Bug#1136248: meshlab: FTBFS with libeigen3-dev 5.0 (major version transition)

[Anton Gladky]

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Package: src:meshlab
Version: 2025.07~dfsg-2
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

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

  https://debusine.debian.net/debian/developers-gladk-eigen3/artifact/3757436/

Here is the most probably relevant part of the failing build log:
    ===========================================
- -- Found OpenMP_CXX: -fopenmp (found version "4.5")
CMake Error at src/cmake/meshlab_tools.cmake:93 (_message):
  Eigen is required - at least one of VCG_ALLOW_SYSTEM_EIGEN or
  VCG_ALLOW_BUNDLED_EIGEN must be enabled and found.
Call Stack (most recent call first):
  src/vcglib/CMakeLists.txt:42 (message)


- -- Configuring incomplete, errors occurred!
	cd obj-x86_64-linux-gnu && tail -v -n \+0 CMakeCache.txt
==> CMakeCache.txt <==

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