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  1. Qt
  2. QTBUG-88248

QObject orphaned connections soft-leak

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    • c2839843f23fb5c289175cb9577981d48dd273fc

      Since 5.14 'receiver' QObjects will, on destruction, move its connection in the 'sender' object to an orphaned list, due for cleanup later.

      The orphan list is cleaned up on the sender's next signal emission, or on its destruction.

      In certain circumstances the sender object rarely or never emits signals, and is long-lived. This leads to a long-lived soft leak every time a connection is made to it.

      Can be seen with this example, which is a reduced example of what happens in QNetworkAccessManager:

      int main(int argc, char* argv[])
{
    QCoreApplication qapp(argc, argv);
    QThread th;
    th.start();
    for (int i = 0; i < 1'000'000; ++i) {
        QObject *o = new QObject;
        QObject::connect(&th, &QThread::finished, o, &QObject::deleteLater);
        o->moveToThread(&th);
        QMetaObject::invokeMethod(o, &QObject::deleteLater);
        QThread::msleep(10);
    }
    return 0;
}

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            fabiankosmale Fabian Kosmale
            manordheim Mårten Nordheim
            Vladimir Minenko Vladimir Minenko
            Alex Blasche Alex Blasche
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              Created:
              Updated:
              Resolved: