On 07.07.15 05:03, raymond.hettinger wrote:
https://hg.python.org/cpython/rev/c9782a9ac031 changeset: 96865:c9782a9ac031 user: Raymond Hettinger <pyt...@rcn.com> date: Mon Jul 06 19:03:01 2015 -0700 summary: Tighten-up code in the set iterator to use an entry pointer rather than indexing.files: Objects/setobject.c | 35 ++++++++++++-------------------- 1 files changed, 13 insertions(+), 22 deletions(-) diff --git a/Objects/setobject.c b/Objects/setobject.c --- a/Objects/setobject.c +++ b/Objects/setobject.c @@ -766,8 +766,8 @@ PyObject_HEAD PySetObject *si_set; /* Set to NULL when iterator is exhausted */ Py_ssize_t si_used; - Py_ssize_t si_pos; Py_ssize_t len; + setentry *entry; } setiterobject; static void @@ -845,8 +845,6 @@ static PyObject *setiter_iternext(setiterobject *si) { - PyObject *key; - Py_ssize_t i, mask; setentry *entry; PySetObject *so = si->si_set; @@ -860,25 +858,18 @@ si->si_used = -1; /* Make this state sticky */ return NULL; } - - i = si->si_pos; - assert(i>=0); - entry = so->table; - mask = so->mask; - while (i <= mask && (entry[i].key == NULL || entry[i].key == dummy)) - i++; - si->si_pos = i+1; - if (i > mask) - goto fail; + if (si->len <= 0) { + Py_DECREF(so); + si->si_set = NULL; + return NULL; + } + entry = si->entry; + while (entry->key == NULL || entry->key == dummy) + entry++; si->len--; - key = entry[i].key; - Py_INCREF(key); - return key; - -fail: - Py_DECREF(so); - si->si_set = NULL; - return NULL; + si->entry = entry + 1; + Py_INCREF(entry->key); + return entry->key; } PyTypeObject PySetIter_Type = { @@ -923,8 +914,8 @@ Py_INCREF(so); si->si_set = so; si->si_used = so->used; - si->si_pos = 0; si->len = so->used; + si->entry = so->table; _PyObject_GC_TRACK(si); return (PyObject *)si; }
What if so->table was reallocated during the iteration, but so->used is left the same? This change looks unsafe to me.
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