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Issue #14794: slice.indices no longer returns OverflowError for out-of-range start, stop, step or length.

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This commit is contained in:
Mark Dickinson 2012-11-10 14:52:10 +00:00
parent ff3d515952
commit c8a6967ea8
3 changed files with 291 additions and 9 deletions
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183
Objects/sliceobject.c
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@ -299,25 +299,192 @@ static PyMemberDef slice_members[] = {
{0}
};
/* Helper function to convert a slice argument to a PyLong, and raise TypeError
with a suitable message on failure. */
static PyObject*
evaluate_slice_index(PyObject *v)
{
if (PyIndex_Check(v)) {
return PyNumber_Index(v);
}
else {
PyErr_SetString(PyExc_TypeError,
"slice indices must be integers or "
"None or have an __index__ method");
return NULL;
}
}
/* Implementation of slice.indices. */
static PyObject*
slice_indices(PySliceObject* self, PyObject* len)
{
Py_ssize_t ilen, start, stop, step, slicelength;
PyObject *start=NULL, *stop=NULL, *step=NULL;
PyObject *length=NULL, *upper=NULL, *lower=NULL, *zero=NULL;
int step_is_negative, cmp;
ilen = PyNumber_AsSsize_t(len, PyExc_OverflowError);
if (ilen == -1 && PyErr_Occurred()) {
zero = PyLong_FromLong(0L);
if (zero == NULL)
return NULL;
/* Compute step and length as integers. */
length = PyNumber_Index(len);
if (length == NULL)
goto error;
if (self->step == Py_None)
step = PyLong_FromLong(1L);
else
step = evaluate_slice_index(self->step);
if (step == NULL)
goto error;
/* Raise ValueError for negative length or zero step. */
cmp = PyObject_RichCompareBool(length, zero, Py_LT);
if (cmp < 0) {
goto error;
}
if (cmp) {
PyErr_SetString(PyExc_ValueError,
"length should not be negative");
goto error;
}
if (PySlice_GetIndicesEx((PyObject*)self, ilen, &start, &stop,
&step, &slicelength) < 0) {
return NULL;
cmp = PyObject_RichCompareBool(step, zero, Py_EQ);
if (cmp < 0) {
goto error;
}
if (cmp) {
PyErr_SetString(PyExc_ValueError,
"slice step cannot be zero");
goto error;
}
return Py_BuildValue("(nnn)", start, stop, step);
/* Find lower and upper bounds for start and stop. */
step_is_negative = PyObject_RichCompareBool(step, zero, Py_LT);
if (step_is_negative < 0) {
goto error;
}
if (step_is_negative) {
lower = PyLong_FromLong(-1L);
if (lower == NULL)
goto error;
upper = PyNumber_Add(length, lower);
if (upper == NULL)
goto error;
}
else {
lower = zero;
Py_INCREF(lower);
upper = length;
Py_INCREF(upper);
}
/* Compute start. */
if (self->start == Py_None) {
start = step_is_negative ? upper : lower;
Py_INCREF(start);
}
else {
start = evaluate_slice_index(self->start);
if (start == NULL)
goto error;
cmp = PyObject_RichCompareBool(start, zero, Py_LT);
if (cmp < 0)
goto error;
if (cmp) {
/* start += length */
PyObject *tmp = PyNumber_Add(start, length);
Py_DECREF(start);
start = tmp;
if (start == NULL)
goto error;
cmp = PyObject_RichCompareBool(start, lower, Py_LT);
if (cmp < 0)
goto error;
if (cmp) {
Py_INCREF(lower);
Py_DECREF(start);
start = lower;
}
}
else {
cmp = PyObject_RichCompareBool(start, upper, Py_GT);
if (cmp < 0)
goto error;
if (cmp) {
Py_INCREF(upper);
Py_DECREF(start);
start = upper;
}
}
}
/* Compute stop. */
if (self->stop == Py_None) {
stop = step_is_negative ? lower : upper;
Py_INCREF(stop);
}
else {
stop = evaluate_slice_index(self->stop);
if (stop == NULL)
goto error;
cmp = PyObject_RichCompareBool(stop, zero, Py_LT);
if (cmp < 0)
goto error;
if (cmp) {
/* stop += length */
PyObject *tmp = PyNumber_Add(stop, length);
Py_DECREF(stop);
stop = tmp;
if (stop == NULL)
goto error;
cmp = PyObject_RichCompareBool(stop, lower, Py_LT);
if (cmp < 0)
goto error;
if (cmp) {
Py_INCREF(lower);
Py_DECREF(stop);
stop = lower;
}
}
else {
cmp = PyObject_RichCompareBool(stop, upper, Py_GT);
if (cmp < 0)
goto error;
if (cmp) {
Py_INCREF(upper);
Py_DECREF(stop);
stop = upper;
}
}
}
Py_DECREF(upper);
Py_DECREF(lower);
Py_DECREF(length);
Py_DECREF(zero);
return Py_BuildValue("(NNN)", start, stop, step);
error:
Py_XDECREF(start);
Py_XDECREF(stop);
Py_XDECREF(step);
Py_XDECREF(upper);
Py_XDECREF(lower);
Py_XDECREF(length);
Py_XDECREF(zero);
return NULL;
}
PyDoc_STRVAR(slice_indices_doc,
"S.indices(len) -> (start, stop, stride)\n\
\n\