Copy listobject.c from CPython 2.7

from_cpython/CMakeLists.txt

@@ -95,6 +95,7 @@ file(GLOB_RECURSE STDOBJECT_SRCS Objects
     fileobject.c
     import.c
     iterobject.c
+    listobject.c
     memoryobject.c
     obmalloc.c
     stringobject.c

from_cpython/Objects/listobject.c

+/* List object implementation */
+
+#include "Python.h"
+
+#ifdef STDC_HEADERS
+#include <stddef.h>
+#else
+#include <sys/types.h>          /* For size_t */
+#endif
+
+/* Ensure ob_item has room for at least newsize elements, and set
+ * ob_size to newsize.  If newsize > ob_size on entry, the content
+ * of the new slots at exit is undefined heap trash; it's the caller's
+ * responsibility to overwrite them with sane values.
+ * The number of allocated elements may grow, shrink, or stay the same.
+ * Failure is impossible if newsize <= self.allocated on entry, although
+ * that partly relies on an assumption that the system realloc() never
+ * fails when passed a number of bytes <= the number of bytes last
+ * allocated (the C standard doesn't guarantee this, but it's hard to
+ * imagine a realloc implementation where it wouldn't be true).
+ * Note that self->ob_item may change, and even if newsize is less
+ * than ob_size on entry.
+ */
+static int
+list_resize(PyListObject *self, Py_ssize_t newsize)
+{
+    PyObject **items;
+    size_t new_allocated;
+    Py_ssize_t allocated = self->allocated;
+
+    /* Bypass realloc() when a previous overallocation is large enough
+       to accommodate the newsize.  If the newsize falls lower than half
+       the allocated size, then proceed with the realloc() to shrink the list.
+    */
+    if (allocated >= newsize && newsize >= (allocated >> 1)) {
+        assert(self->ob_item != NULL || newsize == 0);
+        Py_SIZE(self) = newsize;
+        return 0;
+    }
+
+    /* This over-allocates proportional to the list size, making room
+     * for additional growth.  The over-allocation is mild, but is
+     * enough to give linear-time amortized behavior over a long
+     * sequence of appends() in the presence of a poorly-performing
+     * system realloc().
+     * The growth pattern is:  0, 4, 8, 16, 25, 35, 46, 58, 72, 88, ...
+     */
+    new_allocated = (newsize >> 3) + (newsize < 9 ? 3 : 6);
+
+    /* check for integer overflow */
+    if (new_allocated > PY_SIZE_MAX - newsize) {
+        PyErr_NoMemory();
+        return -1;
+    } else {
+        new_allocated += newsize;
+    }
+
+    if (newsize == 0)
+        new_allocated = 0;
+    items = self->ob_item;
+    if (new_allocated <= (PY_SIZE_MAX / sizeof(PyObject *)))
+        PyMem_RESIZE(items, PyObject *, new_allocated);
+    else
+        items = NULL;
+    if (items == NULL) {
+        PyErr_NoMemory();
+        return -1;
+    }
+    self->ob_item = items;
+    Py_SIZE(self) = newsize;
+    self->allocated = new_allocated;
+    return 0;
+}
+
+/* Debug statistic to compare allocations with reuse through the free list */
+#undef SHOW_ALLOC_COUNT
+#ifdef SHOW_ALLOC_COUNT
+static size_t count_alloc = 0;
+static size_t count_reuse = 0;
+
+static void
+show_alloc(void)
+{
+    fprintf(stderr, "List allocations: %" PY_FORMAT_SIZE_T "d\n",
+        count_alloc);
+    fprintf(stderr, "List reuse through freelist: %" PY_FORMAT_SIZE_T
+        "d\n", count_reuse);
+    fprintf(stderr, "%.2f%% reuse rate\n\n",
+        (100.0*count_reuse/(count_alloc+count_reuse)));
+}
+#endif
+
+/* Empty list reuse scheme to save calls to malloc and free */
+#ifndef PyList_MAXFREELIST
+#define PyList_MAXFREELIST 80
+#endif
+static PyListObject *free_list[PyList_MAXFREELIST];
+static int numfree = 0;
+
+void
+PyList_Fini(void)
+{
+    PyListObject *op;
+
+    while (numfree) {
+        op = free_list[--numfree];
+        assert(PyList_CheckExact(op));
+        PyObject_GC_Del(op);
+    }
+}
+
+PyObject *
+PyList_New(Py_ssize_t size)
+{
+    PyListObject *op;
+    size_t nbytes;
+#ifdef SHOW_ALLOC_COUNT
+    static int initialized = 0;
+    if (!initialized) {
+        Py_AtExit(show_alloc);
+        initialized = 1;
+    }
+#endif
+
+    if (size < 0) {
+        PyErr_BadInternalCall();
+        return NULL;
+    }
+    /* Check for overflow without an actual overflow,
+     *  which can cause compiler to optimise out */
+    if ((size_t)size > PY_SIZE_MAX / sizeof(PyObject *))
+        return PyErr_NoMemory();
+    nbytes = size * sizeof(PyObject *);
+    if (numfree) {
+        numfree--;
+        op = free_list[numfree];
+        _Py_NewReference((PyObject *)op);
+#ifdef SHOW_ALLOC_COUNT
+        count_reuse++;
+#endif
+    } else {
+        op = PyObject_GC_New(PyListObject, &PyList_Type);
+        if (op == NULL)
+            return NULL;
+#ifdef SHOW_ALLOC_COUNT
+        count_alloc++;
+#endif
+    }
+    if (size <= 0)
+        op->ob_item = NULL;
+    else {
+        op->ob_item = (PyObject **) PyMem_MALLOC(nbytes);
+        if (op->ob_item == NULL) {
+            Py_DECREF(op);
+            return PyErr_NoMemory();
+        }
+        memset(op->ob_item, 0, nbytes);
+    }
+    Py_SIZE(op) = size;
+    op->allocated = size;
+    _PyObject_GC_TRACK(op);
+    return (PyObject *) op;
+}
+
+Py_ssize_t
+PyList_Size(PyObject *op)
+{
+    if (!PyList_Check(op)) {
+        PyErr_BadInternalCall();
+        return -1;
+    }
+    else
+        return Py_SIZE(op);
+}
+
+static PyObject *indexerr = NULL;
+
+PyObject *
+PyList_GetItem(PyObject *op, Py_ssize_t i)
+{
+    if (!PyList_Check(op)) {
+        PyErr_BadInternalCall();
+        return NULL;
+    }
+    if (i < 0 || i >= Py_SIZE(op)) {
+        if (indexerr == NULL) {
+            indexerr = PyString_FromString(
+                "list index out of range");
+            if (indexerr == NULL)
+                return NULL;
+        }
+        PyErr_SetObject(PyExc_IndexError, indexerr);
+        return NULL;
+    }
+    return ((PyListObject *)op) -> ob_item[i];
+}
+
+int
+PyList_SetItem(register PyObject *op, register Py_ssize_t i,
+               register PyObject *newitem)
+{
+    register PyObject *olditem;
+    register PyObject **p;
+    if (!PyList_Check(op)) {
+        Py_XDECREF(newitem);
+        PyErr_BadInternalCall();
+        return -1;
+    }
+    if (i < 0 || i >= Py_SIZE(op)) {
+        Py_XDECREF(newitem);
+        PyErr_SetString(PyExc_IndexError,
+                        "list assignment index out of range");
+        return -1;
+    }
+    p = ((PyListObject *)op) -> ob_item + i;
+    olditem = *p;
+    *p = newitem;
+    Py_XDECREF(olditem);
+    return 0;
+}
+
+static int
+ins1(PyListObject *self, Py_ssize_t where, PyObject *v)
+{
+    Py_ssize_t i, n = Py_SIZE(self);
+    PyObject **items;
+    if (v == NULL) {
+        PyErr_BadInternalCall();
+        return -1;
+    }
+    if (n == PY_SSIZE_T_MAX) {
+        PyErr_SetString(PyExc_OverflowError,
+            "cannot add more objects to list");
+        return -1;
+    }
+
+    if (list_resize(self, n+1) == -1)
+        return -1;
+
+    if (where < 0) {
+        where += n;
+        if (where < 0)
+            where = 0;
+    }
+    if (where > n)
+        where = n;
+    items = self->ob_item;
+    for (i = n; --i >= where; )
+        items[i+1] = items[i];
+    Py_INCREF(v);
+    items[where] = v;
+    return 0;
+}
+
+int
+PyList_Insert(PyObject *op, Py_ssize_t where, PyObject *newitem)
+{
+    if (!PyList_Check(op)) {
+        PyErr_BadInternalCall();
+        return -1;
+    }
+    return ins1((PyListObject *)op, where, newitem);
+}
+
+static int
+app1(PyListObject *self, PyObject *v)
+{
+    Py_ssize_t n = PyList_GET_SIZE(self);
+
+    assert (v != NULL);
+    if (n == PY_SSIZE_T_MAX) {
+        PyErr_SetString(PyExc_OverflowError,
+            "cannot add more objects to list");
+        return -1;
+    }
+
+    if (list_resize(self, n+1) == -1)
+        return -1;
+
+    Py_INCREF(v);
+    PyList_SET_ITEM(self, n, v);
+    return 0;
+}
+
+int
+PyList_Append(PyObject *op, PyObject *newitem)
+{
+    if (PyList_Check(op) && (newitem != NULL))
+        return app1((PyListObject *)op, newitem);
+    PyErr_BadInternalCall();
+    return -1;
+}
+
+/* Methods */
+
+static void
+list_dealloc(PyListObject *op)
+{
+    Py_ssize_t i;
+    PyObject_GC_UnTrack(op);
+    Py_TRASHCAN_SAFE_BEGIN(op)
+    if (op->ob_item != NULL) {
+        /* Do it backwards, for Christian Tismer.
