Issue with linking when build in yocto

[sapoluri]

I tried to include this package in meta-ros2-foxy by adding yocto recipes and compile it.
However, it fails with the following:
CMakeFiles/gscam_main.dir/src/gscam_node.cpp.o: undefined reference to symbol 'gst_base_sink_get_type'
| ..../recipe-sysroot/usr/lib/libgstbase-1.0.so.0: error adding symbols: DSO missing from command line

I notice in the CMakeCache.txt that under the gscam_node_LIB_DEPENDS, I see gstapp-1.0.so but gstbase-1.0 and gstreamer-1.0 are missing. Which is causing the above error. However, gstbase-1.0 and gstreamer-1.0 are installed to the same location as gstapp-1.0 and the library files contain the above required symbol.

I am at a complete loss as to why this failure is happening and how to go about debugging this. I am neither a Yocto build expert nor a CMake expert but I have done all the due diligence I know how to, to ensure that all the libraries are available and the paths are set properly.

Can someone please help?!

[clydemcqueen]

The CMakeLists.txt file uses PkgConfig (not CMake) to find gstreamer libraries. I know little about PkgConfig, but the docs are here: https://people.freedesktop.org/~dbn/pkg-config-guide.html

This is building fine on my Ubuntu 20.04 install. If I understand the flow correctly, PkgConfig reads and parses gstreamer-app-1.0.pc, discovers a dependency on gstreamer-1.0 and gstreamer-base-1.0, so PkgConfig further reads and parses gstreamer-base-1.0.pc. There the library gstbase-1.0 is listed. These libraries are bound to the symbol GST_APP, and then the Ament macro ament_target_dependencies add those libraries to the call to target_link_libraries.

I don't know why this flow breaks in your build. I would look at the various *.pc files to see if the PkgConfig dependency chain is broken.

A brute force fix is to add the the library directly: target_link_libraries(gscam_node libgstbase-1.0.so).

You could also try pkg_check_modules(GSTBASE REQUIRED gstreamer-base-1.0) and then add GSTBASE to GSCAM_NODE_DEPS.

[sapoluri]

So I had already tried both the methods that you suggested prior to creating this issue and failed but I eventually did find a way to resolve the issue.

I added the following to the CMakeLists.txt:

target_link_libraries(gscam_main
libgstbase-1.0.so
libgstreamer-1.0.so
libgobject-2.0.so
libglib-2.0.so
)

I am not sure how the build works on ubuntu even though the explicitly link libraries for gscam_main are not specified.