QVariant saving fails on second "consecutive" save

[MateoAero]

Hi all

I have been programming a simulator interface with Qt for a while. Since the very beginning, I opted to store signals in a custom file created directly by serializing and then deserializing them. Code is as follows:

QFile f2(dir.absolutePath() + '/' + filename + ".omp");
	if (f2.open(QFile::WriteOnly))
	{

		QDataStream ds(&f2);
		ds.setVersion(QDataStream::Qt_5_14);
		for (auto sig : mpSignals)
		{
			ds << *sig;
		}
		f2.close();
	}

mpSignals is a QList of XSignal*, and serialization function is defined as:

QDataStream & operator<<(QDataStream & out, const XSignal & data)
{
	auto p = data.metaObject();
	QMap<QByteArray,QVariant> signalAttributes;
	for (auto i = p->propertyOffset(); i < p->propertyCount(); i++)
	{
		auto prop = p->property(i);
		if(prop.isWritable()/* && strcmp(prop.name(),"secSignal")*/)
			signalAttributes[prop.name()] = data.property(prop.name());
	}
	return out << signalAttributes;
}

This has worked flawlessly for more than a year. However, it is starting to present some problems since yesterday. It is very strange, because I intend to move to excel file saving for easier debugging and edition of the signals (using Qxlsx library) and in order to test the new capability, I save the signals in both formats, load it from excel, save it both, in custom format and excel, no problems here, but when I call the first save function again an exception is raised in the ds<<*sig line. If I go as deep as possible into the code, it is raised when saving a QVariant created from an enum, wich works perfectly in the first save in each execution, but not in the second one. The assertion is:

[22/10/2021-21:03:08.570] (ERROR)--> QVariant::save: unable to save type 'XSignal::_pinType' (type id: 1931).
[22/10/2021-21:03:08.571] (FATAL)--> ASSERT failure in QVariant::save: "Invalid type to save", file kernel\qvariant.cpp, line 2601

I checked the line and it is essentially the serialization of the key-value of the created map, which I also checked during debug.

Again, I have checked the XSignal and it is not changed at all between saves (to check it, I did call it twice in a row, same problem). The strangest thing is that the _pinType does not throw an exception on the first save... Any ideas? 5.15.2_msvc2019_64 in use. Thank you!

[SGaist]

Hi,

What is XSignal ?
How did you declare it ?
Did you register it ?

[MateoAero]

It is a derived QObject, it just contains a set of variables within (QStrings, ints, floats, etc.). The only particular thing is it has an Enum, but as I said, this worked flawlessly for months, and it still works on first call to save (it saves around 800 XSignals on first call, on second it breaks on first XSignal).

As I mentioned in my previous post, I did debug this step by step and the signalAttributes QMap is correctly filled. It is on the source line it << it.key() << it.value() line where it breaks, though it seems all ok.

[SGaist]

Are there reason for it to be a QObject ?

Since it's a QObject based class it's not reference counted nor copyable.

[MateoAero]

I just wanted to exploit parent-children capabilities, in order not to worry about pointer deletion at lower level elements. I don't copy it as such: when saving, I serialize all its writable properties (no data is not available as property), when loading, I create a new element, copy each property one by one and then add this new element to the list. This way I don't have to worry about modifying the serialization functions on each modification of the class, for I use the metaobject and it the new properties are saved automatically.

[kshegunov]

@SGaist said in QVariant saving fails on second "consecutive" save:

How did you declare it ?
Did you register it ?

You didn't answer these two. Also you must know that QObjects can't be metatypes, correct?

[MateoAero]

Of course it is not metatype. This is the declaration:

class UTILS_EXPORT XSignal : public QQuickItem
{
	Q_OBJECT;
	Q_PROPERTY(QString url READ url WRITE setUrl NOTIFY urlChanged); 
	Q_PROPERTY(QVariant value READ value WRITE setValue NOTIFY valueChanged);
	Q_PROPERTY(quint32 frequency READ frequency WRITE setFrequency NOTIFY frequencyChanged);
	...
public:
	XSignal(QQuickItem *parent = nullptr);
	~XSignal();

	enum _pinType {
		ARDUINO_BOARD = 0,
		MCP,
		LED,
		DIRECT,
		SCALED,
		MAP,
		LED_POWER,
		PRODUCT,
		UNASSIGNED
	};
	Q_ENUM(_pinType); //The one causing the error on second loop of save

