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dict_popitem(): Repaired last-second 2.1 comment, which misidentified the

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true reason for allocating the tuple before checking the dict size.
This commit is contained in:
Tim Peters 2001-06-02 05:42:29 +00:00
parent eb28ef209e
commit f4b33f61fb
1 changed files with 8 additions and 5 deletions
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13
Objects/dictobject.c
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@ -1362,11 +1362,14 @@ dict_popitem(dictobject *mp, PyObject *args)
if (!PyArg_NoArgs(args)) if (!PyArg_NoArgs(args))
return NULL; return NULL;
/* Allocate the result tuple first. Believe it or not, /* Allocate the result tuple before checking the size. Believe it
* this allocation could trigger a garbage collection which * or not, this allocation could trigger a garbage collection which
* could resize the dict, which would invalidate the pointer * could empty the dict, so if we checked the size first and that
* (ep) into the dict calculated below. * happened, the result would be an infinite loop (searching for an
* So we have to do this first. * entry that no longer exists). Note that the usual popitem()
* idiom is "while d: k, v = d.popitem()". so needing to throw the
* tuple away if the dict *is* empty isn't a significant
* inefficiency -- possible, but unlikely in practice.
*/ */
res = PyTuple_New(2); res = PyTuple_New(2);
if (res == NULL) if (res == NULL)