How to call Registeration-Free COM dll?

Bruce.Zhang

Hi guys, As the topic mentioned, how to call the registration-free COM DLLs from QT?

In C# I see we can use the manifest files, so what if in QT?

hskoglund

Hi, I had written a post above where I more or less gave up, but I made another effort!

It turns out that that ancient Qt enhancement suggestion speaking about manifest files wasn't completely science-fiction. I found this MSDN article and of course some StackOverflow posts helped a lot.

Thanks to your ProcMon trace above we can see it haplessly looking for DataTypesLibrary.dll's type library in the registry. By adding manifest files we can provide a path to that type library.

Actually we need two manifest files. The first you'll add to your TestRegFreeCOM.exe. I'm assuming you're using MSVC 64-bits compiler and ..pro file (not CMake).
Qt already adds an .rc file to your .exe so we also need to remove that (there can only be one manifest). Add this to your TestRegFreeCOM.pro:

CONFIG -= embed_manifest_exe
QMAKE_MANIFEST = $$PWD/TestRegFreeCOM.exe.manifest

then create a text file TestRegFreeCOM.exe.manifest in your project dir with this:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<assembly xmlns="urn:schemas-microsoft-com:asm.v1" manifestVersion="1.0">
  <dependency>
    <dependentAssembly>
      <assemblyIdentity type="win32" name="Microsoft.Windows.Common-Controls" 
       version="6.0.0.0" 
	publicKeyToken="6595b64144ccf1df"
	language="*"
	processorArchitecture="*" />
    </dependentAssembly>
  </dependency>
  <dependency>
    <dependentAssembly>
      <assemblyIdentity 
        name="DataTypesLibrary.X" 
        version="1.0.0.0" 
        type="win32" 
	language="*"
       processorArchitecture="*" />
</dependentAssembly>
  </dependency>
  <trustInfo xmlns="urn:schemas-microsoft-com:asm.v3">
    <security>
      <requestedPrivileges>
        <requestedExecutionLevel level="asInvoker" uiAccess="false"></requestedExecutionLevel>
      </requestedPrivileges>
    </security>
  </trustInfo>
</assembly>

most of the contents is because we're replacing the Qt standard manifest with our own. The relevant part is where we add a dependentAssembly for the DataTypesLibrary. I think the old MSDN article I mentioned above started this trend of suffixing an .X, don't worry it works :-)

The second manifest file is for the DataTypesLibrary.dll, create a text file called DataTypesLibrary.X.manifest with this:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<assembly xmlns="urn:schemas-microsoft-com:asm.v1" manifestVersion="1.0">
 <assemblyIdentity 
    name="DataTypesLibrary.X" 
    version="1.0.0.0" 
    type="win32"
   processorArchitecture="AMD64" />

  <file name="DataTypesLibrary.dll">
  <comClass
    progid="EventData"
    clsid="{0405e972-093d-4f16-9b4f-f9071cc8f9b2}"
    threadingModel = "Apartment" />

   <typelib tlbid="{A9D4AEA1-46D8-4E98-B9AA-BE93A21A58AD}"
    version="1.0" 
    helpdir="" />

  </file>
</assembly>

then put the DataTypesLibrary.X.manifest and DataTypesLibrary.dll both in the same directory as TestRegFreeCOM.exe.

To test, try something like:

auto comObject = new QAxObject("EventData");
qDebug() << comObject->generateDocumentation();

If it fails, you can trace the manifest fiddling with the SXSTrace.exe tool, step 1, start the trace in a separate CMD window:
sxstrace trace -logfile:sxstrace
irun TestRegFreeCOM.exe and press Enter to stop the trace
step 2: decode the trace
sxxtrace parse -logfile:sxstrace -outfile:trace.txt
then you can type trace.txt

If this works for you, you owe me a beer :-))

hskoglund

Hi, as far as I know Qt has no built-in support for calling Registration-Free COM dlls, i.e. reading the manifest file :-(
Some more info on this here.

But you can always do it the hard way by calling DllGetClassObject() in your .dll and then CoCreateInstance() etc.

Christian Ehrlicher

@hskoglund said in How to call Registeration-Free COM dll?:

, as far as I know Qt has no built-in support

Why should Qt has something for this? It's a c++ problem. You need a header file somehow.

