bpo-42923: _Py_DumpExtensionModules() ignores stdlib ext

[vstinner]

https://bugs.python.org/issue42923

[vstinner]

This PR should be rebased on master once PR #24238 (bpo-42955: Add sys.modules_names) will be merged.

[vstinner]

Example with Cinder.

./python -m venv env
./env/bin/python -m pip install wheel
./env/bin/python -m pip install cinder

Without the PR, 43 extensions (stdlib + third party) are listed:

$ ./env/bin/python -X dev -c 'import cinder, ctypes, sys; print(f"{len(sys.modules)=}"); ctypes.string_at(0)'
(...)
len(sys.modules)=220
Fatal Python error: Segmentation fault

Current thread 0x00007ff626de1740 (most recent call first):
  File "/home/vstinner/python/master/Lib/ctypes/__init__.py", line 517 in string_at
  File "<string>", line 1 in <module>

Extension modules: sys, builtins, _imp, _warnings, _weakref, _io, marshal, posix, faulthandler, _codecs, _signal, _abc, _stat, itertools, _operator, _collections, _functools, _sre, _locale, _heapq, _opcode, _struct, greenlet._greenlet, _thread, __original_module__thread, errno, math, __original_module_select, time, __original_module_time, _socket, select, array, _datetime, binascii, _hashlib, _blake2, _cffi_backend, _bisect, _sha512, _string, _ssl, _ctypes
Erreur de segmentation (core dumped)

With the PR, 5 extensions (third party only) are listed:

$ ./env/bin/python -X dev -c 'import cinder, ctypes, sys; print(f"{len(sys.modules)=}"); ctypes.string_at(0)'
(...)
len(sys.modules)=220
Fatal Python error: Segmentation fault

Current thread 0x00007f7421252740 (most recent call first):
  File "/home/vstinner/python/master/Lib/ctypes/__init__.py", line 517 in string_at
  File "<string>", line 1 in <module>

Extension modules: greenlet._greenlet, __original_module__thread, __original_module_select, __original_module_time, _cffi_backend (total: 5)
Erreur de segmentation (core dumped)

cc @pablogsal

[bedevere-bot]

⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot PPC64LE RHEL8 3.x has failed when building commit 66f77ca.

What do you need to do:

1. Don't panic.
2. Check the buildbot page in the devguide if you don't know what the buildbots are or how they work.
3. Go to the page of the buildbot that failed (https://buildbot.python.org/all/#builders/559/builds/599) and take a look at the build logs.
4. Check if the failure is related to this commit (66f77ca) or if it is a false positive.
5. If the failure is related to this commit, please, reflect that on the issue and make a new Pull Request with a fix.

You can take a look at the buildbot page here:

https://buildbot.python.org/all/#builders/559/builds/599

Summary of the results of the build (if available):

== Tests result: ENV CHANGED ==

412 tests OK.

10 slowest tests:

• test_concurrent_futures: 4 min 4 sec
• test_tokenize: 3 min 17 sec
• test_unparse: 2 min 51 sec
• test_peg_generator: 2 min 40 sec
• test_gdb: 2 min 38 sec
• test_multiprocessing_spawn: 2 min 23 sec
• test_lib2to3: 2 min 14 sec
• test_capi: 1 min 49 sec
• test_asyncio: 1 min 39 sec
• test_multiprocessing_forkserver: 1 min 31 sec

1 test altered the execution environment:
test_asyncio

13 tests skipped:
test_devpoll test_ioctl test_kqueue test_msilib test_ossaudiodev
test_startfile test_tix test_tk test_ttk_guionly test_winconsoleio
test_winreg test_winsound test_zipfile64

Total duration: 7 min 28 sec

Click to see traceback logs

Traceback (most recent call last):
  File "/home/buildbot/buildarea/3.x.cstratak-RHEL8-ppc64le/build/Lib/asyncio/sslproto.py", line 321, in __del__
    self.close()
  File "/home/buildbot/buildarea/3.x.cstratak-RHEL8-ppc64le/build/Lib/asyncio/sslproto.py", line 316, in close
    self._ssl_protocol._start_shutdown()
  File "/home/buildbot/buildarea/3.x.cstratak-RHEL8-ppc64le/build/Lib/asyncio/sslproto.py", line 590, in _start_shutdown
    self._abort()
  File "/home/buildbot/buildarea/3.x.cstratak-RHEL8-ppc64le/build/Lib/asyncio/sslproto.py", line 731, in _abort
    self._transport.abort()
  File "/home/buildbot/buildarea/3.x.cstratak-RHEL8-ppc64le/build/Lib/asyncio/selector_events.py", line 680, in abort
    self._force_close(None)
  File "/home/buildbot/buildarea/3.x.cstratak-RHEL8-ppc64le/build/Lib/asyncio/selector_events.py", line 731, in _force_close
    self._loop.call_soon(self._call_connection_lost, exc)
  File "/home/buildbot/buildarea/3.x.cstratak-RHEL8-ppc64le/build/Lib/asyncio/base_events.py", line 745, in call_soon
    self._check_closed()
  File "/home/buildbot/buildarea/3.x.cstratak-RHEL8-ppc64le/build/Lib/asyncio/base_events.py", line 510, in _check_closed
    raise RuntimeError('Event loop is closed')
RuntimeError: Event loop is closed