The plugin [path] uses incompatible Qt Library (4.8.2.) [Debug] (or [Release])

I am having this runtime error when trying to load a plugin with Qt's QPluginLoader.

I am on windows 7 N x64 and VS2010.

The error is:

Quote:

---

The plugin '[absolute path to the .DLL file]/TestPlugin.dll' uses incompatible Qt library. (4.8.2) [debug]

---

Note that if I change build type to Release, the error shown is now

Quote:

---

The plugin '[absolute path to the .DLL file]/TestPlugin.dll' uses incompatible Qt library. (4.8.2) [release]

---

This is the test code I am using:

This is the Interface (it's both in the main app project and in the plugin project)

Code:

---

#ifndef NEWTESTPLUGIN_H
#define NEWTESTPLUGIN_H
 
class INewInterface
{
public 
    virtual ~INewInterface() {}
    virtual void popUp() = 0;
};
 
Q_DECLARE_INTERFACE( INewInterface , "NewInterface")
 
#endif //NEWTESTPLUGIN_H

---

My test plugin.h:

Code:

---

#ifndef NEWTESTPLUGIN_H
#define NEWTESTPLUGIN_H
 
#include "INewInterface.h"
#include "QtGui\\qwidget.h"
#include "QtGui\\qlabel.h"
#include "QtGui\\qboxlayout.h"
class NewTestPlugin : public QWidget, public INewInterface
{
    Q_OBJECT
    Q_INTERFACES(INewInterface)
 
public:
    NewTestPlugin(QObject *parent = 0);
    void popUp();
    QVBoxLayout * m_layout;
    QLabel * m_label;
 
private:
    bool initialized;
};
 
#endif // NEWTESTPLUGIN_H

---

and .cpp

Code:

---

#include "customwidget.h"
 
#include <QtCore/QtPlugin>
#include "newtestplugin.h"
 
NewTestPlugin::NewTestPlugin(QObject *parent)
{
    m_label = new QLabel("ESTO ES UN PLUGIN!");
    m_layout = new QVBoxLayout();
    m_layout->addWidget(m_label);
    setLayout(m_layout);
}
 
void NewTestPlugin::popUp()
{
    this->show();
}
 
Q_EXPORT_PLUGIN2(NewTestPlugin, NewTestPlugin)

---

This is how I try to load it:

Code:

---

if(token==QXmlStreamReader::StartElement)
        {
            if(m_xmlRStream->name()=="Game")
            {
                QString textFromElement = m_xmlRStream->readElementText();
                QPushButton * button = new QPushButton(textFromElement, this);
                button->setMinimumSize(150, 150);
                m_mainLayout->addWidget(button);
 
                //create a pluginLoader
                QPluginLoader loader("C:/Users/TestDllProject/Win32/Debug/TestPlugin.dll");
                QObject * plugin = loader.instance();
                if(plugin)
                {
                    INewInterface* asd = qobject_cast<INewInterface*>(plugin);
                    asd->popUp();
                }
                else
                {
                    QMessageBox * pluginErrorMessageBox = new QMessageBox(this);
                    pluginErrorMessageBox->information(this,"Error loading DLL","Requested DLL wasn't properly loaded.\n \n" + loader.errorString(), pluginErrorMessageBox->Ok);
                    QPluginLoader loader("C:/Users/TestDllProject/Win32/Debug/NewTestPlugin.dll");
                    QObject * plugin = loader.instance();
                    if(plugin)
                    {
                        INewInterface* asd = qobject_cast<INewInterface*>(plugin);
                        asd->popUp();
                    }
                    else
                    {
                        pluginErrorMessageBox = new QMessageBox(this);
                        pluginErrorMessageBox->information(this,"Error loading DLL","Requested DLL wasn't properly loaded.\n \n" + loader.errorString(), pluginErrorMessageBox->Ok);
                        exit(1);
                    }
               }
            }

---

I honestly dont know what I am doing wrong, and all google found out had mostly nothing to do with what I am doing.

I am using 4.8.2, for both the DLL and the .Exe (Also, they are both in the same solution).

Any help on the issue would be greately appreciated.

As always, if I am not providing appropiate info, please let me know what you need.

Thank you.

do you have other versions of qt on your machine?

what version is the plugin built with?
what version is the main app built with?

The only version installed right now is 4.8.2 built with VS2010.
I used to have 4.8.2 precompiled for VS2008, but deleted it shortly after to move onto VS2010.

Both plugin and app are built in 4.8.2

UPDATE I Don't know what I did, but the error changed from the previous one to this:

The file: [Path to dll].dll is not a valid Qt Plugin.

Anyone with an appropiate insigth on this issue?
Also, which is the difference between projects Qt4 Designer Plugin and Qt Library?

Could the .pro file (or lack of a .pro file, to be exact) be the issue here? When I created the project in visual studio 2010, it did not provide me with one.

Is there a way to automatically generate one? Or at least a plugin .pro file's template?

It's been pointed out by a friend of mine that the question might not only be unclear, but it might even be misleading, so I will rewrite it here (because I am unable to edit original post)

I am trying to compile a Qt Library Project to use its DLL as a plugin of my Main Application.
I've come across this particular error and I cannot seem to get past it, no matter what I try.

I believe cluttering the question with code tags is pointless when I can just provide you with the "working issue" (for lack of better wording).

[This is a link to both projects. The main application AND the plugin I am currently testing on.]

(please remember to modify the path in the Application project of the dll. I am using absolute path, which will most likely never be the same one you will use. I used absolute paths to make sure the problem was unrelated to finding the file itself)

So far I've checked:

* My Qt version is, indeed, 4.8.2. Built with VS2010 Command Prompt.
* As far as I understood the documentation, my code (particularly the APlugin project) follows the documentation instructions word by word. There's some space for human error, but I believe I got it right. [as specified here(The Lower-Level API: Extending Qt Applications)]
* I am able to generate other QPluginLoader::errorString() errors (for example, using an invalid path to the .dll file will return a "file not found" error). Thus diminishing the margin of error in its use.

As of today, Google results are, at best, cryptic and/or do not apply to my current context of development (I am on VS2010, Win7 N Ultimate, Qt 4.8.2)

I believe it's better that I provided projects where the issue is reproducible, instead of just cluttering the question with code, but if you think I still should copy-paste my code, let me know and I will provide it explicitely in the question.

The only thing I am able to provide so far is that, albet I don't use a .pro file, I shouldn't need it, because my application will be windows exclusive, and the vcproj file already contains that data.

worked for me but I checked a couple of settings and changed them before trying 'as supplied'.

If you check the properties of generated files in debug/release (the moc_ files) you will see:

For debug config, the debug file does not have any property set for 'exclude from build', whereas the release file has 'exclude from build' set to 'yes'.

I just made sure the debug moc file has 'no' in that setting (for all moc files...).


After I built both solutions with that change the plugin was loaded fine.

I used studio 11 beta with studio 10 tools (studio 10 compilers etc.).


e:
win7 64 home prof.
Qt: 4.6.0 (built with msvc2010 using msvc2008 makespecs)