C++虚函数和线程

Question

这是我的 main.cpp 代码：

#include <opencv2/opencv.hpp>
using std::string;

#include "caffe_thread_learn.hpp"

class VideoCaptureTest : public InternalThread {
public:
    string video;
    explicit VideoCaptureTest(string v) : video(v) { StartInternalThread(); }
protected:
    virtual void InternalThreadEntry();
};

void VideoCaptureTest::InternalThreadEntry(){
    std::cout << "video child" << std::endl;
}

int main(){

    InternalThread* vt = new VideoCaptureTest("/Users/zj-db0655/Documents/data/528100078_5768b1b1764438418.mp4");
    delete vt;

    return 0;
}

caffe_thread.cpp代码：

#include "caffe_thread_learn.hpp"


InternalThread::~InternalThread() {
    StopInternalThread();
}

bool InternalThread::is_started() const {
    return thread_ && thread_->joinable();
}

bool InternalThread::must_stop() {
    return thread_ && thread_->interruption_requested();
}

void InternalThread::StopInternalThread() {
    if (is_started()) {
        thread_->interrupt();
        try {
            thread_->join();
        } catch (boost::thread_interrupted&) {
        } catch (std::exception& e) {
            std::cout << "Thread exception: " << e.what();
        }
    }
}


void InternalThread::StartInternalThread() {
    thread_.reset(new boost::thread(&InternalThread::entry, this));
}

void InternalThread::entry() {
    InternalThreadEntry();
}

caffe_thread.hpp代码

#ifndef caffe_thread_learn_hpp
#define caffe_thread_learn_hpp

#include <stdio.h>

#include <boost/thread.hpp>
#include <boost/shared_ptr.hpp>

namespace boost { class thread; }

class InternalThread {
public:
    InternalThread() : thread_() {}
    virtual ~InternalThread();

    /**
     * Caffe's thread local state will be initialized using the current
     * thread values, e.g. device id, solver index etc. The random seed
     * is initialized using caffe_rng_rand.
     */
    void StartInternalThread();

    /** Will not return until the internal thread has exited. */
    void StopInternalThread();

    bool is_started() const;

protected:
    /* Implement this method in your subclass
     with the code you want your thread to run. */
    virtual void InternalThreadEntry() { std::cout << "parent" << std::endl; }
    virtual void fun() {}

    /* Should be tested when running loops to exit when requested. */
    bool must_stop();

private:
    void entry();

    boost::shared_ptr<boost::thread> thread_;
};

#endif /* caffe_thread_learn_hpp */

实际上，输出是：parant

不过我觉得输出应该是：video child。因为当调用 VideoCaptureTest 中的 StartInternalThread 时，它会新建一个带有参数 (&InternalThread::entry, this) 的线程，我认为这个指针指向 VideoCaptureTest 并将调用 VideoCaptureTest 的 InternalThreadEntry 输出视频子项。但是，它输出 parent.

谢谢！

Answer 1

这可能是您的线程之间的计时问题。您创建了一个新的 VideoCaptureTest 对象，然后在 StartInternalThread 中创建的线程有机会运行之前立即将其删除。调用析构函数时，对象将在生成输出之前被分解为 InternalThread 对象。

要么在 main 中的 new/delete 之间休眠，要么等待线程完成后再销毁它。

C++虚函数和线程

c++ virtual function and thread

c++

caffe