diff --git a/design_pattern/singleton/README.md b/design_pattern/singleton/README.md
index 4601823..b91b82e 100644
--- a/design_pattern/singleton/README.md
+++ b/design_pattern/singleton/README.md
@@ -114,7 +114,7 @@ private:
     static singleton *p;
     static mutex lock_;
 public:
-    singleton *instance();
+    static singleton *instance();
 
     // 实现一个内嵌垃圾回收类
     class CGarbo
@@ -131,6 +131,7 @@ public:
 
 singleton *singleton::p = nullptr;
 singleton::CGarbo Garbo;
+std::mutex singleton::lock_;
 
 singleton* singleton::instance() {
     if (p == nullptr) {
diff --git a/design_pattern/singleton/dcl_singleton.cpp b/design_pattern/singleton/dcl_singleton.cpp
index 88278bb..2b22d03 100644
--- a/design_pattern/singleton/dcl_singleton.cpp
+++ b/design_pattern/singleton/dcl_singleton.cpp
@@ -14,7 +14,7 @@ private:
     static singleton *p;
     static mutex lock_;
 public:
-    singleton *instance();
+    static singleton *instance();
 
     // 实现一个内嵌垃圾回收类
     class CGarbo
@@ -31,6 +31,7 @@ public:
 
 singleton *singleton::p = nullptr;
 singleton::CGarbo Garbo;
+std::mutex singleton::lock_;
 
 singleton* singleton::instance() {
     if (p == nullptr) {
diff --git a/design_pattern/singleton/static_local_singleton.cpp b/design_pattern/singleton/static_local_singleton.cpp
index ddab782..87626bc 100644
--- a/design_pattern/singleton/static_local_singleton.cpp
+++ b/design_pattern/singleton/static_local_singleton.cpp
@@ -11,12 +11,12 @@ private:
     static singleton *p;
     singleton() {}
 public:
-    singleton *instance();
+    static singleton &instance();
 };
 
-singleton *singleton::instance() {
+singleton &singleton::instance() {
     static singleton p;
-    return &p;
+    return p;
 }