Python 3.6: SystemError: Bad call flags in PyCFunction_Call. METH_OLDARGS is no longer supported! (pyo3 v0.14.5)

[Congyuwang]

🐛 Bug Reports

Building on python 3.6.15 fails to run on python 3.6.13. Below is the error message:

❯ python
Python 3.6.13 |Anaconda, Inc.| (default, Feb 23 2021, 12:58:59) 
[GCC Clang 10.0.0 ] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import string_sum
>>> string_sum.sum_as_string(1, 2)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
SystemError: Bad call flags in PyCFunction_Call. METH_OLDARGS is no longer supported!

If I build the same project using python 3.6.13 on my laptop, it runs successfully.

🌍 Build Environment (Github Workflow)

• OS: runs-on: macos-latest, Mac OS X 10.15.7 19H1417
• python version: 3.6.15
• python installation: actions/setup-python@v2, with: python-version: 3.6, architecture: x64
• rust: stable-x86_64-apple-darwin unchanged - rustc 1.55.0 (c8dfcfe04 2021-09-06)
• Your PyO3 version: pyo3 v0.14.5

Run Environment (My Laptop)

• OS: Mac OS X 11.6
• python version: 3.6.13
• python installation: conda install python=3.6

💥 Reproducing

lib.rs

use pyo3::prelude::*;

/// Formats the sum of two numbers as string.
#[pyfunction]
fn sum_as_string(a: usize, b: usize) -> PyResult<String> {
    Ok((a + b).to_string())
}

/// A Python module implemented in Rust. The name of this function must match
/// the `lib.name` setting in the `Cargo.toml`, else Python will not be able to
/// import the module.
#[pymodule]
fn string_sum(_py: Python, m: &PyModule) -> PyResult<()> {
    m.add_function(wrap_pyfunction!(sum_as_string, m)?)?;

    Ok(())
}

Cargo.toml

[package]
name = "string_sum"
version = "0.1.0"
edition = "2018"

# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

[lib]
crate-type = ["cdylib"]

[dependencies]
pyo3 = { version = "0.14.5", features = ["extension-module"] }

pyproject.toml

[project]
name = "congyu_pyo3_bug"
version = "0.0.1"

[build-system]
requires = ["maturin>=0.11,<0.12"]
build-backend = "maturin"

Installing package:

pip install congyu_pyo3_bug==0.0.1 -i https://test.pypi.org/simple

Reproduce bug:

❯ python
Python 3.6.13 |Anaconda, Inc.| (default, Feb 23 2021, 12:58:59) 
[GCC Clang 10.0.0 ] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import string_sum
>>> string_sum.sum_as_string(1, 2)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
SystemError: Bad call flags in PyCFunction_Call. METH_OLDARGS is no longer supported!

The repository where I built this: https://github.com/Congyuwang/congyu_pyo3_debug

Built using GitHub workflow: https://github.com/Congyuwang/congyu_pyo3_debug/blob/master/.github/workflows/blank.yml

[davidhewitt]

See milesgranger/cramjam#62 (comment). I suspect that your github build is somehow configuring for a newer version by accident.

[davidhewitt]

In particular:

Python 3.6 and 3.7 are not supported on Apple Silicon Macs anyway so I've removed universal2 wheels from them.

Sounds like you should not be using --universal2 flag in your call to maturin-action. PyO3/maturin-action#13

[Congyuwang]

However, if I build with --universal2 flag on Python 3.6.13 on my laptop, everything works just fine.

[messense]

@Congyuwang See PyO3/maturin-action@3c86483

Please give it try with uses: messense/maturin-action@main

[Congyuwang]

I changed to uses: messense/maturin-action@main.

The workflow still runs normally: Built wheel for CPython 3.6m to dist/congyu_pyo3_bug-0.0.2-cp36-cp36m-macosx_10_9_x86_64.macosx_11_0_arm64.macosx_10_9_universal2.whl.

Running actions/setup-python@v2, python version has not changed: Successfully setup CPython (3.6.15).

Installing from pip install congyu_pyo3_bug==0.0.2 -i https://test.pypi.org/simple this time actually runs normally:

❯ python                                                            
Python 3.6.13 |Anaconda, Inc.| (default, Feb 23 2021, 12:58:59) 
[GCC Clang 10.0.0 ] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import string_sum
>>> string_sum.sum_as_string(1, 2)
'3'

I don't quite understand why, though.

[messense]

I think it's because pyo3 0.14 actually does use Python metadata from /Applications/Xcode.app/Contents/Developer/Library/Frameworks/Python3.framework/Versions/3.8/lib (which was specified by PYO3_CROSS_LIB_DIR env var in maturin-action) which wasn't used before.

[Congyuwang]

This problem seems solved with latest maturin-action@v1