ChrisW67

@Bruce-Zhang As far as I can see: You use the manifest file to get the COM object into the application's execution context at start up (Windows does this for you). Then you can use the ActiveQt classes exactly the same way you would for a registered COM object.

You would have to craft the manifest file and include it in your application binary though the Windows (not Qt) resource system. You may already have a Windows RC file if you have a included a range of application icons or some UAC escalation magic.

You can see an example manifest file in an ancient Qt enhancement suggestion.

hskoglund

@ChrisW67 said in How to call Registeration-Free COM dll?:

@Bruce-Zhang As far as I can see: You use the manifest file to get the COM object into the application's execution context at start up (Windows does this for you). Then you can use the ActiveQt classes exactly the same way you would for a registered COM object.

That's a great idea! One of QAxObject's constructors takes an IUnknown ptr so one way to do it would be to LoadLibrarying the dll, call DllGetClassObject() and CreateInstance() on the returned IClassFactory. Then construct a QAxObject from the IUnknown you got from CreateInstance() and Bob's your uncle.

P.S. I don't think that code in that ancient QtBug suggestion actually works, it's more of "how it could be written" once ActiveQt starts supporting .manifest files...

Bruce.Zhang

@hskoglund @ChrisW67 @Christian-Ehrlicher
Thanks for replies, I will have a try.

Bruce.Zhang

Thank you for responding, @hskoglund. Can you please provide a straightforward demonstration of this? I would greatly appreciate it.

hskoglund

Hi, here's a demo for you, first you need a COM dll to test on, I built the ActiveQt Wrapper Example using Qt 6.5.2 and MSVC 2019 64-bits (got an linker error when building so that regsvr32 failed, but it doesn't matter, it's not needed since we're working registry-free :-)

Then create a console app (Untitled), I used the same Qt 6.5.2 and MSVC 2019 64-bits compiler. Note: I created the app with qmake (not CMake).
Change untitled.pro to look like this:

QT       = core axcontainer
CONFIG  += c++17 cmdline
SOURCES += main.cpp

and change main.cpp to look like this:

#include <QCoreApplication>

#include "qaxobject.h"
#include "quuid.h"
#include "qlibrary.h"
#include "qdebug.h"
#include "atlbase.h"
int main(int argc, char *argv[])
{
    Q_UNUSED(argc) Q_UNUSED(argv)

// load a COM flavored DLL without using the registry (here we use the Wrapper example)
    QLibrary regFreeLib("C:/Qt/Examples/Qt-6.5.2/activeqt/build-wrapper-Desktop_Qt_6_5_2_MSVC2019_64bit-Release/wrapperax.dll");

// wire up the DllGetClassObject function so we can call it
    auto regFreeGetDllClassObject = reinterpret_cast<HRESULT (__stdcall *)(REFCLSID,REFIID,LPVOID*)> (regFreeLib.resolve("DllGetClassObject"));
    if (nullptr == regFreeGetDllClassObject)
        qFatal("wiring up DLLGetClassObject() failed");

// try to call it
    CComPtr<IClassFactory> pClassFactory;
    HRESULT hr = regFreeGetDllClassObject(QUuid("{6E795DE9-872D-43CF-A831-496EF9D86C68}"),IID_IClassFactory,(LPVOID*) &pClassFactory);
    if (FAILED(hr))
        qFatal("calling DLLGetClassObject() failed");

// and then obtain the IUnknown ptr
    CComPtr<IUnknown> pUnknown;
    hr = pClassFactory->CreateInstance(nullptr,IID_IUnknown,(LPVOID*) &pUnknown);
    if (FAILED(hr))
        qFatal("createInstance() failed");

// if we get this far Bob's your uncle, let Qt take it from here
    auto comObject = new QAxObject(pUnknown);
    if (nullptr == comObject)
        qFatal("QAxObject creation failed");

// as a test, fiddle with checked property of the QCheckBox
    comObject->setProperty("checked",true);
    qDebug() << comObject->property("checked");
    comObject->setProperty("checked",false);
    qDebug() << comObject->property("checked");
}

P.S. If you get a compiler error: "cannot find qaxobject.h" then you might have forgotten to add the "Active Qt" component to your Qt (can be found inside "Additional Libraries" in the Qt Maintainer).

