Hi,

The package FTBFS in unstable:

CMake Error at CMakeLists.txt:379 (find_package):
  Could not find a configuration file for package "Eigen3" that is compatible
  with requested version "3.3.7".

  The following configuration files were considered but not accepted:

    /usr/share/eigen3/cmake/Eigen3Config.cmake, version: 5.0.1
      The version found is not compatible with the version requested.





Full build log is enclosed.

Best,

- --
Pierre
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libeigen3 was updated to version 5.0 in sid, which has some breaking changes.

Changing "find_package(Eigen3 3.3.7 REQUIRED)" to "find_package(Eigen3 3.3...5 REQUIRED)" helps getting the build process going, but there are other issues.

I tried fixing the include path by adding "target_link_libraries(<target> Eigen3::Eigen)" to all affected targets, as documented in [1] - this works mostly, except for libslic3r, which still doesn't build.

Can somebody help?

[1] https://libeigen.gitlab.io/eigen/docs-5.0/TopicCMakeGuide.html

Control: block -1 by 1124285

Dropping Drop-Eigen3-Eigen-link.patch seems to fix these issues.

A bigger issue is the usage of DynamicSparseMatrix in the ancient
vendored libigl. bundled_deps/libigl/CMakeLists.txt uses a system
libigl if it exists, this seems to be the proper way forward for
that issue.

cu
Adrian

We believe that the bug you reported is fixed in the latest version of
slic3r-prusa, which is due to be installed in the Debian FTP archive.

A summary of the changes between this version and the previous one is
attached.

Thank you for reporting the bug, which will now be closed.  If you
have further comments please address them to 1148589@bugs.debian.org,
and the maintainer will reopen the bug report if appropriate.

Debian distribution maintenance software
pp.
Chow Loong Jin <hyperair@debian.org> (supplier of updated slic3r-prusa package)

(This message was generated automatically at their request; if you
believe that there is a problem with it please contact the archive
administrators by mailing ftpmaster@ftp-master.debian.org)
Format: 1.8
Date: Tue, 06 Oct 2026 10:30:58 +0800
Source: slic3r-prusa
Built-For-Profiles: derivative.ubuntu noudeb
Architecture: source
Version: 2.9.6+dfsg-2
Distribution: unstable
Urgency: medium
Maintainer: Debian 3-D Printing Packages <3dprinter-general@lists.alioth.debian.org>
Changed-By: Chow Loong Jin <hyperair@debian.org>
Closes: 1148589
Changes:
 slic3r-prusa (2.9.6+dfsg-2) unstable; urgency=medium
 .
   [ Antoine Lassagne ]
   * Fix Eigen3-related FTBFS (Closes: #1148589)
     - [27612b1] d/patches: support Eigen3 5.0
     - [0caeefb] d/patches: drop Drop_Eigen3_Eigen_link.patch
     - [88ea131] d/patches: adapt the embedded libigl to Eigen3 5
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