Undefined reference to QSqlDatabase and other QtSql headers of Qt CMake project on Linux

[Yihua Liu]

In my Qt C++/QML project, I included <QtSql/QSqlDatabase>, <QtSql/QSqlError>, <QtSql/QSqlRelationalTableModel>, etc. headers. In CMakeLists.txt I write

find_package(Qt6 6.8 REQUIRED COMPONENTS Charts Core Gui Qml Quick Sql)

and

target_link_libraries(MyApp PRIVATE
        Qt6::Charts
        Qt6::Core
        Qt6::Gui
        Qt6::Qml
        Qt6::Quick
        Qt6::Sql
        QXlsx::QXlsx
)

The project can be successfully built and ran on Windows platform, but it fails to build and run on Linux platform:

x86_64-linux-gnu/libOpenGL.so /opt/Qt6.8.0/6.8.0/gcc_64/lib/libQt6Qml.so.6.8.0 /opt/Qt6.8.0/6.8.0/gcc_64/lib/libQt6Network.so.6.8.0 /opt/Qt6.8.0/6.8.0/gcc_64/lib/libQt6Core.so.6.8.0 -Wl,-rpath-link,/opt/Qt6.8.0/6.8.0/gcc_64/lib && :
/usr/bin/ld: content/libcontent.a(SqlTreeModel.cpp.o): in function SqlTreeModel::SqlTreeModel(QObject*)': /home/<username>/MyApp/src/sql/SqlTreeModel.cpp:12:(.text+0x17b): undefined reference to QSqlDatabase::drivers()'
/usr/bin/ld: content/libcontent.a(SqlTreeModel.cpp.o): in function SqlTreeModel::addConnection(QString const&, QString const&, QString const&, QString const&)': /home/<username>/MyApp/src/sql/SqlTreeModel.cpp:182:(.text+0xeeb): undefined reference to QSqlError::QSqlError(QString const&, QString const&, QSqlError::ErrorType, QString const&)'
/usr/bin/ld: /home/<username>/MyApp/src/sql/SqlTreeModel.cpp:209:(.text+0x10b4): undefined reference to `QSqlDatabase::addDatabase(QString const&, QString const&)'

and many lines of other similar errors.
I checked CMake configuration that Qt6Sql_DIR is /opt/Qt6.8.0/6.8.0/gcc_64/lib/cmake/Qt6Sql which exists in my filesystem. I've also built SQL driver plugins on Linux.
What's the possible reason for these errors?

[SGaist]

Hi,

If you are creating a library, you have to link the dependencies which you are not doing here.

[Christian Ehrlicher]

Please post the full CMakeLists.txt

[Yihua Liu]

cmake_minimum_required(VERSION 3.27)

option(LINK_INSIGHT "Link Qt Insight Tracker library" ON)
option(BUILD_QDS_COMPONENTS "Build design studio components" ON)

project(SuisApp
        VERSION 1.0.0
        DESCRIPTION "Open-source Solar Cell Simulator"
        HOMEPAGE_URL "https://github.com/yihuajack/Suis"
        LANGUAGES CXX)

set(CMAKE_INCLUDE_CURRENT_DIR ON)
set(CMAKE_CXX_STANDARD 23)
set(CMAKE_CXX_STANDARD_REQUIRED ON)

find_package(Qt6 6.8 REQUIRED COMPONENTS Charts Core Gui Qml Quick Sql)
set(CMAKE_AUTOMOC ON)
set(CMAKE_AUTOUIC ON)
set(CMAKE_AUTORCC ON)
find_package(Boost 1.83.0 REQUIRED)

include_directories(${Boost_INCLUDE_DIRS})
include_directories(src)  # for content/CMakeLists.txt qt6_add_qml_module SOURCES
include_directories(src/material)
include_directories(src/sql)

if (Qt6_VERSION VERSION_GREATER_EQUAL 6.8)
    qt_standard_project_setup(REQUIRES 6.8)
endif()

qt_add_executable(SuisApp WIN32 MACOSX_BUNDLE)

qt_add_resources(SuisApp "configuration"
        PREFIX "/"
        FILES
        qtquickcontrols2.conf
)

add_subdirectory(src)
include_directories(${ORACLE_INCLUDE_DIR})

include(FetchContent)
FetchContent_Declare(
        QXlsx
        GIT_REPOSITORY https://github.com/QtExcel/QXlsx.git
        GIT_TAG        v1.4.8
        SOURCE_SUBDIR  QXlsx
)
FetchContent_MakeAvailable(QXlsx)

set_target_properties(SuisApp PROPERTIES
        MACOSX_BUNDLE_BUNDLE_VERSION ${PROJECT_VERSION}
        MACOSX_BUNDLE_SHORT_VERSION_STRING ${PROJECT_VERSION_MAJOR}.${PROJECT_VERSION_MINOR}
        MACOSX_BUNDLE TRUE
        WIN32_EXECUTABLE TRUE
)

target_link_libraries(SuisApp PRIVATE
        Qt6::Charts
        Qt6::Core
        Qt6::Gui
        Qt6::Qml
        Qt6::Quick
        Qt6::Sql
        QXlsx::QXlsx
)

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

if (BUILD_QDS_COMPONENTS)
    include(${CMAKE_CURRENT_SOURCE_DIR}/qmlcomponents)
endif()

include(${CMAKE_CURRENT_SOURCE_DIR}/qmlmodules)

if (LINK_INSIGHT)
    include(${CMAKE_CURRENT_SOURCE_DIR}/insight)
endif ()

set(QML_IMPORT_PATH ${PROJECT_BINARY_DIR}/qml CACHE PATH
        "Path to the custom QML components defined by the project")

qt_generate_deploy_qml_app_script(
        TARGET SuisApp
        OUTPUT_SCRIPT deploy_script
        MACOS_BUNDLE_POST_BUILD
        NO_UNSUPPORTED_PLATFORM_ERROR
        DEPLOY_USER_QML_MODULES_ON_UNSUPPORTED_PLATFORM
)

install(SCRIPT ${deploy_script})

src/CMakeLists.txt:

target_sources(SuisApp PRIVATE
        core/BuildDevice.tpp
        core/Device.h
        core/DistFun.h
        core/GetVarSub.h
        core/ParameterClass.h
        # material headers
        material/DbSysModel.h
        material/IniConfigParser.h
        material/MaterialDbModel.h
        material/OpticMaterial.h
        material/ParameterSystem.h
        # material sources
        material/DbSysModel.cpp
        material/IniConfigParser.cpp
        material/MaterialDbModel.cpp
        material/OpticMaterial.cpp
        material/ParameterSystem.cpp
        # optics headers
        optics/FixedMatrix.h
        optics/OpticStack.h
        optics/tmm.h
        optics/TransferMatrix.h
        # optics sources
        optics/FixedMatrix.cpp
        optics/OpticStack.cpp
        optics/tmm.cpp
        optics/tmm_vec.cpp
        # sql headers
        sql/SqlTreeItem.h
        # sql sources
        sql/SqlTreeItem.cpp
        # utils headers
        utils/Approx.h
        utils/Fs.h
        utils/Log.h
        utils/Math.h
        utils/Range.h
        # utils sources
        utils/Approx.cpp
        utils/Fs.cpp
        utils/Log.cpp
        utils/Math.cpp
        utils/Range.cpp
        # top headers
        Application.h
        CommandLineParseResult.h
        Global.h
        Parameter.h
        Preferences.h
        Profile.h
        ProfilePrivate.h
        SettingsStorage.h
        # top sources
        Application.cpp
        CommandLineParseResult.cpp
        Parameter.cpp
        Preferences.cpp
        Profile.cpp
        ProfilePrivate.cpp
        SettingsStorage.cpp
        main.cpp
)

content/CMakeLists.txt:

qt_add_library(content STATIC)
qt6_add_qml_module(content
    URI "content"
    VERSION 1.0
    RESOURCE_PREFIX "/qt/qml"  # qt_policy(SET QTP0001 NEW)
    QML_FILES
        App.qml
        BandDiagramDialog.qml
        DbLoginDialog.qml
        DeviceTableDialog.qml
        ElectricalParsetPage.qml
        ElectricalParsetPageForm.ui.qml
        OpticalDeviceDialog.qml
        OpticalMaterialDialog.qml  # loader qml files cannot be omitted
        OpticalParsetPage.qml
        OpticalParsetPageForm.ui.qml
        ResultPage.qml
        ResultPageForm.ui.qml
        SimPage.qml
        Splash.qml
        SqlBrowserWindow.qml
        WelcomePage.qml
        WelcomePageForm.ui.qml
        WizardFlow.qml
        WizardFlowForm.ui.qml

    RESOURCES
        fonts/fonts.txt
        images/SuisLogo.svg
        images/arrow_icon.png

    SOURCES
        ../src/Process.h ../src/Process.cpp
        ../src/material/DeviceModel.h ../src/material/DeviceModel.cpp
        ../src/material/DevSysModel.h ../src/material/DevSysModel.cpp
        # sql headers
        ../src/sql/SqlTreeModel.h
        # sql sources
        ../src/sql/SqlTreeModel.cpp
)

[SGaist]

Hi,

If you are creating a library, you have to link the dependencies which you are not doing here.

[Yihua Liu]

@SGaist Hi,

It seems that I've already linked the library in qmlmodules:

add_subdirectory(content)
add_subdirectory(imports)

target_link_libraries(${CMAKE_PROJECT_NAME} PRIVATE
    contentplugin
    Suisplugin
)

Do you mean this?

[Yihua Liu]

It seems that the problem could be solved by appending one line

target_link_libraries(content PUBLIC Qt6::Sql)

However, it remains mysterious that on Windows this line is not necessary. Besides, why does only Qt6::Sql need to be explicitly linked but Qt6::Core doesn't?

[SGaist]

No, in your content project you have to link the Qt dependencies you are using.

[Yihua Liu]

@SGaist Thank you for your reminder anyway. Closing this thread