Crash on language change caused by auto generated code when using a QTableWidget

[marco.beninca71]

Hello everybody
I faced a crash on my application when the user tries to change the language. After some investigating I found out that the issue is generated by the auto generated code during the ui'incing process. The behaviour is very easy to reproduce:

• create a QtGuiApplication for desktop and name it QtGuiApplication1

• On the main form add a QTableWidget and with the designer add some column and some rows with some text inside

• Add a translation file and translate the text of the rows on the QTableWidget

• Use the usual code to manage the language change using the QTranlastor class and reimplementing the QtGuiApplication1::changeEvent for the event QEvent::LanguageChange

• In the method where you call QTranslator::Load and then QApplication::installTranslator bofore doing anything delete the sample rows added in design time

• In this case inside the auto generated method retranslateUi (inside the file ui_QtGuiApplication1.h) you will will get a crash

• This is because the code doesn't test if the QTableWidgetItem * is null before trying to translate it

Below my code for QtGuiApplication1 and the auto generated file. I'm using Qt 5.13.0

#include "QtGuiApplication1.h"

QTranslator QtGuiApplication1::translator;

QtGuiApplication1::QtGuiApplication1(QWidget *parent)
	: QMainWindow(parent)
{
	ui.setupUi(this);

	connect(ui.pushButtonTranslate, SIGNAL(clicked()), this, SLOT(onTranslate()));

	inited = false;
}

void QtGuiApplication1::onTranslate()
{

	if (!inited)
	{
		ui.tableWidget->setRowCount(0);
		inited = true;
	}

	QApplication::removeTranslator(&translator);

	// load the new translator
	if (translator.load("qtguiapplication1_it.qm", "E:\\Progetti\\QtGuiApplication1\\x64\\Debug"))
		QApplication::installTranslator(&translator);

}

void QtGuiApplication1::changeEvent(QEvent* event)
{
	if (event && event->type() == QEvent::LanguageChange)
	{
		// retranslate designer form (single inheritance approach)
		ui.retranslateUi(this);
	}
	QWidget::changeEvent(event);

}

#pragma once

#include <QtWidgets/QMainWindow>
#include "ui_QtGuiApplication1.h"
#include <QTranslator>

class QtGuiApplication1 : public QMainWindow
{
	Q_OBJECT

public:
	QtGuiApplication1(QWidget *parent = Q_NULLPTR);

protected slots:

	virtual void changeEvent(QEvent* event);

	void onTranslate();

private:
	bool inited;

	static QTranslator translator;

	Ui::QtGuiApplication1Class ui;
};

/********************************************************************************
** Form generated from reading UI file 'QtGuiApplication1.ui'
**
** Created by: Qt User Interface Compiler version 5.13.0
**
** WARNING! All changes made in this file will be lost when recompiling UI file!
********************************************************************************/

#ifndef UI_QTGUIAPPLICATION1_H
#define UI_QTGUIAPPLICATION1_H

#include <QtCore/QVariant>
#include <QtWidgets/QApplication>
#include <QtWidgets/QHeaderView>
#include <QtWidgets/QMainWindow>
#include <QtWidgets/QMenuBar>
#include <QtWidgets/QPushButton>
#include <QtWidgets/QStatusBar>
#include <QtWidgets/QTableWidget>
#include <QtWidgets/QToolBar>
#include <QtWidgets/QWidget>

QT_BEGIN_NAMESPACE

class Ui_QtGuiApplication1Class
{
public:
    QWidget *centralWidget;
    QTableWidget *tableWidget;
    QPushButton *pushButtonTranslate;
    QMenuBar *menuBar;
    QToolBar *mainToolBar;
    QStatusBar *statusBar;

