diff options
Diffstat (limited to 'Objects/sliceobject.c')
| -rw-r--r-- | Objects/sliceobject.c | 10 |
1 files changed, 9 insertions, 1 deletions
diff --git a/Objects/sliceobject.c b/Objects/sliceobject.c index ee89006..55fda52 100644 --- a/Objects/sliceobject.c +++ b/Objects/sliceobject.c @@ -131,7 +131,8 @@ PySlice_GetIndices(PySliceObject *r, Py_ssize_t length, int PySlice_GetIndicesEx(PySliceObject *r, Py_ssize_t length, - Py_ssize_t *start, Py_ssize_t *stop, Py_ssize_t *step, Py_ssize_t *slicelength) + Py_ssize_t *start, Py_ssize_t *stop, Py_ssize_t *step, + Py_ssize_t *slicelength) { /* this is harder to get right than you might think */ @@ -147,6 +148,13 @@ PySlice_GetIndicesEx(PySliceObject *r, Py_ssize_t length, "slice step cannot be zero"); return -1; } + /* Here *step might be -PY_SSIZE_T_MAX-1; in this case we replace it + * with -PY_SSIZE_T_MAX. This doesn't affect the semantics, and it + * guards against later undefined behaviour resulting from code that + * does "step = -step" as part of a slice reversal. + */ + if (*step < -PY_SSIZE_T_MAX) + *step = -PY_SSIZE_T_MAX; } defstart = *step < 0 ? length-1 : 0; |