将 std::atomic_flag 与工作线程一起使用时出现问题

Question

抱歉冗长 - 我已尽力将我的代码示例压缩为功能最少的 class 和 main() 方法。

我正在尝试使用 atomic_flag 通知我的工作线程中的 _rx() 在调用 stop() 时退出。

我认为问题在于尝试创建我的工作线程，

thread SanityTestThread(&SanityTest::_rx, *this);

这与我的 atomic_flag

有点冲突

代码示例（不编译）：

 #include <cstdio>
 #include <chrono>

 #include <unistd.h>
 #include <atomic>
 #include <iostream>
 #include <thread>

 using namespace std;

 class SanityTest
 {

   public:
     SanityTest(){}
     void start();
     void stop();

   private:
     void _rx();
     atomic_flag flag;

 }; // end class SanityTest

void SanityTest::_rx()
{
  while(flag.test_and_set())
  {
    this_thread::sleep_for(chrono::seconds(1));
    cout << "'sup foo" << endl;
  }
} // end _rx

void SanityTest::start()
{
  flag.test_and_set();
  thread SanityTestThread(&SanityTest::_rx, *this);
  SanityTestThread.detach();
} // end start

void SanityTest::stop()
{
  flag.clear();
} // end start

int main(){
  SanityTest s;// = SanityTest();
  s.start();
  this_thread::sleep_for(chrono::seconds(10));
  s.stop();
  return 0;
} // end main

郑重声明，我可以通过删除对 atomic_flag 的所有引用并将 _rx() 循环替换为 for 循环来编译和运行程序，如下所示：

void SanityTest::_rx()
{
  for(int i=0; i <=10; ++ i)
  {
    this_thread::sleep_for(chrono::seconds(1));
    cout << "'sup foo" << endl;
  }
} // end _rx

编译器错误：

In file included from ./SanityTest.cpp:1:0:
./SanityTest.hpp:14:7: note: ‘SanityTest::SanityTest(SanityTest&&)’ is implicitly deleted because the default definition would be ill-formed:
 class SanityTest
       ^
./SanityTest.hpp:14:7: error: use of deleted function ‘std::atomic_flag::atomic_flag(const std::atomic_flag&)’
In file included from /usr/include/c++/4.8/atomic:41:0,
                 from ./SanityTest.hpp:8,
                 from ./SanityTest.cpp:1:
/usr/include/c++/4.8/bits/atomic_base.h:275:5: error: declared here
     atomic_flag(const atomic_flag&) = delete;
     ^
In file included from /usr/include/c++/4.8/functional:55:0,
                 from /usr/include/c++/4.8/thread:39,
                 from ./SanityTest.hpp:10,
                 from ./SanityTest.cpp:1:

...

In file included from ./SanityTest.cpp:1:0:
./SanityTest.hpp:14:7: note: ‘SanityTest::SanityTest(SanityTest&&)’ is implicitly deleted because the default definition would be ill-formed:
 class SanityTest
       ^
./SanityTest.hpp:14:7: error: use of deleted function ‘std::atomic_flag::atomic_flag(const std::atomic_flag&)’
In file included from /usr/include/c++/4.8/atomic:41:0,
                 from ./SanityTest.hpp:8,
                 from ./SanityTest.cpp:1:
/usr/include/c++/4.8/bits/atomic_base.h:275:5: error: declared here
     atomic_flag(const atomic_flag&) = delete;
     ^
In file included from /usr/include/c++/4.8/functional:55:0,
                 from /usr/include/c++/4.8/thread:39,
                 from ./SanityTest.hpp:10,
                 from ./SanityTest.cpp:1:

p.s。这是用 g++ -pthread -std=c++0x -o SanityTest ./SanityTest.cpp

编译的

Answer 1

只需更换

thread SanityTestThread(&SanityTest::_rx, *this);

和

thread SanityTestThread(&SanityTest::_rx, this);

您可能打算传递一个指向对象的指针而不是对象本身（这将导致复制该对象并在该副本而不是原始对象上调用成员函数指针 &SanityTest::_rx） .

错误消息的原因本质上是 std::atomic_flag 没有复制构造函数，因此编译器不会为您的 SanityTest class 生成默认复制构造函数, 但同样：你不想在这里复制你的 SanityTest 对象。

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