Question

main.cpp中：

#include <QCoreApplication>
#include <QtCore>
#include "myobject.h"

QThread* cThread;
MyObject* cObject;

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);
    cThread = new QThread();
    cObject = new MyObject();
    cObject->moveToThread(cThread);

    QObject::connect(cThread, SIGNAL(started()),
                     cObject, SLOT(doWork()));

    QObject::connect(cThread, SIGNAL(finished()),
                     cThread, SLOT(deleteLater()));

    QObject::connect(cThread, SIGNAL(finished()),
                     cObject, SLOT(deleteLater()));

    cThread->start();

    return a.exec();
}

myobject.cpp：

#include "myobject.h"

MyObject::MyObject(QObject *parent) :
    QObject(parent)
{
}

void MyObject::doWork()
{
    qDebug() << "Hi";
    QThread::currentThread()->quit();
    return;
}

myobject.h：

#ifndef MYOBJECT_H
#define MYOBJECT_H

#include <QtCore>

class MyObject : public QObject
{
    Q_OBJECT
public:
    explicit MyObject(QObject *parent = 0);

signals:

public slots:
    void doWork();

};

#endif // MYOBJECT_H

显然，根据：https://stackoverflow.com/a/16062717，存在内存泄漏，但我该如何解决？我想我必须返回事件循环然后调用退出？但问题是我无法访问事件循环。

Answer 1

没有内存泄漏。如果你坚持object model和object trees and ownership，Qt会正确清理。我也喜欢关注documented examples。

以下是您引用的示例，deleteLater()上添加了观察结果。

的main.cpp

#include <QCoreApplication>
#include <QtCore>
#include <QThread>

class MyThread : public QThread
{
    Q_OBJECT
public slots:
    void deleteLater()
    {
        qDebug() << Q_FUNC_INFO;
        QThread::deleteLater();
    }
};


class MyObject : public QObject
{
    Q_OBJECT
public:
    explicit MyObject(QObject *parent = 0){}

signals:

public slots:
    void deleteLater()
    {
        qDebug() << Q_FUNC_INFO;
        QObject::deleteLater();
    }

    void doWork()
    {
        qDebug() << "Hi";
        QThread::currentThread()->quit(); // It is supposed to stop here, but it doesn't.
        return;
        for (int i = 0; i < 1000000; i++) {
            qDebug() << i;
        }
    }

};

QThread* cThread;
MyObject* cObject;

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);
    cThread = new MyThread();
    cObject = new MyObject();
    cObject->moveToThread(cThread);

    QObject::connect(cThread, SIGNAL(started()),
                     cObject, SLOT(doWork()));

    QObject::connect(cThread, SIGNAL(finished()),
                     cThread, SLOT(deleteLater()));

    QObject::connect(cThread, SIGNAL(finished()),
                     cObject, SLOT(deleteLater()));

    cThread->start();

    return a.exec();
}

输出：

Hi
void __thiscall MyObject::deleteLater(void)
void __thiscall MyThread::deleteLater(void)

希望有所帮助。

Answer 2

根据standard This function does nothing if the thread does not have an event loop.，您在（第二个）主题中没有事件循环。尝试调试代码？

试试这个：

的main.cpp

#include <QCoreApplication>
#include <QtCore>
// #include "myobject.h"

// QThread* cThread;
// MyObject* cObject;

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);
//     cThread = new QThread();
//     cObject = new MyObject();
//     cObject->moveToThread(cThread);

//     QObject::connect(cThread, SIGNAL(started()),
//                      cObject, SLOT(doWork()));

//     QObject::connect(cThread, SIGNAL(finished()),
//                      cThread, SLOT(deleteLater()));

//     QObject::connect(cThread, SIGNAL(finished()),
//                      cObject, SLOT(deleteLater()));

//     cThread->start();

    return a.exec();
}

并查看是否会返回。

没有内存泄漏，因为你的doWork返回正常，删除是由a.exec（）内的main-loop-event完成的。但是a.exec（）永远不会返回。你必须通过QCoreApplication::quit();终止你的申请（但不是在线程中，因为你终止整个应用程序）。

您可以在tutorial。

中阅读

Answer 3

我是链接上的海报。事实上，默认连接没有内存泄漏。通过继承deleteLater和析构函数（如@phyatt），您获得了：

Hi 
void MyObject::deleteLater() 
virtual MyObject::~MyObject()  Being deleted 
void MyThread::deleteLater() 
virtual MyThread::~MyThread()  Being deleted

但是如果您在连接中使用Qt::QueueConnection，则获得：

Hi 
void MyThread::deleteLater() 
virtual MyThread::~MyThread()  Being deleted

对象cObject被泄露了。

当线程 有效地 退出时，它没有记录。所以我不能争论这种行为是否总是一样的。一种可能性是使线程启动器负责执行清理工作。例如：

 void cleanup(){
  cThread->exit();
  cThread->wait();
  delete cThread;
  delete cObject;
 }

要完成整理，您无需使用此代码修复任何内容。

QThread内存泄漏

3 个答案: