SIGSEGV after invoking QML method from C++ thread

MatrixSan

Hello! I'm trying to write GUI for some console applications and I'm stuck on strange problem...

    QQmlApplicationEngine engine(QUrl::fromLocalFile("test.qml"));
 
    Foo fooObject(&engine);
 
    QThread thread;
    fooObject.moveToThread(&thread);
 
    QObject::connect(&thread, SIGNAL(started()), &fooObject, SLOT(start_slot()));
 
    thread.start();

In Foo header file:

QProcess* testProcess;

Slot, invoked after thread started:

    void Foo::start_slot()
    {
        testProcess = new QProcess;
        connect(testProcess, SIGNAL(finished(int)), this, SLOT(finish_slot()));
        testProcess->start("uname -a"); //just for example
    }

After completion this slot SIGSEGV occurs:

    void Foo::finish_slot()
    {
        delete (testProcess); 
        QObject* moduleObject = engineObject->rootObjects().first()->findChild<QObject*>("testModule");
        QMetaObject::invokeMethod(moduleObject, "test");
    }

But this works fine...

    void Foo::finish_slot()
    {
        QObject* moduleObject = engineObject->rootObjects().first()->findChild<QObject*>("testModule");
        QMetaObject::invokeMethod(moduleObject, "test");
        delete (testProcess);
    }

Is it bug or my mistake? Thanks!
I'm using Qt 5.7

? Offline

Hi! It's your fault: testProcess' finished function calls the finish_slot function. After the latter has completed it returns to its caller (the finished function) but before that happens you delete the function's object (testProcess). So you're working with a deleted object and it's pure luck that it works in one case. Instead of calling delete testProcess use testProcess.deleteLater().

MatrixSan

Thank you! Now all works well.