Details
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Bug
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Resolution: Invalid
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P1: Critical
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None
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5.12.0
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Ubuntu 18.10 Desktop 64 bit, gcc 7.3, Qt 5.12
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Linux/X11
Description
There is a Qml Button with 2 states( connect/disconnect ) inside my App. Here is the respective code :
Button {
id : connectDisconnectButton
anchors.centerIn: parent
property bool isConnected : false
text : isConnected ? qsTr("Disconnect") : qsTr("Connect")
antialiasing: true
property var currentConnectionParams : ({})
onClicked: {
if ( isConnected ) {
proxy.disconnectFromEmulatorService();
} else {
connectDisconnectButton.currentConnectionParams["port"] = serviceConnectionPort.getValue();
connectDisconnectButton.currentConnectionParams["ip_addr"] = String(serviceConnectionIpPart_0.getValue())
+ String(".") + String(serviceConnectionIpPart_1.getValue())
+ String(".") + String(serviceConnectionIpPart_2.getValue())
+ String(".") + String(serviceConnectionIpPart_3.getValue());
proxy.connectToEmulatorService( connectDisconnectButton.currentConnectionParams );
}
isConnected = !isConnected;
}
}
What I see is that from time to time I get SIGSEGV while calling connectToEmulatorService method of my C++ proxy. Here is the respective c++ code :
Q_INVOKABLE void connectToEmulatorService( QVariant )
{
m_serviceConnectionParams = in;
emit connectionInitiatedSignal();
m_functorExecutor->executeFunctor( boost::bind(&EmulatorControlProxy::connectToEmulatorServiceImpl, this ) );
}
void connectToEmulatorServiceImpl()
{
QMap<QString, QVariant> connectionParams_ = m_serviceConnectionParams.toMap();
try {
emit connectionOkSignal();
}catch(...) {
Error("connectToEmulatorServiceImpl failure : ip = %s, port = %s",
connectionParams_["ip_addr"].toString().toStdString().c_str(),
connectionParams_["port"].toString().toStdString().c_str() );
emit connectionFailedSignal();
}
}
GDB backtrace gives the following output :
(gdb) backtrace #0 0x00007ffff6e0777b in QV4::QObjectWrapper::virtualGet(QV4::Managed const*, QV4::PropertyKey, QV4::Value const*, bool*) () at /home/developer/Qt5.12.0/5.12.0/gcc_64/lib/libQt5Qml.so.5 #1 0x00007ffff6e8802b in QV4::Runtime::method_loadProperty(QV4::ExecutionEngine*, QV4::Value const&, int) () at /home/developer/Qt5.12.0/5.12.0/gcc_64/lib/libQt5Qml.so.5 #2 0x00007fffe0003d9a in () #3 0x0000000000000000 in ()
PS. The problem is somehow related to
QMap<QString, QVariant> connectionParams_ = m_serviceConnectionParams.toMap();
It seems that temporary QML object map is being deleted before functorExecutor thread tries to access it. But why does it happen, if I copy incoming QVariant to a class member variable? As a workaround I declared a bunch of Q_PROPERTY for my proxy to store QML data there before invoke C++.