[Debichem-devel] Bug#1136308: openbabel: FTBFS with libeigen3-dev 5.0 (major version transition)

[Anton Gladky]

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Package: src:openbabel
Version: 3.1.1+dfsg-14
Severity: important
Tags: sid forky ftbfs
User: debian-devel at lists.debian.org
Usertags: eigen3-5.0

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

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

  https://debusine.debian.net/debian/developers-gladk-eigen3/artifact/3759397/

Here is the most probably relevant part of the failing build log:
    ===========================================
[ 86%] Building CXX object scripts/CMakeFiles/bindings_python.dir/python/openbabel/openbabel-python.cpp.o
cd /build/reproducible-path/openbabel-3.1.1+dfsg/builddir/scripts && /usr/bin/c++ -DHAVE_LIBZ -DHAVE_RADPIJSON -DHAVE_SHARED_POINTER -DHAVE_WXWIDGETS -DUSING_DYNAMIC_LIBS -DWXUSINGDLL -D_FILE_OFFSET_BITS=64 -D__WXGTK__ -Dbindings_python_EXPORTS -I/build/reproducible-path/openbabel-3.1.1+dfsg/builddir/include -I/build/reproducible-path/openbabel-3.1.1+dfsg/data -I/build/reproducible-path/openbabel-3.1.1+dfsg/include -I/usr/include/python3.13 -I/usr/lib/x86_64-linux-gnu/perl/5.40/CORE -isystem /usr/lib/x86_64-linux-gnu/wx/include/gtk3-unicode-3.2 -isystem /usr/include/wx-3.2 -g -O2 -ffile-prefix-map=/build/reproducible-path/openbabel-3.1.1+dfsg=. -fstack-protector-strong -fstack-clash-protection -Wformat -Werror=format-security -fcf-protection -Wdate-time -D_FORTIFY_SOURCE=2 -Wdate-time -D_FORTIFY_SOURCE=2 -pthread -fopenmp -fPIC -MD -MT scripts/CMakeFiles/bindings_python.dir/python/openbabel/openbabel-python.cpp.o -MF CMakeFiles/bindings_python.dir/python/openbabel/openbabel-python.cp
 p.o.d -o CMakeFiles/bindings_python.dir/python/openbabel/openbabel-python.cpp.o -c /build/reproducible-path/openbabel-3.1.1+dfsg/scripts/python/openbabel/openbabel-python.cpp
In file included from /build/reproducible-path/openbabel-3.1.1+dfsg/scripts/python/openbabel/openbabel-python.cpp:3455:
/build/reproducible-path/openbabel-3.1.1+dfsg/include/openbabel/math/align.h:26:10: fatal error: Eigen/Core: No such file or directory
   26 | #include <Eigen/Core>
      |          ^~~~~~~~~~~~
compilation terminated.

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