[3.13] gh-109746: Make _thread.start_new_thread delete state of new thread on its startup failure (GH-109761) (GH-127171)

If Python fails to start newly created thread
due to failure of underlying PyThread_start_new_thread() call,
its state should be removed from interpreter' thread states list
to avoid its double cleanup.

(cherry picked from commit ca3ea9ad05)

Co-authored-by: Radislav Chugunov <52372310+chgnrdv@users.noreply.github.com>

Lib/test/test_threading.py

@@ -1171,6 +1171,41 @@ class ThreadTests(BaseTestCase):
         self.assertEqual(out.strip(), b"OK")
         self.assertIn(b"can't create new thread at interpreter shutdown", err)
 
+    def test_start_new_thread_failed(self):
+        # gh-109746: if Python fails to start newly created thread
+        # due to failure of underlying PyThread_start_new_thread() call,
+        # its state should be removed from interpreter' thread states list
+        # to avoid its double cleanup
+        try:
+            from resource import setrlimit, RLIMIT_NPROC
+        except ImportError as err:
+            self.skipTest(err)  # RLIMIT_NPROC is specific to Linux and BSD
+        code = """if 1:
+            import resource
+            import _thread
+
+            def f():
+                print("shouldn't be printed")
+
+            limits = resource.getrlimit(resource.RLIMIT_NPROC)
+            [_, hard] = limits
+            resource.setrlimit(resource.RLIMIT_NPROC, (0, hard))
+
+            try:
+                _thread.start_new_thread(f, ())
+            except RuntimeError:
+                print('ok')
+            else:
+                print('skip')
+        """
+        _, out, err = assert_python_ok("-u", "-c", code)
+        out = out.strip()
+        if out == b'skip':
+            self.skipTest('RLIMIT_NPROC had no effect; probably superuser')
+        self.assertEqual(out, b'ok')
+        self.assertEqual(err, b'')
+
+
 class ThreadJoinOnShutdown(BaseTestCase):
 
     def _run_and_join(self, script):