Make Node move constructor and assignment operator noexcept (#809)

Move constructor:
 * m_isValid    (bool)                 exchange(rhs.m_isValid, true)
 * m_invalidKey (std::string)          std::move()
 * m_pMemory    (shared_memory_holder) std::move()
 * m_pNode      (node*)                exchange(rhs.m_pNode, nullptr)

 This leaves the moved-from Node as if it was just default constructed.

Move assignment:
 A temporary Node is move constructed (using the above) leaving the moved-from
 Node as if it was just default constructed.

 *this then copy assigns the temporary, using AssignNode() directly to avoid a
 second self-assignment check.

 If an exception is thrown in AssignNode(), m_isValid is set to false.

Signed-off-by: Ted Lyngmo <ted@lyncon.se>

Author: TedLyngmo

include/yaml-cpp/node/impl.h

@@ -14,9 +14,33 @@
 #include "yaml-cpp/node/node.h"
 #include <sstream>
 #include <string>
+#include <utility>
+
+// This is here for compatibility with older versions of Visual Studio
+// which don't support noexcept
+#if defined(_MSC_VER) && _MSC_VER < 1900
+    #define YAML_CPP_NOEXCEPT _NOEXCEPT
+#else
+    #define YAML_CPP_NOEXCEPT noexcept
+#endif
 
 namespace YAML {
-inline Node::Node()
+namespace detail {
+#if __cplusplus >= 201402L
+using ::std::exchange;
+#else
+template<class T, class U = T>
+T exchange(T& obj, U&& new_value) {
+  T old_value = std::move(obj);
+  obj = std::forward<U>(new_value);
+  return old_value;
+}
+#endif
+}  // namespace detail
+}  // namespace YAML
+
+namespace YAML {
+inline Node::Node() YAML_CPP_NOEXCEPT
     : m_isValid(true), m_invalidKey{}, m_pMemory(nullptr), m_pNode(nullptr) {}
 
 inline Node::Node(NodeType::value type)
@@ -44,6 +68,13 @@ inline Node::Node(const detail::iterator_value& rhs)
 
 inline Node::Node(const Node& rhs) = default;
 
+inline Node::Node(Node&& rhs) YAML_CPP_NOEXCEPT
+    : m_isValid(detail::exchange(rhs.m_isValid, true)),
+      m_invalidKey(std::move(rhs.m_invalidKey)),
+      m_pMemory(std::move(rhs.m_pMemory)),
+      m_pNode(detail::exchange(rhs.m_pNode, nullptr)) {
+}
+
 inline Node::Node(Zombie)
     : m_isValid(false), m_invalidKey{}, m_pMemory{}, m_pNode(nullptr) {}
 
@@ -209,6 +240,19 @@ inline Node& Node::operator=(const Node& rhs) {
   return *this;
 }
 
+inline Node& Node::operator=(Node&& rhs) YAML_CPP_NOEXCEPT {
+  if (is(rhs))
+    return *this;
+  Node tmp(std::move(rhs));
+  try {
+    AssignNode(tmp);
+  }
+  catch(...) {
+    m_isValid = false;
+  }
+  return *this;
+}
+
 inline void Node::reset(const YAML::Node& rhs) {
   if (!m_isValid || !rhs.m_isValid)
     throw InvalidNode(m_invalidKey);
@@ -424,4 +468,6 @@ inline void Node::force_insert(const Key& key, const Value& value) {
 inline bool operator==(const Node& lhs, const Node& rhs) { return lhs.is(rhs); }
 }  // namespace YAML
 
+#undef YAML_CPP_NOEXCEPT
+
 #endif  // NODE_IMPL_H_62B23520_7C8E_11DE_8A39_0800200C9A66

include/yaml-cpp/node/node.h

@@ -17,6 +17,14 @@
 #include "yaml-cpp/node/ptr.h"
 #include "yaml-cpp/node/type.h"
 
+// This is here for compatibility with older versions of Visual Studio
+// which don't support noexcept
+#if defined(_MSC_VER) && _MSC_VER < 1900
+    #define YAML_CPP_NOEXCEPT _NOEXCEPT
+#else
+    #define YAML_CPP_NOEXCEPT noexcept
+#endif
+
 namespace YAML {
 namespace detail {
 class node;
@@ -41,12 +49,13 @@ class YAML_CPP_API Node {
   using iterator = YAML::iterator;
   using const_iterator = YAML::const_iterator;
 
-  Node();
+  Node() YAML_CPP_NOEXCEPT;
   explicit Node(NodeType::value type);
   template <typename T>
   explicit Node(const T& rhs);
   explicit Node(const detail::iterator_value& rhs);
   Node(const Node& rhs);
+  Node(Node&& rhs) YAML_CPP_NOEXCEPT;
   ~Node();
 
   YAML::Mark Mark() const;
@@ -81,6 +90,7 @@ class YAML_CPP_API Node {
   template <typename T>
   Node& operator=(const T& rhs);
   Node& operator=(const Node& rhs);
+  Node& operator=(Node&& rhs) YAML_CPP_NOEXCEPT;
   void reset(const Node& rhs = Node());
 
   // size/iterator
@@ -145,4 +155,6 @@ template <typename T>
 struct convert;
 }
 
+#undef YAML_CPP_NOEXCEPT
+
 #endif  // NODE_NODE_H_62B23520_7C8E_11DE_8A39_0800200C9A66