QComboBox selection makes computer crash

IgorRecioH

Hi everyone,

this is my first comment in this forum and I'm quite newbie in Qt C++.

I am developing a personal desktop application for managing expenses at home.

I am having some issues with all of my QComboBox in the app. Let's see if I can explain it correctly:

I click on my QComboBox --> Options appear
If I click outside the QComboBox to close it (don't mind where), application crashes and my Ubuntu user session closes (It does not restart computer but I need to re-enter my credentials)
If I click on any option it works fine and it also works fine if I don't click an option but I press Escape to close the QComboBox.

Is this behaviour expected? Am I doing something wrong?

You can check my code here: https://github.com/igorrecioh/home_expenses_dsktp/blob/main/mainwindow.cpp

Thanks a lot in advance.

Kind regards,

Igor

EDIT: I am using Ubuntu 22.04.1 LTS and application uses Qt6 6.4.2

JonB

@IgorRecioH said in QComboBox selection makes computer crash:

Is this behaviour expected? Am I doing something wrong?

In principle, no. Probably, else there is a problem.

Reduce your code till it either occurs in minimal example and/or run under a debugger and look at the stack trace etc. when it crashes.

IgorRecioH

@JonB
Thanks a lot for your quick response. I have tried running app and debug it but it crashes and I cannot see anything in the stacktrace, quite annoying...

Anyway, I will try with a minimal example and check if it happens too, as you suggest.

I will keep you updated.

Regards,

Igor

JonB

@IgorRecioH
Is the only combobox stuff you do the on_filterByCbx_currentIndexChanged()? What you are describing seems unexpected and not connected to anything in your application. Is that is what is being triggered when it crashes? Does a standalone combobox exhibit this problem? Else edit up/down from there.

IgorRecioH

@JonB

Good, I have just created an empty new project with a unique combobox, and it is also happening the crash. I am starting to think that there is something wrong in my computer or setup. Check code below:

mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>

QT_BEGIN_NAMESPACE
namespace Ui { class MainWindow; }
QT_END_NAMESPACE

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    MainWindow(QWidget *parent = nullptr);
    ~MainWindow();

private:
    Ui::MainWindow *ui;
};
#endif // MAINWINDOW_H

mainwindow.cpp

#include "mainwindow.h"
#include "ui_mainwindow.h"

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    ui->comboBox->addItem("kk");
}

MainWindow::~MainWindow()
{
    delete ui;
}

main.cpp

#include "mainwindow.h"

#include <QApplication>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWindow w;
    w.show();
    return a.exec();
}

mainwindow.ui

<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
 <class>MainWindow</class>
 <widget class="QMainWindow" name="MainWindow">
  <property name="geometry">
   <rect>
    <x>0</x>
    <y>0</y>
    <width>800</width>
    <height>600</height>
   </rect>
  </property>
  <property name="windowTitle">
   <string>MainWindow</string>
  </property>
  <widget class="QWidget" name="centralwidget">
   <widget class="QComboBox" name="comboBox">
    <property name="geometry">
     <rect>
      <x>140</x>
      <y>110</y>
      <width>86</width>
      <height>25</height>
     </rect>
    </property>
   </widget>
  </widget>
  <widget class="QMenuBar" name="menubar">
   <property name="geometry">
    <rect>
     <x>0</x>
     <y>0</y>
     <width>800</width>
     <height>22</height>
    </rect>
   </property>
  </widget>
  <widget class="QStatusBar" name="statusbar"/>
 </widget>
 <resources/>
 <connections/>
</ui>

CMakeLists.txt

cmake_minimum_required(VERSION 3.5)

project(test VERSION 0.1 LANGUAGES CXX)

set(CMAKE_AUTOUIC ON)
set(CMAKE_AUTOMOC ON)
set(CMAKE_AUTORCC ON)

set(CMAKE_CXX_STANDARD 17)
set(CMAKE_CXX_STANDARD_REQUIRED ON)

find_package(QT NAMES Qt6 Qt5 REQUIRED COMPONENTS Widgets)
find_package(Qt${QT_VERSION_MAJOR} REQUIRED COMPONENTS Widgets)

set(PROJECT_SOURCES
        main.cpp
        mainwindow.cpp
        mainwindow.h
        mainwindow.ui
)

if(${QT_VERSION_MAJOR} GREATER_EQUAL 6)
    qt_add_executable(test
        MANUAL_FINALIZATION
        ${PROJECT_SOURCES}
    )
# Define target properties for Android with Qt 6 as:
#    set_property(TARGET test APPEND PROPERTY QT_ANDROID_PACKAGE_SOURCE_DIR
#                 ${CMAKE_CURRENT_SOURCE_DIR}/android)
# For more information, see https://doc.qt.io/qt-6/qt-add-executable.html#target-creation
else()
    if(ANDROID)
        add_library(test SHARED
            ${PROJECT_SOURCES}
        )
# Define properties for Android with Qt 5 after find_package() calls as:
#    set(ANDROID_PACKAGE_SOURCE_DIR "${CMAKE_CURRENT_SOURCE_DIR}/android")
    else()
        add_executable(test
            ${PROJECT_SOURCES}
        )
    endif()
endif()

