Trying to build a Qt 6 application but getting a Qt 5 application; Qt Creator 19 on Gentoo Linux

mgoppelt

I'm new to Qt. I selected Qt 6 in my Desktop kit. When I use ldd on the resulting binary I get
libQt5Widgets.so.5 => /usr/lib64/libQt5Widgets.so.5 (0x00007f4decab7000)
libQt5Gui.so.5 => /usr/lib64/libQt5Gui.so.5 (0x00007f4dec486000)
libQt5Core.so.5 => /usr/lib64/libQt5Core.so.5 (0x00007f4debf27000)
among other shared objects. The binary is linked to Qt 5 instead of Qt 6. My application is a normal Qt Widgets Application. There is no difference between Debug and Release in this regard. When I select Qt 5 nothing changes.

I assume this is not the normal behavior. How can I get to the root cause of this? Where do I start to dig?

JonB

@mgoppelt
Your paths show a Qt5 installed in /usr/lib64, which is presumably supplied by your Linux OS. Quite likely it does not supply a Qt6?

So did you fetch and install (a pre-built) Qt6 yourself? Is your kit and build commands not picking that up and compiling/linking against the system's Qt5?

mgoppelt

Good point. Qt6 is also installed. The shared objects
/usr/lib64/libQt6Core.so.6
/usr/lib64/libQt6Gui.so.6
/usr/lib64/libQt6Widgets.so.6
are available. I'm quite sure that Gentoo builds Qt (both 5 and 6) from the sources.

JonB

@mgoppelt
OK, so for whatever reason even though you have picked a Qt6 kit it's compiling/linking as Qt5. Someone else will doubtless know more. Does the CMakeLists.txt for the project show anything about setting for either Qt6 or Qt5?

mgoppelt

CMakeLists.txt doesn't restrict the build to Qt 5 or Qt 6. There appear two variables regarding the version
${QT_VERSION_MAJOR}
${QT_VERSION}
. I will either attach CMakeLists.txt or dump it into a new reply.

mgoppelt

Here comes CMakeLists.txt:

cmake_minimum_required(VERSION 3.16)

project(Projekt_Muehle 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 20)
set(CMAKE_CXX_STANDARD_REQUIRED ON)

include_directories(${PROJECT_SOURCE_DIR})

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(Projekt_Muehle
        MANUAL_FINALIZATION
        ${PROJECT_SOURCES}
        add_args.h
        add_args.cpp
        mill_view.h mill_view.cpp
        mill_model.h mill_model.cpp
        mill_controller.h mill_controller.cpp
        player.h player.cpp
        board.h board.cpp board.ui
        token.h token.cpp token.ui
        board_label.h board_label.cpp board_label.ui
        res.qrc
    )
# Define target properties for Android with Qt 6 as:
#    set_property(TARGET Projekt_Muehle 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(Projekt_Muehle 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(Projekt_Muehle
            ${PROJECT_SOURCES}
            add_args.cpp add_args.h
            board.cpp board.h board.ui
            board_label.cpp board_label.h board_label.ui
            mill_controller.cpp mill_controller.h
            mill_model.cpp mill_model.h
            mill_view.cpp mill_view.h
            player.cpp player.h
            token.cpp token.h token.ui
        )
    endif()
endif()

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

# Qt for iOS sets MACOSX_BUNDLE_GUI_IDENTIFIER automatically since Qt 6.1.
# If you are developing for iOS or macOS you should consider setting an
# explicit, fixed bundle identifier manually though.
if(${QT_VERSION} VERSION_LESS 6.1.0)
  set(BUNDLE_ID_OPTION MACOSX_BUNDLE_GUI_IDENTIFIER com.example.Projekt_Muehle)
endif()
set_target_properties(Projekt_Muehle PROPERTIES
    ${BUNDLE_ID_OPTION}
    MACOSX_BUNDLE_BUNDLE_VERSION ${PROJECT_VERSION}
    MACOSX_BUNDLE_SHORT_VERSION_STRING ${PROJECT_VERSION_MAJOR}.${PROJECT_VERSION_MINOR}
    MACOSX_BUNDLE TRUE
    WIN32_EXECUTABLE TRUE
)

include(GNUInstallDirs)
install(TARGETS Projekt_Muehle
    BUNDLE DESTINATION .
    LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR}
    RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR}
)

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

SGaist

Hi,

Just to clear things out, can you properly build that project on the command line for each version of Qt ?

mgoppelt

I could only get a Qt 5 build using cmake and ninja.

