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

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

https://debusine.debian.net/debian/developers-gladk-eigen3/artifact/3761157/

Here is the most probably relevant part of the failing build log:
    ===========================================
/bin/bash ../../libtool  --tag=CXX   --mode=compile g++ -DHAVE_CONFIG_H -I. -I../../config  -fno-strict-aliasing -I../../include -I/usr/include/suitesparse -I/usr/include/suitesparse          -Wdate-time -D_FORTIFY_SOURCE=2 -I/usr/include/eigen3  -g  -ffile-prefix-map=/build/reproducible-path/rheolef-7.2=. -fstack-protector-strong -fstack-clash-protection -Wformat -Werror=format-security -fcf-protection -std=c++17 -fpermissive -Wno-unused -Wno-strict-aliasing -Wno-deprecated-declarations -Wno-narrowing -O2  -c -o solver.lo solver.cc
libtool: compile:  g++ -DHAVE_CONFIG_H -I. -I../../config -fno-strict-aliasing -I../../include -I/usr/include/suitesparse -I/usr/include/suitesparse -Wdate-time -D_FORTIFY_SOURCE=2 -I/usr/include/eigen3 -g -ffile-prefix-map=/build/reproducible-path/rheolef-7.2=. -fstack-protector-strong -fstack-clash-protection -Wformat -Werror=format-security -fcf-protection -std=c++17 -fpermissive -Wno-unused -Wno-strict-aliasing -Wno-deprecated-declarations -Wno-narrowing -O2 -c solver.cc  -fPIC -DPIC -o .libs/solver.o
In file included from /usr/include/eigen3/Eigen/src/CholmodSupport/CholmodSupport.h:14,
                 from solver_cholmod.h:32,
                 from solver.cc:26:
/usr/include/eigen3/Eigen/src/CholmodSupport/./InternalHeaderCheck.h:2:2: error: #error "Please include Eigen/CholmodSupport instead of including headers inside the src directory directly."
    2 | #error "Please include Eigen/CholmodSupport instead of including headers inside the src directory directly."
      |  ^~~~~
make[4]: *** [Makefile:793: solver.lo] Error 1
make[3]: *** [Makefile:687: all] Error 2
make[2]: *** [Makefile:458: all-recursive] Error 1
make[1]: *** [Makefile:536: all-recursive] Error 1
dh_auto_build: error: make -j4 returned exit code 2
make: *** [debian/rules:30: binary-arch] Error 25
dpkg-buildpackage: error: debian/rules binary-arch subprocess failed with exit status 2

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