Stackless issue python#81: adapt the interpreter shutdown test to newer versions of Python 3.

The 2.7 detector hook (cleanup of codecs search path) does not work with Python 3.3 and later.
Adapt the test cases to use a different hook (builtins._).

Author: Anselm Kruis

Stackless/test/test_interpreter_shutdown.py

@@ -2,7 +2,7 @@
 import sys
 import _thread as thread
 import stackless
-import codecs
+import builtins
 import os
 import time
 import collections
@@ -63,13 +63,14 @@ def __init__(self, out, checks, tasklets):
         self.checks = checks
         self.tasklets = tasklets
 
-        # register the detector in the codecs search path
-        # it will be cleared after clearing the thread states
-        # this way the detector runs very late
-        def dummy_codecs_search_function(name):
-            return None
-        codecs.register(dummy_codecs_search_function)
-        dummy_codecs_search_function.x = self
+        # In Py_Finalize() the PyImport_Cleanup() runs shortly after 
+        # slp_kill_tasks_with_stacks(NULL).
+        # As very first action of PyImport_Cleanup() the Python
+        # interpreter sets builtins._ to None.
+        # Therefore we can use this assignment to trigger the execution
+        # of this detector. At this point the interpreter is still almost fully
+        # intact.
+        builtins._ = self
 
     def __del__(self):
         if self.debug:

Stackless/unittests/test_shutdown.py

@@ -35,7 +35,7 @@
 from __future__ import print_function, absolute_import, division
 import sys
 import stackless
-import codecs
+import builtins
 import os
 import time
 import collections
@@ -220,13 +220,14 @@ def __init__(self, out, checks, tasklets):
         self.checks = checks
         self.tasklets = tasklets
 
-        # register the detector in the codecs search path
-        # it will be cleared after clearing the thread states
-        # this way the detector runs very late
-        def dummy_codecs_search_function(name):
-            return None
-        codecs.register(dummy_codecs_search_function)
-        dummy_codecs_search_function.x = self
+        # In Py_Finalize() the PyImport_Cleanup() runs shortly after 
+        # slp_kill_tasks_with_stacks(NULL).
+        # As very first action of PyImport_Cleanup() the Python
+        # interpreter sets builtins._ to None.
+        # Therefore we can use this assignment to trigger the execution
+        # of this detector. At this point the interpreter is still almost fully
+        # intact.
+        builtins._ = self
 
     def __del__(self):
         if self.debug:
@@ -405,7 +406,7 @@ def interpreter_shutdown_test():
     test = Test()
     detector = Detector(test.out, test.checks, test.tasklets)
     assert sys.getrefcount(detector) - sys.getrefcount(object()) == 2
-    detector = None  # the last ref is now in the codecs search path
+    detector = None  # the last ref is now in bultins._
     thread.start_new_thread(test.other_thread_main, ())
     ready.acquire()  # Be sure the other thread is ready.
     # print("at end")