I encountered such valgrind warning when testing enginio examples:

==31870== Thread 5:
==31870== Source and destination overlap in memcpy(0xc142718, 0xc142718, 16384)
==31870== at 0x402D09D: memcpy (mc_replace_strmem.c:878)
==31870== by 0x4887162: QIODevicePrivateLinearBuffer::read(char*, int) (qiodevice_p.h:111)
==31870== by 0x4884A32: QSslSocket::readData(char*, long long) (qsslsocket.cpp:1867)
==31870== by 0x4FE253D: QIODevice::read(char*, long long) (qiodevice.cpp:835)
==31870== by 0x47D9919: QHttpNetworkReplyPrivate::readBodyVeryFast(QAbstractSocket*, char*) (qhttpnetworkreply.cpp:616)
==31870== by 0x47E55E8: QHttpNetworkConnectionChannel::_q_receiveReply() (qhttpnetworkconnectionchannel.cpp:470)
==31870== by 0x47E8210: QHttpNetworkConnectionChannel::_q_readyRead() (qhttpnetworkconnectionchannel.cpp:993)
==31870== by 0x47E94F9: QHttpNetworkConnectionChannel::qt_static_metacall(QObject*, QMetaObject::Call, int, void**) (moc_qhttpnetworkconnectionchannel_p.cpp:116)
==31870== by 0x50D279D: QMetaObject::activate(QObject*, int, int, void**) (qobject.cpp:3479)
==31870== by 0x50D20E5: QMetaObject::activate(QObject*, QMetaObject const*, int, void**) (qobject.cpp:3354)
==31870== by 0x515068C: QIODevice::readyRead() (moc_qiodevice.cpp:153)
==31870== by 0x488A2C9: QSslSocketBackendPrivate::transmit() (qsslsocket_openssl.cpp:921)