Issue #18408: Oh, I was wrong: Pickler_New() must call Py_DECREF() to destroy
the newly created pickler, and not PyObject_GC_Del().
diff --git a/Modules/_pickle.c b/Modules/_pickle.c
index adb642e..8b3438e 100644
--- a/Modules/_pickle.c
+++ b/Modules/_pickle.c
@@ -782,7 +782,7 @@
                                                     self->max_output_len);
 
     if (self->memo == NULL || self->output_buffer == NULL) {
-        PyObject_GC_Del(self);
+        Py_DECREF(self);
         return NULL;
     }
     return self;