understanding cmake -part 1-

MasterQ

Hi,

I have a very small cmake project for learning Qt. Now I have put my source code (cpp, h, ui) into a subdirectory (prg) of the project.

CMakeList.txt:

cmake_minimum_required(VERSION 3.16)

project(FoE VERSION 0.1 LANGUAGES CXX)

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

set(CMAKE_CXX_STANDARD 20)
set(CMAKE_CXX_STANDARD_REQUIRED ON)

set(CMAKE_PREFIX_PATH "/home/joachim/Qt/6.7.2/gcc_64/lib/cmake/")

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

add_subdirectory(prg)

and

prg/CMakeList.txt

cmake_minimum_required(VERSION 3.16)

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

add_executable(FoE ${PROJECT_SOURCES})

target_link_libraries(FoE Qt${QT_VERSION_MAJOR}::Widgets Qt${QT_VERSION_MAJOR}::Sql)
target_include_directories(FoE INTERFACE ${CMAKE_CURRENT_SOURCE_DIR})

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

I also have a second cmake project from some month ago and this has to be different. The important part is:

find_package(Qt6 REQUIRED COMPONENTS Widgets)
find_package(Qt6 REQUIRED COMPONENTS Core)
find_package(Qt6 REQUIRED COMPONENTS Sql)

If I omit the lines with find_package(QT NAMES Qt6 REQUIRED COMPONENTS Widgets),
cmakes complains.

CMake Error at CMakeLists.txt:xx (find_package):
  By not providing "FindQt.cmake" in CMAKE_MODULE_PATH this project has asked
  CMake to find a package configuration file provided by "Qt", but CMake did
  not find one.

Why is the behaviour of the two projects different? They are on the same machine, same Qt installation, same IDE, ...

Do I miss something?

Joachim

Christian Ehrlicher

Simply use find_package(Qt6 REQUIRED COMPONTENS Widgets Sql and target_link_libraries(FoE PRIVATE Qt6::Widgets Qt6::Sql) - don't think you will ever support anything other than Qt6 so it's not worth the trouble.

Pl45m4

@MasterQ said in understanding cmake -part 1-:

Why is the behaviour of the two projects different?

If you remove the package dependency, it won't work anymore as expected... so what is different?!

Christian Ehrlicher

Simply use find_package(Qt6 REQUIRED COMPONTENS Widgets Sql and target_link_libraries(FoE PRIVATE Qt6::Widgets Qt6::Sql) - don't think you will ever support anything other than Qt6 so it's not worth the trouble.

MasterQ

@Christian-Ehrlicher said in understanding cmake -part 1-:

Simply use find_package(Qt6 REQUIRED COMPONTENS Widgets Sql and target_link_libraries(FoE PRIVATE Qt6::Widgets Qt6::Sql) - don't think you will ever support anything other than Qt6 so it's not worth the trouble.

Year, that's it.

OK, still not knowing what the real root cause is behind. Nevermind, it is running now.

Thnx