不能通过引用传递给线程 [英] cannot pass by reference to thread

问题描述

我试图通过引用传递一个线程，一个定义为的变量:

I am trying to pass by reference to a thread, a variable defined as:

zmq::context_t context(1);

像这样:

t[thread_nbr] = std::thread(worker_routine, (void *)&context, trained_images);

但是，当我这样做时，我收到以下错误:

However, when I do I get the following error:

/usr/include/c++/5/functional:1505:61: error: no type named ‘type’ in ‘class std::result_of<void* (*(void*, std::vector<TrainedImage>))(void*, std::vector<TrainedImage>&)>’
   typedef typename result_of<_Callable(_Args...)>::type result_type;
                                                         ^
/usr/include/c++/5/functional:1526:9: error: no type named ‘type’ in ‘class std::result_of<void* (*(void*, std::vector<TrainedImage>))(void*, std::vector<TrainedImage>&)>’
     _M_invoke(_Index_tuple<_Indices...>)

如果我尝试使用它执行 std::ref()，我会收到一个已删除的函数错误.

If I try to do std::ref() with it, I get a deleted function error.

有人知道我能做什么吗?

Does anyone know what I can do?

推荐答案

问题似乎出在 trained_images 参数上，您的线程函数将其作为引用参数.这样做的问题是 std::thread 对象不能真正处理引用(它复制线程函数的参数，并且不能复制引用).

The problem seems to be the trained_images argument which your thread-function takes as argument by reference. The problem with this is that the std::thread object can't really handle references (it copies the arguments to the thread function, and references can't be copied).

解决方案是使用包装器对象，如 std::ref 供参考:

The solution is to use wrapper objects like std::ref for references:

t[thread_nbr] = std::thread(worker_routine, &context, std::ref(trained_images));

这篇关于不能通过引用传递给线程的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！