+           There's a simple test case where somehow this reduces
+           thrashing when a *very* large list is created and
+           immediately deleted. */
+        i = Py_SIZE(op);
+        while (--i >= 0) {
+            Py_XDECREF(op->ob_item[i]);
+        }
+        PyMem_FREE(op->ob_item);
+    }
+    if (numfree < PyList_MAXFREELIST && PyList_CheckExact(op))
+        free_list[numfree++] = op;
+    else
+        Py_TYPE(op)->tp_free((PyObject *)op);
+    Py_TRASHCAN_SAFE_END(op)
+}
+
+static int
+list_print(PyListObject *op, FILE *fp, int flags)
+{
+    int rc;
+    Py_ssize_t i;
+    PyObject *item;
+
+    rc = Py_ReprEnter((PyObject*)op);
+    if (rc != 0) {
+        if (rc < 0)
+            return rc;
+        Py_BEGIN_ALLOW_THREADS
+        fprintf(fp, "[...]");
+        Py_END_ALLOW_THREADS
+        return 0;
+    }
+    Py_BEGIN_ALLOW_THREADS
+    fprintf(fp, "[");
+    Py_END_ALLOW_THREADS
+    for (i = 0; i < Py_SIZE(op); i++) {
+        item = op->ob_item[i];
+        Py_INCREF(item);
+        if (i > 0) {
+            Py_BEGIN_ALLOW_THREADS
+            fprintf(fp, ", ");
+            Py_END_ALLOW_THREADS
+        }
+        if (PyObject_Print(item, fp, 0) != 0) {
+            Py_DECREF(item);
+            Py_ReprLeave((PyObject *)op);
+            return -1;
+        }
+        Py_DECREF(item);
+    }
+    Py_BEGIN_ALLOW_THREADS
+    fprintf(fp, "]");
+    Py_END_ALLOW_THREADS
+    Py_ReprLeave((PyObject *)op);
+    return 0;
+}
+
+static PyObject *
+list_repr(PyListObject *v)
+{
+    Py_ssize_t i;
+    PyObject *s, *temp;
+    PyObject *pieces = NULL, *result = NULL;
+
+    i = Py_ReprEnter((PyObject*)v);
+    if (i != 0) {
+        return i > 0 ? PyString_FromString("[...]") : NULL;
+    }
+
+    if (Py_SIZE(v) == 0) {
+        result = PyString_FromString("[]");
+        goto Done;
+    }
+
+    pieces = PyList_New(0);
+    if (pieces == NULL)
+        goto Done;
+
+    /* Do repr() on each element.  Note that this may mutate the list,
+       so must refetch the list size on each iteration. */
+    for (i = 0; i < Py_SIZE(v); ++i) {
+        int status;
+        if (Py_EnterRecursiveCall(" while getting the repr of a list"))
+            goto Done;
+        s = PyObject_Repr(v->ob_item[i]);
+        Py_LeaveRecursiveCall();
+        if (s == NULL)
+            goto Done;
+        status = PyList_Append(pieces, s);
+        Py_DECREF(s);  /* append created a new ref */
+        if (status < 0)
+            goto Done;
+    }
+
+    /* Add "[]" decorations to the first and last items. */
+    assert(PyList_GET_SIZE(pieces) > 0);
+    s = PyString_FromString("[");
+    if (s == NULL)
+        goto Done;
+    temp = PyList_GET_ITEM(pieces, 0);
+    PyString_ConcatAndDel(&s, temp);
+    PyList_SET_ITEM(pieces, 0, s);
+    if (s == NULL)
+        goto Done;
+
+    s = PyString_FromString("]");
+    if (s == NULL)
+        goto Done;
+    temp = PyList_GET_ITEM(pieces, PyList_GET_SIZE(pieces) - 1);
+    PyString_ConcatAndDel(&temp, s);
+    PyList_SET_ITEM(pieces, PyList_GET_SIZE(pieces) - 1, temp);
+    if (temp == NULL)
+        goto Done;
+
+    /* Paste them all together with ", " between. */
+    s = PyString_FromString(", ");
+    if (s == NULL)
+        goto Done;
+    result = _PyString_Join(s, pieces);
+    Py_DECREF(s);
+
+Done:
+    Py_XDECREF(pieces);
+    Py_ReprLeave((PyObject *)v);
+    return result;
+}
+
+static Py_ssize_t
+list_length(PyListObject *a)
+{
+    return Py_SIZE(a);
+}
+
+static int
+list_contains(PyListObject *a, PyObject *el)
+{
+    Py_ssize_t i;
+    int cmp;
+
+    for (i = 0, cmp = 0 ; cmp == 0 && i < Py_SIZE(a); ++i)
+        cmp = PyObject_RichCompareBool(el, PyList_GET_ITEM(a, i),
+                                           Py_EQ);
+    return cmp;
+}
+
+static PyObject *
+list_item(PyListObject *a, Py_ssize_t i)
+{
+    if (i < 0 || i >= Py_SIZE(a)) {
+        if (indexerr == NULL) {
+            indexerr = PyString_FromString(
+                "list index out of range");
+            if (indexerr == NULL)
+                return NULL;
+        }
+        PyErr_SetObject(PyExc_IndexError, indexerr);
+        return NULL;
+    }
+    Py_INCREF(a->ob_item[i]);
+    return a->ob_item[i];
+}
+
+static PyObject *
+list_slice(PyListObject *a, Py_ssize_t ilow, Py_ssize_t ihigh)
+{
+    PyListObject *np;
+    PyObject **src, **dest;
+    Py_ssize_t i, len;
+    if (ilow < 0)
+        ilow = 0;
+    else if (ilow > Py_SIZE(a))
+        ilow = Py_SIZE(a);
+    if (ihigh < ilow)
+        ihigh = ilow;
+    else if (ihigh > Py_SIZE(a))
+        ihigh = Py_SIZE(a);
+    len = ihigh - ilow;
+    np = (PyListObject *) PyList_New(len);
+    if (np == NULL)
+        return NULL;
+
+    src = a->ob_item + ilow;
+    dest = np->ob_item;
+    for (i = 0; i < len; i++) {
+        PyObject *v = src[i];
+        Py_INCREF(v);
+        dest[i] = v;
+    }
+    return (PyObject *)np;
+}
+
+PyObject *
+PyList_GetSlice(PyObject *a, Py_ssize_t ilow, Py_ssize_t ihigh)
+{
+    if (!PyList_Check(a)) {
+        PyErr_BadInternalCall();
+        return NULL;
+    }
+    return list_slice((PyListObject *)a, ilow, ihigh);
+}
+
+static PyObject *
+list_concat(PyListObject *a, PyObject *bb)
+{
+    Py_ssize_t size;
+    Py_ssize_t i;
+    PyObject **src, **dest;
+    PyListObject *np;
+    if (!PyList_Check(bb)) {
+        PyErr_Format(PyExc_TypeError,
+                  "can only concatenate list (not \"%.200s\") to list",
+                  bb->ob_type->tp_name);
+        return NULL;
+    }
+#define b ((PyListObject *)bb)
+    size = Py_SIZE(a) + Py_SIZE(b);
+    if (size < 0)
+        return PyErr_NoMemory();
+    np = (PyListObject *) PyList_New(size);
+    if (np == NULL) {
+        return NULL;
+    }
+    src = a->ob_item;
+    dest = np->ob_item;
+    for (i = 0; i < Py_SIZE(a); i++) {
+        PyObject *v = src[i];
+        Py_INCREF(v);
+        dest[i] = v;
+    }
+    src = b->ob_item;
+    dest = np->ob_item + Py_SIZE(a);
+    for (i = 0; i < Py_SIZE(b); i++) {
+        PyObject *v = src[i];
+        Py_INCREF(v);
+        dest[i] = v;
+    }
+    return (PyObject *)np;
+#undef b
+}
+
+static PyObject *
+list_repeat(PyListObject *a, Py_ssize_t n)
+{
+    Py_ssize_t i, j;
+    Py_ssize_t size;
+    PyListObject *np;
+    PyObject **p, **items;
+    PyObject *elem;
+    if (n < 0)
+        n = 0;
+    if (n > 0 && Py_SIZE(a) > PY_SSIZE_T_MAX / n)
+        return PyErr_NoMemory();
+    size = Py_SIZE(a) * n;
+    if (size == 0)
+        return PyList_New(0);
+    np = (PyListObject *) PyList_New(size);
+    if (np == NULL)
+        return NULL;
+
+    items = np->ob_item;
+    if (Py_SIZE(a) == 1) {
+        elem = a->ob_item[0];
+        for (i = 0; i < n; i++) {
+            items[i] = elem;
+            Py_INCREF(elem);
+        }
+        return (PyObject *) np;
+    }
+    p = np->ob_item;
+    items = a->ob_item;
+    for (i = 0; i < n; i++) {
+        for (j = 0; j < Py_SIZE(a); j++) {
+            *p = items[j];
+            Py_INCREF(*p);
+            p++;
+        }
+    }
+    return (PyObject *) np;
+}
+
+static int
+list_clear(PyListObject *a)
+{
+    Py_ssize_t i;
+    PyObject **item = a->ob_item;
+    if (item != NULL) {
+        /* Because XDECREF can recursively invoke operations on
+           this list, we make it empty first. */
+        i = Py_SIZE(a);
+        Py_SIZE(a) = 0;
+        a->ob_item = NULL;
+        a->allocated = 0;
+        while (--i >= 0) {
+            Py_XDECREF(item[i]);
+        }
+        PyMem_FREE(item);
+    }
+    /* Never fails; the return value can be ignored.
+       Note that there is no guarantee that the list is actually empty
+       at this point, because XDECREF may have populated it again! */
+    return 0;
+}
+
+/* a[ilow:ihigh] = v if v != NULL.
+ * del a[ilow:ihigh] if v == NULL.
+ *
+ * Special speed gimmick:  when v is NULL and ihigh - ilow <= 8, it's
+ * guaranteed the call cannot fail.
+ */
+static int
+list_ass_slice(PyListObject *a, Py_ssize_t ilow, Py_ssize_t ihigh, PyObject *v)
+{
+    /* Because [X]DECREF can recursively invoke list operations on
+       this list, we must postpone all [X]DECREF activity until
+       after the list is back in its canonical shape.  Therefore
+       we must allocate an additional array, 'recycle', into which
+       we temporarily copy the items that are deleted from the
+       list. :-( */
+    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) */
+    Py_ssize_t n; /* # of elements in replacement list */
+    Py_ssize_t norig; /* # of elements in list getting replaced */
+    Py_ssize_t d; /* Change in size */
+    Py_ssize_t k;
+    size_t s;
+    int result = -1;            /* guilty until proved innocent */
+#define b ((PyListObject *)v)
+    if (v == NULL)
+        n = 0;
+    else {
+        if (a == b) {
+            /* Special case "a[i:j] = a" -- copy b first */
+            v = list_slice(b, 0, Py_SIZE(b));
+            if (v == NULL)
+                return result;
+            result = list_ass_slice(a, ilow, ihigh, v);
+            Py_DECREF(v);
+            return result;
+        }
+        v_as_SF = PySequence_Fast(v, "can only assign an iterable");
+        if(v_as_SF == NULL)
+            goto Error;
+        n = PySequence_Fast_GET_SIZE(v_as_SF);
+        vitem = PySequence_Fast_ITEMS(v_as_SF);
+    }
+    if (ilow < 0)
+        ilow = 0;
+    else if (ilow > Py_SIZE(a))
+        ilow = Py_SIZE(a);
+
+    if (ihigh < ilow)
+        ihigh = ilow;
+    else if (ihigh > Py_SIZE(a))
+        ihigh = Py_SIZE(a);
+
+    norig = ihigh - ilow;
+    assert(norig >= 0);
+    d = n - norig;
+    if (Py_SIZE(a) + d == 0) {
+        Py_XDECREF(v_as_SF);
+        return list_clear(a);
+    }
+    item = a->ob_item;
+    /* recycle the items that we are about to remove */
+    s = norig * sizeof(PyObject *);
+    if (s > sizeof(recycle_on_stack)) {
+        recycle = (PyObject **)PyMem_MALLOC(s);
+        if (recycle == NULL) {
+            PyErr_NoMemory();
+            goto Error;
+        }
+    }
+    memcpy(recycle, &item[ilow], s);
+
+    if (d < 0) { /* Delete -d items */
+        memmove(&item[ihigh+d], &item[ihigh],
+            (Py_SIZE(a) - ihigh)*sizeof(PyObject *));
+        list_resize(a, Py_SIZE(a) + d);
+        item = a->ob_item;
+    }
+    else if (d > 0) { /* Insert d items */
+        k = Py_SIZE(a);
+        if (list_resize(a, k+d) < 0)
+            goto Error;
+        item = a->ob_item;
+        memmove(&item[ihigh+d], &item[ihigh],
+            (k - ihigh)*sizeof(PyObject *));
+    }
+    for (k = 0; k < n; k++, ilow++) {
+        PyObject *w = vitem[k];
+        Py_XINCREF(w);
+        item[ilow] = w;
+    }
+    for (k = norig - 1; k >= 0; --k)
+        Py_XDECREF(recycle[k]);
+    result = 0;
+ Error:
+    if (recycle != recycle_on_stack)
+        PyMem_FREE(recycle);
+    Py_XDECREF(v_as_SF);
+    return result;
+#undef b
+}
+
+int
+PyList_SetSlice(PyObject *a, Py_ssize_t ilow, Py_ssize_t ihigh, PyObject *v)
+{
+    if (!PyList_Check(a)) {
+        PyErr_BadInternalCall();
+        return -1;
+    }
+    return list_ass_slice((PyListObject *)a, ilow, ihigh, v);
+}
+
+static PyObject *
+list_inplace_repeat(PyListObject *self, Py_ssize_t n)
+{
+    PyObject **items;
+    Py_ssize_t size, i, j, p;
+
+
+    size = PyList_GET_SIZE(self);
+    if (size == 0 || n == 1) {
+        Py_INCREF(self);
+        return (PyObject *)self;
+    }
+
+    if (n < 1) {
+        (void)list_clear(self);
+        Py_INCREF(self);
+        return (PyObject *)self;
+    }
+
+    if (size > PY_SSIZE_T_MAX / n) {
+        return PyErr_NoMemory();
+    }
+
+    if (list_resize(self, size*n) == -1)
+        return NULL;
+
+    p = size;
+    items = self->ob_item;
+    for (i = 1; i < n; i++) { /* Start counting at 1, not 0 */
+        for (j = 0; j < size; j++) {
+            PyObject *o = items[j];
+            Py_INCREF(o);
+            items[p++] = o;
+        }
+    }
+    Py_INCREF(self);
+    return (PyObject *)self;
+}
+
+static int
+list_ass_item(PyListObject *a, Py_ssize_t i, PyObject *v)
+{
+    PyObject *old_value;
+    if (i < 0 || i >= Py_SIZE(a)) {
+        PyErr_SetString(PyExc_IndexError,
+                        "list assignment index out of range");
+        return -1;
+    }
+    if (v == NULL)
+        return list_ass_slice(a, i, i+1, v);
+    Py_INCREF(v);
+    old_value = a->ob_item[i];
+    a->ob_item[i] = v;
+    Py_DECREF(old_value);
+    return 0;
+}
+
+static PyObject *
+listinsert(PyListObject *self, PyObject *args)
+{
+    Py_ssize_t i;
+    PyObject *v;
+    if (!PyArg_ParseTuple(args, "nO:insert", &i, &v))
+        return NULL;
+    if (ins1(self, i, v) == 0)
+        Py_RETURN_NONE;
+    return NULL;
+}
+
+static PyObject *
+listappend(PyListObject *self, PyObject *v)
+{
+    if (app1(self, v) == 0)
+        Py_RETURN_NONE;
+    return NULL;
+}
+
+static PyObject *
+listextend(PyListObject *self, PyObject *b)
+{
+    PyObject *it;      /* iter(v) */
+    Py_ssize_t m;                  /* size of self */
+    Py_ssize_t n;                  /* guess for size of b */
+    Py_ssize_t mn;                 /* m + n */
+    Py_ssize_t i;
+    PyObject *(*iternext)(PyObject *);
+
+    /* Special cases:
+       1) lists and tuples which can use PySequence_Fast ops
+       2) extending self to self requires making a copy first
+    */
+    if (PyList_CheckExact(b) || PyTuple_CheckExact(b) || (PyObject *)self == b) {
+        PyObject **src, **dest;
+        b = PySequence_Fast(b, "argument must be iterable");
+        if (!b)
+            return NULL;
+        n = PySequence_Fast_GET_SIZE(b);
+        if (n == 0) {
+            /* short circuit when b is empty */
+            Py_DECREF(b);
+            Py_RETURN_NONE;
+        }
+        m = Py_SIZE(self);
+        if (list_resize(self, m + n) == -1) {
+            Py_DECREF(b);
+            return NULL;
+        }
+        /* note that we may still have self == b here for the
+         * situation a.extend(a), but the following code works
+         * in that case too.  Just make sure to resize self
+         * before calling PySequence_Fast_ITEMS.
