Googletest export

Remove linked_ptr and use std::shared_ptr instead

PiperOrigin-RevId: 218618184

9 files changed, 421 insertions, 27 deletions

diff --git a/googletest/CMakeLists.txt b/googletest/CMakeLists.txt
index e33718b1..4c0d6487 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 00000000..d25f7e96
--- /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 f3c1e16e..78bf65f6 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 5dea7b29..67d1b34b 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 9eb98b16..d5d4da95 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 082aaff4..aa98ddb1 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 afd7d1be..332b3e9b 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 00000000..f6802534
--- /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 615b29b7..f948a104 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"