Dear Maintainer,

your package depends on libeigen3-dev. The upstream released a
new major version of this mathematical library, 5.0.0. Some
basic information about new features and changes in this version
can be found here:

https://libeigen.gitlab.io/releases/5.0/

This is a major version change and may require code changes in packages
depending on eigen3. The key breaking changes include:

  - Minimum required C++ standard is now C++14
  - Changes in the build system integration
  - Some API name changes

orocos-kdl FTBFS with libeigen3-dev 5.0.1. The full build log is available at:

https://debusine.debian.net/debian/developers-gladk-eigen3/artifact/3759825/

Here is the most probably relevant part of the failing build log:
    ===========================================
cd /build/reproducible-path/orocos-kdl-1.5.2/.pybuild/cpython3_3.14/build/orocos_kdl/src && /usr/bin/c++ -Dorocos_kdl_EXPORTS -I/build/reproducible-path/orocos-kdl-1.5.2/.pybuild/cpython3_3.14/build/orocos_kdl/src -g -O2 -ffile-prefix-map=/build/reproducible-path/orocos-kdl-1.5.2=. -fstack-protector-strong -fstack-clash-protection -Wformat -Werror=format-security -fcf-protection -Wdate-time -D_FORTIFY_SOURCE=2 -fPIC   -I"" -MD -MT orocos_kdl/src/CMakeFiles/orocos-kdl.dir/chain.cpp.o -MF CMakeFiles/orocos-kdl.dir/chain.cpp.o.d -o CMakeFiles/orocos-kdl.dir/chain.cpp.o -c /build/reproducible-path/orocos-kdl-1.5.2/orocos_kdl/src/chain.cpp
cc1plus: error: to generate dependencies you must specify either ‘-M’ or ‘-MM’
cd /build/reproducible-path/orocos-kdl-1.5.2/.pybuild/cpython3_3.14/build/orocos_kdl/src && /usr/bin/c++ -Dorocos_kdl_EXPORTS -I/build/reproducible-path/orocos-kdl-1.5.2/.pybuild/cpython3_3.14/build/orocos_kdl/src -g -O2 -ffile-prefix-map=/build/reproducible-path/orocos-kdl-1.5.2=. -fstack-protector-strong -fstack-clash-protection -Wformat -Werror=format-security -fcf-protection -Wdate-time -D_FORTIFY_SOURCE=2 -fPIC   -I"" -MD -MT orocos_kdl/src/CMakeFiles/orocos-kdl.dir/chaindynparam.cpp.o -MF CMakeFiles/orocos-kdl.dir/chaindynparam.cpp.o.d -o CMakeFiles/orocos-kdl.dir/chaindynparam.cpp.o -c /build/reproducible-path/orocos-kdl-1.5.2/orocos_kdl/src/chaindynparam.cpp
make[3]: *** [orocos_kdl/src/CMakeFiles/orocos-kdl.dir/build.make:124: orocos_kdl/src/CMakeFiles/orocos-kdl.dir/chainexternalwrenchestimator.cpp.o] Error 1
make[3]: *** Waiting for unfinished jobs....
cc1plus: error: to generate dependencies you must specify either ‘-M’ or ‘-MM’
cc1plus: error: to generate dependencies you must specify either ‘-M’ or ‘-MM’

    ===========================================
libeigen3-dev_5.0.1-1 is available in experimental.

When this package version lands into unstable (probably at the beginning
of June 2026), this bug will be increased in severity to serious.

Thanks,

Anton