gh-145376: Fix GC tracking in structseq.__replace__

Lib/test/test_structseq.py

@@ -1,4 +1,5 @@
 import copy
+import gc
 import os
 import pickle
 import re
@@ -355,6 +356,14 @@ def test_reference_cycle(self):
             type(t).refcyle = t
         """))
 
+    def test_replace_gc_tracked(self):
+        # Verify that __replace__ results are properly GC-tracked
+        time_struct = time.gmtime(0)
+        lst = []
+        replaced_struct = time_struct.__replace__(tm_year=lst)
+        lst.append(replaced_struct)
+
+        self.assertTrue(gc.is_tracked(replaced_struct))
 
 if __name__ == "__main__":
     unittest.main()

Misc/NEWS.d/next/Core_and_Builtins/2026-03-11-21-27-28.gh-issue-145376.LfDvyw.rst

@@ -0,0 +1 @@
+Fix GC tracking in ``structseq.__replace__()``.

Objects/structseq.c

@@ -445,6 +445,7 @@ structseq_replace(PyObject *op, PyObject *args, PyObject *kwargs)
         }
     }
 
+    _PyObject_GC_TRACK(result);
     return (PyObject *)result;
 
 error: