Fix zero-length corner case for iterating over a mutating deque.
diff --git a/Modules/collectionsmodule.c b/Modules/collectionsmodule.c
index c1bd732..a0570cd 100644
--- a/Modules/collectionsmodule.c
+++ b/Modules/collectionsmodule.c
@@ -911,15 +911,14 @@
{
PyObject *item;
- if (it->counter == 0)
- return NULL;
-
if (it->deque->state != it->state) {
it->counter = 0;
PyErr_SetString(PyExc_RuntimeError,
"deque mutated during iteration");
return NULL;
}
+ if (it->counter == 0)
+ return NULL;
assert (!(it->b == it->deque->rightblock &&
it->index > it->deque->rightindex));