Fix memory leak when accessing a const Node with a key that doesn't exist.

include/yaml-cpp/node/detail/impl.h

@@ -58,28 +58,28 @@ struct get_idx<Key, typename boost::enable_if<boost::is_signed<Key> >::type> {
 
 // indexing
 template <typename Key>
-inline node& node_data::get(const Key& key,
+inline node* node_data::get(const Key& key,
                             shared_memory_holder pMemory) const {
   switch (m_type) {
     case NodeType::Map:
       break;
     case NodeType::Undefined:
     case NodeType::Null:
-      return pMemory->create_node();
+      return NULL;
     case NodeType::Sequence:
       if (node* pNode = get_idx<Key>::get(m_sequence, key, pMemory))
-        return *pNode;
-      return pMemory->create_node();
+        return pNode;
+      return NULL;
     case NodeType::Scalar:
       throw BadSubscript();
   }
 
   for (node_map::const_iterator it = m_map.begin(); it != m_map.end(); ++it) {
     if (equals(*it->first, key, pMemory))
-      return *it->second;
+      return it->second;
   }
 
-  return pMemory->create_node();
+  return NULL;
 }
 
 template <typename Key>

include/yaml-cpp/node/detail/node.h

@@ -110,7 +110,10 @@ class node : private boost::noncopyable {
 
   // indexing
   template <typename Key>
-  node& get(const Key& key, shared_memory_holder pMemory) const {
+  node* get(const Key& key, shared_memory_holder pMemory) const {
+    // NOTE: this returns a non-const node so that the top-level Node can wrap
+    // it, and returns a pointer so that it can be NULL (if there is no such
+    // key).
     return static_cast<const node_ref&>(*m_pRef).get(key, pMemory);
   }
   template <typename Key>
@@ -124,7 +127,10 @@ class node : private boost::noncopyable {
     return m_pRef->remove(key, pMemory);
   }
 
-  node& get(node& key, shared_memory_holder pMemory) const {
+  node* get(node& key, shared_memory_holder pMemory) const {
+    // NOTE: this returns a non-const node so that the top-level Node can wrap
+    // it, and returns a pointer so that it can be NULL (if there is no such
+    // key).
     return static_cast<const node_ref&>(*m_pRef).get(key, pMemory);
   }
   node& get(node& key, shared_memory_holder pMemory) {

include/yaml-cpp/node/detail/node_data.h

@@ -63,13 +63,13 @@ class YAML_CPP_API node_data : private boost::noncopyable {
 
   // indexing
   template <typename Key>
-  node& get(const Key& key, shared_memory_holder pMemory) const;
+  node* get(const Key& key, shared_memory_holder pMemory) const;
   template <typename Key>
   node& get(const Key& key, shared_memory_holder pMemory);
   template <typename Key>
   bool remove(const Key& key, shared_memory_holder pMemory);
 
-  node& get(node& key, shared_memory_holder pMemory) const;
+  node* get(node& key, shared_memory_holder pMemory) const;
   node& get(node& key, shared_memory_holder pMemory);
   bool remove(node& key, shared_memory_holder pMemory);
 

include/yaml-cpp/node/detail/node_ref.h

@@ -57,7 +57,7 @@ class node_ref : private boost::noncopyable {
 
   // indexing
   template <typename Key>
-  node& get(const Key& key, shared_memory_holder pMemory) const {
+  node* get(const Key& key, shared_memory_holder pMemory) const {
     return static_cast<const node_data&>(*m_pData).get(key, pMemory);
   }
   template <typename Key>
@@ -69,7 +69,7 @@ class node_ref : private boost::noncopyable {
     return m_pData->remove(key, pMemory);
   }
 
-  node& get(node& key, shared_memory_holder pMemory) const {
+  node* get(node& key, shared_memory_holder pMemory) const {
     return static_cast<const node_data&>(*m_pData).get(key, pMemory);
   }
   node& get(node& key, shared_memory_holder pMemory) {

include/yaml-cpp/node/impl.h

@@ -366,9 +366,12 @@ inline const Node Node::operator[](const Key& key) const {
   if (!m_isValid)
     throw InvalidNode();
   EnsureNodeExists();
-  detail::node& value = static_cast<const detail::node&>(*m_pNode)
+  detail::node* value = static_cast<const detail::node&>(*m_pNode)
                             .get(detail::to_value(key), m_pMemory);
-  return Node(value, m_pMemory);
+  if (!value) {
+    return Node(ZombieNode);
+  }
+  return Node(*value, m_pMemory);
 }
 
 template <typename Key>
@@ -394,9 +397,12 @@ inline const Node Node::operator[](const Node& key) const {
   EnsureNodeExists();
   key.EnsureNodeExists();
   m_pMemory->merge(*key.m_pMemory);
-  detail::node& value =
+  detail::node* value =
       static_cast<const detail::node&>(*m_pNode).get(*key.m_pNode, m_pMemory);
-  return Node(value, m_pMemory);
+  if (!value) {
+    return Node(ZombieNode);
+  }
+  return Node(*value, m_pMemory);
 }
 
 inline Node Node::operator[](const Node& key) {

include/yaml-cpp/node/node.h

@@ -129,6 +129,7 @@ class YAML_CPP_API Node {
   bool m_isValid;
   mutable detail::shared_memory_holder m_pMemory;
   mutable detail::node* m_pNode;
+  mutable const detail::node* m_pConstNode;
 };
 
 YAML_CPP_API bool operator==(const Node& lhs, const Node& rhs);

src/node_data.cpp

@@ -192,16 +192,17 @@ void node_data::insert(node& key, node& value, shared_memory_holder pMemory) {
 }
 
 // indexing
-node& node_data::get(node& key, shared_memory_holder pMemory) const {
-  if (m_type != NodeType::Map)
-    return pMemory->create_node();
+node* node_data::get(node& key, shared_memory_holder /* pMemory */) const {
+  if (m_type != NodeType::Map) {
+    return NULL;
+  }
 
   for (node_map::const_iterator it = m_map.begin(); it != m_map.end(); ++it) {
     if (it->first->is(key))
-      return *it->second;
+      return it->second;
   }
 
-  return pMemory->create_node();
+  return NULL;
 }
 
 node& node_data::get(node& key, shared_memory_holder pMemory) {

util/sandbox.cpp

@@ -26,10 +26,11 @@ class NullEventHandler : public YAML::EventHandler {
 };
 
 int main() {
-  std::stringstream stream("---{header: {id: 1");
-  YAML::Parser parser(stream);
-  //    parser.PrintTokens(std::cout);
-  NullEventHandler handler;
-  parser.HandleNextDocument(handler);
+  const YAML::Node node;
+
+  std::string key = "doesnotexist";
+  for (;;) {
+    node[key];
+  }
   return 0;
 }