fix memory corruption when subclassing variable-size types (e.g. `abi3` + 3.12 subclassing of native types) by davidhewitt · Pull Request #5823 · PyO3/pyo3

Performance Gate Passed

✅ 100 untouched benchmarks

_{Comparing davidhewitt:variable-class-subclassing (e0cab83) with main (fe00ce7)}