Googletest export

Remove linked_ptr and use std::shared_ptr instead

PiperOrigin-RevId: 218618184

24 files changed, 624 insertions, 84 deletions

diff --git a/googlemock/include/gmock/gmock-actions.h b/googlemock/include/gmock/gmock-actions.h
index e4af9d2..d4af949 100644
--- a/googlemock/include/gmock/gmock-actions.h
+++ b/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);
 };
diff --git a/googlemock/include/gmock/gmock-cardinalities.h b/googlemock/include/gmock/gmock-cardinalities.h
index 8fa25eb..f916931 100644
--- a/googlemock/include/gmock/gmock-cardinalities.h
+++ b/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.
diff --git a/googlemock/include/gmock/gmock-generated-actions.h b/googlemock/include/gmock/gmock-generated-actions.h
index 8966f05..0845b22 100644
--- a/googlemock/include/gmock/gmock-generated-actions.h
+++ b/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
diff --git a/googlemock/include/gmock/gmock-generated-actions.h.pump b/googlemock/include/gmock/gmock-generated-actions.h.pump
index 09a39ca..bc22be8 100644
--- a/googlemock/include/gmock/gmock-generated-actions.h.pump
+++ b/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
diff --git a/googlemock/include/gmock/gmock-matchers.h b/googlemock/include/gmock/gmock-matchers.h
index 95bc22c..6e8bc03 100644
--- a/googlemock/include/gmock/gmock-matchers.h
+++ b/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);
diff --git a/googlemock/include/gmock/gmock-spec-builders.h b/googlemock/include/gmock/gmock-spec-builders.h
index 7759cb3..5d4b73b 100644
--- a/googlemock/include/gmock/gmock-spec-builders.h
+++ b/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);
diff --git a/googlemock/include/gmock/internal/gmock-internal-utils.h b/googlemock/include/gmock/internal/gmock-internal-utils.h
index 7514635..fd33c00 100644
--- a/googlemock/include/gmock/internal/gmock-internal-utils.h
+++ b/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.
diff --git a/googlemock/include/gmock/internal/gmock-port.h b/googlemock/include/gmock/internal/gmock-port.h
index c593249..fda27db 100644
--- a/googlemock/include/gmock/internal/gmock-port.h
+++ b/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"
 
