support bazel complie this project and format code.

learn_class/modern_cpp_30/memorymodel_atomic/barrier_singleton.cpp

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+//
+// Created by light on 20-2-7.
+//
+#include <iostream>
+
+using namespace std;
+
+#include <mutex>
+
+#define barrier() __asm__ volatile ("lwsync")
+
+// method 1 operator new + placement new
+//singleton *instance() {
+//    if (p == nullptr) {
+//        lock_guard<mutex> guard(lock_);
+//        if (p == nullptr) {
+//            singleton *tmp = static_cast<singleton *>(operator new(sizeof(singleton)));
+//            new(p)singleton();
+//            p = tmp;
+//        }
+//    }
+//    return p;
+//}
+class singleton {
+private:
+    singleton() {}
+
+    static singleton *p;
+    static mutex lock_;
+public:
+    static singleton *instance();
+};
+
+singleton *singleton::p = nullptr;
+
+singleton *singleton::instance() {
+    if (p == nullptr) {
+        lock_guard<mutex> guard(lock_);
+        barrier();
+        if (p == nullptr) {
+            p = new singleton();
+        }
+    }
+    return p;
+}
+

learn_class/modern_cpp_30/memorymodel_atomic/cpulpuls11_singleton.cpp

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+//
+// Created by light on 20-2-7.
+//
+
+#include <iostream>
+
+using namespace std;
+
+#include <mutex>
+#include <atomic>
+
+//C++ 11版本之后的跨平台实现
+class singleton {
+private:
+    singleton() {}
+
+    static mutex lock_;
+    static atomic<singleton *> p;
+public:
+    singleton *instance();
+};
+
+mutex singleton::lock_;
+atomic<singleton *> singleton::p;
+
+/*
+* std::atomic_thread_fence(std::memory_order_acquire);
+* std::atomic_thread_fence(std::memory_order_release);
+* 这两句话可以保证他们之间的语句不会发生乱序执行。
+*/
+singleton *singleton::instance() {
+    singleton *tmp = p.load(memory_order_relaxed);
+    atomic_thread_fence(memory_order_acquire);
+    if (tmp == nullptr) {
+        lock_guard<mutex> guard(lock_);
+        tmp = p.load(memory_order_relaxed);
+        if (tmp == nullptr) {
+            tmp = new singleton();
+            atomic_thread_fence(memory_order_release);
+            p.store(tmp, memory_order_relaxed);
+        }
+    }
+    return p;
+}
+
+

learn_class/modern_cpp_30/memorymodel_atomic/dcl_singleton.cpp

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+//
+// Created by light on 20-2-7.
+//
+#include <iostream>
+
+using namespace std;
+
+#include <mutex>
+
+class singleton {
+private:
+    singleton() {}
+
+    static singleton *p;
+    static mutex lock_;
+public:
+    singleton *instance();
+
+    // 实现一个内嵌垃圾回收类
+    class CGarbo
+    {
+    public:
+        ~CGarbo()
+        {
+            if(singleton::p)
+                delete singleton::p;
+        }
+    };
+    static CGarbo Garbo; // 定义一个静态成员变量，程序结束时，系统会自动调用它的析构函数从而释放单例对象
+};
+
+singleton *singleton::p = nullptr;
+singleton::CGarbo Garbo;
+
+singleton* singleton::instance() {
+    if (p == nullptr) {
+        lock_guard<mutex> guard(lock_);
+        if (p == nullptr)
+            p = new singleton();
+    }
+    return p;
+}

learn_class/modern_cpp_30/memorymodel_atomic/hungrysingleton.cpp

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+//
+// Created by light on 20-2-6.
+//
+
+class singleton {
+private:
+    singleton() {}
+    static singleton *p;
+public:
+    static singleton *instance();
+};
+
+singleton *singleton::p = new singleton();
+singleton* singleton::instance() {
+    return p;
+}
+

learn_class/modern_cpp_30/memorymodel_atomic/iazysingleton.cpp

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+//
+// Created by light on 20-2-6.
+//
+
+class singleton {
+private:
+    singleton() {}
+    static singleton *p;
+public:
+    static singleton *instance();
+};
+
+singleton *singleton::p = nullptr;
+
+singleton* singleton::instance() {
+    if (p == nullptr)
+        p = new singleton();
+    return p;
+}

learn_class/modern_cpp_30/memorymodel_atomic/lock_singleton.cpp

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+//
+// Created by light on 20-2-7.
+//
+#include <iostream>
+using namespace std;
+
+#include <mutex>
+
+class singleton {
+private:
+    singleton() {}
+    static singleton *p;
+    static mutex lock_;
+public:
+    static singleton *instance();
+};
+
+singleton *singleton::p = nullptr;
+
+singleton* singleton::instance() {
+    lock_guard<mutex> guard(lock_);
+    if (p == nullptr)
+        p = new singleton();
+    return p;
+}

learn_class/modern_cpp_30/memorymodel_atomic/pthreadoncesingleton.cpp

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+//
+// Created by light on 20-2-6.
+//
+
+#include <sys/param.h>
+#include <pthread.h>
+
+class singleton {
+private:
+    singleton(); //私有构造函数，不允许使用者自己生成对象
+    singleton(const singleton &other);
+
+    //要写成静态方法的原因：类成员函数隐含传递this指针（第一个参数）
+    static void init() {
+        p = new singleton();
+    }
+
+    static pthread_once_t ponce_;
+    static singleton *p; //静态成员变量
+public:
+    singleton *instance() {
+        // init函数只会执行一次
+        pthread_once(&ponce_, &singleton::init);
+        return p;
+    }
+};
+
+

learn_class/modern_cpp_30/memorymodel_atomic/static_local_singleton.cpp

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+//
+// Created by light on 20-2-7.
+//
+
+#include <iostream>
+
+using namespace std;
+
+class singleton {
+private:
+    static singleton *p;
+    singleton() {}
+public:
+    singleton *instance();
+};
+
+singleton *singleton::instance() {
+    static singleton p;
+    return &p;
+}
+
+