How to deploy a Find*.cmake file for an Autotools library in the correct place for Yocto?

Question

I created a new layer over an existing Yocto git for my company project.

In this layer I added a few external autotools based libraries. A few applications need to link against this libraries and the application projects are all cmake based.

Taking one of this libraries (e.g. libcoap) I could easily find some FindCoAP.cmake to add to my library recipe.

Now if I was running on PC, it would simply be a matter of placing this FindCoAP.cmake file in cmake's ${CMAKE_ROOT}/Modules dir, but how should I, from inside a bitbake recipe (do_install hook), proceed to make my Find*.cmake modules available to anyone's dependent projects?

Should I try to get Yocto's cmake CMAKE_ROOT variable from system-information like this or is it a safer and more reliable way?

do_install_append() {
    cmake --system-information | grep CMAKE_ROOT | cut -d \" -f2
    install -d ${D}/$CMAKE_ROOT}/Modules
    install ${S}/FindCoAP.cmake ${D}/$CMAKE_ROOT}/Modules
}

Thanks in advance.

Answer 1

To ship FindFoo.cmake with non-yet-cmake project

The ideal way is to update upstream project itself. So you will update your recipe and package FindFoo.cmake appropriately.

If you want to do it right now:

1. Add FindFoo.cmake to your layer (into the files directory next to your recipe).
2. Add that cmake file to SRC_URI (i.e. SRC_URI += "file://FindFoo.cmake").
3. Install it in do_install into the directory ${D}${datadir}/cmake/Modules/ for example.
4. Package it to the dev package by FILES_${PN}-dev variable (see example recipes below).

To use that cmake by other recipe

The usual way is to package .cmake files into the ${PN}-dev package. In your case, your application (which depends on the libcoap) will just set DEPENDS = "libcoap" and all the needed files (like headers, libraries and cmake file) will be copied (well, hardlinked) to the sysroot of your application.

CMake modules are packaged in various recipes for example:

• libeigen
• opencv
• json-spirit

Your application is cmake based, so you will use inherit cmake in the recipe. Native module search path is set in cmake.bbclass.

(BTW, I do a build test of libcoap recipe from homeassistant layer and it worked, but obviously there is no cmake shipped.)