ENH: Port `_rational_tests` to the Limited API using heap types by prathamhole14 · Pull Request #32174 · numpy/numpy

prathamhole14 · 2026-08-03T14:02:55Z

PR summary

Related to: #31913, #32451 and #32747
I will make the PR more verbose soon. I want to see if CI is okay with this.
Benchmark report: https://gist.github.com/prathamhole14/17d187d84837de39d190d7a7db0e0d03

AI Disclosure

In understanding things, and finding places where changes are required.

prathamhole14 · 2026-08-05T11:40:39Z

This PR is ready for review!

prathamhole14

No tp_traverse because a rational holds two ints and no PyObject*, so it cannot be part of a cycle. Heap types normally want both, but that only leaks at interpreter teardown.

prathamhole14 · 2026-08-06T09:37:16Z

I think the failing test is unrelated, this PR is ready for review!

ngoldbaum · 2026-08-07T19:52:28Z

This one is a bit more complicated and needs some C API knowledge because it does some migrating to heap types. @kumaraditya303, would you mind giving it a look?

kumaraditya303 · 2026-08-09T08:25:28Z

A few points for heap types:

Heap types should always be GC types in general, this is because the following cycle is possible instance -> type -> module -> instance.
It is good practise to call tp_slots instead of function directly like tp_alloc instead of PyType_GenericAlloc.
Heap types are mutable by default, so if that is unwanted use IMMUTABLE flag.

…mited # Conflicts: # numpy/_core/meson.build

prathamhole14 · 2026-08-14T06:36:19Z

Thanks for the reviews @kumaraditya303!

One thing worth flagging is I had to set tp_alloc explicitly in the spec. It's inherited unconditionally from np.generic, whose allocator is not GC-aware, so without it you allocate non-GC memory that the dealloc then GC-frees. tp_free sorts itself out and CPython will pick up PyObject_GC_Del from object.

And you were right about the flag check. Once these are GC types it's always true, so the branch is gone now.

On point 3: agreed this is a regression the static type used to reject attribute injection. But IMMUTABLETYPE breaks init here because dtype is set at runtime with PyObject_SetAttrString, and PyType_GetDict isn't in the limited API so I can't seed the type dict directly. Any preference on how to handle that, or leave it mutable for now?

kumaraditya303 · 2026-08-14T11:35:36Z

agreed this is a regression the static type used to reject attribute injection. But IMMUTABLETYPE breaks init here because dtype is set at runtime with PyObject_SetAttrString, and PyType_GetDict isn't in the limited API so I can't seed the type dict directly. Any preference on how to handle that, or leave it mutable for now?

You can PyType_Freeze although IIRC that was only added in 3.14 so you can skip this if you want.

kumaraditya303

LGTM

ngoldbaum

What about a short test like this to make sure the heap type setup is working correctly?

@pytest.mark.thread_unsafe(reason="Relies on global gc state")
def test_rational_subclass_lifetime():
    class R(rational):
        pass

    r = R(1, 2)
    assert r == Rational(1, 2)
    assert gc.is_tracked(r)

    wr = weakref.Ref(R)
    del R
    gc.collect()
    # the instance keeps a reference to its type
    assert wr() is not None

    del r
    gc.collect()
    assert wr() is None

ngoldbaum · 2026-08-16T14:31:50Z

Thanks @prathamhole14!

Add Limited API compliant _rational_tests module

b0debb3

github-actions Bot added the 01 - Enhancement label Aug 3, 2026

prathamhole14 changed the title ~~ENH: Port _rational_tests to the Limited API using heap types [WIP]~~ ENH: Port _rational_tests to the Limited API using heap types Aug 4, 2026

prathamhole14 mentioned this pull request Aug 5, 2026

Tracking Issue: Adoption of CPython limited API #31913

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prathamhole14 commented Aug 5, 2026

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prathamhole14 added 2 commits August 6, 2026 13:44

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remove trivial comment

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prathamhole14 marked this pull request as ready for review August 6, 2026 09:37

prathamhole14 added 2 commits August 7, 2026 23:46

build _rational_tests through the test module loop

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fix abi3t TODO comment

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kumaraditya303 reviewed Aug 8, 2026

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