Issue #26494: Fixed crash on iterating exhausting iterators.

Affected classes are generic sequence iterators, iterators of str, bytes,
bytearray, list, tuple, set, frozenset, dict, OrderedDict, corresponding
views and os.scandir() iterator.

1 files changed, 19 insertions, 0 deletions

diff --git a/Lib/test/support/__init__.py b/Lib/test/support/__init__.py
index b82f9cb..e124fab 100644
--- a/Lib/test/support/__init__.py
+++ b/Lib/test/support/__init__.py
@@ -2366,3 +2366,22 @@ def run_in_subinterp(code):
                                      "memory allocations")
     import _testcapi
     return _testcapi.run_in_subinterp(code)
+
+
+def check_free_after_iterating(test, iter, cls, args=()):
+    class A(cls):
+        def __del__(self):
+            nonlocal done
+            done = True
+            try:
+                next(it)
+            except StopIteration:
+                pass
+
+    done = False
+    it = iter(A(*args))
+    # Issue 26494: Shouldn't crash
+    test.assertRaises(StopIteration, next, it)
+    # The sequence should be deallocated just after the end of iterating
+    gc_collect()
+    test.assertTrue(done)