bpo-45573 added the PY_STDLIB_MOD() autoconf macro, Modules/Setup.stdlib.in template, and setup.py helper method addext().

The macro sets up

* MODULE_{NAME}_TRUE/FALSE conditional
* MODULE_{NAME} variable with values yes, disabled, missing, or n/a
* MODULE_{NAME}_CFLAGS
* MODULE_{NAME}_LDFLAGS

Additionally there is a MODULE_{NAME}_DEPS variable with dependency information.

The Modules/Setup.stdlib.in template and addext() method consume the variables and set up extension compilation and linking. There is no need to look for headers or libraries in setup.py any more.

Let's port all modules to the new approach.

New changeset c8c21bdd199f9feb75fc6cdb398a686dc133b99f by Christian Heimes in branch 'main':
bpo-45847: Port builtin hashlib extensions to PY_STDLIB_MOD (GH-29642)
https://github.com/python/cpython/commit/c8c21bdd199f9feb75fc6cdb398a686dc133b99f

New changeset 5596909eac4abdc9927c2e7751bea34fbcfdc624 by Christian Heimes in branch 'main':
bpo-45847: Port _scproxy to PY_STDLIB_MOD (GH-29644)
https://github.com/python/cpython/commit/5596909eac4abdc9927c2e7751bea34fbcfdc624

New changeset f36c69a26ee880acf62a5ae8c5da49312e84c66d by Christian Heimes in branch 'main':
bpo-45847: Port test modules to PY_STDLIB_MOD (GH-29660)
https://github.com/python/cpython/commit/f36c69a26ee880acf62a5ae8c5da49312e84c66d

New changeset f201d261cf53365b5769a434ca2bb21a892bd23f by Christian Heimes in branch 'main':
bpo-45847: Port grp, spwd, termios, resource, syslog to PY_STDLIB_MOD (GH-29668)
https://github.com/python/cpython/commit/f201d261cf53365b5769a434ca2bb21a892bd23f

New changeset 2afa1a12669e1812a9fe8130c8f60052c4ad8bf8 by Christian Heimes in branch 'main':
bpo-45847: Port codecs and unicodedata to PY_STDLIB_MOD (GH-29685)
https://github.com/python/cpython/commit/2afa1a12669e1812a9fe8130c8f60052c4ad8bf8

New changeset 133c65a870e8bdcce7cd6a2bc6bd0cefbb2fa9f3 by Erlend Egeberg Aasland in branch 'main':
bpo-45847: Port array, _contextvars, math, and cmath to PY_STDLIB_MOD_SIMPLE (GH-29688)
https://github.com/python/cpython/commit/133c65a870e8bdcce7cd6a2bc6bd0cefbb2fa9f3

New changeset 718cee08cc082ece590f5a012253a405422da03d by Erlend Egeberg Aasland in branch 'main':
bpo-45847: Port _bisect, _heapq, _json, _pickle, _random, and _zoneinfo to PY_STDLIB_MOD_SIMPLE (GH-29689)
https://github.com/python/cpython/commit/718cee08cc082ece590f5a012253a405422da03d

45 down, 35 to go.

New changeset 39f7d2ff01eb03f1dd87a019472a32cde6250e84 by Erlend Egeberg Aasland in branch 'main':
bpo-45847: Port _lfprof, _opcode, _asyncio, _queue, _statistics, and _typing to PY_STDLIB_MOD_SIMPLE (GH-29690)
https://github.com/python/cpython/commit/39f7d2ff01eb03f1dd87a019472a32cde6250e84

New changeset 29699a2a2aa2f0d6e790beeae55967fc2f35fe50 by Christian Heimes in branch 'main':
bpo-45847: Various PY_STDLIB_MOD cleanups (GH-29697)
https://github.com/python/cpython/commit/29699a2a2aa2f0d6e790beeae55967fc2f35fe50

