https://hg.python.org/cpython/rev/37aee118e1a3 changeset: 98578:37aee118e1a3 branch: 2.7 parent: 98572:60c44a09c5fc user: Raymond Hettinger <python@rcn.com> date: Tue Oct 06 23:12:02 2015 -0400 summary: Backport early-out 91259f061cfb to reduce the cost of bb1a2944bcb6 files: Modules/_collectionsmodule.c | 6 +++++- 1 files changed, 5 insertions(+), 1 deletions(-) diff --git a/Modules/_collectionsmodule.c b/Modules/_collectionsmodule.c --- a/Modules/_collectionsmodule.c +++ b/Modules/_collectionsmodule.c @@ -651,6 +651,9 @@ Py_ssize_t n; PyObject *item; + if (Py_SIZE(deque) == 0) + return; + /* During the process of clearing a deque, decrefs can cause the deque to mutate. To avoid fatal confusion, we have to make the deque empty before clearing the blocks and never refer to @@ -1083,7 +1086,8 @@ } } deque->maxlen = maxlen; - deque_clear(deque); + if (Py_SIZE(deque) > 0) + deque_clear(deque); if (iterable != NULL) { PyObject *rv = deque_extend(deque, iterable); if (rv == NULL) -- Repository URL: https://hg.python.org/cpython