gmock-spec-builders: add support for non-moveable types.

Do this by ripping out the "untyped perform action" machinery, which isn't
necessary: we can simply template the entry point on the result type, and use
RAII to avoid the need to special case void. This makes it easier to understand
the code and harder to introduce type-related undefined behavior, to boot.
PiperOrigin-RevId: 451493451
Change-Id: I225305f83164752ca92f2916721972eafba33168

1 files changed, 103 insertions, 189 deletions

diff --git a/googlemock/include/gmock/gmock-spec-builders.h b/googlemock/include/gmock/gmock-spec-builders.h
index 60636f0..fd12a06 100644
--- a/googlemock/include/gmock/gmock-spec-builders.h
+++ b/googlemock/include/gmock/gmock-spec-builders.h
@@ -132,9 +132,6 @@ class NaggyMockImpl;
 // calls to ensure the integrity of the mock objects' states.
 GTEST_API_ GTEST_DECLARE_STATIC_MUTEX_(g_gmock_mutex);
 
-// Untyped base class for ActionResultHolder<R>.
-class UntypedActionResultHolderBase;
-
 // Abstract base class of FunctionMocker.  This is the
 // type-agnostic part of the function mocker interface.  Its pure
 // virtual methods are implemented by FunctionMocker.
@@ -157,20 +154,6 @@ class GTEST_API_ UntypedFunctionMockerBase {
   // responsibility to guarantee the correctness of the arguments'
   // types.
 
-  // Performs the default action with the given arguments and returns
-  // the action's result.  The call description string will be used in
-  // the error message to describe the call in the case the default
-  // action fails.
-  // L = *
-  virtual UntypedActionResultHolderBase* UntypedPerformDefaultAction(
-      void* untyped_args, const std::string& call_description) const = 0;
-
-  // Performs the given action with the given arguments and returns
-  // the action's result.
-  // L = *
-  virtual UntypedActionResultHolderBase* UntypedPerformAction(
-      const void* untyped_action, void* untyped_args) const = 0;
-
   // Writes a message that the call is uninteresting (i.e. neither
   // explicitly expected nor explicitly unexpected) to the given
   // ostream.
@@ -214,13 +197,6 @@ class GTEST_API_ UntypedFunctionMockerBase {
   // SetOwnerAndName() has been called.
   const char* Name() const GTEST_LOCK_EXCLUDED_(g_gmock_mutex);
 
-  // Returns the result of invoking this mock function with the given
-  // arguments.  This function can be safely called from multiple
-  // threads concurrently.  The caller is responsible for deleting the
-  // result.
-  UntypedActionResultHolderBase* UntypedInvokeWith(void* untyped_args)
-      GTEST_LOCK_EXCLUDED_(g_gmock_mutex);
-
  protected:
   typedef std::vector<const void*> UntypedOnCallSpecs;
 
@@ -1368,105 +1344,29 @@ class ReferenceOrValueWrapper<T&> {
   T* value_ptr_;
 };
 
-// C++ treats the void type specially.  For example, you cannot define
-// a void-typed variable or pass a void value to a function.
-// ActionResultHolder<T> holds a value of type T, where T must be a
-// copyable type or void (T doesn't need to be default-constructable).
-// It hides the syntactic difference between void and other types, and
-// is used to unify the code for invoking both void-returning and
-// non-void-returning mock functions.
-
-// Untyped base class for ActionResultHolder<T>.
-class UntypedActionResultHolderBase {
- public:
-  virtual ~UntypedActionResultHolderBase() {}
-
-  // Prints the held value as an action's result to os.
-  virtual void PrintAsActionResult(::std::ostream* os) const = 0;
-};
-
-// This generic definition is used when T is not void.
+// Prints the held value as an action's result to os.
 template <typename T>
-class ActionResultHolder : public UntypedActionResultHolderBase {
- public:
-  // 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.
-  void PrintAsActionResult(::std::ostream* os) const override {
-    *os << "\n          Returns: ";
-    // T may be a reference type, so we don't use UniversalPrint().
-    UniversalPrinter<T>::Print(result_.Peek(), os);
-  }
-
-  // Performs the given mock function's default action and returns the
-  // result in a new-ed ActionResultHolder.
-  template <typename F>
-  static ActionResultHolder* PerformDefaultAction(
-      const FunctionMocker<F>* func_mocker,
-      typename Function<F>::ArgumentTuple&& args,
-      const std::string& call_description) {
-    return new ActionResultHolder(Wrapper(
-        func_mocker->PerformDefaultAction(std::move(args), call_description)));
-  }
-
-  // Performs the given action and returns the result in a new-ed
-  // ActionResultHolder.
-  template <typename F>
-  static ActionResultHolder* PerformAction(
-      const Action<F>& action, typename Function<F>::ArgumentTuple&& args) {
-    return new ActionResultHolder(Wrapper(action.Perform(std::move(args))));
-  }
-
- private:
-  typedef ReferenceOrValueWrapper<T> Wrapper;
-
-  explicit ActionResultHolder(Wrapper result) : result_(std::move(result)) {}
-
-  Wrapper result_;
+void PrintAsActionResult(const T& result, std::ostream& os) {
+  os << "\n          Returns: ";
+  // T may be a reference type, so we don't use UniversalPrint().
+  UniversalPrinter<T>::Print(result, &os);
+}
 
-  ActionResultHolder(const ActionResultHolder&) = delete;
-  ActionResultHolder& operator=(const ActionResultHolder&) = delete;
-};
+// Reports an uninteresting call (whose description is in msg) in the
+// manner specified by 'reaction'.
+GTEST_API_ void ReportUninterestingCall(CallReaction reaction,
+                                        const std::string& msg);
 
-// Specialization for T = void.
-template <>
-class ActionResultHolder<void> : public UntypedActionResultHolderBase {
+// A generic RAII type that runs a user-provided function in its destructor.
+class Cleanup final {
  public:
-  void Unwrap() {}
-
-  void PrintAsActionResult(::std::ostream* /* os */) const override {}
-
-  // Performs the given mock function's default action and returns ownership
-  // of an empty ActionResultHolder*.
-  template <typename F>
-  static ActionResultHolder* PerformDefaultAction(
-      const FunctionMocker<F>* func_mocker,
-      typename Function<F>::ArgumentTuple&& args,
-      const std::string& call_description) {
-    func_mocker->PerformDefaultAction(std::move(args), call_description);
-    return new ActionResultHolder;
-  }
-
-  // Performs the given action and returns ownership of an empty
-  // ActionResultHolder*.
-  template <typename F>
-  static ActionResultHolder* PerformAction(
-      const Action<F>& action, typename Function<F>::ArgumentTuple&& args) {
-    action.Perform(std::move(args));
-    return new ActionResultHolder;
-  }
+  explicit Cleanup(std::function<void()> f) : f_(std::move(f)) {}
+  ~Cleanup() { f_(); }
 
  private:
-  ActionResultHolder() {}
-  ActionResultHolder(const ActionResultHolder&) = delete;
-  ActionResultHolder& operator=(const ActionResultHolder&) = delete;
+  std::function<void()> f_;
 };
 
-// Reports an uninteresting call (whose description is in msg) in the
-// manner specified by 'reaction'.
-void ReportUninterestingCall(CallReaction reaction, const std::string& msg);
-
 template <typename F>
 class FunctionMocker;
 
@@ -1547,32 +1447,6 @@ class FunctionMocker<R(Args...)> final : public UntypedFunctionMockerBase {
     return DefaultValue<Result>::Get();
   }
 
-  // Performs the default action with the given arguments and returns
-  // the action's result.  The call description string will be used in
-  // the error message to describe the call in the case the default
-  // action fails.  The caller is responsible for deleting the result.
-  // L = *
-  UntypedActionResultHolderBase* UntypedPerformDefaultAction(
-      void* untyped_args,  // must point to an ArgumentTuple
-      const std::string& call_description) const override {
-    ArgumentTuple* args = static_cast<ArgumentTuple*>(untyped_args);
-    return ResultHolder::PerformDefaultAction(this, std::move(*args),
-                                              call_description);
-  }
-
-  // Performs the given action with the given arguments and returns
-  // the action's result.  The caller is responsible for deleting the
-  // result.
-  // L = *
-  UntypedActionResultHolderBase* UntypedPerformAction(
-      const void* untyped_action, void* untyped_args) const override {
-    // Make a copy of the action before performing it, in case the
-    // action deletes the mock object (and thus deletes itself).
-    const Action<F> action = *static_cast<const Action<F>*>(untyped_action);
-    ArgumentTuple* args = static_cast<ArgumentTuple*>(untyped_args);
-    return ResultHolder::PerformAction(action, std::move(*args));
-  }
-
   // Implements UntypedFunctionMockerBase::ClearDefaultActionsLocked():
   // clears the ON_CALL()s set on this mock function.
   void ClearDefaultActionsLocked() override
@@ -1604,10 +1478,7 @@ class FunctionMocker<R(Args...)> final : public UntypedFunctionMockerBase {
   // arguments.  This function can be safely called from multiple
   // threads concurrently.
   Result Invoke(Args... args) GTEST_LOCK_EXCLUDED_(g_gmock_mutex) {
-    ArgumentTuple tuple(std::forward<Args>(args)...);
-    std::unique_ptr<ResultHolder> holder(DownCast_<ResultHolder*>(
-        this->UntypedInvokeWith(static_cast<void*>(&tuple))));
-    return holder->Unwrap();
+    return InvokeWith(ArgumentTuple(std::forward<Args>(args)...));
   }
 