diff --git a/googlemock/src/gmock-spec-builders.cc b/googlemock/src/gmock-spec-builders.cc
index c93b2b5..5c20ed1 100644
--- a/googlemock/src/gmock-spec-builders.cc
+++ b/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() {}
diff --git a/googlemock/test/gmock-generated-actions_test.cc b/googlemock/test/gmock-generated-actions_test.cc
index 3111d85..2d663a5 100644
--- a/googlemock/test/gmock-generated-actions_test.cc
+++ b/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);
 }
diff --git a/googlemock/test/gmock-internal-utils_test.cc b/googlemock/test/gmock-internal-utils_test.cc
index aa0162b..41498f0 100644
--- a/googlemock/test/gmock-internal-utils_test.cc
+++ b/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>,
diff --git a/googlemock/test/gmock-matchers_test.cc b/googlemock/test/gmock-matchers_test.cc
index 45006bf..f4e9e9f 100644
--- a/googlemock/test/gmock-matchers_test.cc
+++ b/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));
diff --git a/googlemock/test/gmock-more-actions_test.cc b/googlemock/test/gmock-more-actions_test.cc
index b4e0fc3..521f305 100644
--- a/googlemock/test/gmock-more-actions_test.cc
+++ b/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);
diff --git a/googlemock/test/gmock-spec-builders_test.cc b/googlemock/test/gmock-spec-builders_test.cc
index 6502be7..65c9fcc 100644
--- a/googlemock/test/gmock-spec-builders_test.cc
+++ b/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.
diff --git a/googlemock/test/gmock_stress_test.cc b/googlemock/test/gmock_stress_test.cc
index 20725d6..9ae0b1e 100644
--- a/googlemock/test/gmock_stress_test.cc
+++ b/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,
diff --git a/googletest/CMakeLists.txt b/googletest/CMakeLists.txt
index e33718b..4c0d648 100644
--- a/googletest/CMakeLists.txt
+++ b/googletest/CMakeLists.txt
@@ -195,6 +195,7 @@ $env:Path = \"$project_bin;$env:Path\"
   cxx_test(googletest-death-test-test gtest_main)
   cxx_test(gtest_environment_test gtest)
   cxx_test(googletest-filepath-test gtest_main)
+  cxx_test(googletest-linked-ptr-test gtest_main)
   cxx_test(googletest-listener-test gtest_main)
   cxx_test(gtest_main_unittest gtest_main)
   cxx_test(googletest-message-test gtest_main)
diff --git a/googletest/include/gtest/internal/gtest-linked_ptr.h b/googletest/include/gtest/internal/gtest-linked_ptr.h
new file mode 100644
index 0000000..d25f7e9
--- /dev/null
+++ b/googletest/include/gtest/internal/gtest-linked_ptr.h
@@ -0,0 +1,243 @@
+// Copyright 2003 Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+//
+// A "smart" pointer type with reference tracking.  Every pointer to a
+// particular object is kept on a circular linked list.  When the last pointer
+// to an object is destroyed or reassigned, the object is deleted.
+//
+// Used properly, this deletes the object when the last reference goes away.
+// There are several caveats:
+// - Like all reference counting schemes, cycles lead to leaks.
+// - Each smart pointer is actually two pointers (8 bytes instead of 4).
+// - Every time a pointer is assigned, the entire list of pointers to that
+//   object is traversed.  This class is therefore NOT SUITABLE when there
+//   will often be more than two or three pointers to a particular object.
+// - References are only tracked as long as linked_ptr<> objects are copied.
+//   If a linked_ptr<> is converted to a raw pointer and back, BAD THINGS
+//   will happen (double deletion).
+//
+// A good use of this class is storing object references in STL containers.
+// You can safely put linked_ptr<> in a vector<>.
+// Other uses may not be as good.
+//
+// Note: If you use an incomplete type with linked_ptr<>, the class
+// *containing* linked_ptr<> must have a constructor and destructor (even
+// if they do nothing!).
+//
+// Bill Gibbons suggested we use something like this.
+//
+// Thread Safety:
+//   Unlike other linked_ptr implementations, in this implementation
+//   a linked_ptr object is thread-safe in the sense that:
+//     - it's safe to copy linked_ptr objects concurrently,
+//     - it's safe to copy *from* a linked_ptr and read its underlying
+//       raw pointer (e.g. via get()) concurrently, and
+//     - it's safe to write to two linked_ptrs that point to the same
+//       shared object concurrently.
+// FIXME: rename this to safe_linked_ptr to avoid
+// confusion with normal linked_ptr.
+
+// GOOGLETEST_CM0001 DO NOT DELETE
+
+#ifndef GTEST_INCLUDE_GTEST_INTERNAL_GTEST_LINKED_PTR_H_
+#define GTEST_INCLUDE_GTEST_INTERNAL_GTEST_LINKED_PTR_H_
+
+#include <stdlib.h>
+#include <assert.h>
+
+#include "gtest/internal/gtest-port.h"
+
+namespace testing {
+namespace internal {
+
+// Protects copying of all linked_ptr objects.
+GTEST_API_ GTEST_DECLARE_STATIC_MUTEX_(g_linked_ptr_mutex);
+
+// This is used internally by all instances of linked_ptr<>.  It needs to be
+// a non-template class because different types of linked_ptr<> can refer to
+// the same object (linked_ptr<Superclass>(obj) vs linked_ptr<Subclass>(obj)).
+// So, it needs to be possible for different types of linked_ptr to participate
+// in the same circular linked list, so we need a single class type here.
+//
+// DO NOT USE THIS CLASS DIRECTLY YOURSELF.  Use linked_ptr<T>.
+class linked_ptr_internal {
+ public:
+  // Create a new circle that includes only this instance.
+  void join_new() {
+    next_ = this;
+  }
+
+  // Many linked_ptr operations may change p.link_ for some linked_ptr
+  // variable p in the same circle as this object.  Therefore we need
+  // to prevent two such operations from occurring concurrently.
+  //
+  // Note that different types of linked_ptr objects can coexist in a
+  // circle (e.g. linked_ptr<Base>, linked_ptr<Derived1>, and
+  // linked_ptr<Derived2>).  Therefore we must use a single mutex to
+  // protect all linked_ptr objects.  This can create serious
+  // contention in production code, but is acceptable in a testing
+  // framework.
+
+  // Join an existing circle.
+  void join(linked_ptr_internal const* ptr)
+      GTEST_LOCK_EXCLUDED_(g_linked_ptr_mutex) {
+    MutexLock lock(&g_linked_ptr_mutex);
+
+    linked_ptr_internal const* p = ptr;
+    while (p->next_ != ptr) {
+      assert(p->next_ != this &&
+             "Trying to join() a linked ring we are already in. "
+             "Is GMock thread safety enabled?");
+      p = p->next_;
+    }
+    p->next_ = this;
+    next_ = ptr;
+  }
+
+  // Leave whatever circle we're part of.  Returns true if we were the
+  // last member of the circle.  Once this is done, you can join() another.
+  bool depart()
+      GTEST_LOCK_EXCLUDED_(g_linked_ptr_mutex) {
+    MutexLock lock(&g_linked_ptr_mutex);
+
+    if (next_ == this) return true;
+    linked_ptr_internal const* p = next_;
+    while (p->next_ != this) {
+      assert(p->next_ != next_ &&
+             "Trying to depart() a linked ring we are not in. "
+             "Is GMock thread safety enabled?");
+      p = p->next_;
+    }
+    p->next_ = next_;
+    return false;
+  }
+
+ private:
+  mutable linked_ptr_internal const* next_;
+};
+
+template <typename T>
+class linked_ptr {
+ public:
+  typedef T element_type;
+
+  // Take over ownership of a raw pointer.  This should happen as soon as
+  // possible after the object is created.
+  explicit linked_ptr(T* ptr = nullptr) { capture(ptr); }
+  ~linked_ptr() { depart(); }
+
+  // Copy an existing linked_ptr<>, adding ourselves to the list of references.
+  template <typename U> linked_ptr(linked_ptr<U> const& ptr) { copy(&ptr); }
+  linked_ptr(linked_ptr const& ptr) {  // NOLINT
+    assert(&ptr != this);
+    copy(&ptr);
+  }
+
+  // Assignment releases the old value and acquires the new.
+  template <typename U> linked_ptr& operator=(linked_ptr<U> const& ptr) {
+    depart();
+    copy(&ptr);
+    return *this;
+  }
+
+  linked_ptr& operator=(linked_ptr const& ptr) {
+    if (&ptr != this) {
+      depart();
+      copy(&ptr);
+    }
+    return *this;
+  }
+
+  // Smart pointer members.
+  void reset(T* ptr = nullptr) {
+    depart();
+    capture(ptr);
+  }
+  T* get() const { return value_; }
+  T* operator->() const { return value_; }
+  T& operator*() const { return *value_; }
+
+  bool operator==(T* p) const { return value_ == p; }
+  bool operator!=(T* p) const { return value_ != p; }
+  template <typename U>
+  bool operator==(linked_ptr<U> const& ptr) const {
+    return value_ == ptr.get();
+  }
+  template <typename U>
+  bool operator!=(linked_ptr<U> const& ptr) const {
+    return value_ != ptr.get();
+  }
+
+ private:
+  template <typename U>
+  friend class linked_ptr;
+
+  T* value_;
+  linked_ptr_internal link_;
+
+  void depart() {
+    if (link_.depart()) delete value_;
+  }
+
+  void capture(T* ptr) {
+    value_ = ptr;
+    link_.join_new();
+  }
+
+  template <typename U> void copy(linked_ptr<U> const* ptr) {
+    value_ = ptr->get();
+    if (value_)
+      link_.join(&ptr->link_);
+    else
+      link_.join_new();
+  }
+};
+
+template<typename T> inline
+bool operator==(T* ptr, const linked_ptr<T>& x) {
+  return ptr == x.get();
+}
+
+template<typename T> inline
+bool operator!=(T* ptr, const linked_ptr<T>& x) {
+  return ptr != x.get();
+}
+
+// A function to convert T* into linked_ptr<T>
+// Doing e.g. make_linked_ptr(new FooBarBaz<type>(arg)) is a shorter notation
+// for linked_ptr<FooBarBaz<type> >(new FooBarBaz<type>(arg))
+template <typename T>
+linked_ptr<T> make_linked_ptr(T* ptr) {
+  return linked_ptr<T>(ptr);
+}
+
+}  // namespace internal
+}  // namespace testing
+
+#endif  // GTEST_INCLUDE_GTEST_INTERNAL_GTEST_LINKED_PTR_H_
diff --git a/googletest/include/gtest/internal/gtest-param-util-generated.h b/googletest/include/gtest/internal/gtest-param-util-generated.h
index f3c1e16..78bf65f 100644
--- a/googletest/include/gtest/internal/gtest-param-util-generated.h
+++ b/googletest/include/gtest/internal/gtest-param-util-generated.h
@@ -47,8 +47,6 @@
 #ifndef GTEST_INCLUDE_GTEST_INTERNAL_GTEST_PARAM_UTIL_GENERATED_H_
 #define GTEST_INCLUDE_GTEST_INTERNAL_GTEST_PARAM_UTIL_GENERATED_H_
 
