Merged revisions 85392 via svnmerge from

svn+ssh://pythondev@svn.python.org/python/branches/py3k

........
  r85392 | benjamin.peterson | 2010-10-12 17:57:59 -0500 (Tue, 12 Oct 2010) | 1 line

  prefer clearing global objects to obscure module.__dict__ bugs #10068
........

Doc/reference/datamodel.rst

@@ -739,6 +739,13 @@ Modules
    Special read-only attribute: :attr:`__dict__` is the module's namespace as a
    dictionary object.
 
+   .. impl-detail::
+
+      Because of the way CPython clears module dictionaries, the module
+      dictionary will be cleared when the module falls out of scope even if the
+      dictionary still has live references.  To avoid this, copy the dictionary
+      or keep the module around while using its dictionary directly.
+
    .. index::
       single: __name__ (module attribute)
       single: __doc__ (module attribute)

Lib/test/test_module.py

@@ -1,6 +1,6 @@
 # Test the module type
 import unittest
-from test.test_support import run_unittest
+from test.test_support import run_unittest, gc_collect
 
 import sys
 ModuleType = type(sys)
@@ -55,14 +55,29 @@ class ModuleTests(unittest.TestCase):
               {"__name__": "foo", "__doc__": "foodoc", "bar": 42})
         self.assertTrue(foo.__dict__ is d)
 
+    @unittest.expectedFailure
     def test_dont_clear_dict(self):
         # See issue 7140.
         def f():
             foo = ModuleType("foo")
             foo.bar = 4
             return foo
+        gc_collect()
         self.assertEqual(f().__dict__["bar"], 4)
 
+    def test_clear_dict_in_ref_cycle(self):
+        destroyed = []
+        m = ModuleType("foo")
+        m.destroyed = destroyed
+        s = """class A:
+    def __del__(self):
+        destroyed.append(1)
+a = A()"""
+        exec(s, m.__dict__)
+        del m
+        gc_collect()
+        self.assertEqual(destroyed, [1])
+
 def test_main():
     run_unittest(ModuleTests)
 

Misc/NEWS

@@ -10,6 +10,9 @@ What's New in Python 2.7.1?
 Core and Builtins
 -----------------
 
+- Issue #10068: Global objects which have reference cycles with their module's
+  dict are now cleared again. This causes issue #7140 to appear again.
+
 - Issue #9869: Make long() and PyNumber_Long return something of type
   long for a class whose __long__ method returns a plain int.  This
   fixes an interpreter crash when initializing an instance of a long

Objects/moduleobject.c

@@ -175,10 +175,7 @@ module_dealloc(PyModuleObject *m)
 {
     PyObject_GC_UnTrack(m);
     if (m->md_dict != NULL) {
-        /* If we are the only ones holding a reference, we can clear
+        _PyModule_Clear((PyObject *)m);
-           the dictionary. */
-        if (Py_REFCNT(m->md_dict) == 1)
-            _PyModule_Clear((PyObject *)m);
         Py_DECREF(m->md_dict);
     }
     Py_TYPE(m)->tp_free((PyObject *)m);