	//PROPERTIES
	const QVariant& value() const;
	Q_INVOKABLE void setValue(const QVariant& newValue);

	const QString& url() const ;
	void setUrl(const QString& newUrl);
...
};


QDataStream UTILS_EXPORT &operator<<(QDataStream& out, const XSignal& data);
QDataStream UTILS_EXPORT &operator>>(QDataStream &in, XSignal & data);

Then, these operators:

QDataStream & operator<<(QDataStream & out, const XSignal & data)
{
	auto p = data.metaObject();
	QMap<QByteArray,QVariant> signalAttributes;
	for (auto i = p->propertyOffset(); i < p->propertyCount(); i++)
	{
		auto prop = p->property(i);
		if(prop.isWritable()/* && strcmp(prop.name(),"secSignal")*/)
			signalAttributes[prop.name()] = data.property(prop.name());
	}
	return out << signalAttributes;
}

QDataStream & operator>>(QDataStream & in, XSignal & data)
{
	QMap<QByteArray, QVariant> signalAttributes;
	in >> signalAttributes;
	
	for (auto k : signalAttributes.keys())
	{
		if (k == "secSignal")
		{
			auto url = signalAttributes.value("url");
			auto v = signalAttributes.value(k).toString();
			qDebug() << url << v;
		}
		data.setProperty(k, signalAttributes.value(k));
	}

	return in;
}

[SGaist]

@MateoAero said in QVariant saving fails on second "consecutive" save:

QQuickItem

Why is it a QQuickItem and not just a QObject since you are not using any feature of it ?

By the way, making it a QObject to avoid memory management is not really a good idea. QObject is a non trivial class and generating thousands of them has a cost.

You might also want to consider using Q_GADGET which us lighter weight.

[MateoAero]

Yes, I know. I use it as a child in QML of an element that access its properties to show/edit them. I know it can be simplified, but at this very moment in the project it is fine for me as is, and it worked until a couple of days ago. Again, I don't understand why making two saves in a row works the first time but not the second one...

[kshegunov]

Something's not right with the objects, and if I were to hazard a guess, you have a dangling reference. Have you made absolutely sure you're not deleting the object in the meantime? What's the stack trace from the crash exactly?

[MateoAero]

The problem is the stack just states a breakpoint has been triggered, nothing else. The reference are for sure valid, as I can go step by step in

QDataStream & operator<<(QDataStream & out, const XSignal & data)
{
	auto p = data.metaObject();
	QMap<QByteArray,QVariant> signalAttributes;
	for (auto i = p->propertyOffset(); i < p->propertyCount(); i++)
	{
		auto prop = p->property(i);
		if(prop.isWritable()/* && strcmp(prop.name(),"secSignal")*/)
			signalAttributes[prop.name()] = data.property(prop.name());
	}
	return out << signalAttributes;
}

Indeed, I can go as deep as QDataStream.h, line 342:
s << it.key() << it.value();

And it still shows a valid iterator, even when it breaks...

[kshegunov]

@MateoAero said in QVariant saving fails on second "consecutive" save:

The reference are for sure valid, as I can go step by step in

The fact that you can enter the function doesn't, by any measure mean the object's valid, neither can such a thing be deduced by what you see as data from reading the memory. Humor me, provide a stack trace.

[MateoAero]

Re: QVariant saving fails on second "consecutive" save

I don't understand what you mean. So far, whenever I trace an error by debugging step by step I have always been able to locate the problem in memory. Nonetheless, here you have the debug output:

