[Interest] Process started with QProcess::startDetached is still a child, and is killed when parent quits

[Wiebe Cazemier]

I'm trying to get my auto-updater to work for my Qt 5.1 project (running on Windows 7 32 bit, but Windows XP has the same problem). It downloads an installer, starts it, and quits itself. The problem is that when the application quits, the installer is killed along with it, regardless of the fact that the process is started detached.

This is the code in question.

    QScopedPointer<QTemporaryFile> installerFile(new QTemporaryFile());
    installerFile->setFileTemplate(QDir::tempPath() + "/Setup_XXXXXX.exe");
    installerFile->setAutoRemove(false);
    
    if (installerFile->open())
    {
        installerFile->write(setupDownloadReply->readAll());
        installerFile->close();
        QString filename = installerFile->fileName();
        installerFile.reset(); // Delete the object Otherwise Windows doesn't release it.
    
        // Neither of these two options actually start a non-child process
        bool started = QDesktopServices::openUrl(QUrl::fromLocalFile(filename));
        //bool started = QProcess::startDetached(filename);
    
        if (started)
            QApplication::quit();
    }

Sysinternals process explorer shows that the started installer is actually a child of the program starting it, even when I do openUrl. I find this really bizarre.

If I use mainwindow->close() instead of QApplication::quit(), the window disappears, but the process keeps hanging. And then the installer can't overwrite the locked files.

So, how do I really start a detached process? Is there a similar way to how Linux parents orphaned processes to init?