diff --git a/paddle/framework/attribute.h b/paddle/framework/attribute.h
index 72a654bda550ee75811f365403f6eeb5284a102e..3a5820e9c60539e3c771df5da4e82f6c1cae688f 100644
--- a/paddle/framework/attribute.h
+++ b/paddle/framework/attribute.h
@@ -1,3 +1,17 @@
+/* Copyright (c) 2016 PaddlePaddle Authors. All Rights Reserve.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License. */
+
 #pragma once
 
 #include <boost/variant.hpp>
@@ -29,7 +43,7 @@ Attribute GetAttrValue(const AttrDesc& attr_desc);
 template <typename T>
 class LargerThanChecker {
  public:
-  LargerThanChecker(T lower_bound) : lower_bound_(lower_bound) {}
+  explicit LargerThanChecker(T lower_bound) : lower_bound_(lower_bound) {}
   void operator()(T& value) const {
     PADDLE_ENFORCE(value > lower_bound_, "larger_than check fail");
   }
@@ -44,7 +58,8 @@ class LargerThanChecker {
 template <typename T>
 class DefaultValueSetter {
  public:
-  DefaultValueSetter(T default_value) : default_value_(default_value) {}
+  explicit DefaultValueSetter(T default_value)
+      : default_value_(default_value) {}
   void operator()(T& value) const { value = default_value_; }
 
  private:
@@ -87,7 +102,8 @@ class TypedAttrChecker {
   typedef std::function<void(T&)> ValueChecker;
 
  public:
-  TypedAttrChecker(const std::string& attr_name) : attr_name_(attr_name) {}
+  explicit TypedAttrChecker(const std::string& attr_name)
+      : attr_name_(attr_name) {}
 
   TypedAttrChecker& InEnum(const std::unordered_set<T>& range) {
     value_checkers_.push_back(EnumInContainer<T>(range));