gh-121381 Remove subprocess._USE_VFORK escape hatch (#121383)

This flag was added as an escape hatch in gh-91401 and backported to
Python 3.10. The flag broke at some point between its addition and now.
As there is currently no publicly known environments that require this,
remove it rather than work on fixing it.

This leaves the flag in the subprocess module to not break code which
may have used / checked the flag itself.

discussion: https://discuss.python.org/t/subprocess-use-vfork-escape-hatch-broken-fix-or-remove/56915/2

1 files changed, 1 insertions, 21 deletions

diff --git a/Lib/test/test_subprocess.py b/Lib/test/test_subprocess.py
index 9412a2d..f065b9c 100644
--- a/Lib/test/test_subprocess.py
+++ b/Lib/test/test_subprocess.py
@@ -3278,7 +3278,7 @@ class POSIXProcessTestCase(BaseTestCase):
                         1, 2, 3, 4,
                         True, True, 0,
                         None, None, None, -1,
-                        None, True)
+                        None)
                 self.assertIn('fds_to_keep', str(c.exception))
         finally:
             if not gc_enabled:
@@ -3415,25 +3415,6 @@ class POSIXProcessTestCase(BaseTestCase):
 
     @unittest.skipIf(not sysconfig.get_config_var("HAVE_VFORK"),
                      "vfork() not enabled by configure.")
-    @mock.patch("subprocess._fork_exec")
-    @mock.patch("subprocess._USE_POSIX_SPAWN", new=False)
-    def test__use_vfork(self, mock_fork_exec):
-        self.assertTrue(subprocess._USE_VFORK)  # The default value regardless.
-        mock_fork_exec.side_effect = RuntimeError("just testing args")
-        with self.assertRaises(RuntimeError):
-            subprocess.run([sys.executable, "-c", "pass"])
-        mock_fork_exec.assert_called_once()
-        # NOTE: These assertions are *ugly* as they require the last arg
-        # to remain the have_vfork boolean. We really need to refactor away
-        # from the giant "wall of args" internal C extension API.
-        self.assertTrue(mock_fork_exec.call_args.args[-1])
-        with mock.patch.object(subprocess, '_USE_VFORK', False):
-            with self.assertRaises(RuntimeError):
-                subprocess.run([sys.executable, "-c", "pass"])
-            self.assertFalse(mock_fork_exec.call_args_list[-1].args[-1])
-
-    @unittest.skipIf(not sysconfig.get_config_var("HAVE_VFORK"),
-                     "vfork() not enabled by configure.")
     @unittest.skipIf(sys.platform != "linux", "Linux only, requires strace.")
     @mock.patch("subprocess._USE_POSIX_SPAWN", new=False)
     def test_vfork_used_when_expected(self):
@@ -3478,7 +3459,6 @@ class POSIXProcessTestCase(BaseTestCase):
         # Test that each individual thing that would disable the use of vfork
         # actually disables it.
         for sub_name, preamble, sp_kwarg, expect_permission_error in (
-                ("!use_vfork", "subprocess._USE_VFORK = False", "", False),
                 ("preexec", "", "preexec_fn=lambda: None", False),
                 ("setgid", "", f"group={os.getgid()}", True),
                 ("setuid", "", f"user={os.getuid()}", True),