bpo-30281: Fix the default value for stop in PySlice_Unpack() (#1530) (#1480）

diff --git a/Objects/sliceobject.c b/Objects/sliceobject.c
index 6a690213d1451867d29e571b9a58b4202ed0df29..32599476bba0c0cf6feb10b77050a50909407116 100644 (file)
--- a/Objects/sliceobject.c
+++ b/Objects/sliceobject.c
@@ -197,6 +197,8 @@ PySlice_Unpack(PyObject *_r,
     PySliceObject *r = (PySliceObject*)_r;
     /* this is harder to get right than you might think */
 
+    assert(PY_SSIZE_T_MIN + 1 <= -PY_SSIZE_T_MAX);
+
     if (r->step == Py_None) {
         *step = 1;
     }
@@ -217,14 +219,14 @@ PySlice_Unpack(PyObject *_r,
     }
 
     if (r->start == Py_None) {
-        *start = *step < 0 ? PY_SSIZE_T_MAX-1 : 0;;
+        *start = *step < 0 ? PY_SSIZE_T_MAX : 0;
     }
     else {
         if (!_PyEval_SliceIndex(r->start, start)) return -1;
     }
 
     if (r->stop == Py_None) {
-        *stop = *step < 0 ? -PY_SSIZE_T_MAX : PY_SSIZE_T_MAX;
+        *stop = *step < 0 ? PY_SSIZE_T_MIN : PY_SSIZE_T_MAX;
     }
     else {
         if (!_PyEval_SliceIndex(r->stop, stop)) return -1;
@@ -258,7 +260,7 @@ PySlice_AdjustIndices(Py_ssize_t length,
             *stop = (step < 0) ? -1 : 0;
         }
     }
-    else  if (*stop >= length) {
+    else if (*stop >= length) {
         *stop = (step < 0) ? length - 1 : length;
     }
 

diff --git a/Python/ceval.c b/Python/ceval.c
index 3070a90b43dbfbc361edff833c9d6a28d7187fd0..47c5eff64f235e93fb130657b7161aa79b389ff0 100644 (file)
--- a/Python/ceval.c
+++ b/Python/ceval.c
@@ -5095,7 +5095,7 @@ ext_call_fail:
 /* Extract a slice index from a PyLong or an object with the
    nb_index slot defined, and store in *pi.
    Silently reduce values larger than PY_SSIZE_T_MAX to PY_SSIZE_T_MAX,
-   and silently boost values less than -PY_SSIZE_T_MAX-1 to -PY_SSIZE_T_MAX-1.
+   and silently boost values less than PY_SSIZE_T_MIN to PY_SSIZE_T_MIN.
    Return 0 on error, 1 on success.
 */
 int