[SOLVED] QPluginLoader unable to load a Qt Plugin

bharath144

Hello all,

I have an Interface as shown below.

class MyInterface
{
    public:
        virtual ~MyInterface() {}
        virtual int initialize() = 0;
};

Q_DECLARE_INTERFACE(MyInterface, "com.example.MyInterface/1.0")

My plugin implements this interface and declares it in its class as shown below.

class QT_DECL_EXPORT MyPlugin : public QObject, public MyInterface
{
    Q_OBJECT
    Q_INTERFACES(MyInterface)

    public:
        MyPlugin();
        virtual ~MyPlugin();

    public:
        int initialize();

        // ...
};

My plugin's project file sets the target appropriately.

TARGET = $$qtLibraryTarget(MyPlugin)
TEMPLATE = lib

Now, all the modules (including my app) gets compiled. In the app where I have to load the plugin, I have the following code:

// ...

QPluginLoader loader("MyPluginld.dll");
if (! loader.load())
    qDebug() << "Error!";

MyInterface *base = qobject_cast<MyInterface *>(loader.instance());
if (base == NULL)
    qDebug() << "Error!";

// ...

The loader.load() function always fails. Am I making a mistake by providing incorrect name to the QPluginLoader constructor? Or is something else wrong?

Any help would be much appreciated.

Cheers!
Bharath

mcosta

In your code you expect that the DLL is in the same directory of the executable.
Is that TRUE??

bharath144

@mcosta Yes, that is correct. My deployment model ensures that both land up in the same directory.

Cheers!
ಮೈ ಗೋ ಭರತ ನಾರಾಯಣ
Bharath Narayan M G

mcosta

Hi,

if your DLL is in the right place you can use QPluginLoader::errorString()to understand why load fails

bharath144

@mcosta Thanks for that. I will see what the error string says.

bharath144

@mcosta
The errorString prints the following:

"Plugin verification data mismatch in './/MyPluginld.dll'"

mcosta

@bharath144 said:

Plugin verification data mismatch in

Had a quick look to Qt sources.
Seems that you must use this macro to define plugin's metadata.

Reading here, the point 3. of "Writing a plugin involves these steps:" says the same thing

bharath144

@mcosta That did the trick. I saw the step but I overlooked it thinking it may not be mandatory.

Thanks for the help.

LeaA

hello,

can you tell us how you solve your problem?
thank you.