+         */
+        /* populate the end of self with b's items */
+        src = PySequence_Fast_ITEMS(b);
+        dest = self->ob_item + m;
+        for (i = 0; i < n; i++) {
+            PyObject *o = src[i];
+            Py_INCREF(o);
+            dest[i] = o;
+        }
+        Py_DECREF(b);
+        Py_RETURN_NONE;
+    }
+
+    it = PyObject_GetIter(b);
+    if (it == NULL)
+        return NULL;
+    iternext = *it->ob_type->tp_iternext;
+
+    /* Guess a result list size. */
+    n = _PyObject_LengthHint(b, 8);
+    if (n == -1) {
+        Py_DECREF(it);
+        return NULL;
+    }
+    m = Py_SIZE(self);
+    mn = m + n;
+    if (mn >= m) {
+        /* Make room. */
+        if (list_resize(self, mn) == -1)
+            goto error;
+        /* Make the list sane again. */
+        Py_SIZE(self) = m;
+    }
+    /* Else m + n overflowed; on the chance that n lied, and there really
+     * is enough room, ignore it.  If n was telling the truth, we'll
+     * eventually run out of memory during the loop.
+     */
+
+    /* Run iterator to exhaustion. */
+    for (;;) {
+        PyObject *item = iternext(it);
+        if (item == NULL) {
+            if (PyErr_Occurred()) {
+                if (PyErr_ExceptionMatches(PyExc_StopIteration))
+                    PyErr_Clear();
+                else
+                    goto error;
+            }
+            break;
+        }
+        if (Py_SIZE(self) < self->allocated) {
+            /* steals ref */
+            PyList_SET_ITEM(self, Py_SIZE(self), item);
+            ++Py_SIZE(self);
+        }
+        else {
+            int status = app1(self, item);
+            Py_DECREF(item);  /* append creates a new ref */
+            if (status < 0)
+                goto error;
+        }
+    }
+
+    /* Cut back result list if initial guess was too large. */
+    if (Py_SIZE(self) < self->allocated)
+        list_resize(self, Py_SIZE(self));  /* shrinking can't fail */
+
+    Py_DECREF(it);
+    Py_RETURN_NONE;
+
+  error:
+    Py_DECREF(it);
+    return NULL;
+}
+
+PyObject *
+_PyList_Extend(PyListObject *self, PyObject *b)
+{
+    return listextend(self, b);
+}
+
+static PyObject *
+list_inplace_concat(PyListObject *self, PyObject *other)
+{
+    PyObject *result;
+
+    result = listextend(self, other);
+    if (result == NULL)
+        return result;
+    Py_DECREF(result);
+    Py_INCREF(self);
+    return (PyObject *)self;
+}
+
+static PyObject *
+listpop(PyListObject *self, PyObject *args)
+{
+    Py_ssize_t i = -1;
+    PyObject *v;
+    int status;
+
+    if (!PyArg_ParseTuple(args, "|n:pop", &i))
+        return NULL;
+
+    if (Py_SIZE(self) == 0) {
+        /* Special-case most common failure cause */
+        PyErr_SetString(PyExc_IndexError, "pop from empty list");
+        return NULL;
+    }
+    if (i < 0)
+        i += Py_SIZE(self);
+    if (i < 0 || i >= Py_SIZE(self)) {
+        PyErr_SetString(PyExc_IndexError, "pop index out of range");
+        return NULL;
+    }
+    v = self->ob_item[i];
+    if (i == Py_SIZE(self) - 1) {
+        status = list_resize(self, Py_SIZE(self) - 1);
+        assert(status >= 0);
+        return v; /* and v now owns the reference the list had */
+    }
+    Py_INCREF(v);
+    status = list_ass_slice(self, i, i+1, (PyObject *)NULL);
+    assert(status >= 0);
+    /* Use status, so that in a release build compilers don't
+     * complain about the unused name.
+     */
+    (void) status;
+
+    return v;
+}
+
+/* Reverse a slice of a list in place, from lo up to (exclusive) hi. */
+static void
+reverse_slice(PyObject **lo, PyObject **hi)
+{
+    assert(lo && hi);
+
+    --hi;
+    while (lo < hi) {
+        PyObject *t = *lo;
+        *lo = *hi;
+        *hi = t;
+        ++lo;
+        --hi;
+    }
+}
+
+/* Lots of code for an adaptive, stable, natural mergesort.  There are many
+ * pieces to this algorithm; read listsort.txt for overviews and details.
+ */
+
+/* Comparison function.  Takes care of calling a user-supplied
+ * comparison function (any callable Python object), which must not be
+ * NULL (use the ISLT macro if you don't know, or call PyObject_RichCompareBool
+ * with Py_LT if you know it's NULL).
+ * Returns -1 on error, 1 if x < y, 0 if x >= y.
+ */
+static int
+islt(PyObject *x, PyObject *y, PyObject *compare)
+{
+    PyObject *res;
+    PyObject *args;
+    Py_ssize_t i;
+
+    assert(compare != NULL);
+    /* Call the user's comparison function and translate the 3-way
+     * result into true or false (or error).
+     */
+    args = PyTuple_New(2);
+    if (args == NULL)
+        return -1;
+    Py_INCREF(x);
+    Py_INCREF(y);
+    PyTuple_SET_ITEM(args, 0, x);
+    PyTuple_SET_ITEM(args, 1, y);
+    res = PyObject_Call(compare, args, NULL);
+    Py_DECREF(args);
+    if (res == NULL)
+        return -1;
+    if (!PyInt_Check(res)) {
+        PyErr_Format(PyExc_TypeError,
+                     "comparison function must return int, not %.200s",
+                     res->ob_type->tp_name);
+        Py_DECREF(res);
+        return -1;
+    }
+    i = PyInt_AsLong(res);
+    Py_DECREF(res);
+    return i < 0;
+}
+
+/* If COMPARE is NULL, calls PyObject_RichCompareBool with Py_LT, else calls
+ * islt.  This avoids a layer of function call in the usual case, and
+ * sorting does many comparisons.
+ * Returns -1 on error, 1 if x < y, 0 if x >= y.
+ */
+#define ISLT(X, Y, COMPARE) ((COMPARE) == NULL ?                        \
+                 PyObject_RichCompareBool(X, Y, Py_LT) :                \
+                 islt(X, Y, COMPARE))
+
+/* Compare X to Y via "<".  Goto "fail" if the comparison raises an
+   error.  Else "k" is set to true iff X<Y, and an "if (k)" block is
+   started.  It makes more sense in context <wink>.  X and Y are PyObject*s.
+*/
+#define IFLT(X, Y) if ((k = ISLT(X, Y, compare)) < 0) goto fail;  \
+           if (k)
+
+/* binarysort is the best method for sorting small arrays: it does
+   few compares, but can do data movement quadratic in the number of
+   elements.
+   [lo, hi) is a contiguous slice of a list, and is sorted via
+   binary insertion.  This sort is stable.
+   On entry, must have lo <= start <= hi, and that [lo, start) is already
+   sorted (pass start == lo if you don't know!).
+   If islt() complains return -1, else 0.
+   Even in case of error, the output slice will be some permutation of
+   the input (nothing is lost or duplicated).
+*/
+static int
+binarysort(PyObject **lo, PyObject **hi, PyObject **start, PyObject *compare)
+     /* compare -- comparison function object, or NULL for default */
+{
+    register Py_ssize_t k;
+    register PyObject **l, **p, **r;
+    register PyObject *pivot;
+
+    assert(lo <= start && start <= hi);
+    /* assert [lo, start) is sorted */
+    if (lo == start)
+        ++start;
+    for (; start < hi; ++start) {
+        /* set l to where *start belongs */
+        l = lo;
+        r = start;
+        pivot = *r;
+        /* Invariants:
+         * pivot >= all in [lo, l).
+         * pivot  < all in [r, start).
+         * The second is vacuously true at the start.
+         */
+        assert(l < r);
+        do {
+            p = l + ((r - l) >> 1);
+            IFLT(pivot, *p)
+                r = p;
+            else
+                l = p+1;
+        } while (l < r);
+        assert(l == r);
+        /* The invariants still hold, so pivot >= all in [lo, l) and
+           pivot < all in [l, start), so pivot belongs at l.  Note
+           that if there are elements equal to pivot, l points to the
+           first slot after them -- that's why this sort is stable.
+           Slide over to make room.
+           Caution: using memmove is much slower under MSVC 5;
+           we're not usually moving many slots. */
+        for (p = start; p > l; --p)
+            *p = *(p-1);
+        *l = pivot;
+    }
+    return 0;
+
+ fail:
+    return -1;
+}
+
+/*
+Return the length of the run beginning at lo, in the slice [lo, hi).  lo < hi
+is required on entry.  "A run" is the longest ascending sequence, with
+
+    lo[0] <= lo[1] <= lo[2] <= ...
+
+or the longest descending sequence, with
+
+    lo[0] > lo[1] > lo[2] > ...
+
+Boolean *descending is set to 0 in the former case, or to 1 in the latter.
+For its intended use in a stable mergesort, the strictness of the defn of
+"descending" is needed so that the caller can safely reverse a descending
+sequence without violating stability (strict > ensures there are no equal
+elements to get out of order).
+
+Returns -1 in case of error.
