explicit ctor

Author: hchunhui

include/json/value.h

@@ -235,7 +235,7 @@ class JSON_API Value {
 
 private:
   struct StaticInitTag {};
-  Value(StaticInitTag); ///< A special constructor for Value::kNull.
+  explicit Value(StaticInitTag) {} ///< A special constructor for Value::kNull.
   static const Value kNull;
 
 public:

src/lib_json/json_value.cpp

@@ -299,8 +299,6 @@ bool Value::CZString::isStaticString() const { return storage_.policy_ == noDupl
 // //////////////////////////////////////////////////////////////////
 // //////////////////////////////////////////////////////////////////
 
-Value::Value(Value::StaticInitTag) {}
-
 /*! \internal Default constructor initialization must be equivalent to:
  * memset( this, 0, sizeof(Value) )
  * This optimization is used in ValueInternalMap fast allocator.