +43,6 @@ $$}} This meta comment fixes auto-indentation in editors.
 #ifndef GMOCK_INCLUDE_GMOCK_GMOCK_GENERATED_ACTIONS_H_
 #define GMOCK_INCLUDE_GMOCK_GMOCK_GENERATED_ACTIONS_H_
 
-#include <memory>
 #include <utility>
 
 #include "gmock/gmock-actions.h"
@@ -119,7 +118,7 @@ class InvokeCallbackAction {
         callback_.get(), args);
   }
  private:
-  const std::shared_ptr<CallbackType> callback_;
+  const linked_ptr<CallbackType> callback_;
 };
 
 // An INTERNAL macro for extracting the type of a tuple field.  It's

googlemock/include/gmock/gmock-matchers.h

@@ -43,15 +43,14 @@
 #include <algorithm>
 #include <iterator>
 #include <limits>
-#include <memory>
 #include <ostream>  // NOLINT
 #include <sstream>
 #include <string>
 #include <utility>
 #include <vector>
+#include "gtest/gtest.h"
 #include "gmock/internal/gmock-internal-utils.h"
 #include "gmock/internal/gmock-port.h"
-#include "gtest/gtest.h"
 
 #if GTEST_HAS_STD_INITIALIZER_LIST_
 # include <initializer_list>  // NOLINT -- must be after gtest.h
@@ -339,15 +338,29 @@ class MatcherBase {
   virtual ~MatcherBase() {}
 
  private:
-  std::shared_ptr<const MatcherInterface<GTEST_REFERENCE_TO_CONST_(T)>> impl_;
+  // shared_ptr (util/gtl/shared_ptr.h) and linked_ptr have similar
+  // interfaces.  The former dynamically allocates a chunk of memory
+  // to hold the reference count, while the latter tracks all
+  // references using a circular linked list without allocating
+  // memory.  It has been observed that linked_ptr performs better in
+  // typical scenarios.  However, shared_ptr can out-perform
+  // linked_ptr when there are many more uses of the copy constructor
+  // than the default constructor.
+  //
+  // If performance becomes a problem, we should see if using
+  // shared_ptr helps.
+  ::testing::internal::linked_ptr<
+      const MatcherInterface<GTEST_REFERENCE_TO_CONST_(T)> >
+      impl_;
 };
 
 }  // namespace internal
 
 // A Matcher<T> is a copyable and IMMUTABLE (except by assignment)
 // object that can check whether a value of type T matches.  The
-// implementation of Matcher<T> is just a std::shared_ptr to const
-// MatcherInterface<T>.  Don't inherit from Matcher!
+// implementation of Matcher<T> is just a linked_ptr to const
+// MatcherInterface<T>, so copying is fairly cheap.  Don't inherit
+// from Matcher!
 template <typename T>
 class Matcher : public internal::MatcherBase<T> {
  public:
@@ -1573,7 +1586,7 @@ class MatchesRegexMatcher {
   }
 
  private:
-  const std::shared_ptr<const RE> regex_;
+  const internal::linked_ptr<const RE> regex_;
   const bool full_match_;
 
   GTEST_DISALLOW_ASSIGN_(MatchesRegexMatcher);

googlemock/include/gmock/gmock-spec-builders.h

@@ -62,7 +62,6 @@
 #define GMOCK_INCLUDE_GMOCK_GMOCK_SPEC_BUILDERS_H_
 
 #include <map>
-#include <memory>
 #include <set>
 #include <sstream>
 #include <string>
@@ -220,7 +219,8 @@ class GTEST_API_ UntypedFunctionMockerBase {
  protected:
   typedef std::vector<const void*> UntypedOnCallSpecs;
 
-  using UntypedExpectations = std::vector<std::shared_ptr<ExpectationBase>>;
+  typedef std::vector<internal::linked_ptr<ExpectationBase> >
+  UntypedExpectations;
 
   // Returns an Expectation object that references and co-owns exp,
   // which must be an expectation on this mock function.
@@ -498,7 +498,12 @@ class GTEST_API_ Mock {
 //   - Constness is shallow: a const Expectation object itself cannot
 //     be modified, but the mutable methods of the ExpectationBase
 //     object it references can be called via expectation_base().
-
+//   - The constructors and destructor are defined out-of-line because
+//     the Symbian WINSCW compiler wants to otherwise instantiate them
+//     when it sees this class definition, at which point it doesn't have
+//     ExpectationBase available yet, leading to incorrect destruction
+//     in the linked_ptr (or compilation errors if using a checking
+//     linked_ptr).
 class GTEST_API_ Expectation {
  public:
   // Constructs a null object that doesn't reference any expectation.
@@ -550,15 +555,16 @@ class GTEST_API_ Expectation {
   typedef ::std::set<Expectation, Less> Set;
 
