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Tim pointed out a remaining vulnerability in popitem(): the

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PyTuple_New() could *conceivably* clear the dict, so move the test for
an empty dict after the tuple allocation.  It means that we waste time
allocating and deallocating a 2-tuple when the dict is empty, but who
cares.  It also means that when the dict is empty *and* there's no
memory to allocate a 2-tuple, we raise MemoryError, not KeyError --
but that may actually a good idea: if there's no room for a lousy
2-tuple, what are the chances that there's room for a KeyError
instance?
This commit is contained in:
Guido van Rossum 2001-04-16 00:02:32 +00:00
parent a4dd011259
commit e04eaec5b6
1 changed files with 6 additions and 5 deletions
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11
Objects/dictobject.c
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@ -1155,11 +1155,6 @@ dict_popitem(dictobject *mp, PyObject *args)
if (!PyArg_NoArgs(args))
return NULL;
if (mp->ma_used == 0) {
PyErr_SetString(PyExc_KeyError,
"popitem(): dictionary is empty");
return NULL;
}
/* Allocate the result tuple first. Believe it or not,
* this allocation could trigger a garbage collection which
* could resize the dict, which would invalidate the pointer
@ -1169,6 +1164,12 @@ dict_popitem(dictobject *mp, PyObject *args)
res = PyTuple_New(2);
if (res == NULL)
return NULL;
if (mp->ma_used == 0) {
Py_DECREF(res);
PyErr_SetString(PyExc_KeyError,
"popitem(): dictionary is empty");
return NULL;
}
/* Set ep to "the first" dict entry with a value. We abuse the hash
* field of slot 0 to hold a search finger:
* If slot 0 has a value, use slot 0.