Always track frozenset in the GC

Author: vstinner

Lib/test/test_capi/test_set.py

@@ -391,11 +391,10 @@ def test_update_array_steal(self):
         self.check_update_method('update_array_steal')
 
     def test_finish(self):
-        # Test PyFrozenSetWriter_Finish(): track the frozenset in the GC if at
-        # least one item is tracked by the GC
+        # Test PyFrozenSetWriter_Finish(): track the frozenset in the GC
         writer = self.create_writer()
         writer.update([2, 5, 7])
-        self.assertFalse(gc.is_tracked(writer.finish()))
+        self.assertTrue(gc.is_tracked(writer.finish()))
 
         class MyObject:
             pass
@@ -418,19 +417,22 @@ def test_discard(self):
 
     @threading_helper.requires_working_threading()
     def test_thread(self):
-        # PyFrozenSetWriter can be used by multiple threads: it's up to the caller
-        # to implement a lock to prevent concurrent accesses.
+        # PyFrozenSetWriter can be used by multiple threads: it's up to the
+        # caller to implement a lock to prevent concurrent accesses.
         writer = self.create_writer()
 
         def thread_func(writer):
-            writer.add('Hello')
-            writer.update(['World!'])
+            writer.add('a')
+            writer.add_steal('b')
+            writer.update(['c'])
+            writer.update_array(['d'])
+            writer.update_array_steal(['e'])
 
         thread = threading.Thread(target=thread_func, args=(writer,))
         thread.start()
         threading_helper.join_thread(thread)
 
-        self.frozenset_equal(writer.finish(), {'Hello', 'World!'})
+        self.frozenset_equal(writer.finish(), frozenset('abcde'))
 
 
 if __name__ == "__main__":

Objects/setobject.c

@@ -3288,17 +3288,9 @@ PyFrozenSetWriter_Finish(PyFrozenSetWriter *writer)
     assert(frozensetwriter_check_consistency(writer));
     PySetObject *frozenset = _PySet_CAST(writer);
 
-    // Now that the frozenset is fully initialized, it's safe to track it in
-    // the GC. Track the frozenset if at least one item is tracked by the GC.
-    Py_ssize_t pos = 0;
-    setentry *entry;
-    while (set_next(frozenset, &pos, &entry)) {
-        PyObject *item = entry->key;
-        if (_PyObject_IS_GC(item) && _PyObject_GC_IS_TRACKED(item)) {
-            _PyObject_GC_TRACK(frozenset);
-            break;
-        }
-    }
+    // Now that the frozenset is fully initialized, it's safe to track it
+    // in the garbage collector.
+    _PyObject_GC_TRACK(frozenset);
 
     return _PyObject_CAST(frozenset);
 }