First cmake:

markus@ryzen ~/Qt/Projekt_Muehle $ cmake -G Ninja -S Qt/ -B Qt/build/test_build/
-- The CXX compiler identification is GNU 15.2.1
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: /usr/bin/c++ - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Configuring done (0.2s)
-- Generating done (0.0s)
-- Build files have been written to: /home/markus/Qt/Projekt_Muehle/Qt/build/test_build

Then ninja:

markus@ryzen ~/Qt/Projekt_Muehle/Qt/build/test_build $ ls
build.ninja  CMakeCache.txt  CMakeFiles  cmake_install.cmake
markus@ryzen ~/Qt/Projekt_Muehle/Qt/build/test_build $ ninja
[13/13] Linking CXX executable Projekt_Muehle

The files build.ninja and CMakeCache.txt only contain references to Qt 5:

markus@ryzen ~/Qt/Projekt_Muehle/Qt/build/test_build $ grep LINK_LIBRARIES build.ninja
  LINK_LIBRARIES = /usr/lib64/libQt5Widgets.so.5.15.18  /usr/lib64/libQt5Gui.so.5.15.18  /usr/lib64/libQt5Core.so.5.15.18
markus@ryzen ~/Qt/Projekt_Muehle/Qt/build/test_build $ grep -e Qt5Widgets -e Qt5Gui -e Qt5Core CMakeCache.txt
//The directory containing a CMake configuration file for Qt5Core.
Qt5Core_DIR:PATH=/usr/lib64/cmake/Qt5Core
//The directory containing a CMake configuration file for Qt5Gui.
Qt5Gui_DIR:PATH=/usr/lib64/cmake/Qt5Gui
//The directory containing a CMake configuration file for Qt5Widgets.
Qt5Widgets_DIR:PATH=/usr/lib64/cmake/Qt5Widgets
markus@ryzen ~/Qt/Projekt_Muehle/Qt/build/test_build $ grep -e Qt6Widgets -e Qt6Gui -e Qt6Core CMakeCache.txt

These two files were generated by Qt Creator prior to me using the command line:

markus@ryzen ~/Qt/Projekt_Muehle/Qt $ ls CMakeLists.txt .qtcreator/CMakeLists.txt.user 
CMakeLists.txt  .qtcreator/CMakeLists.txt.user

I don't think the second file is relevant for the command line cmake.

mgoppelt

Is there a way to insert a code segment without automatic coloring?

GrecKo

@mgoppelt said in Trying to build a Qt 6 application but getting a Qt 5 application; Qt Creator 19 on Gentoo Linux:

Is there a way to insert a code segment without automatic coloring?

```text
your log
```

Christian Ehrlicher

@mgoppelt And did you install the Qt6 development packages? Remove Qt5 from the CMakeLists.txt and start over with a clean build dir after you made sure the dev packages for Qt6 are installed (and even better - the dev packages for Qt5 are uninstalled).

mgoppelt

I have the development packages for Qt5 and Qt6. As you mentioned it works when I remove Qt5 from the following statement in CMakeLists.txt.

#find_package(QT NAMES Qt6 Qt5 REQUIRED COMPONENTS Widgets)
#find_package(QT NAMES Qt6 REQUIRED COMPONENTS Widgets)
find_package(QT NAMES Qt5 REQUIRED COMPONENTS Widgets)

The first and third line result in a Qt5 build. The second line results in a Qt6 build. The "Qt version" field in my kit seems to have no influence. I set the value to "None".

The issue is resolved. However in a weird way.