Fix Value::copyPayload() and Value::copy() (open-source-parsers#704)

Value copy constructor shares the same code with Value::copy() and Value::copyPayload().
New Value::releasePayload() is used to free payload memory.
Fixes: open-source-parsers#704

Author: okodron

include/json/value.h

@@ -606,6 +606,7 @@ Json::Value obj_value(Json::objectValue); // {}
 
 private:
   void initBasic(ValueType type, bool allocated = false);
+  void releasePayload();
 
   Value& resolveReference(const char* key);
   Value& resolveReference(const char* key, const char* end);

src/lib_json/json_value.cpp

@@ -441,48 +441,11 @@ Value::Value(bool value) {
   value_.bool_ = value;
 }
 
-Value::Value(Value const& other)
-    : type_(other.type_), allocated_(false)
-      ,
-      comments_(0), start_(other.start_), limit_(other.limit_)
-{
-  switch (type_) {
-  case nullValue:
-  case intValue:
-  case uintValue:
-  case realValue:
-  case booleanValue:
-    value_ = other.value_;
-    break;
-  case stringValue:
-    if (other.value_.string_ && other.allocated_) {
-      unsigned len;
-      char const* str;
-      decodePrefixedString(other.allocated_, other.value_.string_,
-          &len, &str);
-      value_.string_ = duplicateAndPrefixStringValue(str, len);
-      allocated_ = true;
-    } else {
-      value_.string_ = other.value_.string_;
-      allocated_ = false;
-    }
-    break;
-  case arrayValue:
-  case objectValue:
-    value_.map_ = new ObjectValues(*other.value_.map_);
-    break;
-  default:
-    JSON_ASSERT_UNREACHABLE;
-  }
-  if (other.comments_) {
-    comments_ = new CommentInfo[numberOfCommentPlacement];
-    for (int comment = 0; comment < numberOfCommentPlacement; ++comment) {
-      const CommentInfo& otherComment = other.comments_[comment];
-      if (otherComment.comment_)
-        comments_[comment].setComment(
-            otherComment.comment_, strlen(otherComment.comment_));
-    }
-  }
+Value::Value(const Value& other) {
+  type_ = nullValue;
+  allocated_ = false;
+  comments_ = 0;
+  copy(other);
 }
 
 #if JSON_HAS_RVALUE_REFERENCES
@@ -494,24 +457,7 @@ Value::Value(Value&& other) {
 #endif
 
 Value::~Value() {
-  switch (type_) {
-  case nullValue:
-  case intValue:
-  case uintValue:
-  case realValue:
-  case booleanValue:
-    break;
-  case stringValue:
-    if (allocated_)
-      releasePrefixedStringValue(value_.string_);
-    break;
-  case arrayValue:
-  case objectValue:
-    delete value_.map_;
-    break;
-  default:
-    JSON_ASSERT_UNREACHABLE;
-  }
+  releasePayload();
 
   delete[] comments_;
 
@@ -534,9 +480,36 @@ void Value::swapPayload(Value& other) {
 }
 
 void Value::copyPayload(const Value& other) {
+  releasePayload();
   type_ = other.type_;
-  value_ = other.value_;
-  allocated_ = other.allocated_;
+  allocated_ = false;
+  switch (type_) {
+  case nullValue:
+  case intValue:
+  case uintValue:
+  case realValue:
+  case booleanValue:
+    value_ = other.value_;
+    break;
+  case stringValue:
+    if (other.value_.string_ && other.allocated_) {
+      unsigned len;
+      char const* str;
+      decodePrefixedString(other.allocated_, other.value_.string_,
+          &len, &str);
+      value_.string_ = duplicateAndPrefixStringValue(str, len);
+      allocated_ = true;
+    } else {
+      value_.string_ = other.value_.string_;
+    }
+    break;
+  case arrayValue:
+  case objectValue:
+    value_.map_ = new ObjectValues(*other.value_.map_);
+    break;
+  default:
+    JSON_ASSERT_UNREACHABLE;
+  }
 }
 
 void Value::swap(Value& other) {
@@ -548,7 +521,18 @@ void Value::swap(Value& other) {
 
 void Value::copy(const Value& other) {
   copyPayload(other);
-  comments_ = other.comments_;
+  delete[] comments_;
+  if (other.comments_) {
+    comments_ = new CommentInfo[numberOfCommentPlacement];
+    for (int comment = 0; comment < numberOfCommentPlacement; ++comment) {
+      const CommentInfo& otherComment = other.comments_[comment];
+      if (otherComment.comment_)
+        comments_[comment].setComment(
+            otherComment.comment_, strlen(otherComment.comment_));
+    }
+  } else {
+    comments_ = 0;
+  }
   start_ = other.start_;
   limit_ = other.limit_;
 }
@@ -1049,6 +1033,27 @@ void Value::initBasic(ValueType vtype, bool allocated) {
   limit_ = 0;
 }
 
+void Value::releasePayload() {
+  switch (type_) {
+  case nullValue:
+  case intValue:
+  case uintValue:
+  case realValue:
+  case booleanValue:
+    break;
+  case stringValue:
+    if (allocated_)
+      releasePrefixedStringValue(value_.string_);
+    break;
+  case arrayValue:
+  case objectValue:
+    delete value_.map_;
+    break;
+  default:
+    JSON_ASSERT_UNREACHABLE;
+  }
+}
+
 // Access an object value by name, create a null member if it does not exist.
 // @pre Type of '*this' is object or null.
 // @param key is null-terminated.