+*/
+static Py_ssize_t
+count_run(PyObject **lo, PyObject **hi, PyObject *compare, int *descending)
+{
+    Py_ssize_t k;
+    Py_ssize_t n;
+
+    assert(lo < hi);
+    *descending = 0;
+    ++lo;
+    if (lo == hi)
+        return 1;
+
+    n = 2;
+    IFLT(*lo, *(lo-1)) {
+        *descending = 1;
+        for (lo = lo+1; lo < hi; ++lo, ++n) {
+            IFLT(*lo, *(lo-1))
+                ;
+            else
+                break;
+        }
+    }
+    else {
+        for (lo = lo+1; lo < hi; ++lo, ++n) {
+            IFLT(*lo, *(lo-1))
+                break;
+        }
+    }
+
+    return n;
+fail:
+    return -1;
+}
+
+/*
+Locate the proper position of key in a sorted vector; if the vector contains
+an element equal to key, return the position immediately to the left of
+the leftmost equal element.  [gallop_right() does the same except returns
+the position to the right of the rightmost equal element (if any).]
+
+"a" is a sorted vector with n elements, starting at a[0].  n must be > 0.
+
+"hint" is an index at which to begin the search, 0 <= hint < n.  The closer
+hint is to the final result, the faster this runs.
+
+The return value is the int k in 0..n such that
+
+    a[k-1] < key <= a[k]
+
+pretending that *(a-1) is minus infinity and a[n] is plus infinity.  IOW,
+key belongs at index k; or, IOW, the first k elements of a should precede
+key, and the last n-k should follow key.
+
+Returns -1 on error.  See listsort.txt for info on the method.
+*/
+static Py_ssize_t
+gallop_left(PyObject *key, PyObject **a, Py_ssize_t n, Py_ssize_t hint, PyObject *compare)
+{
+    Py_ssize_t ofs;
+    Py_ssize_t lastofs;
+    Py_ssize_t k;
+
+    assert(key && a && n > 0 && hint >= 0 && hint < n);
+
+    a += hint;
+    lastofs = 0;
+    ofs = 1;
+    IFLT(*a, key) {
+        /* a[hint] < key -- gallop right, until
+         * a[hint + lastofs] < key <= a[hint + ofs]
+         */
+        const Py_ssize_t maxofs = n - hint;             /* &a[n-1] is highest */
+        while (ofs < maxofs) {
+            IFLT(a[ofs], key) {
+                lastofs = ofs;
+                ofs = (ofs << 1) + 1;
+                if (ofs <= 0)                   /* int overflow */
+                    ofs = maxofs;
+            }
+            else                /* key <= a[hint + ofs] */
+                break;
+        }
+        if (ofs > maxofs)
+            ofs = maxofs;
+        /* Translate back to offsets relative to &a[0]. */
+        lastofs += hint;
+        ofs += hint;
+    }
+    else {
+        /* key <= a[hint] -- gallop left, until
+         * a[hint - ofs] < key <= a[hint - lastofs]
+         */
+        const Py_ssize_t maxofs = hint + 1;             /* &a[0] is lowest */
+        while (ofs < maxofs) {
+            IFLT(*(a-ofs), key)
+                break;
+            /* key <= a[hint - ofs] */
+            lastofs = ofs;
+            ofs = (ofs << 1) + 1;
+            if (ofs <= 0)               /* int overflow */
+                ofs = maxofs;
+        }
+        if (ofs > maxofs)
+            ofs = maxofs;
+        /* Translate back to positive offsets relative to &a[0]. */
+        k = lastofs;
+        lastofs = hint - ofs;
+        ofs = hint - k;
+    }
+    a -= hint;
+
+    assert(-1 <= lastofs && lastofs < ofs && ofs <= n);
+    /* Now a[lastofs] < key <= a[ofs], so key belongs somewhere to the
+     * right of lastofs but no farther right than ofs.  Do a binary
+     * search, with invariant a[lastofs-1] < key <= a[ofs].
+     */
+    ++lastofs;
+    while (lastofs < ofs) {
+        Py_ssize_t m = lastofs + ((ofs - lastofs) >> 1);
+
+        IFLT(a[m], key)
+            lastofs = m+1;              /* a[m] < key */
+        else
+            ofs = m;                    /* key <= a[m] */
+    }
+    assert(lastofs == ofs);             /* so a[ofs-1] < key <= a[ofs] */
+    return ofs;
+
+fail:
+    return -1;
+}
+
+/*
+Exactly like gallop_left(), except that if key already exists in a[0:n],
+finds the position immediately to the right of the rightmost equal value.
+
+The return value is the int k in 0..n such that
+
+    a[k-1] <= key < a[k]
+
+or -1 if error.
+
+The code duplication is massive, but this is enough different given that
+we're sticking to "<" comparisons that it's much harder to follow if
+written as one routine with yet another "left or right?" flag.
+*/
+static Py_ssize_t
+gallop_right(PyObject *key, PyObject **a, Py_ssize_t n, Py_ssize_t hint, PyObject *compare)
+{
+    Py_ssize_t ofs;
+    Py_ssize_t lastofs;
+    Py_ssize_t k;
+
+    assert(key && a && n > 0 && hint >= 0 && hint < n);
+
+    a += hint;
+    lastofs = 0;
+    ofs = 1;
+    IFLT(key, *a) {
+        /* key < a[hint] -- gallop left, until
+         * a[hint - ofs] <= key < a[hint - lastofs]
+         */
+        const Py_ssize_t maxofs = hint + 1;             /* &a[0] is lowest */
+        while (ofs < maxofs) {
+            IFLT(key, *(a-ofs)) {
+                lastofs = ofs;
+                ofs = (ofs << 1) + 1;
+                if (ofs <= 0)                   /* int overflow */
+                    ofs = maxofs;
+            }
+            else                /* a[hint - ofs] <= key */
+                break;
+        }
+        if (ofs > maxofs)
+            ofs = maxofs;
+        /* Translate back to positive offsets relative to &a[0]. */
+        k = lastofs;
+        lastofs = hint - ofs;
+        ofs = hint - k;
+    }
+    else {
+        /* a[hint] <= key -- gallop right, until
+         * a[hint + lastofs] <= key < a[hint + ofs]
+        */
+        const Py_ssize_t maxofs = n - hint;             /* &a[n-1] is highest */
+        while (ofs < maxofs) {
+            IFLT(key, a[ofs])
+                break;
+            /* a[hint + ofs] <= key */
+            lastofs = ofs;
+            ofs = (ofs << 1) + 1;
+            if (ofs <= 0)               /* int overflow */
+                ofs = maxofs;
+        }
+        if (ofs > maxofs)
+            ofs = maxofs;
+        /* Translate back to offsets relative to &a[0]. */
+        lastofs += hint;
+        ofs += hint;
+    }
+    a -= hint;
+
+    assert(-1 <= lastofs && lastofs < ofs && ofs <= n);
+    /* Now a[lastofs] <= key < a[ofs], so key belongs somewhere to the
+     * right of lastofs but no farther right than ofs.  Do a binary
+     * search, with invariant a[lastofs-1] <= key < a[ofs].
+     */
+    ++lastofs;
+    while (lastofs < ofs) {
+        Py_ssize_t m = lastofs + ((ofs - lastofs) >> 1);
+
+        IFLT(key, a[m])
+            ofs = m;                    /* key < a[m] */
+        else
+            lastofs = m+1;              /* a[m] <= key */
+    }
+    assert(lastofs == ofs);             /* so a[ofs-1] <= key < a[ofs] */
+    return ofs;
+
+fail:
+    return -1;
+}
+
+/* The maximum number of entries in a MergeState's pending-runs stack.
+ * This is enough to sort arrays of size up to about
+ *     32 * phi ** MAX_MERGE_PENDING
+ * where phi ~= 1.618.  85 is ridiculouslylarge enough, good for an array
+ * with 2**64 elements.
+ */
+#define MAX_MERGE_PENDING 85
+
+/* When we get into galloping mode, we stay there until both runs win less
+ * often than MIN_GALLOP consecutive times.  See listsort.txt for more info.
+ */
+#define MIN_GALLOP 7
+
+/* Avoid malloc for small temp arrays. */
+#define MERGESTATE_TEMP_SIZE 256
+
+/* One MergeState exists on the stack per invocation of mergesort.  It's just
+ * a convenient way to pass state around among the helper functions.
+ */
+struct s_slice {
+    PyObject **base;
+    Py_ssize_t len;
+};
+
+typedef struct s_MergeState {
+    /* The user-supplied comparison function. or NULL if none given. */
+    PyObject *compare;
+
+    /* This controls when we get *into* galloping mode.  It's initialized
+     * to MIN_GALLOP.  merge_lo and merge_hi tend to nudge it higher for
+     * random data, and lower for highly structured data.
+     */
+    Py_ssize_t min_gallop;
+
+    /* 'a' is temp storage to help with merges.  It contains room for
+     * alloced entries.
+     */
+    PyObject **a;       /* may point to temparray below */
+    Py_ssize_t alloced;
+
+    /* A stack of n pending runs yet to be merged.  Run #i starts at
+     * address base[i] and extends for len[i] elements.  It's always
+     * true (so long as the indices are in bounds) that
+     *
+     *     pending[i].base + pending[i].len == pending[i+1].base
+     *
+     * so we could cut the storage for this, but it's a minor amount,
+     * and keeping all the info explicit simplifies the code.
