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-rw-r--r--Lib/test/test_dict.py20
-rw-r--r--Misc/NEWS3
-rw-r--r--Objects/dictobject.c112
3 files changed, 93 insertions, 42 deletions
diff --git a/Lib/test/test_dict.py b/Lib/test/test_dict.py
index 1507e42..d2740a3 100644
--- a/Lib/test/test_dict.py
+++ b/Lib/test/test_dict.py
@@ -299,6 +299,26 @@ class DictTest(unittest.TestCase):
x.fail = True
self.assertRaises(Exc, d.setdefault, x, [])
+ def test_setdefault_atomic(self):
+ # Issue #13521: setdefault() calls __hash__ and __eq__ only once.
+ class Hashed(object):
+ def __init__(self):
+ self.hash_count = 0
+ self.eq_count = 0
+ def __hash__(self):
+ self.hash_count += 1
+ return 42
+ def __eq__(self, other):
+ self.eq_count += 1
+ return id(self) == id(other)
+ hashed1 = Hashed()
+ y = {hashed1: 5}
+ hashed2 = Hashed()
+ y.setdefault(hashed2, [])
+ self.assertEqual(hashed1.hash_count, 1)
+ self.assertEqual(hashed2.hash_count, 1)
+ self.assertEqual(hashed1.eq_count + hashed2.eq_count, 1)
+
def test_popitem(self):
# dict.popitem()
for copymode in -1, +1:
diff --git a/Misc/NEWS b/Misc/NEWS
index be6f700..5fdd7b2 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -10,6 +10,9 @@ What's New in Python 3.3 Alpha 1?
Core and Builtins
-----------------
+- Issue #13521: dict.setdefault() now does only one lookup for the given key,
+ making it "atomic" for many purposes. Patch by Filip GruszczyƄski.
+
- PEP 409, Issue #6210: "raise X from None" is now supported as a means of
suppressing the display of the chained exception context. The chained
context still remains available as the __context__ attribute.
diff --git a/Objects/dictobject.c b/Objects/dictobject.c
index 5a8a8a7..83957ac 100644
--- a/Objects/dictobject.c
+++ b/Objects/dictobject.c
@@ -517,27 +517,16 @@ _PyDict_MaybeUntrack(PyObject *op)
_PyObject_GC_UNTRACK(op);
}
-
/*
-Internal routine to insert a new item into the table.
-Used both by the internal resize routine and by the public insert routine.
-Eats a reference to key and one to value.
-Returns -1 if an error occurred, or 0 on success.
+Internal routine to insert a new item into the table when you have entry object.
+Used by insertdict.
*/
static int
-insertdict(register PyDictObject *mp, PyObject *key, Py_hash_t hash, PyObject *value)
+insertdict_by_entry(register PyDictObject *mp, PyObject *key, Py_hash_t hash,
+ PyDictEntry *ep, PyObject *value)
{
PyObject *old_value;
- register PyDictEntry *ep;
- typedef PyDictEntry *(*lookupfunc)(PyDictObject *, PyObject *, Py_hash_t);
- assert(mp->ma_lookup != NULL);
- ep = mp->ma_lookup(mp, key, hash);
- if (ep == NULL) {
- Py_DECREF(key);
- Py_DECREF(value);
- return -1;
- }
MAINTAIN_TRACKING(mp, key, value);
if (ep->me_value != NULL) {
old_value = ep->me_value;
@@ -560,6 +549,28 @@ insertdict(register PyDictObject *mp, PyObject *key, Py_hash_t hash, PyObject *v
return 0;
}
+
+/*
+Internal routine to insert a new item into the table.
+Used both by the internal resize routine and by the public insert routine.
+Eats a reference to key and one to value.
+Returns -1 if an error occurred, or 0 on success.
