a segmentation fault

[yaohao@qtcentre]

I was beaten by a segmentation fault,
following is my source code

void PieceThread::slotReadReady()
{
        while(reply!=NULL&&!pauseFlag&&!reply->atEnd())
        {
            QMutexLocker locker(&mutex);
            file->seek(workingPos);
            workingPos+=file->write(reply->read(4096));                                                        //segmentation fault happend here!
            emit this->signalProgressIncrease(workingPos-oldWorkingPos);
            oldWorkingPos=workingPos;
        }
}

void PieceThread::slotReadReady()
{
        while(reply!=NULL&&!pauseFlag&&!reply->atEnd())
        {
            QMutexLocker locker(&mutex);
            file->seek(workingPos);
            workingPos+=file->write(reply->read(4096));                                                        //segmentation fault happend here!
            emit this->signalProgressIncrease(workingPos-oldWorkingPos);
            oldWorkingPos=workingPos;
        }
}

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I promise that the "file" and the "reply" are legal pointer,

following is the Call Stack Window

0 QList<QNetworkReplyImplPrivate::InternalNotificati ons>::contains qlist.h 864 0x680cd407
1 QNetworkReplyImplPrivate::backendNotify qnetworkreplyimpl.cpp 365 0x68048179
2 QNetworkReplyImpl::readData qnetworkreplyimpl.cpp 873 0x6804a2f8
3 QIODevice::read qiodevice.cpp 829 0x6a1ab817
4 QIODevice::read qiodevice.cpp 964 0x6a1abd3b //here is the "read(4096)"
5 PieceThread::slotReadReady piecethread.cpp 48 0x4048e3
6 PieceThread::qt_metacall moc_piecethread.cpp 84 0x408a73
7 QMetaObject::metacall qmetaobject.cpp 237 0x6a2060b0
8 QMetaCallEvent:laceMetaCall qobject.cpp 535 0x6a210d55
9 QObject::event qobject.cpp 1217 0x6a212c60
10 QApplicationPrivate::notify_helper qapplication.cpp 4462 0x7ebde0
11 QApplication::notify qapplication.cpp 3862 0x7e9732
12 QCoreApplication::notifyInternal qcoreapplication.cpp 731 0x6a2015f8
13 QCoreApplication::sendEvent qcoreapplication.h 215 0x6a268308
14 QCoreApplicationPrivate::sendPostedEvents qcoreapplication.cpp 1372 0x6a2026a3
15 qt_internal_proc qeventdispatcher_win.cpp 497 0x6a22499f
16 USER32!GetDC C:\WINDOWS\system32\user32.dll 0 0x77d18734
17 ?? 0 0x3301a4
18 ?? 0 0x401
19 ?? 0

the line 0's call stack source code is from "qlist.h"

Q_OUTOFLINE_TEMPLATE QBool QList<T>::contains(const T &t) const
{
     Node *b = reinterpret_cast<Node *>(p.begin());
     Node *i = reinterpret_cast<Node *>(p.end());
     while (i-- != b)
              if (i->t() == t)                             //segmentation fault happend here
                     return QBool(true);
     return QBool(false);
}

Q_OUTOFLINE_TEMPLATE QBool QList<T>::contains(const T &t) const
{
     Node *b = reinterpret_cast<Node *>(p.begin());
     Node *i = reinterpret_cast<Node *>(p.end());
     while (i-- != b)
              if (i->t() == t)                             //segmentation fault happend here
                     return QBool(true);
     return QBool(false);
}

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thank you for helping me!