   MockSpec<F> With(Matcher<Args>... m) {
@@ -1618,8 +1489,6 @@ class FunctionMocker<R(Args...)> final : public UntypedFunctionMockerBase {
   template <typename Function>
   friend class MockSpec;
 
-  typedef ActionResultHolder<Result> ResultHolder;
-
   // Adds and returns a default action spec for this mock function.
   OnCallSpec<F>& AddNewOnCallSpec(const char* file, int line,
                                   const ArgumentMatcherTuple& m)
@@ -1790,13 +1659,73 @@ class FunctionMocker<R(Args...)> final : public UntypedFunctionMockerBase {
       expectation->DescribeCallCountTo(why);
     }
   }
+
+  // Performs the given action (or the default if it's null) with the given
+  // arguments and returns the action's result.
+  // L = *
+  R PerformAction(const void* untyped_action, ArgumentTuple&& args,
+                  const std::string& call_description) const {
+    if (untyped_action == nullptr) {
+      return PerformDefaultAction(std::move(args), call_description);
+    }
+
+    // Make a copy of the action before performing it, in case the
+    // action deletes the mock object (and thus deletes itself).
+    const Action<F> action = *static_cast<const Action<F>*>(untyped_action);
+    return action.Perform(std::move(args));
+  }
+
+  // Is it possible to store an object of the supplied type in a local variable
+  // for the sake of printing it, then return it on to the caller?
+  template <typename T>
+  using can_print_result = internal::conjunction<
+      // void can't be stored as an object (and we also don't need to print it).
+      internal::negation<std::is_void<T>>,
+      // Non-moveable types can't be returned on to the user, so there's no way
+      // for us to intercept and print them.
+      std::is_move_constructible<T>>;
+
+  // Perform the supplied action, printing the result to os.
+  template <typename T = R,
+            typename std::enable_if<can_print_result<T>::value, int>::type = 0>
+  R PerformActionAndPrintResult(const void* const untyped_action,
+                                ArgumentTuple&& args,
+                                const std::string& call_description,
+                                std::ostream& os) {
+    R result = PerformAction(untyped_action, std::move(args), call_description);
+
+    PrintAsActionResult(result, os);
+    return std::forward<R>(result);
+  }
+
+  // Disable warnings about an unused parameter (due to SFINAE choosing an
+  // overload that doesn't use it).
+  GTEST_DISABLE_MSC_WARNINGS_PUSH_(4100);
+
+  // An overload for when it's not possible to print the result. In this case we
+  // simply perform the action.
+  template <typename T = R,
+            typename std::enable_if<
+                internal::negation<can_print_result<T>>::value, int>::type = 0>
+  R PerformActionAndPrintResult(const void* const untyped_action,
+                                ArgumentTuple&& args,
+                                const std::string& call_description,
+                                std::ostream& os) {
+    return PerformAction(untyped_action, std::move(args), call_description);
+  }
+
+  GTEST_DISABLE_MSC_WARNINGS_POP_();
+
+  // Returns the result of invoking this mock function with the given
+  // arguments. This function can be safely called from multiple
+  // threads concurrently.
+  R InvokeWith(ArgumentTuple&& args) GTEST_LOCK_EXCLUDED_(g_gmock_mutex);
 };  // class FunctionMocker
 