    void setupUi(QMainWindow *QtGuiApplication1Class)
    {
        if (QtGuiApplication1Class->objectName().isEmpty())
            QtGuiApplication1Class->setObjectName(QString::fromUtf8("QtGuiApplication1Class"));
        QtGuiApplication1Class->resize(600, 519);
        centralWidget = new QWidget(QtGuiApplication1Class);
        centralWidget->setObjectName(QString::fromUtf8("centralWidget"));
        tableWidget = new QTableWidget(centralWidget);
        if (tableWidget->columnCount() < 6)
            tableWidget->setColumnCount(6);
        QTableWidgetItem *__qtablewidgetitem = new QTableWidgetItem();
        tableWidget->setHorizontalHeaderItem(0, __qtablewidgetitem);
        QTableWidgetItem *__qtablewidgetitem1 = new QTableWidgetItem();
        tableWidget->setHorizontalHeaderItem(1, __qtablewidgetitem1);
        QTableWidgetItem *__qtablewidgetitem2 = new QTableWidgetItem();
        tableWidget->setHorizontalHeaderItem(2, __qtablewidgetitem2);
        if (tableWidget->rowCount() < 8)
            tableWidget->setRowCount(8);
        QTableWidgetItem *__qtablewidgetitem3 = new QTableWidgetItem();
        tableWidget->setVerticalHeaderItem(0, __qtablewidgetitem3);
        QTableWidgetItem *__qtablewidgetitem4 = new QTableWidgetItem();
        tableWidget->setVerticalHeaderItem(1, __qtablewidgetitem4);
        QTableWidgetItem *__qtablewidgetitem5 = new QTableWidgetItem();
        tableWidget->setVerticalHeaderItem(2, __qtablewidgetitem5);
        QTableWidgetItem *__qtablewidgetitem6 = new QTableWidgetItem();
        tableWidget->setItem(0, 0, __qtablewidgetitem6);
        QTableWidgetItem *__qtablewidgetitem7 = new QTableWidgetItem();
        tableWidget->setItem(0, 1, __qtablewidgetitem7);
        QTableWidgetItem *__qtablewidgetitem8 = new QTableWidgetItem();
        tableWidget->setItem(0, 2, __qtablewidgetitem8);
        QTableWidgetItem *__qtablewidgetitem9 = new QTableWidgetItem();
        tableWidget->setItem(1, 0, __qtablewidgetitem9);
        QTableWidgetItem *__qtablewidgetitem10 = new QTableWidgetItem();
        tableWidget->setItem(1, 1, __qtablewidgetitem10);
        QTableWidgetItem *__qtablewidgetitem11 = new QTableWidgetItem();
        tableWidget->setItem(1, 2, __qtablewidgetitem11);
        QTableWidgetItem *__qtablewidgetitem12 = new QTableWidgetItem();
        tableWidget->setItem(2, 0, __qtablewidgetitem12);
        QTableWidgetItem *__qtablewidgetitem13 = new QTableWidgetItem();
        tableWidget->setItem(2, 1, __qtablewidgetitem13);
        QTableWidgetItem *__qtablewidgetitem14 = new QTableWidgetItem();
        tableWidget->setItem(2, 2, __qtablewidgetitem14);
        tableWidget->setObjectName(QString::fromUtf8("tableWidget"));
        tableWidget->setGeometry(QRect(40, 10, 531, 301));
        tableWidget->setRowCount(8);
        tableWidget->setColumnCount(6);
        pushButtonTranslate = new QPushButton(centralWidget);
        pushButtonTranslate->setObjectName(QString::fromUtf8("pushButtonTranslate"));
        pushButtonTranslate->setGeometry(QRect(40, 340, 161, 61));
        QtGuiApplication1Class->setCentralWidget(centralWidget);
        menuBar = new QMenuBar(QtGuiApplication1Class);
        menuBar->setObjectName(QString::fromUtf8("menuBar"));
        menuBar->setGeometry(QRect(0, 0, 600, 21));
        QtGuiApplication1Class->setMenuBar(menuBar);
        mainToolBar = new QToolBar(QtGuiApplication1Class);
        mainToolBar->setObjectName(QString::fromUtf8("mainToolBar"));
        QtGuiApplication1Class->addToolBar(Qt::TopToolBarArea, mainToolBar);
        statusBar = new QStatusBar(QtGuiApplication1Class);
        statusBar->setObjectName(QString::fromUtf8("statusBar"));
        QtGuiApplication1Class->setStatusBar(statusBar);

        retranslateUi(QtGuiApplication1Class);