'testsd.exe' (Win32): Loaded 'C:\Users\JAVI\source\repos\mcsimxpand\bin\testsd.exe'. Symbols loaded.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\ntdll.dll'. Symbols loaded.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\kernel32.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\KernelBase.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\shell32.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\msvcp_win.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\ucrtbase.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\user32.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\win32u.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\gdi32.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\gdi32full.dll'.
'testsd.exe' (Win32): Loaded 'C:\Users\JAVI\source\repos\mcsimxpand\bin\xutilsd.dll'. Symbols loaded.
'testsd.exe' (Win32): Loaded 'C:\Qt\5.15.2\msvc2019_64\bin\Qt5Qmld.dll'.
'testsd.exe' (Win32): Loaded 'C:\Qt\5.15.2\msvc2019_64\bin\Qt5Cored.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\ws2_32.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\rpcrt4.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\advapi32.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\vcruntime140_1d.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\msvcrt.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\sechost.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\vcruntime140d.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\ole32.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\combase.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\ucrtbased.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\msvcp140d.dll'.
'testsd.exe' (Win32): Loaded 'C:\Qt\5.15.2\msvc2019_64\bin\Qt5Guid.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\shlwapi.dll'.
'testsd.exe' (Win32): Loaded 'C:\Qt\5.15.2\msvc2019_64\bin\Qt5Networkd.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\crypt32.dll'.
'testsd.exe' (Win32): Loaded 'C:\Qt\5.15.2\msvc2019_64\bin\Qt5Quickd.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\mpr.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\version.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\netapi32.dll'.
'testsd.exe' (Win32): Loaded 'C:\Qt\5.15.2\msvc2019_64\bin\Qt5SerialPortd.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\winmm.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\msvcp140_1d.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\setupapi.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\cfgmgr32.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\bcrypt.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\userenv.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\dxgi.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\d3d11.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\IPHLPAPI.DLL'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\dnsapi.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\srvcli.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\netutils.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\cryptbase.dll'.
'testsd.exe' (Win32): Loaded 'C:\Qt\5.15.2\msvc2019_64\bin\Qt5QmlModelsd.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\imm32.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\nsi.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\SHCore.dll'.
'testsd.exe' (QML): Connecting to the QML runtime...
'testsd.exe' (Win32): Loaded 'C:\Qt\5.15.2\msvc2019_64\plugins\platforms\qwindowsd.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\oleaut32.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\dwmapi.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\wtsapi32.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\kernel.appcore.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\bcryptprimitives.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\uxtheme.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\windows.storage.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\wldp.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\profapi.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\powrprof.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\umpdc.dll'.