Bruce.Zhang

@hskoglund Thanks very much.

hskoglund

Hi forgot to mention: how did I find that GUID QUuid("{6E795DE9-872D-43CF-A831-496EF9D86C68}")? It's from line 68 in main.cpp in the Wrapperax example, it's one of the 3 classIDs listed (you can use any one of the 3).

For your dll, you need to find the relevant CLSID, in the manifest file look for the comclass line.
For example, the manifest file shown in that ancient QtBug suggestion shows:

...
<comClass clsid="{6BF52A52-394A-11D3-B153-00C04F79FAA6}" 
...

If you want to use that and open the Windows Media Player dll (wmp.dll) instead, change my demo code above to:

// load a COM flavored DLL without using the registry (here we use wmp.dll)
    QLibrary regFreeLib("wmp.dll");

// wire up the DllGetClassObject function so we can call it
    auto regFreeGetDllClassObject = reinterpret_cast<HRESULT (__stdcall *)(REFCLSID,REFIID,LPVOID*)> (regFreeLib.resolve("DllGetClassObject"));
    if (nullptr == regFreeGetDllClassObject)
        qFatal("wiring up DLLGetClassObject() failed");

// try to open the Windows Media Player:
    CComPtr<IClassFactory> pClassFactory;
    HRESULT hr = regFreeGetDllClassObject(QUuid("{6BF52A52-394A-11D3-B153-00C04F79FAA6}"),IID_IClassFactory,(LPVOID*) &pClassFactory);
    if (FAILED(hr))
        qFatal("calling DLLGetClassObject() failed");

To check that you managed to open the dll correctly, one way is to add a call generateDocumentation at the end, like this:

,,,

// if we get this far we're in business, let Qt take it from here
    auto comObject = new QAxObject(pUnknown);
    if (nullptr == comObject)
        qFatal("QAxObject creation failed");

// check that we have something live
    qDebug() << comObject->generateDocumentation();

the output (if it works) should have some HTML code (save it to a HTML file to view it properly).

Finally, you need to match the bitness of your dll (it it's 32-bits you need to compile a 32-bits Qt app and the other way around). Normally the COM infrastructure allows 32-bit/64-bit crossplaying by loading the .dll out-of-process, but since you're doing LoadLbrary() you are closer to the metal.

Bruce.Zhang

@hskoglund I works for wmp.dll, but don't know why failed on my dll at bellow line:

if (nullptr == regFreeGetDllClassObject)
        qFatal("wiring up DLLGetClassObject() failed");

And GetLastError code is 126, which is cannot find the DLL, maybe the DLL is invalid? but I can use it in my msvc project.

hskoglund

If you get an error 126: if you didn't specify a path to the .dll check that it's placed together with the .exe (or one directory level above if you're running from inside Qt Creator).
To make sure add a qDebug on an explicit .load(), say like this:

...
    QLibrary regFreeLib("wmp.dll");
    qDebug() << "dll loaded ok: " << regFreeLib.load();
...

Also make sure all the other .dlls that your .dll is dependent on are loaded ok (i.e. another reason for error 126).
If you're stuck, fire up ProcessMonitor :-)

Bruce.Zhang

@hskoglund Thanks for reminder, I copied all dlls and can load now, but failed at bellow:

CComPtr<IClassFactory> pClassFactory;
    HRESULT hr = regFreeGetDllClassObject(QUuid("{A9D4AEA1-46D8-4E98-B9AA-BE93A21A58AD}"), IID_IClassFactory, (LPVOID*) &pClassFactory);
    if (FAILED(hr))
    {
        auto err = GetLastError();
        QString str = QString("GetLastError():%1").arg(err);
        qFatal("calling DLLGetClassObject() failed");
    }

GetLastError() Error Number is 3.