New changeset 5b946cadaa1175a5caae98bd2d309840bea52a58 by Erlend Egeberg Aasland in branch 'main':
bpo-45847: Port fcntl to Py_STDLIB_MOD (GH-29696)
https://github.com/python/cpython/commit/5b946cadaa1175a5caae98bd2d309840bea52a58

New changeset b451673f93465a27ee61e408190ee61cb9dbd5b6 by Erlend Egeberg Aasland in branch 'main':
bpo-45847: Port mmap, select, and _xxsubinterpreters to Py_STDLIB_MOD (GH-29703)
https://github.com/python/cpython/commit/b451673f93465a27ee61e408190ee61cb9dbd5b6

New changeset d9cedabeba0d87799f99c0717e81743a1c2d34ce by Christian Heimes in branch 'main':
bpo-45847: Port compression libs to PY_STDLIB_MOD (GH-29702)
https://github.com/python/cpython/commit/d9cedabeba0d87799f99c0717e81743a1c2d34ce

New changeset c6dec7e27a82cba33539d07ef8d7346e0a232421 by Christian Heimes in branch 'main':
bpo-45847: Port nis module to PY_STDLIB_MOD (GH-29699)
https://github.com/python/cpython/commit/c6dec7e27a82cba33539d07ef8d7346e0a232421

Not converted yet:

readline
_curses
_curses_panel
_crypt
_socket
_ssl
_hashlib
_dbm
_gdbm
_ctypes
_multiprocessing
_posixshmem
_tkinter
_uuid
xxlimited
xxlimited_35

_socket coming up...

New changeset eee683cbde499e62fc90ad366f7c45625fe92150 by Erlend Egeberg Aasland in branch 'main':
bpo-45847: Port audioop, _csv, and _posixsubprocess to PY_STDLIB_MOD_SIMPLE (GH-29705)
https://github.com/python/cpython/commit/eee683cbde499e62fc90ad366f7c45625fe92150

_crypt is powered by pkgconf libcrypt or libxcrypt on Linux. On my system  and on Debian, libcrypt.pc is a symlink to libxcrypt.pc. Linux has crypt() and/or crypt_r() in <crypt.h>. On FreeBSD crypt_r() is in <unistd.h> and libc.

_uuid needs similar special handling. It's <uuid/uuid.h>, -luuid, and uuid.pc on Linux. On BSD it's <uuid.h> and symbols are in libc.

_readline uses either libreadline (readline.pc) or libeditline (libeditline.pc). It also needs special handling of tinfo and termcap on some platforms.

ndbm, gdbm, and libdb have no pkgconf providers. My PR GH-29534 has some code to detect them in configure.

New changeset 0e1c2f3ef84572b79fa7d8498a69bc5a56ff0d8d by Christian Heimes in branch 'main':
bpo-45847: port _struct to PY_STDLIB_MOD (GH-29706)
https://github.com/python/cpython/commit/0e1c2f3ef84572b79fa7d8498a69bc5a56ff0d8d

New changeset 2dc7d3dda61e7ce07721f46b14c706fbc879dfd6 by Erlend Egeberg Aasland in branch 'main':
bpo-45847: Port xxlimited and xxlimited_35 to PY_STDLIB_MOD (GH-29707)
https://github.com/python/cpython/commit/2dc7d3dda61e7ce07721f46b14c706fbc879dfd6

New changeset 758a23d1c4db97b578bc16e0ea110074d65c4c52 by Erlend Egeberg Aasland in branch 'main':
bpo-45847: Fix xxlimited and xxlimited_35 build conditions (GH-29715)
https://github.com/python/cpython/commit/758a23d1c4db97b578bc16e0ea110074d65c4c52

New changeset d82f2caf942fa8b94e797a2f116ee54ec303c2df by Erlend Egeberg Aasland in branch 'main':
bpo-45847: Port _socket to PY_STDLIB_MOD (GH-29713)
https://github.com/python/cpython/commit/d82f2caf942fa8b94e797a2f116ee54ec303c2df

