Make tensorflow::Status movable.

PiperOrigin-RevId: 281542191
Change-Id: Ia9e8f3078526fa45228e10c194e5d962d3103bcc

tensorflow/core/lib/core/status.h

@@ -47,7 +47,11 @@ class Status {
 
   /// Copy the specified status.
   Status(const Status& s);
-  void operator=(const Status& s);
+  Status& operator=(const Status& s);
+#ifndef SWIG
+  Status(Status&& s) noexcept;
+  Status& operator=(Status&& s) noexcept;
+#endif  // SWIG
 
   static Status OK() { return Status(); }
 
@@ -133,16 +137,28 @@ class StatusGroup {
 };
 
 inline Status::Status(const Status& s)
-    : state_((s.state_ == NULL) ? NULL : new State(*s.state_)) {}
+    : state_((s.state_ == nullptr) ? nullptr : new State(*s.state_)) {}
 
-inline void Status::operator=(const Status& s) {
+inline Status& Status::operator=(const Status& s) {
   // The following condition catches both aliasing (when this == &s),
   // and the common case where both s and *this are ok.
   if (state_ != s.state_) {
     SlowCopyFrom(s.state_.get());
   }
+  return *this;
 }
 
+#ifndef SWIG
+inline Status::Status(Status&& s) noexcept : state_(std::move(s.state_)) {}
+
+inline Status& Status::operator=(Status&& s) noexcept {
+  if (state_ != s.state_) {
+    state_ = std::move(s.state_);
+  }
+  return *this;
+}
+#endif  // SWIG
+
 inline bool Status::operator==(const Status& x) const {
   return (this->state_ == x.state_) || (ToString() == x.ToString());
 }

tensorflow/core/lib/core/status_test.cc

@@ -58,6 +58,19 @@ TEST(Status, Assign) {
   ASSERT_EQ(a.ToString(), b.ToString());
 }
 
+TEST(Status, Move) {
+  Status a(errors::InvalidArgument("Invalid"));
+  Status b(std::move(a));
+  ASSERT_EQ("Invalid argument: Invalid", b.ToString());
+}
+
+TEST(Status, MoveAssign) {
+  Status a(errors::InvalidArgument("Invalid"));
+  Status b;
+  b = std::move(a);
+  ASSERT_EQ("Invalid argument: Invalid", b.ToString());
+}
+
 TEST(Status, Update) {
   Status s;
   s.Update(Status::OK());

tensorflow/stream_executor/lib/statusor.h

@@ -273,7 +273,9 @@ const Status& StatusOr<T>::status() const & {
 }
 template <typename T>
 Status StatusOr<T>::status() && {
-  return ok() ? Status::OK() : std::move(this->status_);
+  // Note that we copy instead of moving the status here so that
+  // ~StatusOrData() can call ok() without invoking UB.
+  return ok() ? Status::OK() : this->status_;
 }
 
 template <typename T>

tensorflow/stream_executor/lib/statusor_internals.h

@@ -67,7 +67,7 @@ class StatusOrData {
       MakeValue(std::move(other.data_));
       MakeStatus();
     } else {
-      MakeStatus(std::move(other.status_));
+      MakeStatus(other.status_);
     }
   }
 
@@ -87,7 +87,7 @@ class StatusOrData {
       MakeValue(std::move(other.data_));
       MakeStatus();
     } else {
-      MakeStatus(std::move(other.status_));
+      MakeStatus(other.status_);
     }
   }
 
@@ -156,7 +156,9 @@ class StatusOrData {
 
   void Assign(Status&& status) {
     Clear();
-    status_ = std::move(status);
+    // Note that we copy instead of moving the status here so that
+    // status.~StatusOrData() can call ok() without invoking UB.
+    status_ = status;
     EnsureNotOk();
   }