Creating a QT Project with CMake - c++

Question

I am trying to set up a QT project with CMake (and not using QT Creator).
I am currently trying to build a minimum working example, that just shows an empty window. My current code is based (more like coppied) from this tutorial from the official (?) docs and this answer by another user to a similar question.
I then run the following three commands:
cmake .
cmake --build .
.\Debug\helloworld.exe
But nothing happens (when running the program, the first two commands appear to work as intended). If I put the code from main.cpp into an existing QT Creator project it works and shows an empty window. Anyone can tell me, what I am missing?
main.cpp
#include <QApplication>
#include <QWidget>
#include <QMainWindow>
int main(int argc, char *argv[])
{
QApplication app(argc, argv);
//Option 1, like in the mentioned stackoverflow answer
//QWidget window;
//Option 2, to test If maybe the QWidget above was the problem
QMainWindow window;
window.setWindowTitle("Test");
window.show();
return app.exec();
}
CMakeList.txt
cmake_minimum_required(VERSION 3.16)
project(helloworld VERSION 1.0.0 LANGUAGES CXX)
set(CMAKE_CXX_STANDARD 17)
set(CMAKE_CXX_STANDARD_REQUIRED ON)
# Without this line, cmake does not find the package
set(CMAKE_PREFIX_PATH "C:/Qt/6.3.1/msvc2019_64")
find_package(Qt6 REQUIRED COMPONENTS Widgets)
qt_standard_project_setup()
add_executable(helloworld
main.cpp
)
target_link_libraries(helloworld PRIVATE Qt6::Widgets)
set_target_properties(helloworld PROPERTIES
WIN32_EXECUTABLE ON
MACOSX_BUNDLE ON
)
EDIT:
As suggested by Aamir I created an extra build folder. The output of the three comands is as follows:
One more thing, if I replace the code in main.cpp with a simple "Hello World" programm, it works fine. I therefore assumed, that the missing/failed parts in the first cmake command are no problem. Or am I wrong about that part?
PS H:\Coding\QT_Tic_Tac_toe> mkdir build
Directory: H:\Coding\QT_Tic_Tac_toe
Mode LastWriteTime Length Name
---- ------------- ------ ----
d----- 19/08/2022 10:11 build
PS H:\Coding\QT_Tic_Tac_toe> cd .\build\
PS H:\Coding\QT_Tic_Tac_toe\build> cmake ..
-- Building for: Visual Studio 17 2022
-- Selecting Windows SDK version 10.0.19041.0 to target Windows 10.0.19043.
-- The CXX compiler identification is MSVC 19.32.31332.0
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: C:/Program Files/Microsoft Visual Studio/2022/Community/VC/Tools/MSVC/14.32.31326/bin/Hostx64/x64/cl.exe - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Performing Test CMAKE_HAVE_LIBC_PTHREAD
-- Performing Test CMAKE_HAVE_LIBC_PTHREAD - Failed
-- Looking for pthread_create in pthreads
-- Looking for pthread_create in pthreads - not found
-- Looking for pthread_create in pthread
-- Looking for pthread_create in pthread - not found
-- Found Threads: TRUE
-- Performing Test HAVE_STDATOMIC
-- Performing Test HAVE_STDATOMIC - Success
-- Found WrapAtomic: TRUE
-- Could NOT find WrapVulkanHeaders (missing: Vulkan_INCLUDE_DIR)
-- Configuring done
-- Generating done
-- Build files have been written to: H:/Coding/QT_Tic_Tac_toe/build
PS H:\Coding\QT_Tic_Tac_toe\build> cmake --build .
Microsoft (R) Build Engine version 17.2.1+52cd2da31 for .NET Framework
Copyright (C) Microsoft Corporation. All rights reserved.
Checking Build System
Automatic MOC and UIC for target helloworld
Building Custom Rule H:/Coding/QT_Tic_Tac_toe/CMakeLists.txt
mocs_compilation_Debug.cpp
main.cpp
Generating Code...
helloworld.vcxproj -> H:\Coding\QT_Tic_Tac_toe\build\Debug\helloworld.exe
Building Custom Rule H:/Coding/QT_Tic_Tac_toe/CMakeLists.txt
PS H:\Coding\QT_Tic_Tac_toe\build> .\Debug\helloworld.exe
PS H:\Coding\QT_Tic_Tac_toe\build>

Answer 1

You need to add the Qt DLL directory to the PATH environment variable either permanently or before calling the program from the console as follows:
set PATH=C:\Qt\6.3.1\msvc2019_64\bin;%PATH%
If you would have started your application from a cmd console window an error dialog would have popped up notifying you about the missing DLL. But as you were using PowerShell there is a bug pending (see here) that prevents the error dialog to be shown.
NB: You can call cmd from a PowerShell window to get the old console window.