+     */
+    int n;
+    struct s_slice pending[MAX_MERGE_PENDING];
+
+    /* 'a' points to this when possible, rather than muck with malloc. */
+    PyObject *temparray[MERGESTATE_TEMP_SIZE];
+} MergeState;
+
+/* Conceptually a MergeState's constructor. */
+static void
+merge_init(MergeState *ms, PyObject *compare)
+{
+    assert(ms != NULL);
+    ms->compare = compare;
+    ms->a = ms->temparray;
+    ms->alloced = MERGESTATE_TEMP_SIZE;
+    ms->n = 0;
+    ms->min_gallop = MIN_GALLOP;
+}
+
+/* Free all the temp memory owned by the MergeState.  This must be called
+ * when you're done with a MergeState, and may be called before then if
+ * you want to free the temp memory early.
+ */
+static void
+merge_freemem(MergeState *ms)
+{
+    assert(ms != NULL);
+    if (ms->a != ms->temparray)
+        PyMem_Free(ms->a);
+    ms->a = ms->temparray;
+    ms->alloced = MERGESTATE_TEMP_SIZE;
+}
+
+/* Ensure enough temp memory for 'need' array slots is available.
+ * Returns 0 on success and -1 if the memory can't be gotten.
+ */
+static int
+merge_getmem(MergeState *ms, Py_ssize_t need)
+{
+    assert(ms != NULL);
+    if (need <= ms->alloced)
+        return 0;
+    /* Don't realloc!  That can cost cycles to copy the old data, but
+     * we don't care what's in the block.
+     */
+    merge_freemem(ms);
+    if ((size_t)need > PY_SSIZE_T_MAX / sizeof(PyObject*)) {
+        PyErr_NoMemory();
+        return -1;
+    }
+    ms->a = (PyObject **)PyMem_Malloc(need * sizeof(PyObject*));
+    if (ms->a) {
+        ms->alloced = need;
+        return 0;
+    }
+    PyErr_NoMemory();
+    merge_freemem(ms);          /* reset to sane state */
+    return -1;
+}
+#define MERGE_GETMEM(MS, NEED) ((NEED) <= (MS)->alloced ? 0 :   \
+                                merge_getmem(MS, NEED))
+
+/* Merge the na elements starting at pa with the nb elements starting at pb
+ * in a stable way, in-place.  na and nb must be > 0, and pa + na == pb.
+ * Must also have that *pb < *pa, that pa[na-1] belongs at the end of the
+ * merge, and should have na <= nb.  See listsort.txt for more info.
+ * Return 0 if successful, -1 if error.
+ */
+static Py_ssize_t
+merge_lo(MergeState *ms, PyObject **pa, Py_ssize_t na,
+                         PyObject **pb, Py_ssize_t nb)
+{
+    Py_ssize_t k;
+    PyObject *compare;
+    PyObject **dest;
+    int result = -1;            /* guilty until proved innocent */
+    Py_ssize_t min_gallop;
+
+    assert(ms && pa && pb && na > 0 && nb > 0 && pa + na == pb);
+    if (MERGE_GETMEM(ms, na) < 0)
+        return -1;
+    memcpy(ms->a, pa, na * sizeof(PyObject*));
+    dest = pa;
+    pa = ms->a;
+
+    *dest++ = *pb++;
+    --nb;
+    if (nb == 0)
+        goto Succeed;
+    if (na == 1)
+        goto CopyB;
+
+    min_gallop = ms->min_gallop;
+    compare = ms->compare;
+    for (;;) {
+        Py_ssize_t acount = 0;          /* # of times A won in a row */
+        Py_ssize_t bcount = 0;          /* # of times B won in a row */
+
+        /* Do the straightforward thing until (if ever) one run
+         * appears to win consistently.
+         */
+        for (;;) {
+            assert(na > 1 && nb > 0);
+            k = ISLT(*pb, *pa, compare);
+            if (k) {
+                if (k < 0)
+                    goto Fail;
+                *dest++ = *pb++;
+                ++bcount;
+                acount = 0;
+                --nb;
+                if (nb == 0)
+                    goto Succeed;
+                if (bcount >= min_gallop)
+                    break;
+            }
+            else {
+                *dest++ = *pa++;
+                ++acount;
+                bcount = 0;
+                --na;
+                if (na == 1)
+                    goto CopyB;
+                if (acount >= min_gallop)
+                    break;
+            }
+        }
+
+        /* One run is winning so consistently that galloping may
+         * be a huge win.  So try that, and continue galloping until
+         * (if ever) neither run appears to be winning consistently
+         * anymore.
+         */
+        ++min_gallop;
+        do {
+            assert(na > 1 && nb > 0);
+            min_gallop -= min_gallop > 1;
+            ms->min_gallop = min_gallop;
+            k = gallop_right(*pb, pa, na, 0, compare);
+            acount = k;
+            if (k) {
+                if (k < 0)
+                    goto Fail;
+                memcpy(dest, pa, k * sizeof(PyObject *));
+                dest += k;
+                pa += k;
+                na -= k;
+                if (na == 1)
+                    goto CopyB;
+                /* na==0 is impossible now if the comparison
+                 * function is consistent, but we can't assume
+                 * that it is.
+                 */
+                if (na == 0)
+                    goto Succeed;
+            }
+            *dest++ = *pb++;
+            --nb;
+            if (nb == 0)
+                goto Succeed;
+
+            k = gallop_left(*pa, pb, nb, 0, compare);
+            bcount = k;
+            if (k) {
+                if (k < 0)
+                    goto Fail;
+                memmove(dest, pb, k * sizeof(PyObject *));
+                dest += k;
+                pb += k;
+                nb -= k;
+                if (nb == 0)
+                    goto Succeed;
+            }
+            *dest++ = *pa++;
+            --na;
+            if (na == 1)
+                goto CopyB;
+        } while (acount >= MIN_GALLOP || bcount >= MIN_GALLOP);
+        ++min_gallop;           /* penalize it for leaving galloping mode */
+        ms->min_gallop = min_gallop;
+    }
+Succeed:
+    result = 0;
+Fail:
+    if (na)
+        memcpy(dest, pa, na * sizeof(PyObject*));
+    return result;
+CopyB:
+    assert(na == 1 && nb > 0);
+    /* The last element of pa belongs at the end of the merge. */
+    memmove(dest, pb, nb * sizeof(PyObject *));
+    dest[nb] = *pa;
+    return 0;
+}
+
+/* Merge the na elements starting at pa with the nb elements starting at pb
+ * in a stable way, in-place.  na and nb must be > 0, and pa + na == pb.
+ * Must also have that *pb < *pa, that pa[na-1] belongs at the end of the
+ * merge, and should have na >= nb.  See listsort.txt for more info.
+ * Return 0 if successful, -1 if error.
+ */
+static Py_ssize_t
+merge_hi(MergeState *ms, PyObject **pa, Py_ssize_t na, PyObject **pb, Py_ssize_t nb)
+{
+    Py_ssize_t k;
+    PyObject *compare;
+    PyObject **dest;
+    int result = -1;            /* guilty until proved innocent */
+    PyObject **basea;
+    PyObject **baseb;
+    Py_ssize_t min_gallop;
+
+    assert(ms && pa && pb && na > 0 && nb > 0 && pa + na == pb);
+    if (MERGE_GETMEM(ms, nb) < 0)
+        return -1;
+    dest = pb + nb - 1;
+    memcpy(ms->a, pb, nb * sizeof(PyObject*));
+    basea = pa;
+    baseb = ms->a;
+    pb = ms->a + nb - 1;
+    pa += na - 1;
+
+    *dest-- = *pa--;
+    --na;
+    if (na == 0)
+        goto Succeed;
+    if (nb == 1)
+        goto CopyA;
+
+    min_gallop = ms->min_gallop;
+    compare = ms->compare;
+    for (;;) {
+        Py_ssize_t acount = 0;          /* # of times A won in a row */
+        Py_ssize_t bcount = 0;          /* # of times B won in a row */
+
+        /* Do the straightforward thing until (if ever) one run
+         * appears to win consistently.
+         */
+        for (;;) {
+            assert(na > 0 && nb > 1);
+            k = ISLT(*pb, *pa, compare);
+            if (k) {
+                if (k < 0)
+                    goto Fail;
+                *dest-- = *pa--;
+                ++acount;
+                bcount = 0;
+                --na;
+                if (na == 0)
+                    goto Succeed;
+                if (acount >= min_gallop)
+                    break;
+            }
+            else {
+                *dest-- = *pb--;
+                ++bcount;
+                acount = 0;
+                --nb;
+                if (nb == 1)
+                    goto CopyA;
+                if (bcount >= min_gallop)
+                    break;
+            }
+        }
+
+        /* One run is winning so consistently that galloping may
+         * be a huge win.  So try that, and continue galloping until
+         * (if ever) neither run appears to be winning consistently
+         * anymore.