+*/
+static int
+insertdict(register PyDictObject *mp, PyObject *key, Py_hash_t hash, PyObject *value)
+{
+ register PyDictEntry *ep;
+
+ assert(mp->ma_lookup != NULL);
+ ep = mp->ma_lookup(mp, key, hash);
+ if (ep == NULL) {
+ Py_DECREF(key);
+ Py_DECREF(value);
+ return -1;
+ }
+ return insertdict_by_entry(mp, key, hash, ep, value);
+}
+
/*
Internal routine used by dictresize() to insert an item which is
known to be absent from the dict. This routine also assumes that
@@ -783,39 +794,26 @@ PyDict_GetItemWithError(PyObject *op, PyObject *key)
return ep->me_value;
}
-/* CAUTION: PyDict_SetItem() must guarantee that it won't resize the
- * dictionary if it's merely replacing the value for an existing key.
- * This means that it's safe to loop over a dictionary with PyDict_Next()
- * and occasionally replace a value -- but you can't insert new keys or
- * remove them.
- */
-int
-PyDict_SetItem(register PyObject *op, PyObject *key, PyObject *value)
+static int
+dict_set_item_by_hash_or_entry(register PyObject *op, PyObject *key,
+ Py_hash_t hash, PyDictEntry *ep, PyObject *value)
{
register PyDictObject *mp;
- register Py_hash_t hash;
register Py_ssize_t n_used;
- if (!PyDict_Check(op)) {
- PyErr_BadInternalCall();
- return -1;
- }
- assert(key);
- assert(value);
mp = (PyDictObject *)op;
- if (!PyUnicode_CheckExact(key) ||
- (hash = ((PyASCIIObject *) key)->hash) == -1)
- {
- hash = PyObject_Hash(key);
- if (hash == -1)
- return -1;
- }
assert(mp->ma_fill <= mp->ma_mask); /* at least one empty slot */
n_used = mp->ma_used;
Py_INCREF(value);
Py_INCREF(key);
- if (insertdict(mp, key, hash, value) != 0)
- return -1;
+ if (ep == NULL) {
+ if (insertdict(mp, key, hash, value) != 0)
+ return -1;
+ }
+ else {
+ if (insertdict_by_entry(mp, key, hash, ep, value) != 0)
+ return -1;
+ }
/* If we added a key, we can safely resize. Otherwise just return!
* If fill >= 2/3 size, adjust size. Normally, this doubles or
* quaduples the size, but it's also possible for the dict to shrink
@@ -835,6 +833,36 @@ PyDict_SetItem(register PyObject *op, PyObject *key, PyObject *value)
return dictresize(mp, (mp->ma_used > 50000 ? 2 : 4) * mp->ma_used);
}
+/* CAUTION: PyDict_SetItem() must guarantee that it won't resize the
+ * dictionary if it's merely replacing the value for an existing key.
+ * This means that it's safe to loop over a dictionary with PyDict_Next()
+ * and occasionally replace a value -- but you can't insert new keys or
+ * remove them.
+ */
+int
+PyDict_SetItem(register PyObject *op, PyObject *key, PyObject *value)
+{
+ register Py_hash_t hash;
+
+ if (!PyDict_Check(op)) {
+ PyErr_BadInternalCall();
+ return -1;
+ }
+ assert(key);
+ assert(value);
+ if (PyUnicode_CheckExact(key)) {
+ hash = ((PyASCIIObject *) key)->hash;
+ if (hash == -1)
+ hash = PyObject_Hash(key);
+ }
+ else {
+ hash = PyObject_Hash(key);
+ if (hash == -1)
+ return -1;
+ }
+ return dict_set_item_by_hash_or_entry(op, key, hash, NULL, value);
+}
+
int
PyDict_DelItem(PyObject *op, PyObject *key)
{
@@ -1803,9 +1831,9 @@ dict_setdefault(register PyDictObject *mp, PyObject *args)
return NULL;
val = ep->me_value;
if (val == NULL) {
- val = failobj;
- if (PyDict_SetItem((PyObject*)mp, key, failobj))
- val = NULL;
+ if (dict_set_item_by_hash_or_entry((PyObject*)mp, key, hash, ep,
+ failobj) == 0)
+ val = failobj;
}
Py_XINCREF(val);
return val;