bpo-33257: Fix race conditions for non-threaded Tcl

Lib/test/test_tkinter/test_threads.py

@@ -0,0 +1,98 @@
+from __future__ import print_function
+import tkinter
+import random
+import string
+import sys
+import threading
+import time
+
+import unittest
+
+
+class TestThreads(unittest.TestCase):
+    def test_threads(self):
+        import subprocess
+        p = subprocess.Popen([sys.executable, __file__, "run"],
+                             stdout=subprocess.PIPE,
+                             stderr=subprocess.PIPE)
+        self.addCleanup(p.stdout.close)
+        self.addCleanup(p.stderr.close)
+        try:
+            # Test code is designed to complete in a few seconds
+            stdout, stderr = p.communicate(timeout=10)
+        except subprocess.TimeoutExpired:
+            p.kill()
+            stdout, stderr = p.communicate()
+            self.fail("Test code hang. Stderr: " + repr(stderr))
+        rc = p.returncode
+        self.assertTrue(rc == 0,
+                        "Nonzero exit status: " + str(rc) + "; stderr:" + repr(stderr))
+        self.assertTrue(len(stderr) == 0, "stderr: " + repr(stderr))
+
+
+running = True
+
+
+class EventThread(threading.Thread):
+    def __init__(self, target):
+        super(EventThread, self).__init__()
+        self.target = target
+
+    def run(self):
+        while running:
+            time.sleep(0.02)
+            c = random.choice(string.ascii_letters)
+            self.target.event_generate(c)
+
+
+class Main(object):
+    def __init__(self):
+        self.root = tkinter.Tk()
+        self.root.bind('<Key>', dummy_handler)
+        self.threads = []
+
+        self.t_cleanup = threading.Thread(target=self.tf_stop)
+
+    def go(self):
+        self.root.after(0, self.add_threads)
+        self.root.after(500, self.stop)
+        self.root.protocol("WM_DELETE_WINDOW", self.stop)
+        self.root.mainloop()
+        self.t_cleanup.join()
+
+    def stop(self):
+        self.t_cleanup.start()
+
+    def tf_stop(self):
+        global running
+        running = False
+        for t in self.threads: t.join()
+        self.root.after(0, self.root.destroy)
+
+    def add_threads(self):
+        for _ in range(20):
+            t = EventThread(self.root)
+            self.threads.append(t)
+            t.start()
+
+
+def dummy_handler(event):
+    pass
+
+
+tests_gui = (TestThreads,)
+
+if __name__ == '__main__':
+    import sys, os
+
+    if sys.argv[1:] == ['run']:
+        if os.name == 'nt':
+            import ctypes
+
+            # the bug causes crashes
+            ctypes.windll.kernel32.SetErrorMode(3)
+        Main().go()
+    else:
+        from test.support import run_unittest
+
+        run_unittest(*tests_gui)

Misc/NEWS.d/next/Library/2018-04-14-01-26-10.bpo-33257.i32qOW.rst

@@ -0,0 +1 @@
+Fixed race conditions in Tkinter with nonthreaded Tcl