   Expectation(
-      const std::shared_ptr<internal::ExpectationBase>& expectation_base);
+      const internal::linked_ptr<internal::ExpectationBase>& expectation_base);
 
   // Returns the expectation this object references.
-  const std::shared_ptr<internal::ExpectationBase>& expectation_base() const {
+  const internal::linked_ptr<internal::ExpectationBase>&
+  expectation_base() const {
     return expectation_base_;
   }
 
-  // A shared_ptr that co-owns the expectation this handle references.
-  std::shared_ptr<internal::ExpectationBase> expectation_base_;
+  // A linked_ptr that co-owns the expectation this handle references.
+  internal::linked_ptr<internal::ExpectationBase> expectation_base_;
 };
 
 // A set of expectation handles.  Useful in the .After() clause of
@@ -640,8 +646,11 @@ class GTEST_API_ Sequence {
   void AddExpectation(const Expectation& expectation) const;
 
  private:
-  // The last expectation in this sequence.
-  std::shared_ptr<Expectation> last_expectation_;
+  // The last expectation in this sequence.  We use a linked_ptr here
+  // because Sequence objects are copyable and we want the copies to
+  // be aliases.  The linked_ptr allows the copies to co-own and share
+  // the same Expectation object.
+  internal::linked_ptr<Expectation> last_expectation_;
 };  // class Sequence
 
 // An object of this type causes all EXPECT_CALL() statements
@@ -864,7 +873,7 @@ class GTEST_API_ ExpectationBase {
   Cardinality cardinality_;            // The cardinality of the expectation.
   // The immediate pre-requisites (i.e. expectations that must be
   // satisfied before this expectation can be matched) of this
-  // expectation.  We use std::shared_ptr in the set because we want an
+  // expectation.  We use linked_ptr in the set because we want an
   // Expectation object to be co-owned by its FunctionMocker and its
   // successors.  This allows multiple mock objects to be deleted at
   // different times.
@@ -1622,7 +1631,7 @@ class FunctionMockerBase : public UntypedFunctionMockerBase {
     Mock::RegisterUseByOnCallOrExpectCall(MockObject(), file, line);
     TypedExpectation<F>* const expectation =
         new TypedExpectation<F>(this, file, line, source_text, m);
-    const std::shared_ptr<ExpectationBase> untyped_expectation(expectation);
+    const linked_ptr<ExpectationBase> untyped_expectation(expectation);
     // See the definition of untyped_expectations_ for why access to
     // it is unprotected here.
     untyped_expectations_.push_back(untyped_expectation);

googlemock/include/gmock/internal/gmock-internal-utils.h

@@ -92,6 +92,15 @@ inline const typename Pointer::element_type* GetRawPointer(const Pointer& p) {
 template <typename Element>
 inline Element* GetRawPointer(Element* p) { return p; }
 
+// This comparator allows linked_ptr to be stored in sets.
+template <typename T>
+struct LinkedPtrLessThan {
+  bool operator()(const ::testing::internal::linked_ptr<T>& lhs,
+                  const ::testing::internal::linked_ptr<T>& rhs) const {
+    return lhs.get() < rhs.get();
+  }
+};
+
 // Symbian compilation can be done with wchar_t being either a native
 // type or a typedef.  Using Google Mock with OpenC without wchar_t
 // should require the definition of _STLP_NO_WCHAR_T.

googlemock/include/gmock/internal/gmock-port.h

@@ -52,6 +52,7 @@
 // here, as Google Mock depends on Google Test.  Only add a utility
 // here if it's truly specific to Google Mock.
 
+#include "gtest/internal/gtest-linked_ptr.h"
 #include "gtest/internal/gtest-port.h"
 #include "gmock/internal/custom/gmock-port.h"
 

googlemock/src/gmock-spec-builders.cc

@@ -38,7 +38,6 @@
 #include <stdlib.h>
 #include <iostream>  // NOLINT
 #include <map>
-#include <memory>
 #include <set>
 #include <string>
 #include <vector>
@@ -849,7 +848,7 @@ void Mock::ClearDefaultActionsLocked(void* mock_obj)
 Expectation::Expectation() {}
 
 Expectation::Expectation(
-    const std::shared_ptr<internal::ExpectationBase>& an_expectation_base)
+    const internal::linked_ptr<internal::ExpectationBase>& an_expectation_base)
     : expectation_base_(an_expectation_base) {}
 
