bpo-41654: Fix deallocator of MemoryError to account for subclasses (GH-22020)
When allocating MemoryError classes, there is some logic to use
pre-allocated instances in a freelist only if the type that is being
allocated is not a subclass of MemoryError. Unfortunately in the
destructor this logic is not present so the freelist is altered even
with subclasses of MemoryError.
diff --git a/Objects/exceptions.c b/Objects/exceptions.c
index 1195ba1..b08cbdd 100644
--- a/Objects/exceptions.c
+++ b/Objects/exceptions.c
@@ -2286,8 +2286,11 @@
{
PyBaseExceptionObject *self;
- if (type != (PyTypeObject *) PyExc_MemoryError)
+ /* If this is a subclass of MemoryError, don't use the freelist
+ * and just return a fresh object */
+ if (type != (PyTypeObject *) PyExc_MemoryError) {
return BaseException_new(type, args, kwds);
+ }
struct _Py_exc_state *state = get_exc_state();
if (state->memerrors_freelist == NULL) {
@@ -2313,9 +2316,16 @@
static void
MemoryError_dealloc(PyBaseExceptionObject *self)
{
- _PyObject_GC_UNTRACK(self);
BaseException_clear(self);
+ /* If this is a subclass of MemoryError, we don't need to
+ * do anything in the free-list*/
+ if (!Py_IS_TYPE(self, (PyTypeObject *) PyExc_MemoryError)) {
+ return Py_TYPE(self)->tp_free((PyObject *)self);
+ }
+
+ _PyObject_GC_UNTRACK(self);
+
struct _Py_exc_state *state = get_exc_state();
if (state->memerrors_numfree >= MEMERRORS_SAVE) {
Py_TYPE(self)->tp_free((PyObject *)self);