Support mocking methods with move-only return types.

include/gmock/gmock-actions.h

@@ -163,18 +163,27 @@ class DefaultValue {
   // Sets the default value for type T; requires T to be
   // copy-constructable and have a public destructor.
   static void Set(T x) {
-    delete value_;
-    value_ = new T(x);
+    delete producer_;
+    producer_ = new FixedValueProducer(x);
+  }
+
+  // Provides a factory function to be called to generate the default value.
+  // This method can be used even if T is only move-constructible, but it is not
+  // limited to that case.
+  typedef T (*FactoryFunction)();
+  static void SetFactory(FactoryFunction factory) {
+    delete producer_;
+    producer_ = new FactoryValueProducer(factory);
   }
 
   // Unsets the default value for type T.
   static void Clear() {
-    delete value_;
-    value_ = NULL;
+    delete producer_;
+    producer_ = NULL;
   }
 
   // Returns true iff the user has set the default value for type T.
-  static bool IsSet() { return value_ != NULL; }
+  static bool IsSet() { return producer_ != NULL; }
 
   // Returns true if T has a default return value set by the user or there
   // exists a built-in default value.
@@ -183,15 +192,42 @@ class DefaultValue {
   }
 
   // Returns the default value for type T if the user has set one;
-  // otherwise returns the built-in default value if there is one;
-  // otherwise aborts the process.
+  // otherwise returns the built-in default value. Requires that Exists()
+  // is true, which ensures that the return value is well-defined.
   static T Get() {
-    return value_ == NULL ?
-        internal::BuiltInDefaultValue<T>::Get() : *value_;
+    return producer_ == NULL ?
+        internal::BuiltInDefaultValue<T>::Get() : producer_->Produce();
   }
 
  private:
-  static const T* value_;
+  class ValueProducer {
+   public:
+    virtual ~ValueProducer() {}
+    virtual T Produce() = 0;
+  };
+
+  class FixedValueProducer : public ValueProducer {
+   public:
+    explicit FixedValueProducer(T value) : value_(value) {}
+    virtual T Produce() { return value_; }
+
+   private:
+    const T value_;
+    GTEST_DISALLOW_COPY_AND_ASSIGN_(FixedValueProducer);
+  };
+
+  class FactoryValueProducer : public ValueProducer {
+   public:
+    explicit FactoryValueProducer(FactoryFunction factory)
+        : factory_(factory) {}
+    virtual T Produce() { return factory_(); }
+
+   private:
+    const FactoryFunction factory_;
+    GTEST_DISALLOW_COPY_AND_ASSIGN_(FactoryValueProducer);
+  };
+
+  static ValueProducer* producer_;
 };
 
 // This partial specialization allows a user to set default values for
@@ -241,7 +277,7 @@ class DefaultValue<void> {
 
 // Points to the user-set default value for type T.
 template <typename T>
-const T* DefaultValue<T>::value_ = NULL;
+typename DefaultValue<T>::ValueProducer* DefaultValue<T>::producer_ = NULL;
 
 // Points to the user-set default value for type T&.
 template <typename T>

include/gmock/gmock-spec-builders.h

@@ -211,7 +211,7 @@ class GTEST_API_ UntypedFunctionMockerBase {
   // arguments.  This function can be safely called from multiple
   // threads concurrently.  The caller is responsible for deleting the
   // result.
-  const UntypedActionResultHolderBase* UntypedInvokeWith(
+  UntypedActionResultHolderBase* UntypedInvokeWith(
       const void* untyped_args)
           GTEST_LOCK_EXCLUDED_(g_gmock_mutex);
 
@@ -1289,6 +1289,58 @@ class MockSpec {
   GTEST_DISALLOW_ASSIGN_(MockSpec);
 };  // class MockSpec
 
+// Wrapper type for generically holding an ordinary value or lvalue reference.
+// If T is not a reference type, it must be copyable or movable.
+// ReferenceOrValueWrapper<T> is movable, and will also be copyable unless
+// T is a move-only value type (which means that it will always be copyable
+// if the current platform does not support move semantics).
+//
+// The primary template defines handling for values, but function header
+// comments describe the contract for the whole template (including
+// specializations).
+template <typename T>
+class ReferenceOrValueWrapper {
+ public:
+  // Constructs a wrapper from the given value/reference.
+  explicit ReferenceOrValueWrapper(T value)
+      : value_(GTEST_MOVE_(value)) {}
+
+  // Unwraps and returns the underlying value/reference, exactly as
+  // originally passed. The behavior of calling this more than once on
+  // the same object is unspecified.
+  T Unwrap() {
+    return GTEST_MOVE_(value_);
+  }
+
+  // Provides nondestructive access to the underlying value/reference.
+  // Always returns a const reference (more precisely,
+  // const RemoveReference<T>&). The behavior of calling this after
+  // calling Unwrap on the same object is unspecified.
+  const T& Peek() const {
+    return value_;
+  }
+
+ private:
+  T value_;
+};
+
+// Specialization for lvalue reference types. See primary template
+// for documentation.
+template <typename T>
+class ReferenceOrValueWrapper<T&> {
+ public:
+  // Workaround for debatable pass-by-reference lint warning (c-library-team
+  // policy precludes NOLINT in this context)
+  typedef T& reference;
+  explicit ReferenceOrValueWrapper(reference ref)
+      : value_ptr_(&ref) {}
+  T& Unwrap() { return *value_ptr_; }
+  const T& Peek() const { return *value_ptr_; }
+
+ private:
+  T* value_ptr_;
+};
+
 // MSVC warns about using 'this' in base member initializer list, so
 // we need to temporarily disable the warning.  We have to do it for
 // the entire class to suppress the warning, even though it's about
@@ -1320,23 +1372,16 @@ class UntypedActionResultHolderBase {
 template <typename T>
 class ActionResultHolder : public UntypedActionResultHolderBase {
  public:
-  explicit ActionResultHolder(T a_value) : value_(a_value) {}
-
-  // The compiler-generated copy constructor and assignment operator
-  // are exactly what we need, so we don't need to define them.
-
-  // Returns the held value and deletes this object.
-  T GetValueAndDelete() const {
-    T retval(value_);
-    delete this;
-    return retval;
+  // Returns the held value. Must not be called more than once.
+  T Unwrap() {
+    return result_.Unwrap();
   }
 
