Build Qt5 with Cmake in Yocto

Question

We are cross-compiling our Qt5 application within Yocto/Bitbake using CMake for Cortex ARM 9.

No matter what I do, I can't get Cmake to find the required Qt5Config.cmake config file.

The error message is well known out there:

 CMake Error at CMakeLists.txt:71 (find_package):
 By not providing "FindQt5.cmake" in CMAKE_MODULE_PATH this project has
 asked CMake to find a package configuration file provided by "Qt5", but
 CMake did not find one.

 Could not find a package configuration file provided by "Qt5" with any of
 the following names:

     Qt5Config.cmake
     qt5-config.cmake

 Add the installation prefix of "Qt5" to CMAKE_PREFIX_PATH or set "Qt5_DIR"
 to a directory containing one of the above files.  If "Qt5" provides a
 separate development package or SDK, be sure it has been installed.

 -- Configuring incomplete, errors occurred!

The recipy seems to be fine so far. I depend Qt and use Cmake by:

RDEPENDS_${PN} += " qtconnectivity "
inherit pkgconfig cmake

Unfortunately I am uncertain about two things:

When I build Yocto (on 2 cores), why is bitbake building the qt5 packages before or at the same time as my faulty recipe? Shouldn't the dependency sort this out? I also tried to use DEPENDS instead of RDEPENDS, but that doesn't make a difference.
I don't know in which sysroots Qt is being installed. When I do find . -name Qt5Config.cmake I find so many places. One of the places looks a bit more promising than the others. It is: ./tmp/sysroots-components/cortexa9hf-neon-mx6qdl/qtbase/usr/lib/cmake/Qt5/Qt5Config.cmake. But still, shouldn't the Qt libs be in the sysroot of "my recipe"?

So, after all, I try to let CMake know the location of Qt5Config.cmake. I try by setting

export Qt5_DIR = "/home/vagrant/build/tmp/sysroots-components/cortexa9hf-neon-mx6qdl/qtbase/usr/lib/cmake/Qt5/"

in the recipe and can confirm with a CMake output that it knows the path Qt5_DIR. Also setting the path in CMake (with set(Qt5_DIR ...)) doesn't help.

The path remains unknown. Even if I would be happy now to make CMake understand where Qt5 is - there seems to be a misconfiguration, as I would assume that Qt should be known to my recipe automatically.

What else can I try?

mascoj mascoj · Accepted Answer · 2018-07-31T00:29:15

Finally got around to answering. I had the same issue for awhile and discovered the cmake_qt5 bitbake class.

Using this class in place of cmake should populate all the necessary flags needed to use Qt5 with CMake in the Yocto Project.

Build Qt5 with Cmake in Yocto

1 Answers