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

g2o FTBFS with libeigen3-dev 5.0.1. The full build log is available at:

https://debusine.debian.net/debian/developers-gladk-eigen3/artifact/3755814/

Here is the most probably relevant part of the failing build log:
    ===========================================
The following information may help to resolve the situation:

The following packages have unmet dependencies:
 sbuild-build-depends-main-dummy : Depends: debhelper (>= 11) but it is not going to be installed
                                   Depends: cmake but it is not going to be installed
                                   Depends: libopenblas-dev but it is not going to be installed
                                   Depends: libsuitesparse-dev but it is not going to be installed
                                   Depends: libopengl-dev but it is not going to be installed
                                   Depends: libqglviewer-headers but it is not going to be installed
                                   Depends: libeigen3-dev but it is not going to be installed
                                   Depends: libglut-dev but it is not going to be installed
                                   Depends: libtbb-dev but it is not going to be installed
                                   Depends: libmetis-dev but it is not going to be installed
                                   Depends: libceres-dev but it is not going to be installed
                                   Depends: libgmock-dev but it is not going to be installed
E: Unable to satisfy dependencies. Reached two conflicting assignments:
   1. libceres-dev:amd64 is selected for install because:
      1. sbuild-build-depends-main-dummy:amd64=0.invalid.0 is selected for install
      2. sbuild-build-depends-main-dummy:amd64 Depends libceres-dev
   2. libceres-dev:amd64 Depends libeigen3-dev (< 3.4.1)
      but none of the choices are installable:
      - libeigen3-dev:amd64=3.4.0-5 is not selected for install
apt-get failed.
E: Package installation failed

    ===========================================
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

Dear maintainers,

eigen3 5.0 (libeigen3-dev 5.0) is now in unstable, so these FTBFS bugs are
release-critical.  I am therefore raising their severity to serious.

Regards,

Anton