我可以拥有一个增强无锁的lambdas队列吗？

Question

我正在尝试实现一个可以跨多个线程工作的消息传递系统.boost::lockfree::queue似乎是一个很好的方向进入,不幸的是我无法创建任何一个std::function或boost::function类型的队列,因为显然他们没有琐碎的任务和析构函数,这是一个要求boost::lockfree::queue.

我的以下代码:

#include <cassert>
//#include <functional>
#include <iostream>

#include <boost/function.hpp>
#include <boost/lockfree/queue.hpp>

int main()
{
  boost::lockfree::queue<boost::function<void(int)>> queue;
  assert(queue.is_lock_free());

  for(int j = 0; j < 50; ++j) {
    queue.push([] (int i) { std::cout << i << std::endl; });
  }

  int i = 0;
  boost::function<void(int)> functor;
  while (queue.pop(functor)) {
    functor(i++);
  }
}

产生以下输出:

In file included from /usr/include/boost/integer.hpp:23:0,
                 from /usr/include/boost/function/function_base.hpp:21,
                 from /usr/include/boost/function/detail/prologue.hpp:17,
                 from /usr/include/boost/function.hpp:24,
                 from lockfree.cpp:5:
/usr/include/boost/lockfree/queue.hpp: In instantiation of ‘class boost::lockfree::queue<boost::function<void(int)> >’:
lockfree.cpp:10:54:   required from here
/usr/include/boost/lockfree/queue.hpp:81:5: error: static assertion failed (boost::has_trivial_destructor<T>::value)
     BOOST_STATIC_ASSERT((boost::has_trivial_destructor<T>::value));
     ^
/usr/include/boost/lockfree/queue.hpp:85:5: error: static assertion failed (boost::has_trivial_assign<T>::value)
     BOOST_STATIC_ASSERT((boost::has_trivial_assign<T>::value));

有没有办法让这项工作？

Answer 1

你仍然可以使用无状态 lambda和原始函数指针,如果这是一个选项:

#include <cassert>
#include <functional>
#include <iostream>

#include <boost/function.hpp>
#include <boost/lockfree/queue.hpp>

int main() {
    //boost::lockfree::queue<boost::function<void(int)>> queue(50);
    boost::lockfree::queue<void (*)(int)> queue(50);
    assert(queue.is_lock_free());

    for (int j = 0; j < 50; ++j) {
        queue.push([](int i) { std::cout << i << std::endl; });
    }

    int i = 0;
    boost::function<void(int)> functor;
    while (queue.pop(functor)) {
        functor(i++);
    }
}

http://coliru.stacked-crooked.com/a/d57770e3be029760