Build with Py_LIMITED_API fails unknown type name ‘PyModuleDef_Slot’

[tiran]

BPO	46915
Nosy	@vstinner, @tiran, @pablogsal
PRs	bpo-46915: Fix unknown type PyModuleDef_Slot regression #31667

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = 'https://github.com/vstinner'
closed_at = None
created_at = <Date 2022-03-03.21:15:25.727>
labels = ['interpreter-core', 'build', '3.11']
title = 'Build with Py_LIMITED_API fails unknown type name \xe2\x80\x98PyModuleDef_Slot\xe2\x80\x99'
updated_at = <Date 2022-03-12.00:35:14.453>
user = 'https://github.com/tiran'

bugs.python.org fields:

activity = <Date 2022-03-12.00:35:14.453>
actor = 'vstinner'
assignee = 'vstinner'
closed = False
closed_date = None
closer = None
components = ['Build', 'Interpreter Core']
creation = <Date 2022-03-03.21:15:25.727>
creator = 'christian.heimes'
dependencies = []
files = []
hgrepos = []
issue_num = 46915
keywords = ['3.11regression']
message_count = 7.0
messages = ['414473', '414474', '414475', '414476', '414480', '414488', '414956']
nosy_count = 3.0
nosy_names = ['vstinner', 'christian.heimes', 'pablogsal']
pr_nums = ['31667']
priority = 'normal'
resolution = None
stage = 'resolved'
status = 'open'
superseder = None
type = 'compile error'
url = 'https://bugs.python.org/issue46915'
versions = ['Python 3.11']

[tiran]

Extension modules with bare "#define Py_LIMITED_API" without version fail to build with error:

moduleobject.h:82:3: error: unknown type name ‘PyModuleDef_Slot’

The issue was introduced in PR #75709 and bpo-45459. The type PyModuleDef_Slot is only defined when Py_LIMITED_API is set to Python 3.5.0 or higher.

[tiran]

The problem was first reported to PyCA cryptography project in bug pyca/cryptography#6929

[tiran]

With fix:

$ /tmp/python311/bin/pip3 install --no-binary :all: cryptography
Collecting cryptography
  Using cached cryptography-36.0.1.tar.gz (572 kB)
  Installing build dependencies ... done
  Getting requirements to build wheel ... done
    Preparing wheel metadata ... done
Requirement already satisfied: cffi>=1.12 in /tmp/python311/lib/python3.11/site-packages (from cryptography) (1.15.0)
Requirement already satisfied: pycparser in /tmp/python311/lib/python3.11/site-packages (from cffi>=1.12->cryptography) (2.21)
Building wheels for collected packages: cryptography
  Building wheel for cryptography (PEP 517) ... done
  Created wheel for cryptography: filename=cryptography-36.0.1-cp311-cp311-linux_x86_64.whl size=2628351 sha256=fb3cc21f8eaa546cd2c0123ea01a98bf92a9824fcdca36cfcf765b2c044bd186
  Stored in directory: /home/heimes/.cache/pip/wheels/6c/77/a9/3c4762d4e65bef5f742a304c507f9723ca3563a38d108618ad
Successfully built cryptography
Installing collected packages: cryptography
Successfully installed cryptography-36.0.1

Without fix:

gcc -Wsign-compare -DNDEBUG -g -fwrapv -O3 -Wall -fPIC -I/tmp/python311/include/python3.11 -c build/temp.linux-x86_64-3.11/_openssl.c -o build/temp.linux-x86_64-3.11/build/temp.linux-x86_64-3.11/_openssl.o -Wconversion -Wno-error=sign-conversion
In file included from /tmp/python311/include/python3.11/Python.h:66,
from build/temp.linux-x86_64-3.11/_openssl.c:57:
/tmp/python311/include/python3.11/moduleobject.h:82:3: error: unknown type name ‘PyModuleDef_Slot’
82 | PyModuleDef_Slot *m_slots;
| ^~~~~~~~~~~~~~~~

[vstinner]

I proposed a fix: #31668

[vstinner]

Fixed by 0b63215

[tiran]

Please add a blurb entry.

[vstinner]

Fixed by 0b63215

This change is now part of Python 3.11 alpha6 released a few days ago. Python 3.11a6 news entries were merged into the Misc/NEWS.d/3.11.0a6.rst file.

Please add a blurb entry.

I consider that the changelog is for changes which impacts users when they update. The regression was introduced after 3.11 alpha5 but fixed before Python 3.11 alpha6. Only projects using contiguous integration were impacted. Only the cryptography project was impacted in practice.

pyca/cryptography#6929

This issue was closed as with the comment:

"Going to close this as it's an upstream python bug that's now been fixed."

[kumaraditya303]

Since only alpha6 was impacted and is now fixed, I am closing the issue.