如果atomic_flag变量是类的成员，我如何初始化它？ [英] how do I initialise an atomic_flag variable if it is a member of a class?

问题描述

我试图使用atomic_flag实现自旋锁。我知道用C ++ 11我必须初始化atomic_flag变量，但我不能得到它编译。我的代码如下：

I'm trying to implement a spin lock using an atomic_flag. I know that with C++11 I have to initialise the atomic_flag variable, but I can't get it to compile. My code looks like this:

class SpinLock 
{
 public:
  SpinLock()
   :m_flag(ATOMIC_FLAG_INIT)  /// syntax error : missing ')' before '{'
  {
  }

  void lock()
  {
    while (m_flag.test_and_set() == true){}
  }

  void unlock()
  {
    m_flag.clear();
  }

 private:
  SpinLock &operator=(const SpinLock &);

 private:
  std::atomic_flag    m_flag;
};

当我编译代码时，我得到'语法错误：missing'）'before'{''。我还看到ATOMIC_FLAG_INIT定义为{0}，但是这是正确的写法呢？

When I compile the code I get 'syntax error : missing ')' before '{''. I also see that ATOMIC_FLAG_INIT is defined as {0}, but what is the correct way to write this then?

下面的编译，但它仍然是线程安全的？ / p>

The following compiles, but is it still threads safe?

  SpinLock()
  {
         m_flag.clear();
  }

推荐答案

Visual Studio 2012不支持c ++ 11初始值列表（请参阅c ++ 11支持页面）

Visual Studio 2012 does not support c++11 initializer lists (see the c++11 support page)

但是在Visual Studio 2013中支持它（参见均匀初始化文档）

It is however supported in Visual Studio 2013, (see the "initializer_list Constructors" section in the Uniform Initialization docs)

同时在你的情况下，构造函数可以使用一个赋值 m_flag = ATOMIC_FLAG_INIT;

Meanwhile in your case the constructor can just use an assignment m_flag = ATOMIC_FLAG_INIT;

更新：
似乎没有测试上述作业，使用 m_flag.clear（）; 获得相同的结果

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