'testsd.exe' (Win32): Loaded 'C:\Qt\5.15.2\msvc2019_64\plugins\qmltooling\qmldbg_serverd.dll'.
'testsd.exe' (Win32): Loaded 'C:\Qt\5.15.2\msvc2019_64\plugins\qmltooling\qmldbg_debuggerd.dll'.
'testsd.exe' (Win32): Loaded 'C:\Qt\5.15.2\msvc2019_64\plugins\qmltooling\qmldbg_inspectord.dll'.
'testsd.exe' (Win32): Loaded 'C:\Qt\5.15.2\msvc2019_64\plugins\qmltooling\qmldbg_messagesd.dll'.
'testsd.exe' (Win32): Loaded 'C:\Qt\5.15.2\msvc2019_64\plugins\qmltooling\qmldbg_nativedebuggerd.dll'.
'testsd.exe' (Win32): Loaded 'C:\Qt\5.15.2\msvc2019_64\plugins\qmltooling\qmldbg_previewd.dll'.
'testsd.exe' (Win32): Loaded 'C:\Qt\5.15.2\msvc2019_64\plugins\qmltooling\qmldbg_profilerd.dll'.
'testsd.exe' (Win32): Loaded 'C:\Qt\5.15.2\msvc2019_64\plugins\qmltooling\qmldbg_quickprofilerd.dll'.
'testsd.exe' (Win32): Loaded 'C:\Qt\5.15.2\msvc2019_64\plugins\qmltooling\qmldbg_locald.dll'.
QML Debugger: Connecting to socket {4743FBB3-1294-4C9E-96AE-F6C53936C133}...
Initialized.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\clbcatq.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\propsys.dll'.
'testsd.exe' (Win32): Loaded 'C:\Qt\5.15.2\msvc2019_64\qml\QtQuick.2\qtquick2plugind.dll'.
'testsd.exe' (Win32): Loaded 'C:\Qt\5.15.2\msvc2019_64\bin\Qt5QmlWorkerScriptd.dll'.
'testsd.exe' (Win32): Loaded 'C:\Qt\5.15.2\msvc2019_64\qml\QtQuick\Controls.2\qtquickcontrols2plugind.dll'.
'testsd.exe' (Win32): Loaded 'C:\Qt\5.15.2\msvc2019_64\bin\Qt5QuickControls2d.dll'.
'testsd.exe' (Win32): Loaded 'C:\Qt\5.15.2\msvc2019_64\bin\Qt5QuickTemplates2d.dll'.
'testsd.exe' (Win32): Loaded 'C:\Qt\5.15.2\msvc2019_64\qml\QtQuick\Layouts\qquicklayoutsplugind.dll'.
'testsd.exe' (Win32): Loaded 'C:\Qt\5.15.2\msvc2019_64\qml\QtQuick\Window.2\windowplugind.dll'.
'testsd.exe' (Win32): Loaded 'C:\Qt\5.15.2\msvc2019_64\qml\Qt\labs\platform\qtlabsplatformplugind.dll'.
'testsd.exe' (Win32): Loaded 'C:\Qt\5.15.2\msvc2019_64\bin\Qt5Widgetsd.dll'.
'testsd.exe' (Win32): Loaded 'C:\Qt\5.15.2\msvc2019_64\qml\Qt\labs\folderlistmodel\qmlfolderlistmodelplugind.dll'.
'testsd.exe' (Win32): Loaded 'C:\Qt\5.15.2\msvc2019_64\qml\QtQuick\Templates.2\qtquicktemplates2plugind.dll'.
'testsd.exe' (Win32): Loaded 'C:\Qt\5.15.2\msvc2019_64\qml\QtQuick\Controls\qtquickcontrolsplugind.dll'.
'testsd.exe' (Win32): Loaded 'C:\Qt\5.15.2\msvc2019_64\qml\Qt\labs\settings\qmlsettingsplugind.dll'.
'testsd.exe' (Win32): Loaded 'C:\Qt\5.15.2\msvc2019_64\qml\QtQuick\Dialogs\dialogplugind.dll'.
'testsd.exe' (Win32): Loaded 'C:\Qt\5.15.2\msvc2019_64\qml\QtQml\qmlplugind.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\d3d9.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\DriverStore\FileRepository\nvmdi.inf_amd64_799504293a3d3200\nvldumdx.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\msasn1.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\cryptnet.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\drvstore.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\devobj.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\wintrust.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\imagehlp.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\cryptsp.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\rsaenh.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\DriverStore\FileRepository\nvmdi.inf_amd64_799504293a3d3200\nvd3dumx.dll'.
The thread 0x19dc has exited with code 0 (0x0).
'testsd.exe' (Win32): Unloaded 'C:\Windows\System32\DriverStore\FileRepository\nvmdi.inf_amd64_799504293a3d3200\nvd3dumx.dll'
'testsd.exe' (Win32): Unloaded 'C:\Windows\System32\drvstore.dll'
'testsd.exe' (Win32): Unloaded 'C:\Windows\System32\devobj.dll'
'testsd.exe' (Win32): Unloaded 'C:\Windows\System32\DriverStore\FileRepository\nvmdi.inf_amd64_799504293a3d3200\nvldumdx.dll'
