Recursive compare machinery: The code that intended to exempt tuples
was broken because new-in-2.3 code added a tp_as_mapping slot to tuples.
Repaired that.
Added basic docs to check_recursion().
The code that intended to exempt tuples and strings was also broken here,
and in 2.2: these should use PyXYZ_CheckExact(), not PyXYZ_Check() -- we
can't know whether subclass instances are immutable. This part (and this
part alone) is a bugfix candidate.
diff --git a/Objects/object.c b/Objects/object.c
index e3234de..e44edca 100644
--- a/Objects/object.c
+++ b/Objects/object.c
@@ -742,6 +742,14 @@
return inprogress;
}
+/* If the comparison "v op w" is already in progress in this thread, returns
+ * a borrowed reference to Py_None (the caller must not decref).
+ * If it's not already in progress, returns "a token" which must eventually
+ * be passed to delete_token(). The caller must not decref this either
+ * (delete_token decrefs it). The token must not survive beyond any point
+ * where v or w may die.
+ * If an error occurs (out-of-memory), returns NULL.
+ */
static PyObject *
check_recursion(PyObject *v, PyObject *w, int op)
{
@@ -830,10 +838,9 @@
vtp = v->ob_type;
compare_nesting++;
if (compare_nesting > NESTING_LIMIT &&
- (vtp->tp_as_mapping
- || (vtp->tp_as_sequence
- && !PyString_Check(v)
- && !PyTuple_Check(v)))) {
+ (vtp->tp_as_mapping || vtp->tp_as_sequence) &&
+ !PyString_CheckExact(v) &&
+ !PyTuple_CheckExact(v)) {
/* try to detect circular data structures */
PyObject *token = check_recursion(v, w, -1);
@@ -927,11 +934,9 @@
compare_nesting++;
if (compare_nesting > NESTING_LIMIT &&
- (v->ob_type->tp_as_mapping
- || (v->ob_type->tp_as_sequence
- && !PyString_Check(v)
- && !PyTuple_Check(v)))) {
-
+ (v->ob_type->tp_as_mapping || v->ob_type->tp_as_sequence) &&
+ !PyString_CheckExact(v) &&
+ !PyTuple_CheckExact(v)) {
/* try to detect circular data structures */
PyObject *token = check_recursion(v, w, op);
if (token == NULL) {