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Merged
ericsnowcurrently merged 10 commits into from
May 10, 2023
Merged

gh-104252: Immortalize Py_EMPTY_KEYS #104253

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5bc2469
Factor out _dict_state_INIT.
ericsnowcurrently May 6, 2023
e472d94
Immortalize Py_EMPTY_KEYS.
ericsnowcurrently May 6, 2023
87351e0
Handle other uses of dk_refcnt.
ericsnowcurrently May 8, 2023
f5da088
Add a note.
ericsnowcurrently May 8, 2023
db8612f
Drop an old line.
ericsnowcurrently May 8, 2023
58585a9
Drop an unnecessary condition.
ericsnowcurrently May 8, 2023
6b5c952
Drop an unnecessary assert.
ericsnowcurrently May 9, 2023
bdbce5f
Do not bother inc/dec-refing Py_EMPTY_KEYS.
ericsnowcurrently May 9, 2023
aab493a
Do not update Py_Reftotal for Py_EMPTY_KEYS.
ericsnowcurrently May 9, 2023
5aabfd7
Clarify the comment about dictkeys_incref() and dictkeys_decref().
ericsnowcurrently May 9, 2023
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5 changes: 5 additions & 0 deletions Include/internal/pycore_dict_state.h
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Original file line numberDiff line numberDiff line change
Expand Up@@ -38,6 +38,11 @@ struct _Py_dict_state{
PyDict_WatchCallback watchers[DICT_MAX_WATCHERS];
};

#define _dict_state_INIT \
{\
.next_keys_version = 2, \
}


#ifdef __cplusplus
}
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4 changes: 1 addition & 3 deletions Include/internal/pycore_runtime_init.h
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Expand Up@@ -107,9 +107,7 @@ extern PyTypeObject _PyExc_MemoryError;
}, \
}, \
.dtoa = _dtoa_state_INIT(&(INTERP)), \
.dict_state ={\
.next_keys_version = 2, \
}, \
.dict_state = _dict_state_INIT, \
.func_state ={\
.next_version = 1, \
}, \
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32 changes: 21 additions & 11 deletions Objects/dictobject.c
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Expand Up@@ -300,9 +300,19 @@ _PyDict_DebugMallocStats(FILE *out)

static void free_keys_object(PyInterpreterState *interp, PyDictKeysObject *keys);

/* PyDictKeysObject has refcounts like PyObject does, so we have the
following two functions to mirror what Py_INCREF() and Py_DECREF() do.
(Keep in mind that PyDictKeysObject isn't actually a PyObject.)
Likewise a PyDictKeysObject can be immortal (e.g. Py_EMPTY_KEYS),
so we apply a naive version of what Py_INCREF() and Py_DECREF() do
for immortal objects. */

static inline void
dictkeys_incref(PyDictKeysObject *dk)
{
if (dk->dk_refcnt == _Py_IMMORTAL_REFCNT){
return;
}
#ifdef Py_REF_DEBUG
_Py_IncRefTotal(_PyInterpreterState_GET());
#endif
Expand All@@ -312,6 +322,9 @@ dictkeys_incref(PyDictKeysObject *dk)
static inline void
dictkeys_decref(PyInterpreterState *interp, PyDictKeysObject *dk)
{
if (dk->dk_refcnt == _Py_IMMORTAL_REFCNT){
return;
}
assert(dk->dk_refcnt > 0);
#ifdef Py_REF_DEBUG
_Py_DecRefTotal(_PyInterpreterState_GET());
Expand DownExpand Up@@ -447,7 +460,7 @@ estimate_log2_keysize(Py_ssize_t n)
* (which cannot fail and thus can do no allocation).
*/
static PyDictKeysObject empty_keys_struct ={
1, /* dk_refcnt */
_Py_IMMORTAL_REFCNT, /* dk_refcnt */
0, /* dk_log2_size */
0, /* dk_log2_index_bytes */
DICT_KEYS_UNICODE, /* dk_kind */
Expand DownExpand Up@@ -779,6 +792,7 @@ clone_combined_dict_keys(PyDictObject *orig)
assert(PyDict_Check(orig));
assert(Py_TYPE(orig)->tp_iter == (getiterfunc)dict_iter);
assert(orig->ma_values == NULL);
assert(orig->ma_keys != Py_EMPTY_KEYS);
assert(orig->ma_keys->dk_refcnt == 1);

size_t keys_size = _PyDict_KeysSize(orig->ma_keys);
Expand DownExpand Up@@ -833,7 +847,7 @@ PyObject *
PyDict_New(void)
{
PyInterpreterState *interp = _PyInterpreterState_GET();
dictkeys_incref(Py_EMPTY_KEYS);
/* We don't incref Py_EMPTY_KEYS here because it is immortal. */
return new_dict(interp, Py_EMPTY_KEYS, NULL, 0, 0);
}

Expand DownExpand Up@@ -1331,7 +1345,7 @@ insert_to_emptydict(PyInterpreterState *interp, PyDictObject *mp,
Py_DECREF(value);
return -1;
}
dictkeys_decref(interp, Py_EMPTY_KEYS);
/* We don't decref Py_EMPTY_KEYS here because it is immortal. */
mp->ma_keys = newkeys;
mp->ma_values = NULL;

Expand DownExpand Up@@ -1529,14 +1543,10 @@ dictresize(PyInterpreterState *interp, PyDictObject *mp,

// We can not use free_keys_object here because key's reference
// are moved already.
if (oldkeys != Py_EMPTY_KEYS){
#ifdef Py_REF_DEBUG
_Py_DecRefTotal(_PyInterpreterState_GET());
_Py_DecRefTotal(_PyInterpreterState_GET());
#endif
if (oldkeys == Py_EMPTY_KEYS){
oldkeys->dk_refcnt--;
assert(oldkeys->dk_refcnt > 0);
}
else{
assert(oldkeys->dk_kind != DICT_KEYS_SPLIT);
assert(oldkeys->dk_refcnt == 1);
#if PyDict_MAXFREELIST > 0
Expand DownExpand Up@@ -2080,8 +2090,8 @@ PyDict_Clear(PyObject *op)
dictkeys_decref(interp, oldkeys);
}
else{
assert(oldkeys->dk_refcnt == 1);
dictkeys_decref(interp, oldkeys);
assert(oldkeys->dk_refcnt == 1);
dictkeys_decref(interp, oldkeys);
}
ASSERT_CONSISTENT(mp);
}
Expand Down