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rwgk
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Apr 13, 2026
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| else() | ||
| find_package(Eigen3 3.2.7 QUIET CONFIG) | ||
| find_package(Eigen3 3.2.7...5 QUIET CONFIG) |
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With a lot of help from Cursor GPT-5.4 Extra High Fast:
One small suggestion: I think this would be a bit clearer and more robust as a two-step CONFIG probe instead of 3.2.7...5.
I checked this locally, and 3.2.7...5 is not a wildcard for “any 5.x” in standard CMake version semantics. It is a bounded range whose upper endpoint is effectively 5.0.0. The reason this still passed with Eigen 5.0.1 in CI seems to be that the particular package version file accepted it, but that is package-specific behavior rather than something I would want to rely on.
Something like this seems safer and more explicit:
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
@@
- find_package(Eigen3 3.2.7...5 QUIET CONFIG)
- set(EIGEN3_FOUND ${Eigen3_FOUND})
- set(EIGEN3_VERSION ${Eigen3_VERSION})
+ find_package(Eigen3 3.2.7 QUIET CONFIG)
+ if(NOT Eigen3_FOUND)
+ find_package(Eigen3 5 QUIET CONFIG)
+ endif()
+ set(EIGEN3_FOUND ${Eigen3_FOUND})
+ set(EIGEN3_VERSION ${Eigen3_VERSION})
if(NOT EIGEN3_FOUND)
# Couldn't load via target, so fall back to allowing module mode finding, which will pick up
# tools/FindEigen3.cmake
# XXX: MODULE mode does not work with Eigen 5
find_package(Eigen3 3.2.7 QUIET)Also, please add something like the following to the PR description:
This intentionally fixes the
CONFIG-mode path and normalizes the legacyEIGEN3_*variables after theCONFIGprobe. It does not touch the oldtools/FindEigen3.cmakelogic, which is more invasive and easier to get wrong. In other words, this is a targeted compatibility fix for environments that provide anEigen3Config.cmake, while leaving the legacy MODULE-mode finder as a fallback for older setups.
I think that extra explanation would help reviewers understand why this “band-aid” approach is actually a good first step here.
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I just pushed commits to merge master and apply the change suggested here (commit f303db9).
Motivation: Eigen-related CI errors under #6042, blocking the v3.0.4 patch release I'm working on.
The plan is to get the CI working again on master, then cherry-pick the required changes into #6042 to unblock the v3.0.4 release.
Collaborator
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Dumping this here JIC it's useful later: |
Collaborator
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Also dumping this here JIC it's useful later: Cursor GPT-5.4 Extra High Fast 1. What determines which Eigen version a job uses now, and will that float?Jobs fall into two buckets. Jobs that pass - name: Configure
run: >
cmake -S. -Bbuild -Werror=dev
-DPYBIND11_WERROR=ON
-DPYBIND11_PYTEST_ARGS=-v
-DDOWNLOAD_CATCH=ON
-DDOWNLOAD_EIGEN=ON
${{ inputs.cmake-args }}set(PYBIND11_EIGEN_VERSION_AND_HASH
"3.4.0;929bc0e191d0927b1735b9a1ddc0e8b77e3a25ec"
CACHE STRING "Eigen version to use for tests, format: VERSION;HASH")Jobs that do not pass
- uses: actions/checkout@v6
- name: Add Python 3
run: apt-get update; apt-get install -y python3-dev python3-numpy python3-pytest python3-pip libeigen3-dev
- name: Update pip
run: python3 -m pip install --upgrade pip
- name: Update CMake
uses: jwlawson/actions-setup-cmake@v2.2
- name: Configure
shell: bash
run: >
cmake -S . -B build
-DPYBIND11_WERROR=ON
-DDOWNLOAD_CATCH=ON
-DCMAKE_CXX_STANDARD=${{ matrix.std }}
-DCMAKE_CXX_FLAGS="${{ matrix.cxx_flags }}"
-DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)") - sys: mingw64
env: x86_64
extra_install: |
mingw-w64-x86_64-python-numpy
mingw-w64-x86_64-python-scipy
mingw-w64-x86_64-eigen3So the practical answer is:
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Avoid relying on package-specific handling of a bounded version range when discovering Eigen through Eigen3Config.cmake. Made-with: Cursor
Explain that the MODULE-mode fallback only exists for older Eigen 3 setups so the remaining fallback path does not look like an unresolved Eigen 5 issue. Made-with: Cursor
