message: hammer: fixed GCC warnings in
diff: @@ -6872,6 +6872,11 @@ class json_ref
  is_rvalue(true)
  {}
  + // class should be movable only
  + json_ref(json_ref&&) = default;
  + json_ref(const json_ref&) = delete;
  + json_ref& operator=(const json_ref&) = delete;
  +
  value_type moved_or_copied() const
  {
  if (is_rvalue)
  @@ -6895,7 +6900,7 @@ class json_ref
  }
  private:
  - mutable value_type owned_value;
  + mutable value_type owned_value = nullptr;
  value_type* value_ref = nullptr;
  const bool is_rvalue;
  };
  @@ -9826,6 +9831,7 @@ class basic_json
  */
  template < typename ValueType, typename std::enable_if <
  not std::is_pointer<ValueType>::value and
  + not std::is_same<ValueType, detail::json_ref<basic_json>>::value and
  not std::is_same<ValueType, typename string_t::value_type>::value
  #ifndef _MSC_VER // fix for issue #167 operator<< ambiguity under VS2015
  and not std::is_same<ValueType, std::initializer_list<typename string_t::value_type>>::value
  