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[3.10] bpo-42161: mathmodule.c: move _PyLong_GetOne() loop invariant (GH-26391) #26393

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Merged
merged 1 commit into from
May 26, 2021
Merged

[3.10] bpo-42161: mathmodule.c: move _PyLong_GetOne() loop invariant (GH-26391) #26393

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20 changes: 12 additions & 8 deletions Modules/mathmodule.c
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Original file line number Diff line number Diff line change
Expand Up @@ -845,13 +845,15 @@ math_gcd(PyObject *module, PyObject * const *args, Py_ssize_t nargs)
Py_SETREF(res, PyNumber_Absolute(res));
return res;
}

PyObject *one = _PyLong_GetOne(); // borrowed ref
for (i = 1; i < nargs; i++) {
x = _PyNumber_Index(args[i]);
if (x == NULL) {
Py_DECREF(res);
return NULL;
}
if (res == _PyLong_GetOne()) {
if (res == one) {
/* Fast path: just check arguments.
It is okay to use identity comparison here. */
Py_DECREF(x);
Expand Down Expand Up @@ -918,13 +920,15 @@ math_lcm(PyObject *module, PyObject * const *args, Py_ssize_t nargs)
Py_SETREF(res, PyNumber_Absolute(res));
return res;
}

PyObject *zero = _PyLong_GetZero(); // borrowed ref
for (i = 1; i < nargs; i++) {
x = PyNumber_Index(args[i]);
if (x == NULL) {
Py_DECREF(res);
return NULL;
}
if (res == _PyLong_GetZero()) {
if (res == zero) {
/* Fast path: just check arguments.
It is okay to use identity comparison here. */
Py_DECREF(x);
Expand Down Expand Up @@ -3293,10 +3297,10 @@ math_perm_impl(PyObject *module, PyObject *n, PyObject *k)
goto done;
}

factor = n;
Py_INCREF(factor);
factor = Py_NewRef(n);
PyObject *one = _PyLong_GetOne(); // borrowed ref
for (i = 1; i < factors; ++i) {
Py_SETREF(factor, PyNumber_Subtract(factor, _PyLong_GetOne()));
Py_SETREF(factor, PyNumber_Subtract(factor, one));
if (factor == NULL) {
goto error;
}
Expand Down Expand Up @@ -3415,10 +3419,10 @@ math_comb_impl(PyObject *module, PyObject *n, PyObject *k)
goto done;
}

factor = n;
Py_INCREF(factor);
factor = Py_NewRef(n);
PyObject *one = _PyLong_GetOne(); // borrowed ref
for (i = 1; i < factors; ++i) {
Py_SETREF(factor, PyNumber_Subtract(factor, _PyLong_GetOne()));
Py_SETREF(factor, PyNumber_Subtract(factor, one));
if (factor == NULL) {
goto error;
}
Expand Down