+         */
+        ++min_gallop;
+        do {
+            assert(na > 0 && nb > 1);
+            min_gallop -= min_gallop > 1;
+            ms->min_gallop = min_gallop;
+            k = gallop_right(*pb, basea, na, na-1, compare);
+            if (k < 0)
+                goto Fail;
+            k = na - k;
+            acount = k;
+            if (k) {
+                dest -= k;
+                pa -= k;
+                memmove(dest+1, pa+1, k * sizeof(PyObject *));
+                na -= k;
+                if (na == 0)
+                    goto Succeed;
+            }
+            *dest-- = *pb--;
+            --nb;
+            if (nb == 1)
+                goto CopyA;
+
+            k = gallop_left(*pa, baseb, nb, nb-1, compare);
+            if (k < 0)
+                goto Fail;
+            k = nb - k;
+            bcount = k;
+            if (k) {
+                dest -= k;
+                pb -= k;
+                memcpy(dest+1, pb+1, k * sizeof(PyObject *));
+                nb -= k;
+                if (nb == 1)
+                    goto CopyA;
+                /* nb==0 is impossible now if the comparison
+                 * function is consistent, but we can't assume
+                 * that it is.
+                 */
+                if (nb == 0)
+                    goto Succeed;
+            }
+            *dest-- = *pa--;
+            --na;
+            if (na == 0)
+                goto Succeed;
+        } while (acount >= MIN_GALLOP || bcount >= MIN_GALLOP);
+        ++min_gallop;           /* penalize it for leaving galloping mode */
+        ms->min_gallop = min_gallop;
+    }
+Succeed:
+    result = 0;
+Fail:
+    if (nb)
+        memcpy(dest-(nb-1), baseb, nb * sizeof(PyObject*));
+    return result;
+CopyA:
+    assert(nb == 1 && na > 0);
+    /* The first element of pb belongs at the front of the merge. */
+    dest -= na;
+    pa -= na;
+    memmove(dest+1, pa+1, na * sizeof(PyObject *));
+    *dest = *pb;
+    return 0;
+}
+
+/* Merge the two runs at stack indices i and i+1.
+ * Returns 0 on success, -1 on error.
+ */
+static Py_ssize_t
+merge_at(MergeState *ms, Py_ssize_t i)
+{
+    PyObject **pa, **pb;
+    Py_ssize_t na, nb;
+    Py_ssize_t k;
+    PyObject *compare;
+
+    assert(ms != NULL);
+    assert(ms->n >= 2);
+    assert(i >= 0);
+    assert(i == ms->n - 2 || i == ms->n - 3);
+
+    pa = ms->pending[i].base;
+    na = ms->pending[i].len;
+    pb = ms->pending[i+1].base;
+    nb = ms->pending[i+1].len;
+    assert(na > 0 && nb > 0);
+    assert(pa + na == pb);
+
+    /* Record the length of the combined runs; if i is the 3rd-last
+     * run now, also slide over the last run (which isn't involved
+     * in this merge).  The current run i+1 goes away in any case.
+     */
+    ms->pending[i].len = na + nb;
+    if (i == ms->n - 3)
+        ms->pending[i+1] = ms->pending[i+2];
+    --ms->n;
+
+    /* Where does b start in a?  Elements in a before that can be
+     * ignored (already in place).
+     */
+    compare = ms->compare;
+    k = gallop_right(*pb, pa, na, 0, compare);
+    if (k < 0)
+        return -1;
+    pa += k;
+    na -= k;
+    if (na == 0)
+        return 0;
+
+    /* Where does a end in b?  Elements in b after that can be
+     * ignored (already in place).
+     */
+    nb = gallop_left(pa[na-1], pb, nb, nb-1, compare);
+    if (nb <= 0)
+        return nb;
+
+    /* Merge what remains of the runs, using a temp array with
+     * min(na, nb) elements.
+     */
+    if (na <= nb)
+        return merge_lo(ms, pa, na, pb, nb);
+    else
+        return merge_hi(ms, pa, na, pb, nb);
+}
+
+/* Examine the stack of runs waiting to be merged, merging adjacent runs
+ * until the stack invariants are re-established:
+ *
+ * 1. len[-3] > len[-2] + len[-1]
+ * 2. len[-2] > len[-1]
+ *
+ * See listsort.txt for more info.
+ *
+ * Returns 0 on success, -1 on error.
+ */
+static int
+merge_collapse(MergeState *ms)
+{
+    struct s_slice *p = ms->pending;
+
+    assert(ms);
+    while (ms->n > 1) {
+        Py_ssize_t n = ms->n - 2;
+        if (n > 0 && p[n-1].len <= p[n].len + p[n+1].len) {
+            if (p[n-1].len < p[n+1].len)
+                --n;
+            if (merge_at(ms, n) < 0)
+                return -1;
+        }
+        else if (p[n].len <= p[n+1].len) {
+                 if (merge_at(ms, n) < 0)
+                        return -1;
+        }
+        else
+            break;
+    }
+    return 0;
+}
+
+/* Regardless of invariants, merge all runs on the stack until only one
+ * remains.  This is used at the end of the mergesort.
+ *
+ * Returns 0 on success, -1 on error.
+ */
+static int
+merge_force_collapse(MergeState *ms)
+{
+    struct s_slice *p = ms->pending;
+
+    assert(ms);
+    while (ms->n > 1) {
+        Py_ssize_t n = ms->n - 2;
+        if (n > 0 && p[n-1].len < p[n+1].len)
+            --n;
+        if (merge_at(ms, n) < 0)
+            return -1;
+    }
+    return 0;
+}
+
+/* Compute a good value for the minimum run length; natural runs shorter
+ * than this are boosted artificially via binary insertion.
+ *
+ * If n < 64, return n (it's too small to bother with fancy stuff).
+ * Else if n is an exact power of 2, return 32.
+ * Else return an int k, 32 <= k <= 64, such that n/k is close to, but
+ * strictly less than, an exact power of 2.
+ *
+ * See listsort.txt for more info.
+ */
+static Py_ssize_t
+merge_compute_minrun(Py_ssize_t n)
+{
+    Py_ssize_t r = 0;           /* becomes 1 if any 1 bits are shifted off */
+
+    assert(n >= 0);
+    while (n >= 64) {
+        r |= n & 1;
+        n >>= 1;
+    }
+    return n + r;
+}
+
+/* Special wrapper to support stable sorting using the decorate-sort-undecorate
+   pattern.  Holds a key which is used for comparisons and the original record
+   which is returned during the undecorate phase.  By exposing only the key
+   during comparisons, the underlying sort stability characteristics are left
+   unchanged.  Also, if a custom comparison function is used, it will only see
+   the key instead of a full record. */
+
+typedef struct {
+    PyObject_HEAD
+    PyObject *key;
+    PyObject *value;
+} sortwrapperobject;
+
+PyDoc_STRVAR(sortwrapper_doc, "Object wrapper with a custom sort key.");
+static PyObject *
+sortwrapper_richcompare(sortwrapperobject *, sortwrapperobject *, int);
+static void
+sortwrapper_dealloc(sortwrapperobject *);
+
+static PyTypeObject sortwrapper_type = {
+    PyVarObject_HEAD_INIT(&PyType_Type, 0)
+    "sortwrapper",                              /* tp_name */
+    sizeof(sortwrapperobject),                  /* tp_basicsize */
+    0,                                          /* tp_itemsize */
+    /* methods */
+    (destructor)sortwrapper_dealloc,            /* tp_dealloc */
+    0,                                          /* tp_print */
+    0,                                          /* tp_getattr */
+    0,                                          /* tp_setattr */
+    0,                                          /* tp_compare */
+    0,                                          /* tp_repr */
+    0,                                          /* tp_as_number */
+    0,                                          /* tp_as_sequence */
+    0,                                          /* tp_as_mapping */
+    0,                                          /* tp_hash */
+    0,                                          /* tp_call */
+    0,                                          /* tp_str */
+    PyObject_GenericGetAttr,                    /* tp_getattro */
+    0,                                          /* tp_setattro */
+    0,                                          /* tp_as_buffer */
+    Py_TPFLAGS_DEFAULT |
+    Py_TPFLAGS_HAVE_RICHCOMPARE,                /* tp_flags */
+    sortwrapper_doc,                            /* tp_doc */
+    0,                                          /* tp_traverse */
+    0,                                          /* tp_clear */
+    (richcmpfunc)sortwrapper_richcompare,       /* tp_richcompare */
+};
+
+
+static PyObject *
+sortwrapper_richcompare(sortwrapperobject *a, sortwrapperobject *b, int op)
+{
+    if (!PyObject_TypeCheck(b, &sortwrapper_type)) {
+        PyErr_SetString(PyExc_TypeError,
+            "expected a sortwrapperobject");
+        return NULL;
+    }
+    return PyObject_RichCompare(a->key, b->key, op);
+}
+
+static void
+sortwrapper_dealloc(sortwrapperobject *so)
+{
+    Py_XDECREF(so->key);
+    Py_XDECREF(so->value);
+    PyObject_Del(so);
+}
+
+/* Returns a new reference to a sortwrapper.