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\opengl32.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\glu32.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\msctf.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\AppXDeploymentClient.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\DriverStore\FileRepository\nvmdi.inf_amd64_799504293a3d3200\nvoglv64.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\drvstore.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\devobj.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\ntmarta.dll'.
The thread 0x19f0 has exited with code 0 (0x0).
The thread 0x131c has exited with code 0 (0x0).
The thread 0x3acc has exited with code 0 (0x0).
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\DXCore.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\winsta.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\DWrite.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\NapiNSP.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\pnrpnsp.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\wshbth.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\nlaapi.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\mswsock.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\winrnr.dll'.
'testsd.exe' (Win32): Loaded 'C:\Program Files\Bonjour\mdnsNSP.dll'.
'testsd.exe' (Win32): Loaded 'C:\Qt\5.15.2\msvc2019_64\plugins\imageformats\qgifd.dll'.
'testsd.exe' (Win32): Loaded 'C:\Qt\5.15.2\msvc2019_64\plugins\imageformats\qicnsd.dll'.
'testsd.exe' (Win32): Loaded 'C:\Qt\5.15.2\msvc2019_64\plugins\imageformats\qicod.dll'.
'testsd.exe' (Win32): Loaded 'C:\Qt\5.15.2\msvc2019_64\plugins\imageformats\qjpegd.dll'.
'testsd.exe' (Win32): Loaded 'C:\Qt\5.15.2\msvc2019_64\plugins\imageformats\qsvgd.dll'.
'testsd.exe' (Win32): Loaded 'C:\Qt\5.15.2\msvc2019_64\bin\Qt5Svgd.dll'.
'testsd.exe' (Win32): Loaded 'C:\Qt\5.15.2\msvc2019_64\plugins\imageformats\qtgad.dll'.
'testsd.exe' (Win32): Loaded 'C:\Qt\5.15.2\msvc2019_64\plugins\imageformats\qtiffd.dll'.
'testsd.exe' (Win32): Loaded 'C:\Qt\5.15.2\msvc2019_64\plugins\imageformats\qwbmpd.dll'.
'testsd.exe' (Win32): Loaded 'C:\Qt\5.15.2\msvc2019_64\plugins\imageformats\qwebpd.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\winhttp.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\dhcpcsvc6.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\dhcpcsvc.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\sspicli.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\OnDemandConnRouteHelper.dll'.
'testsd.exe' (Win32): Unloaded 'C:\Windows\System32\OnDemandConnRouteHelper.dll'
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\DriverStore\FileRepository\nvmdi.inf_amd64_799504293a3d3200\nvldumdx.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\DriverStore\FileRepository\nvmdi.inf_amd64_799504293a3d3200\nvd3dumx.dll'.
The thread 0x25e4 has exited with code 0 (0x0).
'testsd.exe' (Win32): Unloaded 'C:\Windows\System32\DriverStore\FileRepository\nvmdi.inf_amd64_799504293a3d3200\nvd3dumx.dll'
'testsd.exe' (Win32): Unloaded 'C:\Windows\System32\DriverStore\FileRepository\nvmdi.inf_amd64_799504293a3d3200\nvldumdx.dll'
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\DataExchange.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\dcomp.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\twinapi.appcore.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\TextInputFramework.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\CoreMessaging.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\CoreUIComponents.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\WinTypes.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\WinTypes.dll'.
'testsd.exe' (Win32): Unloaded 'C:\Windows\System32\WinTypes.dll'
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\WinTypes.dll'.
'testsd.exe' (Win32): Unloaded 'C:\Windows\System32\WinTypes.dll'
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\oleacc.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\UIAutomationCore.dll'.
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\sxs.dll'.
mincore\com\oleaut32\dispatch\ups.cpp(2122)\OLEAUT32.dll!00007FFD53A99DD6: (caller: 00007FFD53A991E9) ReturnHr(1) tid(2d44) 8002801D Library not registered.
Debug Error!