Part of my .idl file like this：

[
    uuid(A9D4AEA1-46D8-4E98-B9AA-BE93A21A58AD),
    version(1.0),
]
library DataTypesLibraryLib
{
    importlib("stdole2.tlb");

    typedef
    [
        uuid(C15BA150-A8BA-4A10-8C5C-0D65F97A9840),
        version(1.0)
    ]

    enum EventTypes
    {
        EVENT_UNKNOWN = 0,
        EVENT_FROM_RECIPE = 10000,
        EVENT_START_HISTORICAL_JOB = 10001,
        EVENT_WEB_POSITION_AND_SPEED = 10005,
        EVENT_BLOB_OVERRUN = 10009,
        EVENT_CUT_SIGNAL = 10019,
        EVENT_START_JOB = 10023,
        EVENT_STOP_JOB = 10024,
        EVENT_START_INSPECTION = 10025,
        EVENT_STOP_INSPECTION = 10026,
        EVENT_WEB_EDGE = 10036,
        EVENT_PAUSE_INSPECTION = 10045,
        EVENT_RESTART_INSPECTION = 10046,
        EVENT_JOB_PASSED = 10049,
        EVENT_JOB_FAILED = 10050,
        EVENT_DOFF_PASSED = 10051,
        EVENT_DOFF_FAILED = 10052,
        EVENT_ROLL_PASSED = 10053,
        EVENT_ROLL_FAILED = 10054,
        EVENT_EXTERNAL_RUNNEXTJOB = 10055,
        EVENT_DENSITY_EVENT = 10079,
        EVENT_WET_CAMERA_STATUS = 10180,
        EVENT_WET_START_CALIBRATION = 10181,
        EVENT_WET_STOP_CALIBRATION = 10182
    } EventTypes;

    enum CommandTypes
    {
        COMMAND_UNINITIALIZED = -1,
        COMMAND_START_JOB = 1,
        COMMAND_STOP_JOB,
        COMMAND_LINEPROFILE_START,
        COMMAND_LINEPROFILE_STOP,
        COMMAND_SNAPIMAGE
    };

    [
        uuid(0405e972-093d-4f16-9b4f-f9071cc8f9b2)
    ]
    coclass EventData
    {
        [default] interface IEventData;
    };
}

hskoglund

Once you're in the COM world, GetLastError() is less interesting.
You need the qdebug dump the hr (HResult) that GetDllClassObjet returned. Preferable in hex, something like 0x80040154 will be shown...

Bruce.Zhang

@hskoglund said in How to call Registeration-Free COM dll?:

Once you're in the COM world, GetLastError() is less interesting.
You need the qdebug dump the hr (HResult) that GetDllClassObjet returned. Preferable in hex, something like 0x80040154 will be shown...

I've got the error code 0x80040111:In this specific case, the error code "80040111" translates to "CLASS_E_CLASSNOTAVAILABLE" Seems the specified class is not correct. I don't know why got this error, the GUID was wrong?

hskoglund

Yeah you got bad luck and selected the wrong GUID :-( That one at the top is the library UUID, but we're only interested in coclass-flavored UUIDs (i.e. that is what DllGetClassObject wants).
They're usually found at the end of an .idl file, in your case:

...
 [
     uuid(0405e972-093d-4f16-9b4f-f9071cc8f9b2)
// try this one ^
]
coclass EventData
{
    [default] interface IEventData;
};

Bruce.Zhang

@hskoglund Finally, I can run it now, but with some error output.
bellow is my code snippet:

 LPVOID rev = nullptr;
    CoInitialize(rev);// Add this line because there will be  another output  of missing the CoInitialize. 

    // load a COM flavored DLL without using the registry (here we use the Wrapper example)
    QLibrary regFreeLib("DataTypesLibrary.dll");
    qDebug() << "dll loaded ok: " << regFreeLib.load();

    // wire up the DllGetClassObject function so we can call it
    auto regFreeGetDllClassObject = reinterpret_cast<HRESULT(__stdcall*)(REFCLSID, REFIID, LPVOID*)> (regFreeLib.resolve("DllGetClassObject"));

    if (nullptr == regFreeGetDllClassObject)
    {
        auto err = GetLastError();
        QString str = QString("GetLastError():%1").arg(err);
        qFatal("wiring up DLLGetClassObject() failed");
    }

    // try to call it
    CComPtr<IClassFactory> pClassFactory;
    HRESULT hr = regFreeGetDllClassObject(QUuid("{0b4be3c3-f304-4f98-a870-e2933dee5b7e}"), IID_IClassFactory, (LPVOID*) &pClassFactory);

    if (FAILED(hr))
    {
        auto err = GetLastError();
        QString str = QString("DLLGetClassObject GetLastError():%1 HRESULT:%2").arg(err).arg(hr, 8,  16, QLatin1Char('0'));
        qFatal(str.toStdString().c_str());
    }

    for (int i = 0; i < 1000000; i++)
    {
        // and then obtain the IUnknown ptr
        CComPtr<IUnknown> pUnknown;
        hr = pClassFactory->CreateInstance(nullptr, IID_IUnknown, (LPVOID*) &pUnknown);

        if (FAILED(hr))
            qFatal("createInstance() failed");