 // Calculates the result of invoking this mock function with the given
-// arguments, prints it, and returns it.  The caller is responsible
-// for deleting the result.
-inline UntypedActionResultHolderBase*
-UntypedFunctionMockerBase::UntypedInvokeWith(void* const untyped_args)
+// arguments, prints it, and returns it.
+template <typename R, typename... Args>
+R FunctionMocker<R(Args...)>::InvokeWith(ArgumentTuple&& args)
     GTEST_LOCK_EXCLUDED_(g_gmock_mutex) {
   // See the definition of untyped_expectations_ for why access to it
   // is unprotected here.
@@ -1829,23 +1758,23 @@ UntypedFunctionMockerBase::UntypedInvokeWith(void* const untyped_args)
 
     if (!need_to_report_uninteresting_call) {
       // Perform the action without printing the call information.
-      return this->UntypedPerformDefaultAction(
-          untyped_args, "Function call: " + std::string(Name()));
+      return this->PerformDefaultAction(
+          std::move(args), "Function call: " + std::string(Name()));
     }
 
     // Warns about the uninteresting call.
     ::std::stringstream ss;
-    this->UntypedDescribeUninterestingCall(untyped_args, &ss);
-
-    // Calculates the function result.
-    UntypedActionResultHolderBase* const result =
-        this->UntypedPerformDefaultAction(untyped_args, ss.str());
+    this->UntypedDescribeUninterestingCall(&args, &ss);
 
-    // Prints the function result.
-    if (result != nullptr) result->PrintAsActionResult(&ss);
+    // Perform the action, print the result, and then report the uninteresting
+    // call.
+    //
+    // We use RAII to do the latter in case R is void or a non-moveable type. In
+    // either case we can't assign it to a local variable.
+    const Cleanup report_uninteresting_call(
+        [&] { ReportUninterestingCall(reaction, ss.str()); });
 
-    ReportUninterestingCall(reaction, ss.str());
-    return result;
+    return PerformActionAndPrintResult(nullptr, std::move(args), ss.str(), ss);
   }
 
   bool is_excessive = false;
@@ -1858,7 +1787,7 @@ UntypedFunctionMockerBase::UntypedInvokeWith(void* const untyped_args)
   // releases g_gmock_mutex.
 
   const ExpectationBase* const untyped_expectation =
-      this->UntypedFindMatchingExpectation(untyped_args, &untyped_action,
+      this->UntypedFindMatchingExpectation(&args, &untyped_action,
                                            &is_excessive, &ss, &why);
   const bool found = untyped_expectation != nullptr;
 
@@ -1870,13 +1799,11 @@ UntypedFunctionMockerBase::UntypedInvokeWith(void* const untyped_args)
       !found || is_excessive || LogIsVisible(kInfo);
   if (!need_to_report_call) {
     // Perform the action without printing the call information.
-    return untyped_action == nullptr
-               ? this->UntypedPerformDefaultAction(untyped_args, "")
-               : this->UntypedPerformAction(untyped_action, untyped_args);
+    return PerformAction(untyped_action, std::move(args), "");
   }
 
   ss << "    Function call: " << Name();
-  this->UntypedPrintArgs(untyped_args, &ss);
+  this->UntypedPrintArgs(&args, &ss);
 
   // In case the action deletes a piece of the expectation, we
   // generate the message beforehand.
@@ -1884,14 +1811,12 @@ UntypedFunctionMockerBase::UntypedInvokeWith(void* const untyped_args)
     untyped_expectation->DescribeLocationTo(&loc);
   }
 
-  UntypedActionResultHolderBase* result = nullptr;
-
-  auto perform_action = [&] {
-    return untyped_action == nullptr
-               ? this->UntypedPerformDefaultAction(untyped_args, ss.str())
-               : this->UntypedPerformAction(untyped_action, untyped_args);
-  };
-  auto handle_failures = [&] {
+  // Perform the action, print the result, and then fail or log in whatever way
+  // is appropriate.
+  //
+  // We use RAII to do the latter in case R is void or a non-moveable type. In
+  // either case we can't assign it to a local variable.
+  const Cleanup handle_failures([&] {
     ss << "\n" << why.str();
 
     if (!found) {
@@ -1906,21 +1831,10 @@ UntypedFunctionMockerBase::UntypedInvokeWith(void* const untyped_args)
       // described in ss.
       Log(kInfo, loc.str() + ss.str(), 2);
     }
-  };
-#if GTEST_HAS_EXCEPTIONS
-  try {
-    result = perform_action();
-  } catch (...) {
-    handle_failures();
-    throw;
-  }
-#else
-  result = perform_action();
-#endif
+  });
 
-  if (result != nullptr) result->PrintAsActionResult(&ss);
-  handle_failures();
-  return result;
+  return PerformActionAndPrintResult(untyped_action, std::move(args), ss.str(),
+                                     ss);
 }
 
 }  // namespace internal