By default, you can not throw exceptions from signals and slots, and if you try it, you get the following message:

Qt has caught an exception thrown from an event handler. Throwing exceptions from an event handler is not supported in Qt. You must reimplement QApplication::notify() and catch all exceptions there.

So, what to do? The answer is simple: Overwrite the function bool QApplication::notify(QObject * receiver, QEvent * event) so that it catches all thrown exceptions. Here is some sample code:

#include <QtGui>
#include <QApplication>
class MyApplication : public QApplication {
    MyApplication(int& argc, char ** argv) :
        QApplication(argc, argv) { }
    virtual ~MyApplication() { }

    // reimplemented from QApplication so we can throw exceptions in slots
    virtual bool notify(QObject * receiver, QEvent * event) {
        try {
            return QApplication::notify(receiver, event);
        } catch(std::exception& e) {
            qCritical() << "Exception thrown:" << e.what();
        return false;
int main(int argc, char* argv[]) {
    MyApplication app(argc, argv);
    // ...

Of course, you can also inherit from QCoreApplication to get rid of the QtGui dependency, or display a nice dialog box instead of printing the messages to the console, or…

Found at: Stack Overflow: Qt and error handling strategy