 Expectation::~Expectation() {}

googlemock/test/gmock-generated-actions_test.cc

@@ -35,7 +35,6 @@
 #include "gmock/gmock-generated-actions.h"
 
 #include <functional>
-#include <memory>
 #include <sstream>
 #include <string>
 #include "gmock/gmock.h"
@@ -1130,9 +1129,9 @@ ACTION_TEMPLATE(ReturnSmartPointer,
 }
 
 TEST(ActionTemplateTest, WorksForTemplateTemplateParameters) {
-  const Action<std::shared_ptr<int>()> a =
-      ReturnSmartPointer<std::shared_ptr>(42);
-  std::shared_ptr<int> p = a.Perform(std::make_tuple());
+  using ::testing::internal::linked_ptr;
+  const Action<linked_ptr<int>()> a = ReturnSmartPointer<linked_ptr>(42);
+  linked_ptr<int> p = a.Perform(std::make_tuple());
   EXPECT_EQ(42, *p);
 }
 
@@ -1162,10 +1161,11 @@ ACTION_TEMPLATE(ReturnGiant,
 }
 
 TEST(ActionTemplateTest, WorksFor10TemplateParameters) {
-  using Giant = GiantTemplate<std::shared_ptr<int>, bool, double, 5, true, 6,
-                              char, unsigned, int>;
-  const Action<Giant()> a = ReturnGiant<int, bool, double, 5, true, 6, char,
-                                        unsigned, int, std::shared_ptr>(42);
+  using ::testing::internal::linked_ptr;
+  typedef GiantTemplate<linked_ptr<int>, bool, double, 5,
+      true, 6, char, unsigned, int> Giant;
+  const Action<Giant()> a = ReturnGiant<
+      int, bool, double, 5, true, 6, char, unsigned, int, linked_ptr>(42);
   Giant giant = a.Perform(std::make_tuple());
   EXPECT_EQ(42, giant.value);
 }

googlemock/test/gmock-internal-utils_test.cc

@@ -123,6 +123,8 @@ TEST(ConvertIdentifierNameToWordsTest, WorksWhenNameIsMixture) {
 }
 
 TEST(PointeeOfTest, WorksForSmartPointers) {
+  CompileAssertTypesEqual<const char,
+      PointeeOf<internal::linked_ptr<const char> >::type>();
 #if GTEST_HAS_STD_UNIQUE_PTR_
   CompileAssertTypesEqual<int, PointeeOf<std::unique_ptr<int> >::type>();
 #endif  // GTEST_HAS_STD_UNIQUE_PTR_
@@ -149,6 +151,10 @@ TEST(GetRawPointerTest, WorksForSmartPointers) {
   const std::shared_ptr<double> p2(raw_p2);
   EXPECT_EQ(raw_p2, GetRawPointer(p2));
 #endif  // GTEST_HAS_STD_SHARED_PTR_
+
+  const char* const raw_p4 = new const char('a');  // NOLINT
+  const internal::linked_ptr<const char> p4(raw_p4);
+  EXPECT_EQ(raw_p4, GetRawPointer(p4));
 }
 
 TEST(GetRawPointerTest, WorksForRawPointers) {
@@ -681,7 +687,7 @@ TEST(StlContainerViewTest, WorksForDynamicNativeArray) {
                      StlContainerView<std::tuple<const int*, size_t> >::type>();
   StaticAssertTypeEq<
       NativeArray<double>,
-      StlContainerView<std::tuple<std::shared_ptr<double>, int> >::type>();
+      StlContainerView<std::tuple<linked_ptr<double>, int> >::type>();
 
   StaticAssertTypeEq<
       const NativeArray<int>,

googlemock/test/gmock-matchers_test.cc

@@ -143,11 +143,13 @@ using testing::internal::ExplainMatchFailureTupleTo;
 using testing::internal::FloatingEqMatcher;
 using testing::internal::FormatMatcherDescription;
 using testing::internal::IsReadableTypeName;
+using testing::internal::linked_ptr;
 using testing::internal::MatchMatrix;
 using testing::internal::RE;
 using testing::internal::scoped_ptr;
 using testing::internal::StreamMatchResultListener;
 using testing::internal::Strings;
+using testing::internal::linked_ptr;
 using testing::internal::scoped_ptr;
 using testing::internal::string;
 
