Application won't always start

[tilz0R]

I'm learning Qt for C++ (with Python I made pretty good progress) and I have notices that sometimes my window won't pop-up, logs in the window constructor won't get printed (qDebug()<<"message..." and similar type of messages).

I'm communicating with my DLL to access serial port, so I though this may have an impact, but after removing it, I don't see difference. Still, out of 10 attempts to start .exe, Window will show maybe around 60% of the times.

Some other info:

• Windows 11
• Qt version 6.5
• CMake as build system, developed under vscode
• Qt paths set accordingly
• There is no error at all, application seems to start and do something in the background, but windows doesn't open

If it's needed, below is main.c and mainwindow.cpp.

#include "mainwindow.h"
#include <QApplication>

int
main(int argc, char* argv[]) {
    QApplication a(argc, argv);
    
    //These 2 prints sometimes don't show in the console at all
    qDebug() << "Before MainWindow constructor";
    MainWindow w;
    qDebug() << "After MainWindow constructor";
    w.show();
    return a.exec();
}

mainwindow class constructor

MainWindow::MainWindow(QWidget* parent) : QMainWindow(parent), ui(new Ui::MainWindow) {
    ui->setupUi(this);

    /* Create custom views */
    view_can_config = new ViewCanConfig();
    view_debug = new ViewDebug();
    view_fw_update = new ViewFwUpdate();
    view_logger = new ViewLogger();
    view_tx_msg_config = new ViewTxMsgConfig();
    views_list.append(view_can_config);
    views_list.append(view_debug);
    views_list.append(view_fw_update);
    views_list.append(view_logger);
    views_list.append(view_tx_msg_config);
    connect(view_tx_msg_config, ViewTxMsgConfig::onSendMessage, this, MainWindow::send_can_message);
    connect(view_logger, ViewLogger::onSendMessage, this, MainWindow::send_can_message);

    /* Connect debug messages */
    connect(view_can_config, ViewCanConfig::send_debug, view_debug, ViewDebug::add_debug_message);
    connect(view_debug, ViewDebug::send_debug, view_debug, ViewDebug::add_debug_message);
    connect(view_fw_update, ViewFwUpdate::send_debug, view_debug, ViewDebug::add_debug_message);
    connect(view_logger, ViewLogger::send_debug, view_debug, ViewDebug::add_debug_message);
    connect(view_tx_msg_config, ViewTxMsgConfig::send_debug, view_debug, ViewDebug::add_debug_message);
    connect(this, MainWindow::send_debug, view_debug, ViewDebug::add_debug_message);

    /* Add views to the layouts */
    ui->layout_tab_logger->addWidget(view_logger);
    ui->layout_tab_debug->addWidget(view_debug);
    ui->layout_tab_fdcan_config->addWidget(view_can_config);
    ui->layout_tab_tx_msg_config->addWidget(view_tx_msg_config);
    ui->layout_tab_fw_update->addWidget(view_fw_update);

    /* Add quick TX widget to the logger view using default configuration */
    view_logger->add_quick_tx_widget(view_tx_msg_config->create_new_tx_msg_config_window());

    /* Set status bar */
    statusbar = new StatusBar(this);
    ui->statusbar->addWidget(statusbar);

    /* Triggers */
    connect(ui->btn_com_port_refresh, &QPushButton::clicked, this, &MainWindow::load_com_ports);
    connect(ui->btn_com_port_connect_disconnect, &QPushButton::clicked, this, &MainWindow::toggle_connect_to_port);

    /* Get system com ports */
#if 1
    load_com_ports();

    /* Reset values */
    ca_evt_read_ptr = 0;
    ca_evt_write_ptr = 0;

    /* Queue processing timer */
    timer_queue = new QTimer(this);
    timer_queue->setSingleShot(false);
    timer_queue->setInterval(50);
    connect(timer_queue, &QTimer::timeout, this, &MainWindow::timer_ca_queue_check_expired);
    timer_queue->start();

    emit send_debug(CaUtils::DebugLevel::Info, "APP", "Application running");

    /* Initialize CANanalyzer interface */
    if (ca_init((ca_evt_fn)&prv_ca_evt_fn)) {
        emit send_debug(CaUtils::DebugLevel::Info, "DLL", "App ready to use");
    }
#endif
}

Am I missing something? What could be common reasons that app wouldn't always start properly?

