Qt-Signal未在虚拟机中连接

Question

我在 RedHat 7.4 上使用 GCC 4.8.5 和 Qt 4.8.5 进行开发和编译。代码必须是静态链接的。然后在运行 Scientific Linux 6.7 版的虚拟机上执行。 memcpy-Wrap 用于防止依赖于较新的 GLIBC >= 2.4

我有以下 MWE：

#include <iostream>
#include <unistd.h>
#include <QtCore>
#include <QThread>

__asm__(".symver memcpy, memcpy@GLIBC_2.2.5");
extern "C" {
void *__wrap_memcpy(void *dest, const void *src, size_t n) { return memcpy(dest, src, n); }
}

class Worker : public QThread {
    void run() {
        std::cout << "WORKER: Started." << std::endl;
        QObject::connect(this, SIGNAL(finished()), QCoreApplication::instance(), SLOT(quit()));
        int i=0;
        while(i++<3) {
            std::cout << "WORKER: I am running." << std::endl;
            usleep(1e6);
        }
        std::cout << "WORKER: Finished." << std::endl;
    }
};

int main(int argc, char** argv) {

    std::cout << "MAIN: Init QCoreApplication" << std::endl;
    QCoreApplication qtApplication(argc, argv);

    std::cout << "MAIN: Init Worker" << std::endl;
    Worker myWorker;
    myWorker.start();

    std::cout << "MAIN: Start Event-Loop." << std::endl;
    qtApplication.exec();

    std::cout << "MAIN: Event-Loop finished." << std::endl;
    return 0;
}

这段代码是在 RedHat 系统上编译的

g++ -I$QTD/mkspecs/linux-g++ -I$QTD/include -I$QTD/include/QtCore -o mwe mwe.cpp  -Wl,--wrap=memcpy -L$QTD/lib/ -lQtCore -lQtNetwork -lglib-2.0 -lrt -lpthread -ldl -lz

$QTD 存放我安装的 Qt-4.8.5 的位置。

在 Red-Hat 系统上预期并观察到以下行为：

MAIN: Init QCoreApplication
MAIN: Init Worker
MAIN: Start Event-Loop.
WORKER: Started.
WORKER: I am running.
WORKER: I am running.
WORKER: I am running.
WORKER: Finished.
MAIN: Event-Loop finished.

在 Scientific-Linux-System 上观察到以下行为：

MAIN: Init QCoreApplication
MAIN: Init Worker
MAIN: Start Event-Loop.
WORKER: Started.
WORKER: I am running.
WORKER: I am running.
WORKER: I am running.
WORKER: Finished.

然后应用程序永远不会完成。

似乎在 Red-Hat-System 中，来自工作线程的完成信号连接到核心应用程序中的退出槽。这似乎不会在 Scientific-Linux-System 中发生。有没有人有任何建议为什么会发生这种情况以及如何调试它？

Answer 1

你必须以正确的方式使用 QThread。 重载 run() 函数是不安全的，Nokia 之前接受过它并展示了如何使用 QThread。

Look at this documentation.

Answer 2

如前所述 - 不推荐在 Qt 中使用线程。但这对你的情况很好。无论如何，我建议您尝试下一种方法：

class Worker : public QThread {
    Q_OBJECT // Don't forget this macro
    void run() {
        std::cout << "WORKER: Started." << std::endl;
        // QObject::connect(this, SIGNAL(finished()), QCoreApplication::instance(), SLOT(quit()));
        int i=0;
        while(i++<3) {
            std::cout << "WORKER: I am running." << std::endl;
            usleep(1e6);
        }
        std::cout << "WORKER: Finished." << std::endl;
        this->deleteLater();
    }
};

int main(int argc, char** argv) {

    std::cout << "MAIN: Init QCoreApplication" << std::endl;
    QCoreApplication qtApplication(argc, argv);

    std::cout << "MAIN: Init Worker" << std::endl;
    Worker *myWorker = new Worker();
    QObject::connect( myWorker, SIGNAL(destroyed()), &qtApplication, SLOT(quit());
    myWorker->start();

    std::cout << "MAIN: Start Event-Loop." << std::endl;
    qtApplication.exec();

    std::cout << "MAIN: Event-Loop finished." << std::endl;
    return 0;
}