        // if we get this far we're in business, let Qt take it from here
        auto comObject = new QAxObject(pUnknown);
        auto pEventData = reinterpret_cast<DataTypesLibraryLib::IEventData*>(comObject);
        pEventData->SetCD(20.22);
        qDebug() << "CD:" << pEventData->CD();
        delete pEventData;

    }

    qDebug() << "This is the End";

And bellow is the output when exec "pEventData->SetCD(20.22);" each loop.

mincore\com\oleaut32\typelib\tlibapi.cpp(2279)\OLEAUT32.dll!00007FF8FE894743: (caller: 00007FF8FE87847B) ReturnHr(239969) tid(5a8c) 8002801D Library not registered.
void __cdecl MetaObjectGenerator::readClassInfo(void): IDispatch 0x28bf7aa0040 does not provide interface information
CD: 20.22

BTW: I generated the .h & .cpp using "dumpcpp DataTypesLibrary.dll". And DataTypesLibraryLib::IEventData is from the .h file.

hskoglund

Hi, dumpcpp can be a useful tool but it does not support RegistrationFree COM dlls. Usually the .cpp code generated (in DataTypesLibrarylib.cpp) will, in the constructor, include a call to QAxWidget->setControl(), and that call relies on the registry to work :-(
And that's probably why you get that error "Library not registered".

Once you've started using a QAxObject, best is to avoid stunts like ... reinterpret_cast<DataTypesLibraryLib::IEventData*>(comObject); it will only come back to haunt you :-)

I see you're not using the UUID i suggested but another one?

Once you gotten a QAxObject up and running, start by checking it's validity by calling generateDocumentation: (i.e. from my code earlier in this topic):

/ check that we have something live
    qDebug() << comObject->generateDocumentation();

If that works, then try using your comObject say like this:

comObject->setProperty("CD",20.22);
qDebug() << "CD:" << comObject->property("CD");

Bruce.Zhang

@hskoglund Actually the last GUID is what I pasted. I tried the comObject->generateDocumentation();
The output also contains .... Library not registered.


mincore\com\oleaut32\typelib\tlibapi.cpp(2279)\OLEAUT32.dll!00007FFCB00B4743: (caller: 00007FFCB009847B) ReturnHr(1) tid(3864) 8002801D Library not registered.
void __cdecl MetaObjectGenerator::readClassInfo(void): IDispatch 0x22af47e0000 does not provide interface information
mincore\com\oleaut32\typelib\tlibapi.cpp(2279)\OLEAUT32.dll!00007FFCB00B4743: (caller: 00007FFCB009847B) ReturnHr(2) tid(3864) 8002801D Library not registered.
mincore\com\oleaut32\typelib\tlibapi.cpp(2279)\OLEAUT32.dll!00007FFCB00B4743: (caller: 00007FFCB009847B) ReturnHr(3) tid(3864) 8002801D Library not registered.
"<h1 align=center> Reference</h1>\n<p>The  COM object is a QAxObject with the CLSID .</p>\n<h3>Interfaces</h3>\n<ul>\n</ul>\n<h3>Event Interfaces</h3>\n<ul>\n</ul>\n<h2>Public Slots:</h2>\n<ul>\n</ul>\n<h2>Signals:</h2>\n<ul>\n<li>void <a href=\"#exception\"><b>exception</b></a>(int code, QString source, QString disc, QString help);</li>\n<li>void <a href=\"#propertyChanged\"><b>propertyChanged</b></a>(QString name);</li>\n<li>void <a href=\"#signal\"><b>signal</b></a>(QString name, int argc, void* argv);</li>\n</ul>\n<h2>Properties:</h2>\n<ul>\n<li>QString <a href=\"#objectName\"><b>objectName</b></a>;</li>\n<li>QString <a href=\"#control\"><b>control</b></a>;</li>\n</ul>\n<hr><h2>Member Function Documentation</h2>\n<h3><a name=exception></a>void exception (int code, QString source, QString disc, QString help)<tt> [signal]</tt></h3>\n<p>Connect a slot to this signal:<pre>\n\tQObject::connect(object, SIGNAL(exception(int, QString, QString, QString)), receiver, SLOT(someSlot(int, QString, QString, QString)));</pre>\n\n<h3><a name=propertyChanged></a>void propertyChanged (QString name)<tt> [signal]</tt></h3>\n<p>Connect a slot to this signal:<pre>\n\tQObject::connect(object, SIGNAL(propertyChanged(QString)), receiver, SLOT(someSlot(QString)));</pre>\n\n<h3><a name=signal></a>void signal (QString name, int argc, void* argv)<tt> [signal]</tt></h3>\n<p>Connect a slot to this signal:<pre>\n\tQObject::connect(object, SIGNAL(signal(QString, int, void*)), receiver, SLOT(someSlot(QString, int, void*)));</pre>\n\n<hr><h2>Property Documentation</h2>\n<h3><a name=objectName></a>QString objectName</h3>\n<p>\n<p>Read this property's value using QObject::property:<pre>\n\tQString val = object->property(\"objectName\").toString();\n</pre>\nSet this property' value using QObject::setProperty:<pre>\n\tQString newValue = ...\n\tobject->setProperty(\"objectName\", newValue);\n</pre>\nOr using the <a href=\"#setObjectName\">setObjectName</a> slot.\n\n<h3><a name=control></a>QString control</h3>\n<p>\n<p>Read this property's value using QObject::property:<pre>\n\tQString val = object->property(\"control\").toString();\n</pre>\nSet this property' value using QObject::setProperty:<pre>\n\tQString newValue = ...\n\tobject->setProperty(\"control\", newValue);\n</pre>\nOr using the <a href=\"#setControl\">setControl</a> slot.\n\n"