-#include <memory>
-
 #include "gtest/internal/gtest-param-util.h"
 #include "gtest/internal/gtest-port.h"
 
@@ -164,7 +162,7 @@ class CartesianProductGenerator2
     const typename ParamGenerator<T2>::iterator begin2_;
     const typename ParamGenerator<T2>::iterator end2_;
     typename ParamGenerator<T2>::iterator current2_;
-    std::shared_ptr<ParamType> current_value_;
+    linked_ptr<ParamType> current_value_;
   };  // class CartesianProductGenerator2::Iterator
 
   // No implementation - assignment is unsupported.
@@ -295,7 +293,7 @@ class CartesianProductGenerator3
     const typename ParamGenerator<T3>::iterator begin3_;
     const typename ParamGenerator<T3>::iterator end3_;
     typename ParamGenerator<T3>::iterator current3_;
-    std::shared_ptr<ParamType> current_value_;
+    linked_ptr<ParamType> current_value_;
   };  // class CartesianProductGenerator3::Iterator
 
   // No implementation - assignment is unsupported.
@@ -445,7 +443,7 @@ class CartesianProductGenerator4
     const typename ParamGenerator<T4>::iterator begin4_;
     const typename ParamGenerator<T4>::iterator end4_;
     typename ParamGenerator<T4>::iterator current4_;
-    std::shared_ptr<ParamType> current_value_;
+    linked_ptr<ParamType> current_value_;
   };  // class CartesianProductGenerator4::Iterator
 
   // No implementation - assignment is unsupported.
@@ -611,7 +609,7 @@ class CartesianProductGenerator5
     const typename ParamGenerator<T5>::iterator begin5_;
     const typename ParamGenerator<T5>::iterator end5_;
     typename ParamGenerator<T5>::iterator current5_;
-    std::shared_ptr<ParamType> current_value_;
+    linked_ptr<ParamType> current_value_;
   };  // class CartesianProductGenerator5::Iterator
 
   // No implementation - assignment is unsupported.
@@ -795,7 +793,7 @@ class CartesianProductGenerator6
     const typename ParamGenerator<T6>::iterator begin6_;
     const typename ParamGenerator<T6>::iterator end6_;
     typename ParamGenerator<T6>::iterator current6_;
-    std::shared_ptr<ParamType> current_value_;
+    linked_ptr<ParamType> current_value_;
   };  // class CartesianProductGenerator6::Iterator
 
   // No implementation - assignment is unsupported.
@@ -997,7 +995,7 @@ class CartesianProductGenerator7
     const typename ParamGenerator<T7>::iterator begin7_;
     const typename ParamGenerator<T7>::iterator end7_;
     typename ParamGenerator<T7>::iterator current7_;
-    std::shared_ptr<ParamType> current_value_;
+    linked_ptr<ParamType> current_value_;
   };  // class CartesianProductGenerator7::Iterator
 
   // No implementation - assignment is unsupported.
@@ -1218,7 +1216,7 @@ class CartesianProductGenerator8
     const typename ParamGenerator<T8>::iterator begin8_;
     const typename ParamGenerator<T8>::iterator end8_;
     typename ParamGenerator<T8>::iterator current8_;
-    std::shared_ptr<ParamType> current_value_;
+    linked_ptr<ParamType> current_value_;
   };  // class CartesianProductGenerator8::Iterator
 
   // No implementation - assignment is unsupported.
@@ -1456,7 +1454,7 @@ class CartesianProductGenerator9
     const typename ParamGenerator<T9>::iterator begin9_;
     const typename ParamGenerator<T9>::iterator end9_;
     typename ParamGenerator<T9>::iterator current9_;
-    std::shared_ptr<ParamType> current_value_;
+    linked_ptr<ParamType> current_value_;
   };  // class CartesianProductGenerator9::Iterator
 
   // No implementation - assignment is unsupported.
@@ -1711,7 +1709,7 @@ class CartesianProductGenerator10
     const typename ParamGenerator<T10>::iterator begin10_;
     const typename ParamGenerator<T10>::iterator end10_;
     typename ParamGenerator<T10>::iterator current10_;
-    std::shared_ptr<ParamType> current_value_;
+    linked_ptr<ParamType> current_value_;
   };  // class CartesianProductGenerator10::Iterator
 
   // No implementation - assignment is unsupported.
diff --git a/googletest/include/gtest/internal/gtest-param-util-generated.h.pump b/googletest/include/gtest/internal/gtest-param-util-generated.h.pump
index 5dea7b2..67d1b34 100644
--- a/googletest/include/gtest/internal/gtest-param-util-generated.h.pump
+++ b/googletest/include/gtest/internal/gtest-param-util-generated.h.pump
@@ -43,8 +43,6 @@ $var maxtuple = 10  $$ Maximum number of Combine arguments we want to support.
 
 // GOOGLETEST_CM0001 DO NOT DELETE
 
-#include <memory>
-
 #ifndef GTEST_INCLUDE_GTEST_INTERNAL_GTEST_PARAM_UTIL_GENERATED_H_
 #define GTEST_INCLUDE_GTEST_INTERNAL_GTEST_PARAM_UTIL_GENERATED_H_
 
@@ -175,7 +173,7 @@ $for j [[
     typename ParamGenerator<T$j>::iterator current$(j)_;
 ]]
 
-    std::shared_ptr<ParamType> current_value_;
+    linked_ptr<ParamType> current_value_;
   };  // class CartesianProductGenerator$i::Iterator
 
   // No implementation - assignment is unsupported.
diff --git a/googletest/include/gtest/internal/gtest-param-util.h b/googletest/include/gtest/internal/gtest-param-util.h
index 9eb98b1..d5d4da9 100644
--- a/googletest/include/gtest/internal/gtest-param-util.h
+++ b/googletest/include/gtest/internal/gtest-param-util.h
@@ -38,13 +38,13 @@
 #include <ctype.h>
 
 #include <iterator>
-#include <memory>
 #include <set>
 #include <tuple>
 #include <utility>
 #include <vector>
 
 #include "gtest/internal/gtest-internal.h"
+#include "gtest/internal/gtest-linked_ptr.h"
 #include "gtest/internal/gtest-port.h"
 #include "gtest/gtest-printers.h"
 
@@ -193,7 +193,7 @@ class ParamGenerator {
   iterator end() const { return iterator(impl_->End()); }
 
  private:
-  std::shared_ptr<const ParamGeneratorInterface<T> > impl_;
+  linked_ptr<const ParamGeneratorInterface<T> > impl_;
 };
 
 // Generates values from a range of two comparable values. Can be used to
@@ -519,8 +519,9 @@ class ParameterizedTestCaseInfo : public ParameterizedTestCaseInfoBase {
   void AddTestPattern(const char* test_case_name,
                       const char* test_base_name,
                       TestMetaFactoryBase<ParamType>* meta_factory) {
-    tests_.push_back(std::shared_ptr<TestInfo>(
-        new TestInfo(test_case_name, test_base_name, meta_factory)));
+    tests_.push_back(linked_ptr<TestInfo>(new TestInfo(test_case_name,
+                                                       test_base_name,
+                                                       meta_factory)));
   }
   // INSTANTIATE_TEST_CASE_P macro uses AddGenerator() to record information
   // about a generator.
@@ -540,7 +541,7 @@ class ParameterizedTestCaseInfo : public ParameterizedTestCaseInfoBase {
   virtual void RegisterTests() {
     for (typename TestInfoContainer::iterator test_it = tests_.begin();
          test_it != tests_.end(); ++test_it) {
-      std::shared_ptr<TestInfo> test_info = *test_it;
+      linked_ptr<TestInfo> test_info = *test_it;
       for (typename InstantiationContainer::iterator gen_it =
                instantiations_.begin(); gen_it != instantiations_.end();
                ++gen_it) {
@@ -604,7 +605,7 @@ class ParameterizedTestCaseInfo : public ParameterizedTestCaseInfoBase {
     const std::string test_base_name;
     const scoped_ptr<TestMetaFactoryBase<ParamType> > test_meta_factory;
   };
-  using TestInfoContainer = ::std::vector<std::shared_ptr<TestInfo> >;
+  typedef ::std::vector<linked_ptr<TestInfo> > TestInfoContainer;
   // Records data received from INSTANTIATE_TEST_CASE_P macros:
   //  <Instantiation name, Sequence generator creation function,
   //     Name generator function, Source file, Source line>
diff --git a/googletest/src/gtest-port.cc b/googletest/src/gtest-port.cc
index 082aaff..aa98ddb 100644
--- a/googletest/src/gtest-port.cc
+++ b/googletest/src/gtest-port.cc
@@ -31,11 +31,10 @@
 #include "gtest/internal/gtest-port.h"
 
