Wt

According to the Wt::WPopupWidget documentation, a Wt::WPopupWidget may be destructed inside the event handler connected to the Wt::WPopupWidget::hidden signal:

popupWidget_->hidden().connect([this](){ popupWidget_.reset(); });

However Wt still tries to access the (deleted) WPopupWidget after the hidden signal is emitted inside WPopupWidget::setHidden.

Minimal example

std::unique_ptr<Wt::WPopupWidget> popup = std::make_unique<Wt::WPopupWidget>(std::make_unique<Wt::WContainerWidget>());
popup->hidden().connect([&popup](){
    popup.reset(); 
});
popup->show();
popup->hide();

Side note

The documentation of the Wt::WPopupWidget::hidden and Wt::WPopupWidget::show aren't consistent with the implementation. Those signals are also called when show/hide/setHidden is called programmatically.