tuple.__repr__ did not consider a reference loop as it is not possible from
Python code; but it is possible from C. object.__str__ had the issue of not
expecting a type to doing something within it's tp_str implementation that
could trigger an infinite recursion, but it could in C code.. Both found
thanks to BaseException and how it handles its repr.
Closes issue #1686386. Thanks to Thomas Herve for taking an initial stab at
coming up with a solution.
diff --git a/Objects/tupleobject.c b/Objects/tupleobject.c
index b85762a..38304dd 100644
--- a/Objects/tupleobject.c
+++ b/Objects/tupleobject.c
@@ -216,6 +216,15 @@
PyObject *s, *temp;
PyObject *pieces, *result = NULL;
+ /* While not mutable, it is still possible to end up with a cycle in a
+ tuple through an object that stores itself within a tuple (and thus
+ infinitely asks for the repr of itself). This should only be
+ possible within a type. */
+ i = Py_ReprEnter((PyObject *)v);
+ if (i != 0) {
+ return i > 0 ? PyString_FromString("(...)") : NULL;
+ }
+
n = Py_Size(v);
if (n == 0)
return PyString_FromString("()");
@@ -226,7 +235,10 @@
/* Do repr() on each element. */
for (i = 0; i < n; ++i) {
+ if (Py_EnterRecursiveCall(" while getting the repr of a tuple"))
+ goto Done;
s = PyObject_Repr(v->ob_item[i]);
+ Py_LeaveRecursiveCall();
if (s == NULL)
goto Done;
PyTuple_SET_ITEM(pieces, i, s);
@@ -261,6 +273,7 @@
Done:
Py_DECREF(pieces);
+ Py_ReprLeave((PyObject *)v);
return result;
}