QPluginLoader doesn't accept plugin name

[Gourmet]

I'm weird. Just made plugin as described in books. All looks fine. In main application I try load it but got unexpected problem:

MainWindow::MainWindow(QApplication* a, QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    QDir dir( QApplication::applicationDirPath() );
    QString abspath = dir.absoluteFilePath( "EmptyPlugin.dll" ); // name correct in abspath
    QPluginLoader PluginLoader( abspath );
    abspath = PluginLoader.fileName(); // name empty!!! ?????????
    QObject * plugin = qobject_cast<QObject*>( PluginLoader.instance() );
    QString errstr;
    if( ! plugin )
        errstr = PluginLoader.errorString(); // contains "Unknown error"
}

MainWindow::MainWindow(QApplication* a, QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    QDir dir( QApplication::applicationDirPath() );
    QString abspath = dir.absoluteFilePath( "EmptyPlugin.dll" ); // name correct in abspath
    QPluginLoader PluginLoader( abspath );
    abspath = PluginLoader.fileName(); // name empty!!! ?????????
    QObject * plugin = qobject_cast<QObject*>( PluginLoader.instance() );
    QString errstr;
    if( ! plugin )
        errstr = PluginLoader.errorString(); // contains "Unknown error"
}

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1st time abspath is correct, but 2nd time it... is empty

tried this:

MainWindow::MainWindow(QApplication* a, QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    QDir dir( QApplication::applicationDirPath() );
    QString abspath = dir.absoluteFilePath( "EmptyPlugin.dll" ); // name correct
    QPluginLoader PluginLoader( "" );
    PluginLoader.setFileName( abspath );
    abspath = PluginLoader.fileName(); // name empty!!! ?????????
    QObject * plugin = qobject_cast<QObject*>( PluginLoader.instance() );
    QString errstr;
    if( ! plugin )
        errstr = PluginLoader.errorString(); // contains "Unknown error"
}

MainWindow::MainWindow(QApplication* a, QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    QDir dir( QApplication::applicationDirPath() );
    QString abspath = dir.absoluteFilePath( "EmptyPlugin.dll" ); // name correct
    QPluginLoader PluginLoader( "" );
    PluginLoader.setFileName( abspath );
    abspath = PluginLoader.fileName(); // name empty!!! ?????????
    QObject * plugin = qobject_cast<QObject*>( PluginLoader.instance() );
    QString errstr;
    if( ! plugin )
        errstr = PluginLoader.errorString(); // contains "Unknown error"
}

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effect is the same, no plugin file name assigned

why this can happen? PLEASE HELP!

[joyer83]

Err, you have defined the abspath two times in same scope.
Have you actually compiled your code successfully?

[Gourmet]

sorry, this was my copy-paste error just in message, I fixed it

the code exactly is little different (like now in first message) and compiles and starts well

I even did the following:

QPluginLoader PluginLoader("");
    PluginLoader.setFileName( "I:/Qt/2010.05s/projects/sources/SCPS-M-build-desktop/debug/EmptyPlugin.dll" ); // file definitely exists and pathname is right
    QString errstr = PluginLoader.errorString(); // "Unknown error"
    errstr = PluginLoader.fileName(); // empty

QPluginLoader PluginLoader("");
    PluginLoader.setFileName( "I:/Qt/2010.05s/projects/sources/SCPS-M-build-desktop/debug/EmptyPlugin.dll" ); // file definitely exists and pathname is right
    QString errstr = PluginLoader.errorString(); // "Unknown error"
    errstr = PluginLoader.fileName(); // empty

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and following:

QPluginLoader PluginLoader("");
    PluginLoader.setFileName( "I:\\Qt\\2010.05s\\projects\\sources\\SCPS-M-build-desktop\\debug\\EmptyPlugin.dll" ); // file definitely exists and pathname is right
    QString errstr = PluginLoader.errorString(); // "Unknown error"
    errstr = PluginLoader.fileName(); // empty

QPluginLoader PluginLoader("");
    PluginLoader.setFileName( "I:\\Qt\\2010.05s\\projects\\sources\\SCPS-M-build-desktop\\debug\\EmptyPlugin.dll" ); // file definitely exists and pathname is right
    QString errstr = PluginLoader.errorString(); // "Unknown error"
    errstr = PluginLoader.fileName(); // empty

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both with same result

looks like a bug in Qt 4.7 for Windows - QPluginLoader does not accept absolute plugin path

QLibrary itself works well, I tested - but I need plugins because of C++ classes

---

Added after 1:

ANYBODY CONFIRM OR DECLINE THIS BEHAVIOUR!

I want write bug report but need more statistic.

[Gourmet]

SOLVED. Application was made static because of wrong Qt selected in it's project. Dynamically linked plugins don't work with static applications.