[Python-checkins] bpo-1635741: Fix unicode_dealloc() for mortal interned string (GH-21270)
Victor Stinner
webhook-mailer at python.org
Fri Jul 3 10:59:22 EDT 2020
https://github.com/python/cpython/commit/3549ca313a6103a3adb281ef3a849298b7d7f72c
commit: 3549ca313a6103a3adb281ef3a849298b7d7f72c
branch: master
author: Victor Stinner <vstinner at python.org>
committer: GitHub <noreply at github.com>
date: 2020-07-03T16:59:12+02:00
summary:
bpo-1635741: Fix unicode_dealloc() for mortal interned string (GH-21270)
When unicode_dealloc() is called on a mortal interned string, the
string reference counter is now reset at zero.
files:
M Objects/unicodeobject.c
diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index 37e7fe5c0eff2..ca68c57534b22 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -1943,13 +1943,20 @@ unicode_dealloc(PyObject *unicode)
break;
case SSTATE_INTERNED_MORTAL:
- /* revive dead object temporarily for DelItem */
- Py_SET_REFCNT(unicode, 3);
#ifdef INTERNED_STRINGS
+ /* Revive the dead object temporarily. PyDict_DelItem() removes two
+ references (key and value) which were ignored by
+ PyUnicode_InternInPlace(). Use refcnt=3 rather than refcnt=2
+ to prevent calling unicode_dealloc() again. Adjust refcnt after
+ PyDict_DelItem(). */
+ assert(Py_REFCNT(unicode) == 0);
+ Py_SET_REFCNT(unicode, 3);
if (PyDict_DelItem(interned, unicode) != 0) {
_PyErr_WriteUnraisableMsg("deletion of interned string failed",
NULL);
}
+ assert(Py_REFCNT(unicode) == 1);
+ Py_SET_REFCNT(unicode, 0);
#endif
break;
@@ -15710,8 +15717,9 @@ PyUnicode_InternInPlace(PyObject **p)
return;
}
- /* The two references in interned are not counted by refcnt.
- The deallocator will take care of this */
+ /* The two references in interned dict (key and value) are not counted by
+ refcnt. unicode_dealloc() and _PyUnicode_ClearInterned() take care of
+ this. */
Py_SET_REFCNT(s, Py_REFCNT(s) - 2);
_PyUnicode_STATE(s).interned = SSTATE_INTERNED_MORTAL;
#endif
@@ -15780,6 +15788,8 @@ _PyUnicode_ClearInterned(PyThreadState *tstate)
#endif
break;
case SSTATE_INTERNED_MORTAL:
+ // Restore the two references (key and value) ignored
+ // by PyUnicode_InternInPlace().
Py_SET_REFCNT(s, Py_REFCNT(s) + 2);
#ifdef INTERNED_STATS
mortal_size += PyUnicode_GET_LENGTH(s);
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