 #include <limits.h>
-#include <stdio.h>
 #include <stdlib.h>
+#include <stdio.h>
 #include <string.h>
 #include <fstream>
-#include <memory>
 
 #if GTEST_OS_WINDOWS
 # include <windows.h>
@@ -476,7 +475,7 @@ class ThreadLocalRegistryImpl {
           thread_local_values
               .insert(std::make_pair(
                   thread_local_instance,
-                  std::shared_ptr<ThreadLocalValueHolderBase>(
+                  linked_ptr<ThreadLocalValueHolderBase>(
                       thread_local_instance->NewValueForCurrentThread())))
               .first;
     }
@@ -485,7 +484,7 @@ class ThreadLocalRegistryImpl {
 
   static void OnThreadLocalDestroyed(
       const ThreadLocalBase* thread_local_instance) {
-    std::vector<std::shared_ptr<ThreadLocalValueHolderBase> > value_holders;
+    std::vector<linked_ptr<ThreadLocalValueHolderBase> > value_holders;
     // Clean up the ThreadLocalValues data structure while holding the lock, but
     // defer the destruction of the ThreadLocalValueHolderBases.
     {
@@ -513,7 +512,7 @@ class ThreadLocalRegistryImpl {
 
   static void OnThreadExit(DWORD thread_id) {
     GTEST_CHECK_(thread_id != 0) << ::GetLastError();
-    std::vector<std::shared_ptr<ThreadLocalValueHolderBase> > value_holders;
+    std::vector<linked_ptr<ThreadLocalValueHolderBase> > value_holders;
     // Clean up the ThreadIdToThreadLocals data structure while holding the
     // lock, but defer the destruction of the ThreadLocalValueHolderBases.
     {
@@ -540,8 +539,7 @@ class ThreadLocalRegistryImpl {
  private:
   // In a particular thread, maps a ThreadLocal object to its value.
   typedef std::map<const ThreadLocalBase*,
-                   std::shared_ptr<ThreadLocalValueHolderBase> >
-      ThreadLocalValues;
+                   linked_ptr<ThreadLocalValueHolderBase> > ThreadLocalValues;
   // Stores all ThreadIdToThreadLocals having values in a thread, indexed by
   // thread's ID.
   typedef std::map<DWORD, ThreadLocalValues> ThreadIdToThreadLocals;
diff --git a/googletest/src/gtest.cc b/googletest/src/gtest.cc
index afd7d1b..332b3e9 100644
--- a/googletest/src/gtest.cc
+++ b/googletest/src/gtest.cc
@@ -423,6 +423,9 @@ void AssertHelper::operator=(const Message& message) const {
                       );  // NOLINT
 }
 
+// Mutex for linked pointers.
+GTEST_API_ GTEST_DEFINE_STATIC_MUTEX_(g_linked_ptr_mutex);
+
 // A copy of all command line arguments.  Set by InitGoogleTest().
 static ::std::vector<std::string> g_argvs;
 
