Import Upstream version 2.7.18

Lib/test/leakers/README.txt

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+This directory contains test cases that are known to leak references.
+The idea is that you can import these modules while in the interpreter
+and call the leak function repeatedly.  This will only be helpful if
+the interpreter was built in debug mode.  If the total ref count
+doesn't increase, the bug has been fixed and the file should be removed
+from the repository.
+
+Note:  be careful to check for cyclic garbage.  Sometimes it may be helpful
+to define the leak function like:
+
+def leak():
+    def inner_leak():
+        # this is the function that leaks, but also creates cycles
+    inner_leak()
+    gc.collect() ; gc.collect() ; gc.collect()
+
+Here's an example interpreter session for test_gestalt which still leaks:
+
+>>> from test.leakers.test_gestalt import leak
+[24275 refs]
+>>> leak()
+[28936 refs]
+>>> leak()
+[28938 refs]
+>>> leak()
+[28940 refs]
+>>> 
+
+Once the leak is fixed, the test case should be moved into an appropriate
+test (even if it was originally from the test suite).  This ensures the
+regression doesn't happen again.  And if it does, it should be easier
+to track down.

Lib/test/leakers/test_ctypes.py

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+
+# Taken from Lib/ctypes/test/test_keeprefs.py, PointerToStructure.test().
+
+from ctypes import Structure, c_int, POINTER
+import gc
+
+def leak_inner():
+    class POINT(Structure):
+        _fields_ = [("x", c_int)]
+    class RECT(Structure):
+        _fields_ = [("a", POINTER(POINT))]
+
+def leak():
+    leak_inner()
+    gc.collect()

Lib/test/leakers/test_dictself.py

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+'''Test case for "self.__dict__ = self" circular reference bug (#1469629)'''
+
+import gc
+
+class LeakyDict(dict):
+    pass
+
+def leak():
+    ld = LeakyDict()
+    ld.__dict__ = ld
+    del ld
+    gc.collect(); gc.collect(); gc.collect()

Lib/test/leakers/test_gestalt.py

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+import sys
+
+if sys.platform != 'darwin':
+    raise ValueError, "This test only leaks on Mac OS X"
+
+def leak():
+    # taken from platform._mac_ver_lookup()
+    from gestalt import gestalt
+    import MacOS
+
+    try:
+        gestalt('sysu')
+    except MacOS.Error:
+        pass

Lib/test/leakers/test_selftype.py

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+# Reference cycles involving only the ob_type field are rather uncommon
+# but possible.  Inspired by SF bug 1469629.
+
+import gc
+
+def leak():
+    class T(type):
+        pass
+    class U(type):
+        __metaclass__ = T
+    U.__class__ = U
+    del U
+    gc.collect(); gc.collect(); gc.collect()