[tilz0R]

Found the problem. It was uninitialized variable in another class that was constructed in the constructor of MainWindow, causing for loop to go to to 2^32 or other random number.

Sorry for taking your time for this.

The Before MainWindow... was NOT always printed. It may have to do with flushing of the data in the system.

I will continue monitoring but it looks good for the moment.

[Axel Spoerl]

@tilz0R
How is the application compiled and how is it launched?
Are you always launching the debug build?

To narrow the issue down: Use qInfo()instead of qDebug()and start your executable from the command line. Watch out for error messages on startup.

[tilz0R]

@Axel-Spoerl

Compiled with CMake:

# configure
cmake -DCMAKE_BUILD_TYPE=Debug -DCMAKE_EXPORT_COMPILE_COMMANDS=ON -DCMAKE_TOOLCHAIN_FILE=D:/.../cmakefile/x86_64-w64-mingw32-gcc.cmake -SD:/.../gui_cpp -BD:/.../build/Win64-Debug -G Ninja
# Build
cmake --build path/to/dir

Toolchain file

set(CMAKE_SYSTEM_NAME               Windows)

# Some default GCC settings
set(CMAKE_C_COMPILER                x86_64-w64-mingw32-gcc)
set(CMAKE_CXX_COMPILER              x86_64-w64-mingw32-g++)

set(CMAKE_TRY_COMPILE_TARGET_TYPE STATIC_LIBRARY)

Toolchain

x86_64-w64-mingw32-gcc --version
x86_64-w64-mingw32-gcc (Rev6, Built by MSYS2 project) 12.2.0
Copyright (C) 2022 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

CMakeLists file

cmake_minimum_required(VERSION 3.22)

project("CANanalyzer" VERSION 0.1 LANGUAGES C CXX)

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

set(CMAKE_CXX_STANDARD          17)
set(CMAKE_CXX_STANDARD_REQUIRED ON)
#set(CMAKE_PREFIX_PATH "c:/Qt6.5.0/6.5.0/mingw_64/")

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

# Define include paths
set(PROJECT_INCLUDES
    ${CMAKE_CURRENT_LIST_DIR}/
    ${CMAKE_CURRENT_LIST_DIR}/include
    ${CMAKE_CURRENT_LIST_DIR}/models
    ${CMAKE_CURRENT_LIST_DIR}/widgetss
    ${CMAKE_CURRENT_LIST_DIR}/views
    ${CMAKE_CURRENT_LIST_DIR}/../common/include
    ${CMAKE_CURRENT_LIST_DIR}/../common/proto
    ${CMAKE_CURRENT_LIST_DIR}/../libs/nanopb
    ${CMAKE_CURRENT_LIST_DIR}/../libs/mbedtls/include
)

# Define project sources
set(PROJECT_SOURCES
    ${CMAKE_CURRENT_LIST_DIR}/main.cpp
    ${CMAKE_CURRENT_LIST_DIR}/mainwindow.cpp

    # Widgets & views
    ${CMAKE_CURRENT_LIST_DIR}/widgets/tx_msg_config_entry_widget.cpp
    ${CMAKE_CURRENT_LIST_DIR}/widgets/can_clock_config_entry_widget.cpp
    ${CMAKE_CURRENT_LIST_DIR}/widgets/can_clock_config_entry_widget_timepar.cpp
    ${CMAKE_CURRENT_LIST_DIR}/widgets/statusbar.cpp
    ${CMAKE_CURRENT_LIST_DIR}/views/view_can_config.cpp
    ${CMAKE_CURRENT_LIST_DIR}/views/view_debug.cpp
    ${CMAKE_CURRENT_LIST_DIR}/views/view_logger.cpp
    ${CMAKE_CURRENT_LIST_DIR}/views/view_fw_update.cpp
    ${CMAKE_CURRENT_LIST_DIR}/views/view_tx_msg_config.cpp
    