Program: C:\Qt\5.15.2\msvc2019_64\bin\Qt5Cored.dll
Module: 5.15.2
File: kernel\qvariant.cpp
Line: 2601

ASSERT failure in QVariant::save: "Invalid type to save", file kernel\qvariant.cpp, line 2601

(Press Retry to debug the application)
'testsd.exe' (Win32): Loaded 'C:\Windows\System32\TextShaping.dll'.
testsd.exe has triggered a breakpoint.

If you meant the call stack:
Qt5Cored.dll!00007ffc8791815d() Unknown
Qt5Cored.dll!00007ffc8791692f() Unknown
Qt5Cored.dll!00007ffc8790801d() Unknown
Qt5Cored.dll!00007ffc87dd45da() Unknown
Qt5Cored.dll!00007ffc87dd549d() Unknown

xutilsd.dll!QtPrivate::writeAssociativeContainer<QMap<QByteArray,QVariant>>(QDataStream & s, const QMap<QByteArray,QVariant> & c) Line 343 C++
xutilsd.dll!operator<<<QByteArray,QVariant>(QDataStream & s, const QMap<QByteArray,QVariant> & map) Line 480 C++
xutilsd.dll!operator<<(QDataStream & out, const XSignal & data) Line 802 C++
xutilsd.dll!XSignalManager::saveSignals(const QString & filename) Line 245 C++
xutilsd.dll!XSignalManager::addSignal(XSignal * refSignal) Line 203 C++
xutilsd.dll!XSignalManager::qt_static_metacall(QObject * _o, QMetaObject::Call _c, int _id, void * * _a) Line 168 C++
xutilsd.dll!XSignalManager::qt_metacall(QMetaObject::Call _c, int id, void * * a) Line 307 C++
Qt5Cored.dll!00007ffc87d540b8() Unknown
Qt5Qmld.dll!00007ffc8bb6d6d0() Unknown
Qt5Qmld.dll!00007ffc8b912a95() Unknown
Qt5Qmld.dll!00007ffc8b913846() Unknown
Qt5Qmld.dll!00007ffc8b90f988() Unknown
Qt5Qmld.dll!00007ffc8b90f47b() Unknown
Qt5Qmld.dll!00007ffc8b702eaf() Unknown
Qt5Qmld.dll!00007ffc8b9553e5() Unknown
Qt5Qmld.dll!00007ffc8b951d45() Unknown
Qt5Qmld.dll!00007ffc8b890774() Unknown
Qt5Qmld.dll!00007ffc8bb9fcaf() Unknown
Qt5Qmld.dll!00007ffc8bb10601() Unknown
Qt5Qmld.dll!00007ffc8bb10d5a() Unknown
Qt5Qmld.dll!00007ffc8bb6c4ed() Unknown
Qt5Qmld.dll!00007ffc8bad3219() Unknown
Qt5Cored.dll!00007ffc87db6426() Unknown
Qt5Cored.dll!00007ffc87da36d7() Unknown
Qt5QuickTemplates2d.dll!00007ffc88b29034() Unknown
Qt5QuickTemplates2d.dll!00007ffc88a1cc68() Unknown
Qt5QuickTemplates2d.dll!00007ffc88a1bf28() Unknown
Qt5QuickTemplates2d.dll!00007ffc88a5c78f() Unknown
Qt5Quickd.dll!00007ffc85f3f173() Unknown
Qt5QuickTemplates2d.dll!00007ffc88a1b34d() Unknown
Qt5Cored.dll!00007ffc87d45f41() Unknown
Qt5Cored.dll!00007ffc87d479df() Unknown
Qt5Cored.dll!00007ffc87d43341() Unknown
Qt5Guid.dll!00007ffc868fd6be() Unknown
Qt5Cored.dll!00007ffc87d44aaf() Unknown
Qt5Cored.dll!00007ffc87d42b92() Unknown
Qt5Quickd.dll!00007ffc85f8b8f7() Unknown
Qt5Quickd.dll!00007ffc85f8f7e7() Unknown
Qt5Quickd.dll!00007ffc85f8e18c() Unknown
Qt5Quickd.dll!00007ffc85f86f2c() Unknown
Qt5Guid.dll!00007ffc869271f7() Unknown
Qt5Quickd.dll!00007ffc85f86c75() Unknown
Qt5Cored.dll!00007ffc87d45f41() Unknown
Qt5Cored.dll!00007ffc87d479df() Unknown
Qt5Cored.dll!00007ffc87d43341() Unknown
Qt5Guid.dll!00007ffc868fd6be() Unknown
Qt5Cored.dll!00007ffc87d44aaf() Unknown
Qt5Cored.dll!00007ffc87d4494b() Unknown
Qt5Guid.dll!00007ffc86901ab3() Unknown
Qt5Guid.dll!00007ffc86905016() Unknown
Qt5Guid.dll!00007ffc868cf102() Unknown
qwindowsd.dll!00007ffc8ab14802() Unknown
Qt5Cored.dll!00007ffc87e170b2() Unknown
qwindowsd.dll!00007ffc8ab147b4() Unknown
Qt5Cored.dll!00007ffc87d3f39b() Unknown
Qt5Cored.dll!00007ffc87d3f604() Unknown
Qt5Cored.dll!00007ffc87d42919() Unknown
Qt5Guid.dll!00007ffc868fd648() Unknown
testsd.exe!main(int argc, char * * argv) Line 67 C++
testsd.exe!WinMain(HINSTANCE * formal, HINSTANCE * __formal, char * __formal, int __formal) Line 97 C++
testsd.exe!invoke_main() Line 107 C++
testsd.exe!__scrt_common_main_seh() Line 288 C++
testsd.exe!__scrt_common_main() Line 331 C++
testsd.exe!WinMainCRTStartup(void * __formal) Line 17 C++
kernel32.dll!00007ffd55757034() Unknown
ntdll.dll!RtlUserThreadStart() Unknown

[kshegunov]

I find it odd that you apparently have the debug libraries, but the trace doesn't show the functions called. Anyway, I have this creeping suspicion that the SignalManager outlives its employees, or rather that the QML engine frees them at some point while you still keep a pointer around. What you can try to do, is to keep a QPointer<XSignal> instead of a raw pointer. If at saveSignals any of these QPointers is null, then I'm correct.

