Have vfork specific tests disable posix_spawn.

Author: gpshead

Lib/test/test_subprocess.py

@@ -3348,6 +3348,7 @@ def exit_handler():
  @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")
@@ -3366,9 +3367,13 @@ def test__use_vfork(self, mock_fork_exec):
  @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):
  # This is a performance regression test to ensure we default to using
  # vfork() when possible.
+ # Technically this test could pass when posix_spawn is used as well
+ # because libc tends to implement that internally using vfork. But
+ # that'd just be testing a libc+kernel implementation detail.
  strace_binary = "/usr/bin/strace"
  # The only system calls we are interested in.
  strace_filter = "--trace=clone,clone2,clone3,fork,vfork,exit,exit_group"