传递给新线程的struct具有错误的值

Question

我需要将多个值传递给新线程（使用_beginthreadex函数创建）。我为此创建了一个结构。

struct CaptureThreadInput {
    std::mutex* eventMutex;
    std::condition_variable* eventCv;
    std::vector<DispatchEvent>* eventVector;
    int capId, width, height;
};

我在主线程中使用Dispatch对象的私有函数启动一个新线程。

void Dispatch::startCaptureThread(int i) {
    CaptureThreadInput params = {
        &eventMutex,
        &eventCv,
        &eventVector,
        i, 1280, 720
    };
    CaptureThreadInput* data = &params;
    cout << "Address from dispatch " << std::addressof(*data) << "\n";
    cout << "Mutex from dispatcher " << std::addressof(*(data->eventMutex)) << "\n";
    cout << "CapId from dispatcher " << data->capId << "\n";
    cout << "Width from dispatcher " << data->width << "\n";
    _beginthreadex(NULL, 0, &(CaptureThread::initThread), &params, 0, 0);
}

在启动的线程中，我只调试输出。 CaptureThread::initThread是一个公共静态函数。

unsigned int __stdcall CaptureThread::initThread(void* in) {
    CaptureThreadInput* data = (CaptureThreadInput*)in;
    cout << "Address from thrd " << std::addressof(*data) << "\n";
    cout << "Mutex from thread " << std::addressof(*(data->eventMutex)) << "\n";
    cout << "CapId from thread " << data->capId << "\n";
    cout << "Width from thread " << data->width << "\n";
    return 0;
}

然而，我在Dispatch::startCaptureThread和新创建的线程中从创建的结构中获得不同的值。 Struct在两个线程中的每一个中返回不同的地址。控制台输出：

Address from dispatch 0000001A83EFF568
Mutex from dispatcher 0000001A83EFFD10
CapId from dispatcher 0
Width from dispatcher 1280
Address from thrd 0000001A83EFF568
Mutex from thread CCCCCCCCCCCCCCCC
CapId from thread -858993460
Width from thread -858993460

我也试着评论eventMutex，eventCv和eventVector只留下结构中的整数，结果是一样的。

知道是什么导致了这个，我怎么能改变我的代码来修复它？

使用Microsoft Visual Studio for Windows x64平台进行开发。

Answer 1

你在本地创建params，然后将引用传递给_beginthreadex，它会立即返回。那时你的startCaptureThread退出，导致params超出范围。要么阻止params超出范围，要么通过值传递params