gh-103092: Isolate socket

[erlend-aasland]

• Issue: Isolate Stdlib Extension Modules #103092

[bedevere-bot]

🤖 New build scheduled with the buildbot fleet by @erlend-aasland for commit b4edf64 🤖

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[erlend-aasland]

There's some leaks that needs to be adressed:

$ ./python.exe measure.py
before=46451, after=47809
before=47811, after=48549
before=48549, after=49287
before=49287, after=50025
before=50025, after=50763

measure.py

import gc
import sys

for _ in range(5):
    gc.collect()
    before = sys.gettotalrefcount()

    import _socket
    del sys.modules["_socket"]
    del _socket

    gc.collect()
    after = sys.gettotalrefcount()

    print(f"{before=}, {after=}")
    # assert after == before

... and these two:

$ ./python.exe -m test -R : test_socket -m RecvmsgIntoSCMRightsStreamTest                                                                              Raised RLIMIT_NOFILE: 256 -> 1024
0:00:00 load avg: 1.96 Run tests sequentially
0:00:00 load avg: 1.96 [1/1] test_socket
beginning 9 repetitions
123456789
.........
test_socket leaked [10, 10, 10, 10] file descriptors, sum=40
test_socket failed (reference leak)

== Tests result: FAILURE ==

1 test failed:
    test_socket

Total duration: 1.8 sec
Tests result: FAILURE
$ ./python.exe -m test -R : test_socket -m RecvmsgSCMRightsStreamTest                                                                                  Raised RLIMIT_NOFILE: 256 -> 1024
0:00:00 load avg: 2.52 Run tests sequentially
0:00:00 load avg: 2.52 [1/1] test_socket
beginning 9 repetitions
123456789
.........
test_socket leaked [10, 10, 10, 10] file descriptors, sum=40
test_socket failed (reference leak)

== Tests result: FAILURE ==

1 test failed:
    test_socket

Total duration: 1.8 sec
Tests result: FAILURE

[erlend-aasland]

Regarding #103094 (comment): the file descriptors leak on main as well, so it is not a regression introduced by this PR. Let's not bother with those. There's still references leaked by repeated init of the module, though.

[erlend-aasland]

Seems like the leaks are due to the capsulated C API not being freed.

[erlend-aasland]

I'd like to hold this PR until #103261 has landed.

[bedevere-bot]

🤖 New build scheduled with the buildbot fleet by @erlend-aasland for commit 2019a93 🤖

If you want to schedule another build, you need to add the 🔨 test-with-refleak-buildbots label again.

[kumaraditya303]

LGTM