    # Models
    ${CMAKE_CURRENT_LIST_DIR}/models/canloggerdatamodel.cpp

    # UI files
    ${CMAKE_CURRENT_LIST_DIR}/mainwindow.ui
    ${CMAKE_CURRENT_LIST_DIR}/widgets/can_clock_config_entry_widget.ui
    ${CMAKE_CURRENT_LIST_DIR}/widgets/tx_msg_config_entry_widget.ui
    ${CMAKE_CURRENT_LIST_DIR}/views/view_can_config.ui
    ${CMAKE_CURRENT_LIST_DIR}/views/view_logger.ui
    ${CMAKE_CURRENT_LIST_DIR}/views/view_fw_update.ui
    ${CMAKE_CURRENT_LIST_DIR}/views/view_debug.ui
    ${CMAKE_CURRENT_LIST_DIR}/views/view_tx_msg_config.ui

    # Missing this, MOC won't run for custom header files !!
    ${CMAKE_CURRENT_LIST_DIR}/views/custom_tab_widget_base.h
)

# Add mbedTLS
file(GLOB MBEDTLS_FILES ${CMAKE_CURRENT_LIST_DIR}/../libs/mbedtls/library/*.c)
set(PROJECT_SOURCES ${PROJECT_SOURCES} ${MBEDTLS_FILES})

# Create executable file
qt_add_executable(${CMAKE_PROJECT_NAME}
    MANUAL_FINALIZATION
    ${PROJECT_SOURCES}
)

# Set application firmware version -> read from the file directly
include(../cmake/version.cmake)

# Add to build
target_compile_definitions(${CMAKE_PROJECT_NAME} PUBLIC
    # Version setup
    "CA_FW_VERSION_MAJOR=${CA_FW_VERSION_MAJOR}"
    "CA_FW_VERSION_MINOR=${CA_FW_VERSION_MINOR}"
    "CA_FW_VERSION_PATCH=${CA_FW_VERSION_PATCH}"
    "CA_FW_VERSION_TYPE=${CA_FW_VERSION_TYPE}"
    "CA_FW_VERSION_REV=${CA_FW_VERSION_REV}"

    # Nano protobuf
    "PB_FIELD_32BIT"
)

# Set include paths
target_include_directories(${CMAKE_PROJECT_NAME} PUBLIC ${PROJECT_INCLUDES})

# Link Qt libraries
target_link_libraries(${CMAKE_PROJECT_NAME} PRIVATE
    Qt${QT_VERSION_MAJOR}::Widgets
    Qt${QT_VERSION_MAJOR}::Core
    Qt${QT_VERSION_MAJOR}::SerialPort
)

# Add cananalyzer library
target_link_directories(${PROJECT_NAME} PUBLIC build/Win64-Debug)
target_link_libraries(${CMAKE_PROJECT_NAME} PRIVATE libCANanalyzer)

set_target_properties(${CMAKE_PROJECT_NAME} 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 OFF
)

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

if(QT_VERSION_MAJOR EQUAL 6)
    qt_finalize_executable(${CMAKE_PROJECT_NAME})
endif()

Start command

gui_cpp\build\Win64-Debug>.\CANanalyzer.exe
Before MainWindow constructor

For instance, I got Before MainWindow constructor but then no After MainWindow message. No log messages are returned.

[Christian Ehrlicher]

Then start it in your debugger and see why it crashes. Minimize the ctor until it works reliable.

[Axel Spoerl]

@tilz0R
Ok, but the before constructor message is always printed, right?

[Axel Spoerl]

@tilz0R said in Application won't always start:

load_com_ports();

As @Christian-Ehrlicher said, you could start by commenting this line out.

I have no clue what the application actually does, but com ports can be a bit flaky at times. So maybe this function blocks.

[tilz0R]

Found the problem. It was uninitialized variable in another class that was constructed in the constructor of MainWindow, causing for loop to go to to 2^32 or other random number.

Sorry for taking your time for this.

The Before MainWindow... was NOT always printed. It may have to do with flushing of the data in the system.

I will continue monitoring but it looks good for the moment.