[MateoAero]

The pointer is not null. I added a trace in the loop:

		QDataStream ds(&f2);
		ds.setVersion(QDataStream::Qt_5_14);
		for (auto sig : mpSignals)
		{
			ds << *sig;
			qDebug() << sig;
		}
		f2.close();

The result on the first signal on the first call to saveSignals():

[27/10/2021-18:12:22.399] (DEBUG)--> void __cdecl XSignalManager::saveSignals(const class QString &)Saving omp signals

[27/10/2021-18:12:22.400] (DEBUG)--> class QDataStream &__cdecl operator <<(class QDataStream &,const class XSignal &)Saving signal "com.Generic.MCP_Indicators"

[27/10/2021-18:12:22.400] (DEBUG)--> class QDataStream &__cdecl operator <<(class QDataStream &,const class XSignal &)QMap(("alias", QVariant(QString, "MCP"))("col", QVariant(ushort, 65535))("defaultValue", QVariant(int, 0))("frequency", QVariant(uint, 20))("hideOnSignal", QVariant(QString, ""))("inverted", QVariant(bool, false))("led", QVariant(ushort, 65535))("ledDigits", QVariant(ushort, 65535))("mappedValues", QVariant(QByteArray, "\x00\x00\x00\x00"))("mcp", QVariant(ushort, 65535))("minDigits", QVariant(ushort, 65535))("oSignal", QVariant(QString, ""))("pin", QVariant(ushort, 5))("pinType", QVariant(int, 0))("pwm0", QVariant(ushort, 0))("pwm255", QVariant(ushort, 255))("row", QVariant(ushort, 65535))("secSignal", QVariant(QString, ""))("sigScale", QVariant(double, 1))("url", QVariant(QString, "com.Generic.MCP_Indicators"))("value", QVariant(QString, ""))("zeroDigits", QVariant(ushort, 65535)))

The result when saving the first signal for the second time:
[27/10/2021-18:12:28.616] (DEBUG)--> void __cdecl XSignalManager::saveSignals(const class QString &)Saving omp signals

[27/10/2021-18:12:28.616] (DEBUG)--> class QDataStream &__cdecl operator <<(class QDataStream &,const class XSignal &)Saving signal "com.Generic.MCP_Indicators"

[27/10/2021-18:12:28.617] (DEBUG)--> class QDataStream &__cdecl operator <<(class QDataStream &,const class XSignal &)QMap(("alias", QVariant(QString, "MCP"))("col", QVariant(ushort, 65535))("defaultValue", QVariant(int, 0))("frequency", QVariant(uint, 20))("hideOnSignal", QVariant(QString, ""))("inverted", QVariant(bool, false))("led", QVariant(ushort, 65535))("ledDigits", QVariant(ushort, 65535))("mappedValues", QVariant(QByteArray, "\x00\x00\x00\x00"))("mcp", QVariant(ushort, 65535))("minDigits", QVariant(ushort, 65535))("oSignal", QVariant(QString, ""))("pin", QVariant(ushort, 5))("pinType", QVariant(XSignal::_pinType, "ARDUINO_BOARD"))("pwm0", QVariant(ushort, 0))("pwm255", QVariant(ushort, 255))("row", QVariant(ushort, 65535))("secSignal", QVariant(QString, ""))("sigScale", QVariant(double, 1))("url", QVariant(QString, "com.Generic.MCP_Indicators"))("value", QVariant(QString, ""))("zeroDigits", QVariant(ushort, 65535)))

[27/10/2021-18:12:28.617] (ERROR)--> QVariant::save: unable to save type 'XSignal::_pinType' (type id: 1941).

[27/10/2021-18:12:28.618] (FATAL)--> ASSERT failure in QVariant::save: "Invalid type to save", file kernel\qvariant.cpp, line 2601

However, it seems that when loading them pinType is returned as an int, and is thus writable without any issue. However, when saving the second time, I don't know still why, it is already the correct type (XSignal:_pinType) and thus fails. Thank you for the support! I will mark it as solved, if I need help figuring out when it changes to the correct type I will create a separate post :)

[MateoAero]

Just for the record, in case it may serve anyone:

The problem was that, as reflected above, the data was stored as an int and thus, when loaded, the first access to it as as an int. I still have not found the specific point in my code (too long to see in such a short time) where the correct type was set to the variant (I reckon it will be in some access to it). In order to get rid of this problem, I had to define the << and >> operators for the affected types (Enums) and register them by means of:

qRegisterMetaTypeStreamOperators<XSignal::_pinType>("XSignal::_pinType");