[zfergus]

Description

The Eigen ABI pin from #297 now applies even when a parent project's own eigen.cmake recipe shadows the toolkit's. A guard in the library fails the build if the pin is ever lost.

• CMakeLists.txt calls ipc_toolkit_pin_eigen_abi(Eigen3::Eigen ...) right after include(eigen), and cmake/recipes/eigen.cmake goes back to its pre-Pin Eigen's ABI on the Eigen target #297 form.
  • include(eigen) loads the first eigen.cmake on CMAKE_MODULE_PATH. Parents such as CloIPC and PolyFEM put their own recipe first, so code in the toolkit's recipe never runs.
  • ipc_toolkit_eigen_abi.cmake has a name no parent will reuse, so the pin now runs whichever recipe created Eigen3::Eigen.
• src/ipc/utils/eigen_abi.cpp raises an #error when IPC_TOOLKIT_WITH_SIMD is set without EIGEN_DONT_VECTORIZE, or IPC_TOOLKIT_WITH_CUDA is set without EIGEN_MAX_ALIGN_BYTES=0 and EIGEN_MAX_STATIC_ALIGN_BYTES=0.
  • eigen_abi_matches_library() cannot catch a missing pin, because the library and its consumers then agree on the wrong ABI.

Impact

• Before: in a parent with a shadowing recipe, no target got any of the three definitions. In CloIPC (SIMD + CUDA), the host compiles with -march=native and nvcc does not, so TestAirDampingEnergy aborted in free() with heap corruption.
• After: every target that links Eigen carries all three definitions, whichever recipe created the target.
• No API changes.

Type of change

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

• Configured CloIPC (feature/internal-damping, which shadows eigen.cmake) as the parent project, with SIMD and CUDA on. I checked CXX_DEFINES/CUDA_DEFINES in every flags.make that includes Eigen:
  • main (f388443): 0 of 8 Eigen-linking targets have the definitions.
  • This branch: 8 of 8 have all three.
• Compiled the new eigen_abi.cpp with main's unpinned ipc_toolkit flags from that build. Both #errors fire.
• CloIPC's tests against this branch: 303 of 305 cases pass and 2 are skipped, including [AirDampingEnergy], which aborted on main.
• Toolkit test preset (Debug, CUDA on): 485 of 485 ctest tests pass (6 skipped by design).

Test Configuration:

• OS and Version: AlmaLinux 9.8, NVIDIA RTX 5080
• Compiler and Version: GCC 11.5 (toolkit), GCC 14 (CloIPC), nvcc 12.8

Checklist

• I have followed the project style guide
• My code follows the clang-format style guidelines of this project
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.86%. Comparing base (f388443) to head (d215dc8).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #300   +/-   ##
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  Coverage   96.86%   96.86%           
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  Files         229      229           
  Lines       23047    23047           
  Branches     1619     1619           
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  Hits        22324    22324           
  Misses        723      723           

Flag	Coverage Δ
unittests	96.86% <ø> (ø)

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