        QMetaObject::connectSlotsByName(QtGuiApplication1Class);
    } // setupUi

    void retranslateUi(QMainWindow *QtGuiApplication1Class)
    {
        QtGuiApplication1Class->setWindowTitle(QCoreApplication::translate("QtGuiApplication1Class", "QtGuiApplication1", nullptr));
        QTableWidgetItem *___qtablewidgetitem = tableWidget->horizontalHeaderItem(0);
        ___qtablewidgetitem->setText(QCoreApplication::translate("QtGuiApplication1Class", "col 1", nullptr));
        QTableWidgetItem *___qtablewidgetitem1 = tableWidget->horizontalHeaderItem(1);
        ___qtablewidgetitem1->setText(QCoreApplication::translate("QtGuiApplication1Class", "col2", nullptr));
        QTableWidgetItem *___qtablewidgetitem2 = tableWidget->horizontalHeaderItem(2);
        ___qtablewidgetitem2->setText(QCoreApplication::translate("QtGuiApplication1Class", "col3", nullptr));
        QTableWidgetItem *___qtablewidgetitem3 = tableWidget->verticalHeaderItem(0);
        ___qtablewidgetitem3->setText(QCoreApplication::translate("QtGuiApplication1Class", "New Row", nullptr));
        QTableWidgetItem *___qtablewidgetitem4 = tableWidget->verticalHeaderItem(1);
        ___qtablewidgetitem4->setText(QCoreApplication::translate("QtGuiApplication1Class", "New Row", nullptr));
        QTableWidgetItem *___qtablewidgetitem5 = tableWidget->verticalHeaderItem(2);
        ___qtablewidgetitem5->setText(QCoreApplication::translate("QtGuiApplication1Class", "New Row", nullptr));

        const bool __sortingEnabled = tableWidget->isSortingEnabled();
        tableWidget->setSortingEnabled(false);
        QTableWidgetItem *___qtablewidgetitem6 = tableWidget->item(0, 0);
        ___qtablewidgetitem6->setText(QCoreApplication::translate("QtGuiApplication1Class", "aaaa", nullptr));
        QTableWidgetItem *___qtablewidgetitem7 = tableWidget->item(0, 1);
        ___qtablewidgetitem7->setText(QCoreApplication::translate("QtGuiApplication1Class", "aaaa", nullptr));
        QTableWidgetItem *___qtablewidgetitem8 = tableWidget->item(0, 2);
        ___qtablewidgetitem8->setText(QCoreApplication::translate("QtGuiApplication1Class", "aaaa", nullptr));
        QTableWidgetItem *___qtablewidgetitem9 = tableWidget->item(1, 0);
        ___qtablewidgetitem9->setText(QCoreApplication::translate("QtGuiApplication1Class", "bbbb", nullptr));
        QTableWidgetItem *___qtablewidgetitem10 = tableWidget->item(1, 1);
        ___qtablewidgetitem10->setText(QCoreApplication::translate("QtGuiApplication1Class", "bbbb", nullptr));
        QTableWidgetItem *___qtablewidgetitem11 = tableWidget->item(1, 2);
        ___qtablewidgetitem11->setText(QCoreApplication::translate("QtGuiApplication1Class", "bbbb", nullptr));
        QTableWidgetItem *___qtablewidgetitem12 = tableWidget->item(2, 0);
        ___qtablewidgetitem12->setText(QCoreApplication::translate("QtGuiApplication1Class", "cccc", nullptr));
        QTableWidgetItem *___qtablewidgetitem13 = tableWidget->item(2, 1);
        ___qtablewidgetitem13->setText(QCoreApplication::translate("QtGuiApplication1Class", "cccc", nullptr));
        QTableWidgetItem *___qtablewidgetitem14 = tableWidget->item(2, 2);
        ___qtablewidgetitem14->setText(QCoreApplication::translate("QtGuiApplication1Class", "cccc", nullptr));
        tableWidget->setSortingEnabled(__sortingEnabled);

        pushButtonTranslate->setText(QCoreApplication::translate("QtGuiApplication1Class", "Translate", nullptr));
    } // retranslateUi

};

namespace Ui {
    class QtGuiApplication1Class: public Ui_QtGuiApplication1Class {};
} // namespace Ui

QT_END_NAMESPACE

#endif // UI_QTGUIAPPLICATION1_H

[mrjj]

Hi
And if you in the process,
completely delete ui_QtGuiApplication1.h
and rebuild build all ?

It sounds like some code left overs.

"This is because the code doesn't test if the QTableWidgetItem * "
Why would it be NULL ?
If you delete from the UI (visually) that code should no longer be there.