diff --git a/googletest/test/googletest-linked-ptr-test.cc b/googletest/test/googletest-linked-ptr-test.cc
new file mode 100644
index 0000000..f680253
--- /dev/null
+++ b/googletest/test/googletest-linked-ptr-test.cc
@@ -0,0 +1,151 @@
+// Copyright 2003, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <stdlib.h>
+
+#include "gtest/internal/gtest-linked_ptr.h"
+#include "gtest/gtest.h"
+
+namespace {
+
+using testing::Message;
+using testing::internal::linked_ptr;
+
+int num;
+Message* history = nullptr;
+
+// Class which tracks allocation/deallocation
+class A {
+ public:
+  A(): mynum(num++) { *history << "A" << mynum << " ctor\n"; }
+  virtual ~A() { *history << "A" << mynum << " dtor\n"; }
+  virtual void Use() { *history << "A" << mynum << " use\n"; }
+ protected:
+  int mynum;
+};
+
+// Subclass
+class B : public A {
+ public:
+  B() { *history << "B" << mynum << " ctor\n"; }
+  ~B() { *history << "B" << mynum << " dtor\n"; }
+  virtual void Use() { *history << "B" << mynum << " use\n"; }
+};
+
+class LinkedPtrTest : public testing::Test {
+ public:
+  LinkedPtrTest() {
+    num = 0;
+    history = new Message;
+  }
+
+  virtual ~LinkedPtrTest() {
+    delete history;
+    history = nullptr;
+  }
+};
+
+TEST_F(LinkedPtrTest, GeneralTest) {
+  {
+    linked_ptr<A> a0, a1, a2;
+    // Use explicit function call notation here to suppress self-assign warning.
+    a0.operator=(a0);
+    a1 = a2;
+    ASSERT_EQ(a0.get(), static_cast<A*>(nullptr));
+    ASSERT_EQ(a1.get(), static_cast<A*>(nullptr));
+    ASSERT_EQ(a2.get(), static_cast<A*>(nullptr));
+    ASSERT_TRUE(a0 == nullptr);
+    ASSERT_TRUE(a1 == nullptr);
+    ASSERT_TRUE(a2 == nullptr);
+
+    {
+      linked_ptr<A> a3(new A);
+      a0 = a3;
+      ASSERT_TRUE(a0 == a3);
+      ASSERT_TRUE(a0 != nullptr);
+      ASSERT_TRUE(a0.get() == a3);
+      ASSERT_TRUE(a0 == a3.get());
+      linked_ptr<A> a4(a0);
+      a1 = a4;
+      linked_ptr<A> a5(new A);
+      ASSERT_TRUE(a5.get() != a3);
+      ASSERT_TRUE(a5 != a3.get());
+      a2 = a5;
+      linked_ptr<B> b0(new B);
+      linked_ptr<A> a6(b0);
+      ASSERT_TRUE(b0 == a6);
+      ASSERT_TRUE(a6 == b0);
+      ASSERT_TRUE(b0 != nullptr);
+      a5 = b0;
+      a5 = b0;
+      a3->Use();
+      a4->Use();
+      a5->Use();
+      a6->Use();
+      b0->Use();
+      (*b0).Use();
+      b0.get()->Use();
+    }
+
+    a0->Use();
+    a1->Use();
+    a2->Use();
+
+    a1 = a2;
+    a2.reset(new A);
+    a0.reset();
+
+    linked_ptr<A> a7;
+  }
+
+  ASSERT_STREQ(
+    "A0 ctor\n"
+    "A1 ctor\n"
+    "A2 ctor\n"
+    "B2 ctor\n"
+    "A0 use\n"
+    "A0 use\n"
+    "B2 use\n"
+    "B2 use\n"
+    "B2 use\n"
+    "B2 use\n"
+    "B2 use\n"
+    "B2 dtor\n"
+    "A2 dtor\n"
+    "A0 use\n"
+    "A0 use\n"
+    "A1 use\n"
+    "A3 ctor\n"
+    "A0 dtor\n"
+    "A3 dtor\n"
+    "A1 dtor\n",
+    history->GetString().c_str());
+}
+
+}  // Unnamed namespace
diff --git a/googletest/test/gtest_all_test.cc b/googletest/test/gtest_all_test.cc
index 615b29b..f948a10 100644
--- a/googletest/test/gtest_all_test.cc
+++ b/googletest/test/gtest_all_test.cc
@@ -33,6 +33,7 @@
 // Sometimes it's desirable to build most of Google Test's own tests
 // by compiling a single file.  This file serves this purpose.
 #include "test/googletest-filepath-test.cc"
+#include "test/googletest-linked-ptr-test.cc"
 #include "test/googletest-message-test.cc"
 #include "test/googletest-options-test.cc"
 #include "test/googletest-port-test.cc"