list_ass_slice(): The difference between "recycle" and "recycled" was

impossible to remember, so renamed one to something obvious.  Headed
off potential signed-vs-unsigned compiler complaints I introduced by
changing the type of a vrbl to unsigned.  Removed the need for the
tedious explanation about "backward pointer loops" by looping on an
int instead.

diff --git a/Objects/listobject.c b/Objects/listobject.c
index 179dd14e9e6683a9aebb5214fcf1351f8cad1991..91c0a1cbe9fb52fbdb13f2667a76d58218769dab 100644 (file)
--- a/Objects/listobject.c
+++ b/Objects/listobject.c
@@ -528,15 +528,15 @@ list_ass_slice(PyListObject *a, int ilow, int ihigh, PyObject *v)
           we must allocate an additional array, 'recycle', into which
           we temporarily copy the items that are deleted from the
           list. :-( */
-       PyObject *recycled[8];
-       PyObject **recycle = recycled; /* will allocate more if needed */
+       PyObject *recycle_on_stack[8];
+       PyObject **recycle = recycle_on_stack; /* will allocate more if needed */
        PyObject **item;
        PyObject **vitem = NULL;
        PyObject *v_as_SF = NULL; /* PySequence_Fast(v) */
        int n; /* # of elements in replacement list */
        int norig; /* # of elements in list getting replaced */
        int d; /* Change in size */
-       int k; /* Loop index */
+       int k;
        size_t s;
        int result = -1;        /* guilty until proved innocent */
 #define b ((PyListObject *)v)
@@ -578,7 +578,7 @@ list_ass_slice(PyListObject *a, int ilow, int ihigh, PyObject *v)
        item = a->ob_item;
        /* recycle the items that we are about to remove */
        s = norig * sizeof(PyObject *);
-       if (s > sizeof(recycled)) {
+       if (s > sizeof(recycle_on_stack)) {
                recycle = (PyObject **)PyMem_MALLOC(s);
                if (recycle == NULL) {
                        PyErr_NoMemory();
@@ -594,30 +594,23 @@ list_ass_slice(PyListObject *a, int ilow, int ihigh, PyObject *v)
                item = a->ob_item;
        }
        else if (d > 0) { /* Insert d items */
-               s = a->ob_size;
-               if (list_resize(a, s+d) < 0)
+               k = a->ob_size;
+               if (list_resize(a, k+d) < 0)
                        goto Error;
                item = a->ob_item;
                memmove(&item[ihigh+d], &item[ihigh],
-                       (s - ihigh)*sizeof(PyObject *));
+                       (k - ihigh)*sizeof(PyObject *));
        }
        for (k = 0; k < n; k++, ilow++) {
                PyObject *w = vitem[k];
                Py_XINCREF(w);
                item[ilow] = w;
        }
-       /* Convoluted:  there's some obscure reason for wanting to do
-        * the decrefs "backwards", but C doesn't guarantee you can compute
-        * a pointer to one slot *before* an allocated vector.  So checking
-        * for item >= recycle is incorrect.
-        */
-       for (item = recycle + norig; item > recycle; ) {
-               --item;
-               Py_XDECREF(*item);
-       }
+       for (k = norig - 1; k >= 0; --k)
+               Py_XDECREF(recycle[k]);
        result = 0;
  Error:
-       if (recycle != recycled)
+       if (recycle != recycle_on_stack)
                PyMem_FREE(recycle);
        Py_XDECREF(v_as_SF);
        return result;