具有 std::atomic 成员变量的类的复制构造函数/赋值运算符出错 [英] Error with copy constructor/assignment operator for a class which has std::atomic member variable

问题描述

我有一个如下所示的课程.

I have a class like below.

#include <atomic>

static const long  myValue = 0;

class Sequence
{

public:

    Sequence(long initial_value = myValue) : value_(initial_value) {}


private:

     std::atomic<long> value_;
};

int main()
{
         Sequence firstSequence;
         Sequence secondSequence = firstSequence;
         return 0;
}

我收到这样的编译错误，

I am getting compilation error like this,

test.cpp:21:36: error: use of deleted function ‘Sequence::Sequence(const Sequence&)’
test.cpp:5:7: error: ‘Sequence::Sequence(const Sequence&)’ is implicitly deleted because the default definition would be ill-formed:
test.cpp:5:7: error: use of deleted function ‘std::atomic<long int>::atomic(const std::atomic<long int>&)’

在这种情况下，默认的复制构造函数和赋值运算符是否不起作用?

Is that the default copy constructor and assignment opertaor do not work in such case?

PS:我使用的是 gcc 4.6.3 版

PS: I am using gcc version 4.6.3

推荐答案

您不能使用标准复制构造函数复制原子，因为所有加载和存储都必须显式发生.您必须为 Sequence 编写自己的复制构造函数，它对 value_(rhs.value_.load()) 形式进行一些初始化(可能具有更宽松的内存排序)).

You can't copy atomics with a standard copy constructor, since all loads and stores must happen explicitly. You'll have to write your own copy constructor for Sequence which does some initialization of the form value_(rhs.value_.load()) (possibly with more relaxed memory ordering).

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