feat(python): add mutable EventData proxy bindings with lifetime safety#5571
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kodiakhq[bot] merged 5 commits intoJun 18, 2026
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andiwand
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Jun 11, 2026
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drafting for now until we have a conclusion on the discussion which takes load off the gitlab ci |
benjaminhuth
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Hi, really cool initiative. I think personally it would be cool to have a mechanism like this to avoid segfaults on the python-level that are due to our C++ ownership model.
I think there are still some things to be discussed about the implementation.
andiwand
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Jun 11, 2026
andiwand
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Jun 11, 2026
- Merge DisownTestBindings.cpp into EventData.cpp as acts._testing submodule - Add explicit constructor to ProxyTether to prevent uninitialized aliveFn - Add Owner template parameter to ProxyTether; single-owner proxies derive the alive check at compile time, multi-owner proxies (MeasTether) retain the runtime AliveFn override constructor - Rename CheckedIterator -> IteratorTether, CheckedIndexIterator -> IndexIteratorTether for naming consistency
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feat(python): add mutable EventData proxy bindings with lifetime safety
Add mutable Python bindings for
SpacePointContainer2,SeedContainer2, and measurement containers, together with lifetime-safeproxy and iterator handling.
Python proxies currently hold raw pointers into their backing C++
containers. If the container is consumed by a
std::unique_ptr<T>transfer, for example through the whiteboard, the Python wrapper can
remain alive while the C++ object has been moved out. Accessing an
existing proxy then dereferences freed memory.
This PR introduces
ProxyTether, a binding-side wrapper that keeps theowning
py::objectand revalidates it before proxy access. If thebacking container has been disowned, access now raises
ValueErrorinstead of causing undefined behaviour or a segfault.
Also guard optional
SpacePointColumnsaccess so missing columns raiseAttributeErrorinstead of relying on C++ assertions.--- END COMMIT MESSAGE ---
Changes
Add mutable
SpacePointContainer2/MutableSpacePointProxy2bindings:createSpacePoint()__getitem____iter__Add
SeedContainer2/MutableSeedProxy2bindings:createSeed()assignSpacePointContainer()assignSpacePointIndices()qualityandvertexZMake
MeasurementContainer/MeasurementSubsetproxy access use tethered proxies.Add checked iterator handling for example flat multimaps.
Add
py::keep_alivetoConstTrackContainerproxy accessors.ProxyTetherProxyTetherstores the Python owner object, the proxy value, and a type-erased owner-validity check.Before each proxy access, the owner is re-cast to the backing C++ type. If pybind11's
smart_holderhas disowned the object after aunique_ptr<T>transfer, this fails and is translated into a PythonValueError.This handles both relevant lifetime cases:
py::objectis retained;Tests
Adds a test-only pybind11 module,
_acts_core_test_bindings, with helpers that consumeSpacePointContainer2andSeedContainer2viastd::unique_ptr<T>. This reproduces the same disowning behaviour as the whiteboard without depending onacts.examples.test_event_data.pynow covers:AttributeError,All added tests pass.
Known follow-up work
This PR focuses on proxies and iterators whose own backing container has been consumed/disowned. It does not fully solve separate cross-owner or buffer-lifetime cases, including:
sourceLinkssub-iterators whose underlying container is transferred after the iterator is created;SeedContainer2references to an assignedSpacePointContainer2if future Python APIs expose dereferencing that relationship;TrackProxyobjects kept alive aftermakeConst()drains the mutable track container;MeasurementSubsetviews after the originalMeasurementContaineris independently transferred;Those require separate true-owner or buffer-base lifetime handling and are left for follow-up PRs.
cc @benjaminhuth @andiwand