[3dprinter-general] Bug#1148589: FTBFS: Could not find a configuration file for Eigen3

[Adrian Bunk]

Control: block -1 by 1124285

On Wed, Sep 23, 2026 at 08:20:39PM +0200, Gregor Riepl wrote:
> > 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.
> 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?
>...

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