bpo-41995: Fix a null pointer dereference in _tracemalloc.c

[Yunlongs]

bpo-41995 :fix a null pointer dereference in _tracemalloc.c
https://bugs.python.org/issue41995

https://bugs.python.org/issue41995

[the-knights-who-say-ni]

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[vstinner]

The fix is correct, but I will wait until you sign the CLA to merge it.

[Yunlongs]

The fix is correct, but I will wait until you sign the CLA to merge it.

Ok,i have signed the CLA

[miss-islington]

Thanks @Yunlongs for the PR, and @vstinner for merging it 🌮🎉.. I'm working now to backport this PR to: 3.9.
🐍🍒⛏🤖

[miss-islington]

Sorry @Yunlongs and @vstinner, I had trouble checking out the 3.9 backport branch.
Please backport using cherry_picker on command line.
cherry_picker 66c28f50c76e4f23af7146e0e580457c5fd6bde7 3.9

[miss-islington]

Thanks @Yunlongs for the PR, and @vstinner for merging it 🌮🎉.. I'm working now to backport this PR to: 3.9.
🐍🍒⛏🤖

[bedevere-bot]

GH-22681 is a backport of this pull request to the 3.9 branch.

[miss-islington]

Thanks @Yunlongs for the PR, and @vstinner for merging it 🌮🎉.. I'm working now to backport this PR to: 3.8.
🐍🍒⛏🤖

[miss-islington]

Sorry, @Yunlongs and @vstinner, I could not cleanly backport this to 3.8 due to a conflict.
Please backport using cherry_picker on command line.
cherry_picker 66c28f50c76e4f23af7146e0e580457c5fd6bde7 3.8

[vstinner]

Oh, Python 3.8 is not affected: tracemalloc_copy_trace() is new in Python 3.9.

[bedevere-bot]

⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot s390x RHEL8 3.x has failed when building commit 66c28f5.

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/509/builds/179) and take a look at the build logs.
4. Check if the failure is related to this commit (66c28f5) 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/509/builds/179

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

== Tests result: ENV CHANGED ==

409 tests OK.

10 slowest tests:

• test_concurrent_futures: 3 min 43 sec
• test_multiprocessing_spawn: 1 min 48 sec
• test_peg_generator: 1 min 41 sec
• test_tokenize: 1 min 37 sec
• test_capi: 1 min 28 sec
• test_asyncio: 1 min 21 sec
• test_multiprocessing_forkserver: 1 min 18 sec
• test_unparse: 1 min 17 sec
• test_gdb: 1 min 10 sec
• test_multiprocessing_fork: 1 min 4 sec

1 test altered the execution environment:
test_asyncio

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

Total duration: 6 min 57 sec

Click to see traceback logs

Traceback (most recent call last):
  File "/home/dje/cpython-buildarea/3.x.edelsohn-rhel8-z/build/Lib/asyncio/sslproto.py", line 321, in __del__
    self.close()
  File "/home/dje/cpython-buildarea/3.x.edelsohn-rhel8-z/build/Lib/asyncio/sslproto.py", line 316, in close
    self._ssl_protocol._start_shutdown()
  File "/home/dje/cpython-buildarea/3.x.edelsohn-rhel8-z/build/Lib/asyncio/sslproto.py", line 590, in _start_shutdown
    self._abort()
  File "/home/dje/cpython-buildarea/3.x.edelsohn-rhel8-z/build/Lib/asyncio/sslproto.py", line 731, in _abort
    self._transport.abort()
  File "/home/dje/cpython-buildarea/3.x.edelsohn-rhel8-z/build/Lib/asyncio/selector_events.py", line 680, in abort
    self._force_close(None)
  File "/home/dje/cpython-buildarea/3.x.edelsohn-rhel8-z/build/Lib/asyncio/selector_events.py", line 731, in _force_close
    self._loop.call_soon(self._call_connection_lost, exc)
  File "/home/dje/cpython-buildarea/3.x.edelsohn-rhel8-z/build/Lib/asyncio/base_events.py", line 746, in call_soon
    self._check_closed()
  File "/home/dje/cpython-buildarea/3.x.edelsohn-rhel8-z/build/Lib/asyncio/base_events.py", line 510, in _check_closed
    raise RuntimeError('Event loop is closed')
RuntimeError: Event loop is closed