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;
| ^~~~~~~~~~~~~~~~