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how to release the memory in QtConcurrent the new thread func?

  • QtConcurrent::run(func, p);

    before the main()
    void func(pointer* p)
    Class* xxx = new Class();
    while (true)
    delete xxx;

    1. what should i do when i close the app, eg.teminate this new thread, but how?
    2. can delete xxx; implement? will the memory leak in this way? if it does leak, what should i modify the code above?

    thank you

  • You will always leak in your case, I presume. First off I would suggest you to use QScopedPointer, not delete. Second, when quitting your application you should wait for all futures to finish and then quit. The line:

    QtConcurrent::run(func, p);

    ... generates QFuture< void > object. One way is to wait the future to finish either using QFuture< T >::waitForFinished() or better off by using a QFutureWatcher which would asynchronously notify you when the future is ready. You could also cancel the future upon a request to quit the application.
    So the steps are:

    1. Set QGuiApplication::setQuitOnLastWindowClosed( false ) so that to prevent the application from quitting immediately after the last of its windows is closed.
    2. Connect a slot to the QGuiApplication::lastWindowClosed() signal.
    3. Create a QFutureWatcher< void >* (using new) for every QFuture< void > you create using QtConcurrent::run and keep the instances of the future watchers in the object which receives the last window closed notification.
    4. Hook to the finished() signal of the QFutureWatcher< void > in the object which also tracks whether application quit has been requested. Remove the kept instance of the QFutureWatcher
    5. Upon receiving the last window closed notification set a flag in the same object that an application quit has been requested - the last window has been closed.
    6. On each QFutureWatcher< void >::finished() and on QGuiApplication::lastWindowClosed() check if there are no cached QFutureWatcher's e.g. no futures are running.

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