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[3.10] gh-91401: Conservative backport of subprocess._USE_VFORK (#91932)

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This does not alter the `_posixsubprocess.fork_exec()` private API to
avoid issues for anyone relying on that (bad idea) or for anyone who's
`subprocess.py` and `_posixsubprocess.so` upgrades may not become
visible to existing Python 3.10 processes at the same time.

Backports the concept of cd5726fe67.

Provides a fail-safe way to disable vfork for #91401.

I didn't backport the documentation as I don't actually expect this to be used and `.. versionadded: 3.10.5` always looks weird in docs. It's being done more to have a fail-safe in place for people just in case.
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Gregory P. Smith 2022-05-01 16:09:50 -07:00 • committed by GitHub
parent e7de543219
commit ea1eba03e7
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4 changed files with 55 additions and 2 deletions
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22
Lib/test/test_subprocess.py
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@ -1702,6 +1702,28 @@ class RunFuncTestCase(BaseTestCase):
msg="TimeoutExpired was delayed! Bad traceback:\n```\n"
f"{stacks}```")
@unittest.skipIf(not sysconfig.get_config_var("HAVE_VFORK"),
"vfork() not enabled by configure.")
def test__use_vfork(self):
# Attempts code coverage within _posixsubprocess.c on the code that
# probes the subprocess module for the existence and value of this
# attribute in 3.10.5.
self.assertTrue(subprocess._USE_VFORK) # The default value regardless.
with mock.patch.object(subprocess, "_USE_VFORK", False):
self.assertEqual(self.run_python("pass").returncode, 0,
msg="False _USE_VFORK failed")
class RaisingBool:
def __bool__(self):
raise RuntimeError("force PyObject_IsTrue to return -1")
with mock.patch.object(subprocess, "_USE_VFORK", RaisingBool()):
self.assertEqual(self.run_python("pass").returncode, 0,
msg="odd bool()-error _USE_VFORK failed")
del subprocess._USE_VFORK
self.assertEqual(self.run_python("pass").returncode, 0,
msg="lack of a _USE_VFORK attribute failed")
def _get_test_grp_name():
for name_group in ('staff', 'nogroup', 'grp', 'nobody', 'nfsnobody'):