address review comments from @vstinner

Author: TheSkyC

Lib/test/test_itertools.py

@@ -755,38 +755,36 @@ def keys():
         next(g)  # must pass with address sanitizer
 
     def test_grouper_reentrant_eq_does_not_crash(self):
-            # regression test for gh-146613
-            grouper_iter = None
-            class Key:
-                __hash__ = None
-
-                def __init__(self, do_advance):
-                    self.do_advance = do_advance
-                    self.payload = bytearray(256)
-
-                def __eq__(self, other):
-                    nonlocal grouper_iter
-                    if self.do_advance:
-                        self.do_advance = False
-                        if grouper_iter is not None:
-                            try:
-                                next(grouper_iter)
-                            except StopIteration:
-                                pass
-                        for _ in range(50):
-                            bytearray(256)
-                        return NotImplemented
-                    return True
-
-            def keyfunc(element):
-                if element == 0:
-                    return Key(do_advance=True)
-                return Key(do_advance=False)
-
-            g = itertools.groupby(range(4), keyfunc)
-            key, grouper_iter = next(g)
-            items = list(grouper_iter)
-            self.assertEqual(len(items), 1)
+        # regression test for gh-146613
+        grouper_iter = None
+        
+        class Key:
+            __hash__ = None
+
+            def __init__(self, do_advance):
+                self.do_advance = do_advance
+
+            def __eq__(self, other):
+                nonlocal grouper_iter
+                if self.do_advance:
+                    self.do_advance = False
+                    if grouper_iter is not None:
+                        try:
+                            next(grouper_iter)
+                        except StopIteration:
+                            pass
+                    return NotImplemented
+                return True
+
+        def keyfunc(element):
+            if element == 0:
+                return Key(do_advance=True)
+            return Key(do_advance=False)
+
+        g = itertools.groupby(range(4), keyfunc)
+        key, grouper_iter = next(g)
+        items = list(grouper_iter)
+        self.assertEqual(len(items), 1)
 
     def test_filter(self):
         self.assertEqual(list(filter(isEven, range(6))), [0,2,4])

Misc/NEWS.d/next/Library/2026-04-01-11-05-36.gh-issue-146613.GzjUFK.rst

@@ -1,4 +1,4 @@
-:mod:`itertools`: Fix re-entrant use-after-free in ``_grouper.__next__``
+:mod:`itertools`: Fix re-entrant use-after-free in ``itertools.groupby()``
 that could lead to a segmentation fault when a user-defined ``__eq__``
 re-enters the grouper iterator. The same pattern was previously fixed
-in ``groupby.__next__`` (gh-143543).
+in gh-143543.