Collaborator
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The CI passed:
I'll push another commit to update just a comment, marked with |
Document the Eigen 5 CMake package detection fix in the 3.0.4 release notes before merging the PR. Made-with: Cursor
Collaborator
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I replaced the PR description. I'll merge to unblock #6042. |
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Apr 18, 2026
* build: support Eigen 5 fix pybind#6034 * build: probe Eigen 3 and 5 separately in CMake config mode Avoid relying on package-specific handling of a bounded version range when discovering Eigen through Eigen3Config.cmake. Made-with: Cursor * [skip ci] build: clarify Eigen 5 module fallback comment Explain that the MODULE-mode fallback only exists for older Eigen 3 setups so the remaining fallback path does not look like an unresolved Eigen 5 issue. Made-with: Cursor * [skip ci] docs: add Eigen 5 entry to v3.0.4 changelog Document the Eigen 5 CMake package detection fix in the 3.0.4 release notes before merging the PR. Made-with: Cursor --------- Co-authored-by: Eisuke Kawashima <e-kwsm@users.noreply.github.com> Co-authored-by: Ralf W. Grosse-Kunstleve <rgrossekunst@nvidia.com>
rwgk
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* build: support Eigen 5 fix pybind#6034 * build: probe Eigen 3 and 5 separately in CMake config mode Avoid relying on package-specific handling of a bounded version range when discovering Eigen through Eigen3Config.cmake. Made-with: Cursor * build: clarify Eigen 5 module fallback comment Explain that the MODULE-mode fallback only exists for older Eigen 3 setups so the remaining fallback path does not look like an unresolved Eigen 5 issue. Made-with: Cursor * docs: add Eigen 5 entry to v3.0.4 changelog Document the Eigen 5 CMake package detection fix in the 3.0.4 release notes before merging the PR. Made-with: Cursor --------- Co-authored-by: Eisuke Kawashima <e-kwsm@users.noreply.github.com> Co-authored-by: Ralf W. Grosse-Kunstleve <rgrossekunst@nvidia.com>
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Apr 19, 2026
* build: support Eigen 5 fix #6034 * build: probe Eigen 3 and 5 separately in CMake config mode Avoid relying on package-specific handling of a bounded version range when discovering Eigen through Eigen3Config.cmake. Made-with: Cursor * build: clarify Eigen 5 module fallback comment Explain that the MODULE-mode fallback only exists for older Eigen 3 setups so the remaining fallback path does not look like an unresolved Eigen 5 issue. Made-with: Cursor * docs: add Eigen 5 entry to v3.0.4 changelog Document the Eigen 5 CMake package detection fix in the 3.0.4 release notes before merging the PR. Made-with: Cursor --------- Co-authored-by: Eisuke Kawashima <e-kwsm@users.noreply.github.com> Co-authored-by: Ralf W. Grosse-Kunstleve <rgrossekunst@nvidia.com>
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Fix #6034.
This PR improves test-time Eigen discovery so environments with an installed Eigen 5 package can be found through
Eigen3Config.cmakewithout regressing older Eigen 3 setups.What changes
CONFIGmode explicitly for Eigen 3 first, then for Eigen 5.EIGEN3_FOUNDandEIGEN3_VERSIONvariables after a successfulCONFIG-mode probe so the existing test logic continues to work regardless of which config package was found.MODULE-mode fallback for older Eigen 3 environments.v3.0.4changelog entry.Why this approach
This intentionally fixes the
CONFIG-mode path and normalizes the legacyEIGEN3_*variables after theCONFIGprobe. It does not try to update the oldtools/FindEigen3.cmakelogic to understand Eigen 5, because that path is more invasive and easier to get wrong. In other words, this is a targeted compatibility fix for environments that provide anEigen3Config.cmake, while leaving the legacyMODULE-mode finder as a fallback for older Eigen 3 setups.This also avoids relying on package-specific handling of a bounded CMake version range for Eigen 5 discovery. The separate probes make the intent explicit: accept supported Eigen 3 installs first, and if that does not match, try Eigen 5 directly.
📚 Documentation preview 📚: https://pybind11--6036.org.readthedocs.build/