[BUG] PyO3 0.29 abi3 modules on android linked against `libpython3` fail to load

Bug Description

Environment

• PyO3: 0.28 (working), 0.29 (broken)
• Python: 3.13
• Platform: aarch64 Linux (Termux/Android)
• Rust: 1.96.0

Problem

Building a PyO3 extension with abi3-py312 on aarch64 Linux / Python 3.13
produces a .so that references _Py_NoneStruct, which was removed in
Python 3.13:

ImportError: dlopen failed: cannot locate symbol "_Py_NoneStruct"

Confirmed version bisect

• PyO3 0.28 + abi3-py312 → builds cleanly, imports successfully ✅
• PyO3 0.29 + abi3-py312 → _Py_NoneStruct linked, crashes on import ❌

Proof

nm -D _core.abi3.so | grep -i none
→ U _Py_NoneStruct

strings _core.abi3.so | grep -i "limited|Py_LIMITED"
→ nothing found

Py_LIMITED_API is not being set during compilation despite abi3-py312
being enabled. PyO3 correctly guards _Py_NoneStruct behind:

#[cfg(all(not(GraalPy), not(all(Py_3_13, Py_LIMITED_API))))]

Without Py_LIMITED_API, that guard is skipped and the removed
symbol gets linked.

Reproduction

Any package using PyO3 0.29 + abi3-py312 built from source on
aarch64 Linux / Python 3.13 will reproduce this. Confirmed via
django-bolt (github.com/dj-bolt/django-bolt):

pip install django-bolt  # builds from sdist on aarch64
python3 -c "import django_bolt._core"
→ ImportError: cannot locate symbol "_Py_NoneStruct"

Downgrading django-bolt to 0.7.6 (which uses PyO3 0.28) fixes it.

Impact

Affects all aarch64 Linux users building PyO3 0.29 extensions
from source, including:

• AWS Graviton instances
• Raspberry Pi
• Any ARM Linux server
• Termux/Android

Workaround

Downgrade to PyO3 0.28 until fixed.***

Steps to Reproduce

Steps to Reproduce

1. Use an aarch64 Linux machine (tested on Termux/Android)

2. Install Python 3.13

3. Create a virtual environment and activate it

4. Install any package that uses PyO3 0.29 with abi3-py312
   and builds from source (no prebuilt aarch64 wheel).
   Example using django-bolt:

   pip install django-bolt==0.8.3

5. Try to import the extension module:

   python3 -c "import django_bolt._core"

Expected Result

Module imports successfully (as it did with PyO3 0.28)

Actual Result

ImportError: dlopen failed: cannot locate symbol "_Py_NoneStruct"

Verification

nm -D _core.abi3.so | grep -i none
→ U _Py_NoneStruct

strings _core.abi3.so | grep -i "Py_LIMITED"
→ nothing (Py_LIMITED_API was never set during build)

Confirmed Bisect

• django-bolt 0.7.6 (PyO3 0.28) → works ✅
• django-bolt 0.8.3 (PyO3 0.29) → broken ❌

Backtrace

Your operating system and version

Android 14, aarch64 (Termux)

Your Python version (python --version)

3.13

Your Rust version (rustc --version)

1.96.0

Your PyO3 version

0.29.0

How did you install python? Did you use a virtualenv?

apt install python

yes using python -m venv

Additional Info

No response

Start by reproducing the aarch64 Linux/Android build with PyO3 0.29 and abi3-py312, then inspect the build configuration responsible for defining Py_LIMITED_API and compare it with PyO3 0.28. Use nm and strings on the generated extension to verify the unresolved symbol is removed; done means the module imports successfully without referencing _Py_NoneStruct.