   // Prints the held value as an action's result to os.
   virtual void PrintAsActionResult(::std::ostream* os) const {
     *os << "\n          Returns: ";
     // T may be a reference type, so we don't use UniversalPrint().
-    UniversalPrinter<T>::Print(value_, os);
+    UniversalPrinter<T>::Print(result_.Peek(), os);
   }
 
   // Performs the given mock function's default action and returns the
@@ -1346,8 +1391,8 @@ class ActionResultHolder : public UntypedActionResultHolderBase {
       const FunctionMockerBase<F>* func_mocker,
       const typename Function<F>::ArgumentTuple& args,
       const string& call_description) {
-    return new ActionResultHolder(
-        func_mocker->PerformDefaultAction(args, call_description));
+    return new ActionResultHolder(Wrapper(
+        func_mocker->PerformDefaultAction(args, call_description)));
   }
 
   // Performs the given action and returns the result in a new-ed
@@ -1356,42 +1401,52 @@ class ActionResultHolder : public UntypedActionResultHolderBase {
   static ActionResultHolder*
   PerformAction(const Action<F>& action,
                 const typename Function<F>::ArgumentTuple& args) {
-    return new ActionResultHolder(action.Perform(args));
+    return new ActionResultHolder(Wrapper(action.Perform(args)));
   }
 
  private:
-  T value_;
+  typedef ReferenceOrValueWrapper<T> Wrapper;
 
-  // T could be a reference type, so = isn't supported.
-  GTEST_DISALLOW_ASSIGN_(ActionResultHolder);
+  explicit ActionResultHolder(Wrapper result)
+      : result_(GTEST_MOVE_(result)) {}
+
+  Wrapper result_;
+
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(ActionResultHolder);
 };
 
 // Specialization for T = void.
 template <>
 class ActionResultHolder<void> : public UntypedActionResultHolderBase {
  public:
-  void GetValueAndDelete() const { delete this; }
+  void Unwrap() { }
 
   virtual void PrintAsActionResult(::std::ostream* /* os */) const {}
 
-  // Performs the given mock function's default action and returns NULL;
+  // Performs the given mock function's default action and returns ownership
+  // of an empty ActionResultHolder*.
   template <typename F>
   static ActionResultHolder* PerformDefaultAction(
       const FunctionMockerBase<F>* func_mocker,
       const typename Function<F>::ArgumentTuple& args,
       const string& call_description) {
     func_mocker->PerformDefaultAction(args, call_description);
-    return NULL;
+    return new ActionResultHolder;
   }
 
-  // Performs the given action and returns NULL.
+  // Performs the given action and returns ownership of an empty
+  // ActionResultHolder*.
   template <typename F>
   static ActionResultHolder* PerformAction(
       const Action<F>& action,
       const typename Function<F>::ArgumentTuple& args) {
     action.Perform(args);
-    return NULL;
+    return new ActionResultHolder;
   }
+
+ private:
+  ActionResultHolder() {}
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(ActionResultHolder);
 };
 
 // The base of the function mocker class for the given function type.
@@ -1526,8 +1581,9 @@ class FunctionMockerBase : public UntypedFunctionMockerBase {
   // threads concurrently.
   Result InvokeWith(const ArgumentTuple& args)
         GTEST_LOCK_EXCLUDED_(g_gmock_mutex) {
-    return static_cast<const ResultHolder*>(
-        this->UntypedInvokeWith(&args))->GetValueAndDelete();
+    scoped_ptr<ResultHolder> holder(
+        DownCast_<ResultHolder*>(this->UntypedInvokeWith(&args)));
+    return holder->Unwrap();
   }
 
   // Adds and returns a default action spec for this mock function.

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

@@ -361,17 +361,30 @@ template <typename T> struct DecayArray<T[]> {
   typedef const T* type;
 };
 
-// Invalid<T>() returns an invalid value of type T.  This is useful
+// Disable MSVC warnings for infinite recursion, since in this case the
+// the recursion is unreachable.
+#ifdef _MSC_VER
+# pragma warning(push)
+# pragma warning(disable:4717)
+#endif
+
+// Invalid<T>() is usable as an expression of type T, but will terminate
+// the program with an assertion failure if actually run.  This is useful
 // when a value of type T is needed for compilation, but the statement
 // will not really be executed (or we don't care if the statement
 // crashes).
 template <typename T>
 inline T Invalid() {
-  return const_cast<typename remove_reference<T>::type&>(
-      *static_cast<volatile typename remove_reference<T>::type*>(NULL));
+  Assert(false, "", -1, "Internal error: attempt to return invalid value");
+  // This statement is unreachable, and would never terminate even if it
+  // could be reached. It is provided only to placate compiler warnings
+  // about missing return statements.
+  return Invalid<T>();
 }
-template <>
-inline void Invalid<void>() {}
+
+#ifdef _MSC_VER
+# pragma warning(pop)
+#endif
 
 // Given a raw type (i.e. having no top-level reference or const
 // modifier) RawContainer that's either an STL-style container or a