Yocto SDK with cmake toolchain file

Question

I provide a Yocto SDK to cross-build an application for an embedded target. The application itself is built using CMake. The SDK setup script provides many necessary environment variables (like location of the cross-compiler, sysroot, etc.), which so far was enough to build the application.

However, since recently the application has a dependency to the Boost library (through the command find_package(Boost REQUIRED) in the CMakeLists.txt). Now CMake complains that it cannot find the library, even though it's installed in the SDK sysroot. But if I build the application directly in Yocto, it works fine.

After some research it turned out that Yocto generates a toolchain.cmake file which is added to the cmake call. In this file, the variable CMAKE_FIND_ROOT_PATH is set, which CMake needs to find libraries. Using such a toolchain file, I can also build using the SDK.

Now I'm wondering if Yocto provides any mechanism to export such a toolchain file with the SDK. Or alternatively if the SDK provides a script or something to automatically create a toolchain file directly on the SDK build host.

Or shall I just tell the users of the SDK to manually create a toolchain file and add it to their cmake call?

Answer 1

Assuming that you're using the image based SDK, i.e. building it with bitbake <image> -c populate_sdk, adding the following toimage.bb should fix it:

TOOLCHAIN_HOST_TASK += "nativesdk-cmake"

That should give you a OEToolchainConfig.cmake file in the SDK. After sourcing the SDK environment file, cmake will be an alias to cmake -DCMAKE_TOOLCHAIN_FILE=$OECORE_NATIVE_SYSROOT/usr/share/cmake/OEToolchainConfig.cmake to further help your developers.