gh-151510: Fix __lazy_import__ without frame

[aisk]

I did not add a test because the fix is a straightforward, and exercising this would require extra _testcapi scaffolding to call __lazy_import__ without a Python frame.

Test added.

• Issue: bltinmodule.c: lazy_import NULL deref without Python frame #151510

[sobolevn]

Can we test this?

[sobolevn]

LGTM! Thanks!

[pablogsal]

Thanks for the fix @aisk !

[miss-islington-app]

Thanks @aisk for the PR, and @pablogsal for merging it 🌮🎉.. I'm working now to backport this PR to: 3.15.
🐍🍒⛏🤖

[bedevere-app]

GH-151610 is a backport of this pull request to the 3.15 branch.

[bedevere-bot]

⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot AMD64 Debian root 3.x (tier-1) has failed when building commit eff805b.

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/#/builders/345/builds/14521) and take a look at the build logs.
4. Check if the failure is related to this commit (eff805b) 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/#/builders/345/builds/14521

Failed tests:

• test.test_multiprocessing_fork.test_misc

Failed subtests:

• test_large_pool - test.test_multiprocessing_fork.test_misc.MiscTestCase.test_large_pool

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

==

Click to see traceback logs

Traceback (most recent call last):
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/test/_test_multiprocessing.py", line 7311, in test_large_pool
    rc, out, err = script_helper.assert_python_ok(testfn)
                   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/test/support/script_helper.py", line 182, in assert_python_ok
    return _assert_python(True, *args, **env_vars)
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/test/support/script_helper.py", line 167, in _assert_python
    res.fail(cmd_line)
    ~~~~~~~~^^^^^^^^^^
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/test/support/script_helper.py", line 80, in fail
    raise AssertionError(f"Process return code is {exitcode}\n"
    ...<10 lines>...
                         f"---")
AssertionError: Process return code is 1
command line: ['/root/buildarea/3.x.angelico-debian-amd64/build/python', '-X', 'faulthandler', '-I', '@test_1237050_tmpæ']


Traceback (most recent call last):
  File "<string>", line 1, in <module>
    import sys; from multiprocessing.forkserver import main; main(10, 11, ['__main__'], sys_argv=sys.argv[1:], **{'sys_path': ['/root/buildarea/3.x.angelico-debian-amd64/build/target/lib/python316.zip', '/root/buildarea/3.x.angelico-debian-amd64/build/Lib', '/root/buildarea/3.x.angelico-debian-amd64/build/build/lib.linux-x86_64-3.16'], 'main_path': '/root/buildarea/3.x.angelico-debian-amd64/build/build/test_python_1237050æ/@test_1237050_tmpæ', 'authkey_r': 13})
                                                             ~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/forkserver.py", line 406, in main
    pid = os.fork()
OSError: [Errno 12] Cannot allocate memory
Traceback (most recent call last):
  File "/root/buildarea/3.x.angelico-debian-amd64/build/build/test_python_1237050æ/@test_1237050_tmpæ", line 4, in <module>
    with multiprocessing.Pool(200) as p:
         ~~~~~~~~~~~~~~~~~~~~^^^^^
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/context.py", line 119, in Pool
    return Pool(processes, initializer, initargs, maxtasksperchild,
                context=self.get_context())
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/pool.py", line 215, in __init__
    self._repopulate_pool()
    ~~~~~~~~~~~~~~~~~~~~~^^
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/pool.py", line 306, in _repopulate_pool
    return self._repopulate_pool_static(self._ctx, self.Process,
           ~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^
                                        self._processes,
                                        ^^^^^^^^^^^^^^^^
    ...<3 lines>...
                                        self._maxtasksperchild,
                                        ^^^^^^^^^^^^^^^^^^^^^^^
                                        self._wrap_exception)
                                        ^^^^^^^^^^^^^^^^^^^^^
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/pool.py", line 329, in _repopulate_pool_static
    w.start()
    ~~~~~~~^^
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/process.py", line 121, in start
    self._popen = self._Popen(self)
                  ~~~~~~~~~~~^^^^^^
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/context.py", line 309, in _Popen
    return Popen(process_obj)
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/popen_forkserver.py", line 35, in __init__
    super().__init__(process_obj)
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/popen_fork.py", line 20, in __init__
    self._launch(process_obj)
    ~~~~~~~~~~~~^^^^^^^^^^^^^
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/popen_forkserver.py", line 59, in _launch
    self.pid = forkserver.read_signed(self.sentinel)
               ~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/multiprocessing/forkserver.py", line 472, in read_signed
    raise EOFError('unexpected EOF')
EOFError: unexpected EOF
---

[aisk]

The buildbot failure should be unrelated.