While experimenting with a CodeSonar plugin we develop, we noticed a potential bug in file "cpython/Objects/sliceobject.c" line 116 function PySlice_GetIndices.

if (r->start == Py_None) {
    *start = *step < 0 ? length-1 : 0;
} else {
    if (!PyInt_Check(r->start) && !PyLong_Check(r->step)) return -1;//HERE
    *start = PyInt_AsSsize_t(r->start);
    if (*start < 0) *start += length;
}

Shouldn't start field of r be used in the second check (instead of step)?

In a related potential issue, in line 123, shouldn't r->stop be checked in the second verification?

Thanks,
Petru Florin Mihancea