pybind / pybind/pybind11

[BUG]: static numpy array_t leads to segfault on exit on Python 3.12

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Description

Required prerequisites
What version (or hash if on master) of pybind11 are you using?

2.13.1

Problem description

Observed behaviour: When exiting a Python script after constructing a bound class with an initialized static pybind11::array_t, there is a segfault calling decref on the array on Python 3.12.

Expected behaviour: No segfault, as is the case on Python < 3.12.

I have tested with several combinations of package version but can definitely confirm that on a Fedora 40 conda env with gxx=14.1.0, numpy=2.0.0 and pybind11=2.13.1 the segfault occurs with Python 3.12 but not 3.11, so this does not appear to be a regression in pybind11.

I compiled the module as follows:
g++ -Wall -shared -fPIC -std=c++17 $(python3 -m pybind11 --includes) test_image.cc -o test_static$(python3-config --extension-suffix)
and tested with:
python -c "from test_static import Static; Static()"

It is possible to defer the problem by adding a destructor like so:
~Static() { PYARRAY().release(); }
... however, this only fixes the trivial example and fails as soon as one instance is deleted, and the following example fails upon constructing a second instance:
python -c "from test_static import Static; x = Static(); del x; y = Static()"

Reproducible example code
#include <cassert>

#include <pybind11/pybind11.h>
#include <pybind11/numpy.h>

namespace py = pybind11;
using namespace pybind11::literals;

struct Static {
public:
    Static() { assert(this->PYARRAY().ndim() == 2); }

    py::array_t<double>& PYARRAY() const {
        static py::array_t<double> array(py::array::ShapeContainer({1, 1}));
        return array;
    }
};

PYBIND11_MODULE(test_static, m) {
    py::class_<Static, std::shared_ptr<Static>>(m, "Static").def(py::init<>());
}
Is this a regression? Put the last known working version here if it is.

Not a regression in pybind11 but perhaps in CPython?

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  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start by reproducing the Python 3.12 failure with the provided test_static module and compare it with Python 3.11, then inspect pybind11/numpy.h and the Static::PYARRAY() static array lifetime. Check both the basic construction command and the construction/deletion sequence. Done means neither scenario segfaults at interpreter exit or while deleting and recreating Static instances.

Written by the indexing model from the issue text.

Assessment

Tech stack
cpp, numpy, python
Domain
backend
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
35/100

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