The messages outputs when execute "comObject->generateDocumentation();"

hskoglund

Hmm if you're testing on a pretty old Windows 10, you might have been bitten by this bug:
https://bugreports.qt.io/browse/QTBUG-63789

Also I dug up some old code for debugging COM, try these lines:

...
// try to call it
    CComPtr<IClassFactory> pClassFactory;
    HRESULT hr = regFreeGetDllClassObject(QUuid("{0405e972-093d-4f16-9b4f-f9071cc8f9b2}"),IID_IClassFactory,(LPVOID*) &pClassFactory);
    if (FAILED(hr))
        qFatal("calling DLLGetClassObject() failed");

// and then obtain the IUnknown ptr
    CComPtr<IUnknown> pUnknown;
    hr = pClassFactory->CreateInstance(nullptr,IID_IUnknown,(LPVOID*) &pUnknown);
    if (FAILED(hr))
        qFatal("createInstance() failed");

// if we get this far we're in business, let Qt take it from here
    auto comObject = new QAxObject(pUnknown);
    if (nullptr == comObject)
        qFatal("QAxObject creation failed");

// *** some debugging code
// try to obtain a IDispatch ptr
    CComPtr<IDispatch> pDispatch;
    comObject->queryInterface(QUuid(IID_IDispatch),(void**) &pDispatch);
    if (nullptr == pDispatch)
        qFatal("Error: an IDispatch interface was not found.");

// get the ITypeInfo ptr
    UINT uTypeInfo;
    hr = pDispatch->GetTypeInfoCount(&uTypeInfo);
    if (FAILED(hr) || (uTypeInfo < 1))
        qFatal("Sorry, could not locate any type information");
    if (1 != uTypeInfo)
        qFatal("Expected GetTypeInfoCount() to return 1 but alas");

    CComPtr<ITypeInfo> pTypeInfo;
    if FAILED(pDispatch->GetTypeInfo(0,LOCALE_SYSTEM_DEFAULT,&pTypeInfo))
        qFatal("Error: GetTypeInfo() failed");

// ok have ITypeInfo, use it to get the ITypeLib
    CComPtr<ITypeLib> pTypeLib;
    UINT uTypeInfoIndex;
    if FAILED(pTypeInfo->GetContainingTypeLib(&pTypeLib,&uTypeInfoIndex))
        qFatal("Error: GetContainingTypeLib() failed");

// if you get this far you comObject is most likely ok (never mind generateDocumentation) so try your dll
    comObject->setProperty("CD",20.22);
    qDebug() << "CD:" << comObject->property("CD");