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Use _PyLong_GetOne() and _PyLong_GetZero() in long_invmod() #125044

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Merged
vstinner merged 1 commit into from
Oct 7, 2024
Merged

Use _PyLong_GetOne() and _PyLong_GetZero() in long_invmod() #125044

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13 changes: 2 additions & 11 deletions Objects/longobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -4828,21 +4828,12 @@ long_divmod(PyObject *a, PyObject *b)
static PyLongObject *
long_invmod(PyLongObject *a, PyLongObject *n)
{
PyLongObject *b, *c;

/* Should only ever be called for positive n */
assert(_PyLong_IsPositive(n));

b = (PyLongObject *)PyLong_FromLong(1L);
if (b == NULL) {
return NULL;
}
c = (PyLongObject *)PyLong_FromLong(0L);
if (c == NULL) {
Py_DECREF(b);
return NULL;
}
Py_INCREF(a);
PyLongObject *b = (PyLongObject *)Py_NewRef(_PyLong_GetOne());

@eendebakpt eendebakpt Oct 14, 2024

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@vstinner Out of curiosity: why did you add the Py_NewRef when _PyLong_GetOne is documented to return an immortal singleton?
(or can modern compilers optimize this away?)

@vstinner vstinner Oct 15, 2024

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The Py_NewRef() is useless. I added it because the code wants a strong refererence and I didn't pay attention that these two constants are immortal.

(or can modern compilers optimize this away?)

No, Py_NewRef() is not optimized.

See also my PR gh-124076 attempt.

PyLongObject *c = (PyLongObject *)Py_NewRef(_PyLong_GetZero());
Py_INCREF(n);

/* references now owned: a, b, c, n */
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