Qt. Copying file error while trying to run the project. How to fix a mistake and why is it happening?

Question

I’m trying to install and create the first Qt project. I am using CLion with CMake and Qt 6. I set up CMake:

cmake_minimum_required(VERSION 3.17)
project(QSnake)

set(CMAKE_CXX_STANDARD 20)
set(CMAKE_AUTOMOC ON)
set(CMAKE_AUTORCC ON)
set(CMAKE_AUTOUIC ON)

set(QT_VERSION 6)
set(REQUIRED_LIBS Core Gui Widgets)
set(REQUIRED_LIBS_QUALIFIED Qt6::Core Qt6::Gui Qt6::Widgets)

set(CMAKE_PREFIX_PATH D:/Qt/6.0.2/mingw81_64/lib/cmake)

add_executable(${PROJECT_NAME} main.cpp)

if(NOT CMAKE_PREFIX_PATH)
    message(WARNING "CMAKE_PREFIX_PATH is not defined, you may need to set it "
                    "(-DCMAKE_PREFIX_PATH=\"path/to/Qt/lib/cmake\" or -DCMAKE_PREFIX_PATH=/usr/include/{host}/qt{version}/ on Ubuntu)")
endif()
find_package(Qt${QT_VERSION} COMPONENTS ${REQUIRED_LIBS} REQUIRED)
target_link_libraries(${PROJECT_NAME} ${REQUIRED_LIBS_QUALIFIED})
if(WIN32)
    set(DEBUG_SUFFIX)
    if (CMAKE_BUILD_TYPE MATCHES "Debug")
        set(DEBUG_SUFFIX "d")
    endif()
    set(QT_INSTALL_PATH "${CMAKE_PREFIX_PATH}")
    if(NOT EXISTS "${QT_INSTALL_PATH}/bin")
        set(QT_INSTALL_PATH "${QT_INSTALL_PATH}/..")
        if(NOT EXISTS "${QT_INSTALL_PATH}/bin")
            set(QT_INSTALL_PATH "${QT_INSTALL_PATH}/..")
        endif()
    endif()
    if(EXISTS "${QT_INSTALL_PATH}/plugins/platforms/qwindows${DEBUG_SUFFIX}.dll")
        add_custom_command(TARGET ${PROJECT_NAME} POST_BUILD
                COMMAND ${CMAKE_COMMAND} -E make_directory
                "$<TARGET_FILE_DIR:${PROJECT_NAME}>/plugins/platforms/")
        add_custom_command(TARGET ${PROJECT_NAME} POST_BUILD
                COMMAND ${CMAKE_COMMAND} -E copy
                "${QT_INSTALL_PATH}/plugins/platforms/qwindows${DEBUG_SUFFIX}.dll"
                "$<TARGET_FILE_DIR:${PROJECT_NAME}>/plugins/platforms/")
    endif()
    foreach(QT_LIB ${REQUIRED_LIBS})
        add_custom_command(TARGET ${PROJECT_NAME} POST_BUILD
                COMMAND ${CMAKE_COMMAND} -E copy
                "${QT_INSTALL_PATH}/bin/Qt${QT_VERSION}${QT_LIB}${DEBUG_SUFFIX}.dll"
                "$<TARGET_FILE_DIR:${PROJECT_NAME}>")
    endforeach(QT_LIB)
endif()

Actually, this is how it was generated when the CLion project was created. I only set the path: D:/Qt/6.0.2/mingw81_64/lib/cmake

Just in case, I will also add the main.c code. It is also generated by CLion.

#include <QApplication>
#include <QPushButton>

int
main(int argc,
     char *argv[])
{
    QApplication a(argc, argv);
    QPushButton button("Hello world!", nullptr);
    button.resize(200, 100);
    button.show();
    return QApplication::exec();
}

I don’t see any problems with CMake, but when I try to run the project there is an error:

Error copying file "D:/Qt/6.0.2/mingw81_64/lib/cmake/../../bin/Qt6Cored.dll" to "D:/QSnake/cmake-build-debug".
mingw32-make[3]: *** [CMakeFiles\QSnake.dir\build.make:126: QSnake.exe] Error 1
mingw32-make[3]: *** Deleting file 'QSnake.exe'
mingw32-make[2]: *** [CMakeFiles\Makefile2:96: CMakeFiles/QSnake.dir/all] Error 2
mingw32-make[1]: *** [CMakeFiles\Makefile2:103: CMakeFiles/QSnake.dir/rule] Error 2
mingw32-make: *** [Makefile:137: QSnake] Error 2

What is this error and how do I fix it? I understand that there is no problem with build - only a copying error. And should copied dll be called "Cored" and not "Core"?

Thank you for your attention! If you need any additional information, please let me know - I will try to clarify the question.

Answer 1

Problem solved. Whether it is useful to anyone, but the CMake automatically generated by CLion contains rows that cause an error in debug mode (adds 'd' suffix to all dll files):

if (CMAKE_BUILD_TYPE MATCHES "Debug")
    set(DEBUG_SUFFIX "d")
endif()

Deleting those lines saved me :)