gh-152017: Fix deque_clear to no longer alters exceptions

Author: brijkapadia

Lib/test/test_collections.py

@@ -15,6 +15,7 @@
 from test.support.import_helper import import_fresh_module
 import types
 import unittest
+import _testcapi
 
 from collections import namedtuple, Counter, OrderedDict, _count_elements
 from collections import UserDict, UserString, UserList
@@ -2475,6 +2476,22 @@ def test_symmetric_difference(self):
             pp ^= qq
             self.assertEqual(pp, r)
 
+################################################################################
+### Deque
+################################################################################
+
+class TestDeque(unittest.TestCase):
+
+    def test_deque_oom(self):
+        for n in range(1, 80):
+            d = deque(range(200))
+            _testcapi.set_nomemory(n, 0)
+            try:
+                d.copy()
+                _testcapi.remove_mem_hooks()
+                break
+            except MemoryError:
+                _testcapi.remove_mem_hooks()
 
 def load_tests(loader, tests, pattern):
     tests.addTest(doctest.DocTestSuite(collections))

Modules/_collectionsmodule.c

@@ -746,9 +746,10 @@ deque_clear(PyObject *self)
        adversary could cause it to never terminate).
     */
 
+    PyObject *old_exc = PyErr_GetRaisedException();
     b = newblock(deque);
+    PyErr_SetRaisedException(old_exc);
     if (b == NULL) {
-        PyErr_Clear();
         goto alternate_method;
     }