Compiled Python extension does not work with Python 3.12 #12186
Description
What version of protobuf and what language are you using?
Version: 3.19.6 – but I searched the source code and verified that the current release (22.1) and main should also be affected
Language: Python
What operating system (Linux, Windows, ...) and version?
Fedora Linux Rawhide/39, plus experimental Python 3.12: https://copr.fedorainfracloud.org/coprs/g/python/python3.12/
What runtime / compiler are you using (e.g., python version or gcc version)
Python 3.12.0a5, GCC 13.0.1
What did you do?
Steps to reproduce the behavior:
- Build the C++ version of the Python protobuf extension.
from google.protobuf.pyext import _message
This import occurred in the generated proto bindings in googleapis-common-protos; see downstream bug https://bugzilla.redhat.com/show_bug.cgi?id=2176158.
What did you expect to see
Successful import with no output.
What did you see instead?
[…] File "/builddir/build/BUILDROOT/python-googleapis-common-protos-1.58.0-2.fc39~bootstrap.x86_64/usr/lib/python3.12/site-packages/google/api/annotations_pb2.py", line 20, in <module> from google.protobuf import descriptor as _descriptor File "/usr/lib64/python3.12/site-packages/google/protobuf/descriptor.py", line 47, in <module> from google.protobuf.pyext import _message TypeError: Metaclasses with custom tp_new are not supported. Added the new limited C API function PyType_FromMetaclass(), which generalizes the existing PyType_FromModuleAndSpec() using an additional metaclass argument. (Contributed by Wenzel Jakob in gh-93012.) The metaclass is used to construct the resulting type object. When metaclass is NULL, the metaclass is derived from bases (or Py_tp_base[s] slots if bases is NULL, see below). Note that metaclasses that override tp_new are not supported. https://github.com/python/cpython/issues/93012 https://docs.python.org/3.12/whatsnew/3.12.html Make sure you include information that can help us debug (full error message, exception listing, stack trace, logs).
Anything else we should know about your project / environment
See python/cpython#93012.
Grepping for tp_new in main gives:
python/google/protobuf/pyext/descriptor.cc 1600: nullptr, // tp_new python/google/protobuf/pyext/unknown_field_set.cc 197: unknown_field_set::New, // tp_new python/google/protobuf/pyext/message_factory.cc 293: message_factory::New, // tp_new python/google/protobuf/pyext/field.cc 126: nullptr, // tp_new python/google/protobuf/pyext/message.cc 275: ScopedPyObjectPtr result(PyType_Type.tp_new(type, new_args.get(), nullptr)); 502: message_meta::New, // tp_new 2762: cmessage::New, // tp_new python/google/protobuf/pyext/descriptor_pool.cc 750: cdescriptor_pool::New, // tp_new python/google/protobuf/pyext/descriptor_containers.cc 596: nullptr, // tp_new 783: nullptr, // tp_new 929: nullptr, // tp_new