@@ -1175,6 +1177,24 @@ TEST(IsNullTest, MatchesNullPointer) {
 #endif
 }
 
+TEST(IsNullTest, LinkedPtr) {
+  const Matcher<linked_ptr<int> > m = IsNull();
+  const linked_ptr<int> null_p;
+  const linked_ptr<int> non_null_p(new int);
+
+  EXPECT_TRUE(m.Matches(null_p));
+  EXPECT_FALSE(m.Matches(non_null_p));
+}
+
+TEST(IsNullTest, ReferenceToConstLinkedPtr) {
+  const Matcher<const linked_ptr<double>&> m = IsNull();
+  const linked_ptr<double> null_p;
+  const linked_ptr<double> non_null_p(new double);
+
+  EXPECT_TRUE(m.Matches(null_p));
+  EXPECT_FALSE(m.Matches(non_null_p));
+}
+
 #if GTEST_LANG_CXX11
 TEST(IsNullTest, StdFunction) {
   const Matcher<std::function<void()>> m = IsNull();
@@ -1206,18 +1226,18 @@ TEST(NotNullTest, MatchesNonNullPointer) {
 }
 
 TEST(NotNullTest, LinkedPtr) {
-  const Matcher<std::shared_ptr<int>> m = NotNull();
-  const std::shared_ptr<int> null_p;
-  const std::shared_ptr<int> non_null_p(new int);
+  const Matcher<linked_ptr<int> > m = NotNull();
+  const linked_ptr<int> null_p;
+  const linked_ptr<int> non_null_p(new int);
 
   EXPECT_FALSE(m.Matches(null_p));
   EXPECT_TRUE(m.Matches(non_null_p));
 }
 
 TEST(NotNullTest, ReferenceToConstLinkedPtr) {
-  const Matcher<const std::shared_ptr<double>&> m = NotNull();
-  const std::shared_ptr<double> null_p;
-  const std::shared_ptr<double> non_null_p(new double);
+  const Matcher<const linked_ptr<double>&> m = NotNull();
+  const linked_ptr<double> null_p;
+  const linked_ptr<double> non_null_p(new double);
 
   EXPECT_FALSE(m.Matches(null_p));
   EXPECT_TRUE(m.Matches(non_null_p));

googlemock/test/gmock-more-actions_test.cc

@@ -35,11 +35,11 @@
 #include "gmock/gmock-more-actions.h"
 
 #include <functional>
-#include <memory>
 #include <sstream>
 #include <string>
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
+#include "gtest/internal/gtest-linked_ptr.h"
 
 namespace testing {
 namespace gmock_more_actions_test {
@@ -61,6 +61,7 @@ using testing::StaticAssertTypeEq;
 using testing::Unused;
 using testing::WithArg;
 using testing::WithoutArgs;
+using testing::internal::linked_ptr;
 
 // For suppressing compiler warnings on conversion possibly losing precision.
 inline short Short(short n) { return n; }  // NOLINT
@@ -528,6 +529,14 @@ TEST(SaveArgPointeeActionTest, WorksForCompatibleType) {
   EXPECT_EQ('a', result);
 }
 
+TEST(SaveArgPointeeActionTest, WorksForLinkedPtr) {
+  int result = 0;
+  linked_ptr<int> value(new int(5));
+  const Action<void(linked_ptr<int>)> a1 = SaveArgPointee<0>(&result);
+  a1.Perform(std::make_tuple(value));
+  EXPECT_EQ(5, result);
+}
+
 TEST(SetArgRefereeActionTest, WorksForSameType) {
   int value = 0;
   const Action<void(int&)> a1 = SetArgReferee<0>(1);

googlemock/test/gmock-spec-builders_test.cc

@@ -34,7 +34,6 @@
 
 #include "gmock/gmock-spec-builders.h"
 
-#include <memory>
 #include <ostream>  // NOLINT
 #include <sstream>
 #include <string>
@@ -100,6 +99,7 @@ using testing::internal::kFail;
 using testing::internal::kInfoVerbosity;
 using testing::internal::kWarn;
 using testing::internal::kWarningVerbosity;
+using testing::internal::linked_ptr;
 
 #if GTEST_HAS_STREAM_REDIRECTION
 using testing::HasSubstr;
@@ -172,7 +172,7 @@ class ReferenceHoldingMock {
  public:
   ReferenceHoldingMock() {}
 
-  MOCK_METHOD1(AcceptReference, void(std::shared_ptr<MockA>*));
+  MOCK_METHOD1(AcceptReference, void(linked_ptr<MockA>*));
 
  private:
   GTEST_DISALLOW_COPY_AND_ASSIGN_(ReferenceHoldingMock);
@@ -2619,7 +2619,7 @@ TEST(VerifyAndClearTest, DoesNotAffectOtherMockObjects) {
 
