[3.8] bpo-39492: Fix a reference cycle between reducer_override and a Pickler instance (GH-18266) (#18316)
https://bugs.python.org/issue39492
Automerge-Triggered-By: @pitrou
(cherry picked from commit 0f2f35e)
Co-authored-by: Pierre Glaser <pierreglaser@msn.com>
diff --git a/Modules/_pickle.c b/Modules/_pickle.c
index 8150bf3..9f6e66f 100644
--- a/Modules/_pickle.c
+++ b/Modules/_pickle.c
@@ -4457,12 +4457,13 @@
dump(PicklerObject *self, PyObject *obj)
{
const char stop_op = STOP;
+ int status = -1;
PyObject *tmp;
_Py_IDENTIFIER(reducer_override);
if (_PyObject_LookupAttrId((PyObject *)self, &PyId_reducer_override,
&tmp) < 0) {
- return -1;
+ goto error;
}
/* Cache the reducer_override method, if it exists. */
if (tmp != NULL) {
@@ -4479,7 +4480,7 @@
assert(self->proto >= 0 && self->proto < 256);
header[1] = (unsigned char)self->proto;
if (_Pickler_Write(self, header, 2) < 0)
- return -1;
+ goto error;
if (self->proto >= 4)
self->framing = 1;
}
@@ -4487,9 +4488,22 @@
if (save(self, obj, 0) < 0 ||
_Pickler_Write(self, &stop_op, 1) < 0 ||
_Pickler_CommitFrame(self) < 0)
- return -1;
+ goto error;
+
+ // Success
+ status = 0;
+
+ error:
self->framing = 0;
- return 0;
+
+ /* Break the reference cycle we generated at the beginning this function
+ * call when setting the reducer_override attribute of the Pickler instance
+ * to a bound method of the same instance. This is important as the Pickler
+ * instance holds a reference to each object it has pickled (through its
+ * memo): thus, these objects wont be garbage-collected as long as the
+ * Pickler itself is not collected. */
+ Py_CLEAR(self->reducer_override);
+ return status;
}
/*[clinic input]