Installed Qt6 to Linux ... cmake ... Target "Qt6::Core" was not found

Joachim W

Ran qt-unified-linux-x64-4.2.0-online.run to install Qt6 to /usr/local/Qt6.

Set Qt6_DIR to /usr/local/Qt6/6.2.3/gcc_64/.

Updated my CMake scripts, replacing all occurences of Qt5 by Qt6.

Running cmake. Fails at line

find_package(Qt6 REQUIRED COMPONENTS Core Gui Widgets)

with error message

-- Could NOT find Qt6CoreTools (missing: Qt6CoreTools_DIR)
CMake Warning at /usr/local/Qt6/6.2.3/gcc_64/lib/cmake/Qt6/Qt6Config.cmake:177 (find_package):
  Found package configuration file:

    /usr/local/Qt6/6.2.3/gcc_64/lib/cmake/Qt6Core/Qt6CoreConfig.cmake

  but it set Qt6Core_FOUND to FALSE so package "Qt6Core" is considered to be
  NOT FOUND.  Reason given by package:

  Target "Qt6::Core" was not found.

Call Stack (most recent call first):
  CMakeLists.txt:52 (find_package)

and similar messages for components Gui and Widgets.

AlQuemist

Assuming that Qt6 is installed in /usr/local/opt/Qt/6.2.3, the following method succeeds to find Qt6 and its required components:

CMakeLists.txt:

cmake_minimum_required(VERSION 3.15 FATAL_ERROR)
project(testQt6)
set(CMAKE_CXX_STANDARD 17)
find_package(Qt6 REQUIRED COMPONENTS Core Gui Widgets)

CMake command:

cmake -B build -DCMAKE_PREFIX_PATH="/usr/local/Qt/6.2.3/gcc_64/lib/cmake"

Tested with CMake 3.22 and Qt 6.2.3 with 'Desktop gcc 64-bit' component installed, on Linux/Debian 11.

kkoehne

This looks dubious. Does that also reproduce with a minimal example, or when configuring an example from Qt?

Joachim W

Confirm with minimal example:

$ cat CMakeLists.txt

cmake_minimum_required(VERSION 3.15 FATAL_ERROR)

project(libFooBar)

set(CMAKE_CXX_STANDARD 17)

find_package(Qt6 REQUIRED COMPONENTS Core Gui Widgets)

$ export Qt6_DIR=/usr/local/Qt6/6.2.3/gcc_64/

$ cmake .
-- The C compiler identification is GNU 11.2.0
-- The CXX compiler identification is GNU 11.2.0
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working C compiler: /usr/lib/ccache/cc - skipped
-- Detecting C compile features
-- Detecting C compile features - done
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: /usr/lib/ccache/c++ - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Looking for pthread.h
-- Looking for pthread.h - found
-- Performing Test CMAKE_HAVE_LIBC_PTHREAD
-- Performing Test CMAKE_HAVE_LIBC_PTHREAD - Failed
-- Check if compiler accepts -pthread
-- Check if compiler accepts -pthread - yes
-- Found Threads: TRUE  
-- Performing Test HAVE_STDATOMIC
-- Performing Test HAVE_STDATOMIC - Success
-- Found WrapAtomic: TRUE  
-- Could NOT find Qt6CoreTools (missing: Qt6CoreTools_DIR)
CMake Warning at /usr/local/Qt6/6.2.3/gcc_64/lib/cmake/Qt6/Qt6Config.cmake:177 (find_package):
  Found package configuration file:

    /usr/local/Qt6/6.2.3/gcc_64/lib/cmake/Qt6Core/Qt6CoreConfig.cmake

  but it set Qt6Core_FOUND to FALSE so package "Qt6Core" is considered to be
  NOT FOUND.  Reason given by package:

  Target "Qt6::Core" was not found.

Call Stack (most recent call first):
  CMakeLists.txt:7 (find_package)


-- Found OpenGL: /usr/lib/x86_64-linux-gnu/libOpenGL.so   
-- Found WrapOpenGL: TRUE  
-- Could NOT find XKB (missing: XKB_LIBRARY XKB_INCLUDE_DIR) (Required is at least version "0.5.0")
-- Found WrapVulkanHeaders: /usr/include  
-- Could NOT find Qt6GuiTools (missing: Qt6GuiTools_DIR)
...

(corrected; previous version had CMake output obtained with other Qt6_DIR)

AlQuemist

Assuming that Qt6 is installed in /usr/local/opt/Qt/6.2.3, the following method succeeds to find Qt6 and its required components:

CMakeLists.txt:

cmake_minimum_required(VERSION 3.15 FATAL_ERROR)
project(testQt6)
set(CMAKE_CXX_STANDARD 17)
find_package(Qt6 REQUIRED COMPONENTS Core Gui Widgets)

CMake command:

cmake -B build -DCMAKE_PREFIX_PATH="/usr/local/Qt/6.2.3/gcc_64/lib/cmake"

Tested with CMake 3.22 and Qt 6.2.3 with 'Desktop gcc 64-bit' component installed, on Linux/Debian 11.

Harlock21

I am using the latest cmake 3.24.0 rc2 , qt 6.3.1 and can confirm that the issue still persists.
My cmake command is:
cmake .. -DCMAKE_PREFIX_PATH=/home/michal/Qt/6.3.1/gcc_64/lib/cmake/Qt6

Is there any solution for that? can it be the cmake rc ?

Croitor Alexandru

Finding Qt just by setting Qt6_DIR currently does not work.
That is tracked in https://bugreports.qt.io/browse/QTBUG-97615 and will be fixed in a future Qt version, but only for desktop platforms.

For cross-compiled Qt, that won't be sufficient. For details, check https://forum.qt.io/topic/137551/cmake-finds-cross-compiled-qt6-config-files-but-qt6_found-is-set-to-false/5