bpo-41654: Fix deallocator of MemoryError to account for subclasses (GH-22020)
When allocating MemoryError classes, there is some logic to use
pre-allocated instances in a freelist only if the type that is being
allocated is not a subclass of MemoryError. Unfortunately in the
destructor this logic is not present so the freelist is altered even
with subclasses of MemoryError.
diff --git a/Lib/test/test_exceptions.py b/Lib/test/test_exceptions.py
index 2ffe8ca..1ec4468 100644
--- a/Lib/test/test_exceptions.py
+++ b/Lib/test/test_exceptions.py
@@ -1,6 +1,7 @@
# Python test set -- part 5, built-in exceptions
import copy
+import gc
import os
import sys
import unittest
@@ -1330,6 +1331,36 @@
del AssertionError
self.fail('Expected exception')
+ def test_memory_error_subclasses(self):
+ # bpo-41654: MemoryError instances use a freelist of objects that are
+ # linked using the 'dict' attribute when they are inactive/dead.
+ # Subclasses of MemoryError should not participate in the freelist
+ # schema. This test creates a MemoryError object and keeps it alive
+ # (therefore advancing the freelist) and then it creates and destroys a
+ # subclass object. Finally, it checks that creating a new MemoryError
+ # succeeds, proving that the freelist is not corrupted.
+
+ class TestException(MemoryError):
+ pass
+
+ try:
+ raise MemoryError
+ except MemoryError as exc:
+ inst = exc
+
+ try:
+ raise TestException
+ except Exception:
+ pass
+
+ for _ in range(10):
+ try:
+ raise MemoryError
+ except MemoryError as exc:
+ pass
+
+ gc_collect()
+
class ImportErrorTests(unittest.TestCase):