Python 3.13.0b1: SystemError: Objects/abstract.c:430: bad argument to internal function

[hroncok]

Hello. We see 3 test failures in Fedora when we try to build pycairo with Python 3.13.0b1.

I reproduced the failures in https://github.com/pygobject/pycairo/pull/364

============================= test session starts ==============================
platform linux -- Python 3.13.0b1, pytest-8.2.1, pluggy-1.5.0
rootdir: /home/runner/work/pycairo/pycairo
configfile: pyproject.toml
plugins: hypothesis-6.103.0
collected 282 items / 2 skipped
tests/test_api.py ...............FF                                      [  6%]
tests/test_cmod.py .                                                     [  6%]
tests/test_context.py .................................................. [ 24%]
.................s                                                       [ 30%]
tests/test_device.py ...........                                         [ 34%]
tests/test_enums.py .......                                              [ 36%]
tests/test_error.py ....                                                 [ 38%]
tests/test_font.py sssss..............................                   [ 50%]
tests/test_glyph.py ..                                                   [ 51%]
tests/test_hypothesis.py ...........                                     [ 55%]
tests/test_matrix.py ...........                                         [ 59%]
tests/test_path.py ....                                                  [ 60%]
tests/test_pattern.py ..............................s                    [ 71%]
tests/test_rectangle.py ...                                              [ 72%]
tests/test_region.py ...........                                         [ 76%]
tests/test_surface.py ...............s.......................F.......... [ 94%]
...........s                                                             [ 98%]
tests/test_textcluster.py .                                              [ 98%]
tests/test_textextents.py ..                                             [ 99%]
tests/test_typing.py .                                                   [100%]
=================================== FAILURES ===================================
__________________ test_surface_get_set_mime_data_references ___________________
    @pytest.mark.skipif(not hasattr(sys, "getrefcount"), reason="PyPy")
    def test_surface_get_set_mime_data_references():
        surface = cairo.ImageSurface(cairo.FORMAT_RGB24, 1, 1)
        v = memoryview(b"bla")
        x = v[:1]
        recfcount_v = sys.getrefcount(v)
        recfcount_x = sys.getrefcount(x)
        assert recfcount_v == recfcount_x
>       surface.set_mime_data("foo", v)
E       SystemError: Objects/abstract.c:430: bad argument to internal function
tests/test_api.py:282: SystemError
________________________ test_surface_mime_data_for_pdf ________________________
    @pytest.mark.skipif(
        sysconfig.get_platform().startswith("win"), reason="msvc fixme")
    def test_surface_mime_data_for_pdf():
        jpeg_bytes = zlib.decompress(base64.b64decode(
            b'eJz7f+P/AwYBLzdPNwZGRkYGDyBk+H+bwRnEowj8P8TAzcHACDJHkOH/EQYRIBsV'
            b'cP6/xcDBCBJlrLcHqRBAV8EAVcHIylSPVwGbPQEFjPaK9XDrBAipBSq4CQB9jiS0'
        ))

        file_like = io.BytesIO()
        surface = cairo.PDFSurface(file_like, 3, 3)
        context = cairo.Context(surface)
        image = cairo.ImageSurface(cairo.FORMAT_RGB24, 1, 1)
>       image.set_mime_data(cairo.MIME_TYPE_JPEG, jpeg_bytes)
E       SystemError: Objects/abstract.c:430: bad argument to internal function
tests/test_api.py:308: SystemError
________________________ test_surface_get_set_mime_data ________________________
    def test_surface_get_set_mime_data():
        surface = cairo.ImageSurface(cairo.FORMAT_RGB24, 1, 1)
        assert surface.get_mime_data("foo") is None
        assert surface.get_mime_data(cairo.MIME_TYPE_JPEG) is None

>       surface.set_mime_data("foo", b"bar")
E       SystemError: Objects/abstract.c:430: bad argument to internal function
tests/test_surface.py:478: SystemError
=========================== short test summary info ============================
FAILED tests/test_api.py::test_surface_get_set_mime_data_references - SystemError: Objects/abstract.c:430: bad argument to internal function
FAILED tests/test_api.py::test_surface_mime_data_for_pdf - SystemError: Objects/abstract.c:430: bad argument to internal function
FAILED tests/test_surface.py::test_surface_get_set_mime_data - SystemError: Objects/abstract.c:430: bad argument to internal function
================== 3 failed, 270 passed, 11 skipped in 24.83s ==================

Not sure if this is a CPython bug or a problem in pycairo. Will try to investigate later.

[hroncok]

Similar issue elsewhere: https://github.com/kovidgoyal/kitty/issues/7426

[hroncok]

https://github.com/pygobject/pycairo/blob/da92fff1a31bbe4ee533ab2a9553fac97a9d2333/cairo/surface.c#L487

https://github.com/python/cpython/pull/114707

PyObject_GetBuffer now raises a SystemError if called with PyBUF_READ or PyBUF_WRITE as flags. These flags should only be used with the PyMemoryView_* C API.

[hroncok]

I will try replacing that with PyBUF_SIMPLE which might be the correct thing to do (not sure yet).

[lazka]

New release is out