Current build configuration produces the following error on my linux platform:

[ 49%] Automatic MOC and UIC for target pcl_cc_tool_fpfh_estimation
[ 49%] Built target pcl_cc_tool_fpfh_estimation_autogen
[ 49%] Building CXX object apps/cloud_composer/CMakeFiles/pcl_cc_tool_fpfh_estimation.dir/pcl_cc_tool_fpfh_estimation_autogen/mocs_compilation.cpp.o
[ 49%] Building CXX object apps/cloud_composer/CMakeFiles/pcl_cc_tool_fpfh_estimation.dir/tools/fpfh_estimation.cpp.o
[ 49%] Linking CXX shared library ../../lib/cloud_composer_plugins/libpcl_cc_tool_fpfh_estimation.so
/usr/bin/ld: ../../lib/libpcl_cc_tool_interface.a(cloud_item.cpp.o): warning: relocation against `_ZN3pcl6traits4nameINS_12_PointXYZRGBENS_6fields1yELi0EE5valueE' in read-only section `.text._ZN3pcl13createMappingINS_11PointXYZRGBEEEvRKSt6vectorINS_13PCLPointFieldESaIS3_EERS2_INS_6detail12FieldMappingESaIS9_EE[_ZN3pcl13createMappingINS_11PointXYZRGBEEEvRKSt6vectorINS_13PCLPointFieldESaIS3_EERS2_INS_6detail12FieldMappingESaIS9_EE]'
/usr/bin/ld: ../../lib/libpcl_cc_tool_interface.a(mocs_compilation.cpp.o): relocation R_X86_64_PC32 against symbol `_ZN3pcl14cloud_composer15PropertiesModel16staticMetaObjectE' can not be used when making a shared object; recompile with -fPIC
/usr/bin/ld: final link failed: bad value
collect2: error: ld returned 1 exit status
make[2]: *** [apps/cloud_composer/CMakeFiles/pcl_cc_tool_fpfh_estimation.dir/build.make:209: lib/cloud_composer_plugins/libpcl_cc_tool_fpfh_estimation.so.1.15.1.99] Error 1
make[1]: *** [CMakeFiles/Makefile2:9741: apps/cloud_composer/CMakeFiles/pcl_cc_tool_fpfh_estimation.dir/all] Error 2
make: *** [Makefile:136: all] Error 2

At the moment I can not confirm neither necessity, neither the lack of necessity of pcl_cc_tool_interface to be a static library in recent versions of PCL. But these changes will fix the error.

Could you elaborate a bit @sumir0 - since it is already building on both 20.04, 22.04 and 24.04 on our CI before this?

I have seen it fail a few times on the ubuntu-variety CI: https://dev.azure.com/PointCloudLibrary/pcl/_build?definitionId=15 So far it only happened when gcc was used. Might also be related to CMAKE_BUILD_TYPE?

@larshg I did a few more tests, and it is probably not related to the chosen value of CMAKE_BUILD_TYPE. Instead, I found that the error happens with gcc when Qt6 is used, but not when Qt5 is used (everything else kept the same, VTK build from source both times). I don't know why this is the case, but then it is clear why the error only appears on the ubuntu-variety CI: because only there, PCL is built with gcc+Qt6. The regular "Build" CI uses gcc+Qt5 or MSVC+Qt6 or Clang on macOS + Qt6

Thank you for tests and #6415! I couldn't figure out the reason to why CI doesn't fail and my build fails at the time. But now reading your comments I think it is indeed somehow caused by the fact that I build PCL with GCC and Qt6

@larshg I would propose that we merge this PR soon. I know that you started #6415 which could make this one unnecessary, but currently that PR does not build successfully and I don't know how long it will take until that one is ready? So I think it would be good to merge this one as soon as possible to have the PCL apps build successfully on Ubuntu 26.04 again. And when #6415 is ready, we can still merge that one for the other fixes it provides.