c ++单例实现STL线程安全 [英] c++ singleton implementation STL thread safe

问题描述

我一直在尝试使用STL的某些C ++ 11功能来实现单例.我了解了一些实现，并发现它非常不错: http://silviuardelean .ro/2012/06/05/few-singleton-approaches/我进行了一些更改，使波纹管代码在VS2013上正常工作，但我仍然想知道:

I've been trying to implement a singleton with some C++11 features from STL. I read about a few implementations and I found this pretty good: http://silviuardelean.ro/2012/06/05/few-singleton-approaches/ I made a few changes and got the bellow code working on VS2013, but I still would like to know:

a)此实现是线程安全的吗?

a) Is this implementation thread-safe?

b)可以(从习惯上)从GetInstance返回shared_ptr而不是引用吗?

b) Is it ok (good practice) to return a shared_ptr from GetInstance instead of a reference?

PS .:我的单例是OpenGL接口(这就是这个名称的原因).

PS.: My singleton is ment to be an OpenGL interface (that's the reason for the name).

HandlerOpenGL.h

HandlerOpenGL.h

#pragma once



// STL headers
#include <memory> // shared_ptr
#include <mutex> // once_flag



// OpenGL Handler Singleton
class HandlerOpenGL
{
public:
    // Constructor/Destructor interface
    static std::shared_ptr<HandlerOpenGL> GetInstance(void);    // Only way to access singleton
    ~HandlerOpenGL(void);
    HandlerOpenGL(const HandlerOpenGL&) = delete;   // Avoid any copy/move
    HandlerOpenGL(HandlerOpenGL&&) = delete;
    HandlerOpenGL& operator=(const HandlerOpenGL&) = delete;
    HandlerOpenGL& operator=(HandlerOpenGL&&) = delete;

private:
    // Hide construction method/variables
    HandlerOpenGL(void);    // Private to be created once
    static std::shared_ptr<HandlerOpenGL> _instance;
    static std::once_flag _flag;
};

HandlerOpenGL.cpp

HandlerOpenGL.cpp

// Own header
#include "HandlerOpenGL.h"
// STL headers
#include <memory> // shared_ptr, make_shared
#include <mutex> // once_flag, call_once



// instanciate static members
std::shared_ptr<HandlerOpenGL> HandlerOpenGL::_instance(nullptr);
std::once_flag HandlerOpenGL::_flag;



std::shared_ptr<HandlerOpenGL> HandlerOpenGL::GetInstance(void)
{
    std::call_once(_flag, [](){ _instance.reset(new HandlerOpenGL); });
    return _instance;
}



HandlerOpenGL::~HandlerOpenGL(void)
{
}



HandlerOpenGL::HandlerOpenGL(void)
{
}

推荐答案

我根本看不到在其中使用shared_ptr的意思.如果是单例，则不会被复制.那么为什么要使用shared_ptr?

I do not see a point of using shared_ptr there at all. If it is a singleton, it will not be copied. So why use shared_ptr?

我还相信，Meyers单例操作起来非常容易，需要更少的键入，并且不依赖于动态分配，所以我想知道为什么有人还会做其他事情.

I also believe, a Meyers singleton is so much easier to do, requires less typing, and doesn't rely on dynamic allocation, so I wonder why would anybody would do anything else.

尽管如此，我没有看到与此相关的特定线程问题.

Despite all this, I do not see a specific threading issues with that.

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