target_link_libraries(test PRIVATE Qt${QT_VERSION_MAJOR}::Widgets)

set_target_properties(test PROPERTIES
    MACOSX_BUNDLE_GUI_IDENTIFIER my.example.com
    MACOSX_BUNDLE_BUNDLE_VERSION ${PROJECT_VERSION}
    MACOSX_BUNDLE_SHORT_VERSION_STRING ${PROJECT_VERSION_MAJOR}.${PROJECT_VERSION_MINOR}
    MACOSX_BUNDLE TRUE
    WIN32_EXECUTABLE TRUE
)

install(TARGETS test
    BUNDLE DESTINATION .
    LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR})

if(QT_VERSION_MAJOR EQUAL 6)
    qt_finalize_executable(test)
endif()

IgorRecioH

@JonB

@JonB said in QComboBox selection makes computer crash:

@IgorRecioH
Is the only combobox stuff you do the on_filterByCbx_currentIndexChanged()? What you are describing seems unexpected and not connected to anything in your application. Is that is what is being triggered when it crashes? Does a standalone combobox exhibit this problem? Else edit up/down from there.

That combobox you mention is the only one which has currentIndexChanged signal. The value of the rest of comboboxes are read when clicking a button. Anyway, all of them exhibit this problem, yes.

Quite crazy, must say. When I try one of the examples provided in QtDesigner, they work fine. It is true that this example do not have a .ui file, I mean, they create the objects directly in C++ code.

IgorRecioH

Just as update: I have compiled my Qt app in a Windows10 VM and I cannot reproduce the problem and it's working fine. So maybe it is related to Ubuntu.

Furthermore, exploring /var/log/syslog I found this line when crashing the app:

Feb  9 21:17:27 igorrecio-XXX gnome-shell[53810]: GNOME Shell crashed with signal 11
Feb  9 21:17:27 igorrecio-XXX gnome-shell[53810]: == Stack trace for context 0x56459ff96490 ==

Searching on the internet, seems to be something related to GNOME, specifically in Ubuntu 22.04...

JonB

@IgorRecioH
Since there was nothing in your code changing combobox behaviour it does sound right that any combobox will do it and it is some issue on your platform. But I (and others) use Ubuntu 22.04 with GNOME and have no trouble, though I am Qt5. It would be very serious if what you report happens to everyone, you are saying 22.04/GNOME/Qt6 cannot work with a combobox, I would have expected to hear about this! Maybe try a Qt other than 6.4.2?

SamuelAdesola

I am experiencing same problem now

? Offline

I have also same problem using Qt6 6.4.2. I am waiting for a solution. I don't want to migrate Qt5 because of this problem.

JoeCFD

@Dogukan-Arat I tested the /widgets/painting/basicdrawing example which has a few combo boxes and do not see any crash.
Qt 6.5.0 and LUbuntu 22.04

JonB

@JoeCFD
I seem to remember some recent post on something "similar" to this may have stated that Lubuntu worked but Ubuntu did not?

JoeCFD

@JonB I will check it out later.

JoeCFD

@JoeCFD Tried the same example on Qt 6.4.0 and Ubuntu 22.04. No crash.

iPriyonto

I am having the same problem too. However, in my case, it crashes only when I have the combo box open, and I try to interact with other widgets I have on the window.

Mriv31

Same problem.

Ubuntu 22.04 LTS - Wayland
PyQt6 6.5.0

Li Kui

同样的问题，VMware，Ubuntu-22.04.2，Qt6.5

BosGemiler

I have same issue. When I clicked on combobox, I can see dropdown menu, and everything is fine so far. But when I click on any item in dropdown menu, there appears a crash and I find myself on log in page of ubuntu.

It's not the only bug I faced in ubuntu. There are many others too. Unfortunately, I didn't see any good release of Ubuntu except Ubuntu 14 and 18.

Goodbye Ubuntu, Welcome Debian !

JoeCFD

@BosGemiler It could be a wayland related issue. Switch to Xorg and try it again.
On Login screen, there is a setting icon and click it to switch to Xorg. The default on Ubuntu now is Wayland.

default

I faced the same issue while working with PyQt6 on Ubuntu 22.04

So I ran the following minimal example:-

from PyQt6.QtWidgets import (
  QApplication,
  QWidget,
  QComboBox,
)

import sys


class Window(QWidget):
  def __init__(self):
    super().__init__()

    combobox = QComboBox(self)
    combobox.addItems(['option 1', 'option 2', 'option 3'])

    self.setGeometry(0,0,500,500)
    self.setWindowTitle('Combobox Bug')
    self.show()


if __name__ == '__main__':
  app = QApplication([])
  window = Window()
  sys.exit(app.exec())

Wayland : It crashes and I am sent to login screen where I have to login again.
Xorg: No crash

Same thing happens on PySide6.