 TEST(VerifyAndClearTest,
      DestroyingChainedMocksDoesNotDeadlockThroughExpectations) {
-  std::shared_ptr<MockA> a(new MockA);
+  linked_ptr<MockA> a(new MockA);
   ReferenceHoldingMock test_mock;
 
   // EXPECT_CALL stores a reference to a inside test_mock.
@@ -2639,7 +2639,7 @@ TEST(VerifyAndClearTest,
 
 TEST(VerifyAndClearTest,
      DestroyingChainedMocksDoesNotDeadlockThroughDefaultAction) {
-  std::shared_ptr<MockA> a(new MockA);
+  linked_ptr<MockA> a(new MockA);
   ReferenceHoldingMock test_mock;
 
   // ON_CALL stores a reference to a inside test_mock.

googlemock/test/gmock_stress_test.cc

@@ -60,8 +60,87 @@ void JoinAndDelete(ThreadWithParam<T>* t) {
   delete t;
 }
 
+using internal::linked_ptr;
+
+// Helper classes for testing using linked_ptr concurrently.
+
+class Base {
+ public:
+  explicit Base(int a_x) : x_(a_x) {}
+  virtual ~Base() {}
+  int x() const { return x_; }
+ private:
+  int x_;
+};
+
+class Derived1 : public Base {
+ public:
+  Derived1(int a_x, int a_y) : Base(a_x), y_(a_y) {}
+  int y() const { return y_; }
+ private:
+  int y_;
+};
+
+class Derived2 : public Base {
+ public:
+  Derived2(int a_x, int a_z) : Base(a_x), z_(a_z) {}
+  int z() const { return z_; }
+ private:
+  int z_;
+};
+
+linked_ptr<Derived1> pointer1(new Derived1(1, 2));
+linked_ptr<Derived2> pointer2(new Derived2(3, 4));
+
 struct Dummy {};
 
+// Tests that we can copy from a linked_ptr and read it concurrently.
+void TestConcurrentCopyAndReadLinkedPtr(Dummy /* dummy */) {
+  // Reads pointer1 and pointer2 while they are being copied from in
+  // another thread.
+  EXPECT_EQ(1, pointer1->x());
+  EXPECT_EQ(2, pointer1->y());
+  EXPECT_EQ(3, pointer2->x());
+  EXPECT_EQ(4, pointer2->z());
+
+  // Copies from pointer1.
+  linked_ptr<Derived1> p1(pointer1);
+  EXPECT_EQ(1, p1->x());
+  EXPECT_EQ(2, p1->y());
+
+  // Assigns from pointer2 where the LHS was empty.
+  linked_ptr<Base> p2;
+  p2 = pointer1;
+  EXPECT_EQ(1, p2->x());
+
+  // Assigns from pointer2 where the LHS was not empty.
+  p2 = pointer2;
+  EXPECT_EQ(3, p2->x());
+}
+
+const linked_ptr<Derived1> p0(new Derived1(1, 2));
+
+// Tests that we can concurrently modify two linked_ptrs that point to
+// the same object.
+void TestConcurrentWriteToEqualLinkedPtr(Dummy /* dummy */) {
+  // p1 and p2 point to the same, shared thing.  One thread resets p1.
+  // Another thread assigns to p2.  This will cause the same
+  // underlying "ring" to be updated concurrently.
+  linked_ptr<Derived1> p1(p0);
+  linked_ptr<Derived1> p2(p0);
+
+  EXPECT_EQ(1, p1->x());
+  EXPECT_EQ(2, p1->y());
+
+  EXPECT_EQ(1, p2->x());
+  EXPECT_EQ(2, p2->y());
+
+  p1.reset();
+  p2 = p0;
+
+  EXPECT_EQ(1, p2->x());
+  EXPECT_EQ(2, p2->y());
+}
 
 // Tests that different mock objects can be used in their respective
 // threads.  This should generate no Google Test failure.
@@ -196,6 +275,8 @@ void TestPartiallyOrderedExpectationsWithThreads(Dummy /* dummy */) {
 // Tests using Google Mock constructs in many threads concurrently.
 TEST(StressTest, CanUseGMockWithThreads) {
   void (*test_routines[])(Dummy dummy) = {
+    &TestConcurrentCopyAndReadLinkedPtr,
+    &TestConcurrentWriteToEqualLinkedPtr,
     &TestConcurrentMockObjects,
     &TestConcurrentCallsOnSameObject,
     &TestPartiallyOrderedExpectationsWithThreads,