We are down to 9 missing modules:

readline
_curses
_curses_panel
_dbm
_ctypes
_multiprocessing
_posixshmem
_tkinter
_uuid

New changeset 095bc8f0d6845dded8f67fbc6eca20dfac8b3929 by Christian Heimes in branch 'main':
bpo-45847: Port _crypt to PY_STDLIB_MOD (GH-29725)
https://github.com/python/cpython/commit/095bc8f0d6845dded8f67fbc6eca20dfac8b3929

New changeset b9e9292d75fdea621e05e39b8629e6935d282d0d by Christian Heimes in branch 'main':
bpo-45847: Port _ssl and _hashlib to PY_STDLIB_MOD (GH-29727)
https://github.com/python/cpython/commit/b9e9292d75fdea621e05e39b8629e6935d282d0d

New changeset 9cf5646bb465b7d3d68bfe6d4711feb43d565051 by Christian Heimes in branch 'main':
bpo-45847: Port _gdbm to PY_STDLIB_MOD (GH-29720)
https://github.com/python/cpython/commit/9cf5646bb465b7d3d68bfe6d4711feb43d565051

New changeset 324527012fa1078428a6207918640cf860e28c81 by Erlend Egeberg Aasland in branch 'main':
bpo-45847: Port _posixshmem to PY_STDLIB_MOD (GH-29738)
https://github.com/python/cpython/commit/324527012fa1078428a6207918640cf860e28c81

New changeset 8af6481f6b7d43646c47d8fa6cc6d5eb465e2b0f by Christian Heimes in branch 'main':
bpo-45847: Port _uuid to PY_STDLIB_MOD (GH-29741)
https://github.com/python/cpython/commit/8af6481f6b7d43646c47d8fa6cc6d5eb465e2b0f

New changeset 64c3807da93fc3e0c15bc376f220b2d24551023e by Christian Heimes in branch 'main':
bpo-45847: Fix _crypt detection on Ubuntu (GH-29743)
https://github.com/python/cpython/commit/64c3807da93fc3e0c15bc376f220b2d24551023e

Some info regarding _multiprocessing:

Modules/_multiprocessing/semaphore.c is currently conditionally included in setup.py (HAVE_SEM_OPEN && !POSIX_SEMAPHORES_NOT_ENABLED), but always included in Modules/Setup.

Here's some historical bpo's (more or less) relevant to Modules/_multiprocessing/semaphore.c:

- bpo-7272
- bpo-5545
- bpo-3770


Commit 99c48a8d315fe55c8e1e8eac2e01cd930cb89686 message says:
    Author: Hye-Shik Chang <hyeshik@gmail.com>
    Date:   Sat Jun 28 01:04:31 2008 +0000

    Give information for compililation of _multiprocessing.SemLock on FreeBSD:
    
    FreeBSD's P1003.1b semaphore support is highly experimental and
    it's disabled by default.  Even if a user loads the experimental
    kernel module manually, _multiprocessing doesn't work correctly due
    to several known incompatibilities around sem_unlink and sem_getvalue,
    yet.


Excerpt from the FreeBSD 9.0 release notes[^1], released four years later (2012-01-12):

    kern.features.sysv_sem.                   System V semaphores support
    kern.features.p1003_1b_mqueue.            POSIX P1003.1B message queues support
    kern.features.p1003_1b_semaphores.        POSIX P1003.1B semaphores support
    kern.features.kposix_priority_scheduling  POSIX P1003.1B real-time extensions


I haven't checked OpenBSD or NetBSD yet.


Other relevant commits:

  - c4920e86ef7511b4e858028e870b1811437a71d0
  - 40a6164afa79f6b97e7e40e0f35f6081fde437c2



[^1]: https://www.freebsd.org/releases/9.0R/relnotes-detailed/