+   Consumes the references to the two underlying objects. */
+
+static PyObject *
+build_sortwrapper(PyObject *key, PyObject *value)
+{
+    sortwrapperobject *so;
+
+    so = PyObject_New(sortwrapperobject, &sortwrapper_type);
+    if (so == NULL)
+        return NULL;
+    so->key = key;
+    so->value = value;
+    return (PyObject *)so;
+}
+
+/* Returns a new reference to the value underlying the wrapper. */
+static PyObject *
+sortwrapper_getvalue(PyObject *so)
+{
+    PyObject *value;
+
+    if (!PyObject_TypeCheck(so, &sortwrapper_type)) {
+        PyErr_SetString(PyExc_TypeError,
+            "expected a sortwrapperobject");
+        return NULL;
+    }
+    value = ((sortwrapperobject *)so)->value;
+    Py_INCREF(value);
+    return value;
+}
+
+/* Wrapper for user specified cmp functions in combination with a
+   specified key function.  Makes sure the cmp function is presented
+   with the actual key instead of the sortwrapper */
+
+typedef struct {
+    PyObject_HEAD
+    PyObject *func;
+} cmpwrapperobject;
+
+static void
+cmpwrapper_dealloc(cmpwrapperobject *co)
+{
+    Py_XDECREF(co->func);
+    PyObject_Del(co);
+}
+
+static PyObject *
+cmpwrapper_call(cmpwrapperobject *co, PyObject *args, PyObject *kwds)
+{
+    PyObject *x, *y, *xx, *yy;
+
+    if (!PyArg_UnpackTuple(args, "", 2, 2, &x, &y))
+        return NULL;
+    if (!PyObject_TypeCheck(x, &sortwrapper_type) ||
+        !PyObject_TypeCheck(y, &sortwrapper_type)) {
+        PyErr_SetString(PyExc_TypeError,
+            "expected a sortwrapperobject");
+        return NULL;
+    }
+    xx = ((sortwrapperobject *)x)->key;
+    yy = ((sortwrapperobject *)y)->key;
+    return PyObject_CallFunctionObjArgs(co->func, xx, yy, NULL);
+}
+
+PyDoc_STRVAR(cmpwrapper_doc, "cmp() wrapper for sort with custom keys.");
+
+static PyTypeObject cmpwrapper_type = {
+    PyVarObject_HEAD_INIT(&PyType_Type, 0)
+    "cmpwrapper",                               /* tp_name */
+    sizeof(cmpwrapperobject),                   /* tp_basicsize */
+    0,                                          /* tp_itemsize */
+    /* methods */
+    (destructor)cmpwrapper_dealloc,             /* tp_dealloc */
+    0,                                          /* tp_print */
+    0,                                          /* tp_getattr */
+    0,                                          /* tp_setattr */
+    0,                                          /* tp_compare */
+    0,                                          /* tp_repr */
+    0,                                          /* tp_as_number */
+    0,                                          /* tp_as_sequence */
+    0,                                          /* tp_as_mapping */
+    0,                                          /* tp_hash */
+    (ternaryfunc)cmpwrapper_call,               /* tp_call */
+    0,                                          /* tp_str */
+    PyObject_GenericGetAttr,                    /* tp_getattro */
+    0,                                          /* tp_setattro */
+    0,                                          /* tp_as_buffer */
+    Py_TPFLAGS_DEFAULT,                         /* tp_flags */
+    cmpwrapper_doc,                             /* tp_doc */
+};
+
+static PyObject *
+build_cmpwrapper(PyObject *cmpfunc)
+{
+    cmpwrapperobject *co;
+
+    co = PyObject_New(cmpwrapperobject, &cmpwrapper_type);
+    if (co == NULL)
+        return NULL;
+    Py_INCREF(cmpfunc);
+    co->func = cmpfunc;
+    return (PyObject *)co;
+}
+
+/* An adaptive, stable, natural mergesort.  See listsort.txt.
+ * Returns Py_None on success, NULL on error.  Even in case of error, the
+ * list will be some permutation of its input state (nothing is lost or
+ * duplicated).
+ */
+static PyObject *
+listsort(PyListObject *self, PyObject *args, PyObject *kwds)
+{
+    MergeState ms;
+    PyObject **lo, **hi;
+    Py_ssize_t nremaining;
+    Py_ssize_t minrun;
+    Py_ssize_t saved_ob_size, saved_allocated;
+    PyObject **saved_ob_item;
+    PyObject **final_ob_item;
+    PyObject *compare = NULL;
+    PyObject *result = NULL;            /* guilty until proved innocent */
+    int reverse = 0;
+    PyObject *keyfunc = NULL;
+    Py_ssize_t i;
+    PyObject *key, *value, *kvpair;
+    static char *kwlist[] = {"cmp", "key", "reverse", 0};
+
+    assert(self != NULL);
+    assert (PyList_Check(self));
+    if (args != NULL) {
+        if (!PyArg_ParseTupleAndKeywords(args, kwds, "|OOi:sort",
+            kwlist, &compare, &keyfunc, &reverse))
+            return NULL;
+    }
+    if (compare == Py_None)
+        compare = NULL;
+    if (compare != NULL &&
+        PyErr_WarnPy3k("the cmp argument is not supported in 3.x", 1) < 0)
+        return NULL;
+    if (keyfunc == Py_None)
+        keyfunc = NULL;
+    if (compare != NULL && keyfunc != NULL) {
+        compare = build_cmpwrapper(compare);
+        if (compare == NULL)
+            return NULL;
+    } else
+        Py_XINCREF(compare);
+
+    /* The list is temporarily made empty, so that mutations performed
+     * by comparison functions can't affect the slice of memory we're
+     * sorting (allowing mutations during sorting is a core-dump
+     * factory, since ob_item may change).
+     */
+    saved_ob_size = Py_SIZE(self);
+    saved_ob_item = self->ob_item;
+    saved_allocated = self->allocated;
+    Py_SIZE(self) = 0;
+    self->ob_item = NULL;
+    self->allocated = -1; /* any operation will reset it to >= 0 */
+
+    if (keyfunc != NULL) {
+        for (i=0 ; i < saved_ob_size ; i++) {
+            value = saved_ob_item[i];
+            key = PyObject_CallFunctionObjArgs(keyfunc, value,
+                                               NULL);
+            if (key == NULL) {
+                for (i=i-1 ; i>=0 ; i--) {
+                    kvpair = saved_ob_item[i];
+                    value = sortwrapper_getvalue(kvpair);
+                    saved_ob_item[i] = value;
+                    Py_DECREF(kvpair);
+                }
+                goto dsu_fail;
+            }
+            kvpair = build_sortwrapper(key, value);
+            if (kvpair == NULL)
+                goto dsu_fail;
+            saved_ob_item[i] = kvpair;
+        }
+    }
+
+    /* Reverse sort stability achieved by initially reversing the list,
+    applying a stable forward sort, then reversing the final result. */
+    if (reverse && saved_ob_size > 1)
+        reverse_slice(saved_ob_item, saved_ob_item + saved_ob_size);
+
+    merge_init(&ms, compare);
+
+    nremaining = saved_ob_size;
+    if (nremaining < 2)
+        goto succeed;
+
+    /* March over the array once, left to right, finding natural runs,
+     * and extending short natural runs to minrun elements.
+     */
+    lo = saved_ob_item;
+    hi = lo + nremaining;
+    minrun = merge_compute_minrun(nremaining);
+    do {
+        int descending;
+        Py_ssize_t n;
+
+        /* Identify next run. */
+        n = count_run(lo, hi, compare, &descending);
+        if (n < 0)
+            goto fail;
+        if (descending)
+            reverse_slice(lo, lo + n);
+        /* If short, extend to min(minrun, nremaining). */
+        if (n < minrun) {
+            const Py_ssize_t force = nremaining <= minrun ?
+                              nremaining : minrun;
+            if (binarysort(lo, lo + force, lo + n, compare) < 0)
+                goto fail;
+            n = force;
+        }
+        /* Push run onto pending-runs stack, and maybe merge. */
+        assert(ms.n < MAX_MERGE_PENDING);
+        ms.pending[ms.n].base = lo;
+        ms.pending[ms.n].len = n;
+        ++ms.n;
+        if (merge_collapse(&ms) < 0)
+            goto fail;
+        /* Advance to find next run. */
+        lo += n;
+        nremaining -= n;
+    } while (nremaining);
+    assert(lo == hi);
+
+    if (merge_force_collapse(&ms) < 0)
+        goto fail;
+    assert(ms.n == 1);
+    assert(ms.pending[0].base == saved_ob_item);
+    assert(ms.pending[0].len == saved_ob_size);
+
+succeed:
+    result = Py_None;
+fail:
+    if (keyfunc != NULL) {
+        for (i=0 ; i < saved_ob_size ; i++) {
+            kvpair = saved_ob_item[i];
+            value = sortwrapper_getvalue(kvpair);
+            saved_ob_item[i] = value;
+            Py_DECREF(kvpair);
+        }
+    }
+
+    if (self->allocated != -1 && result != NULL) {
+        /* The user mucked with the list during the sort,
+         * and we don't already have another error to report.
+         */
+        PyErr_SetString(PyExc_ValueError, "list modified during sort");
+        result = NULL;
+    }
+
+    if (reverse && saved_ob_size > 1)
+        reverse_slice(saved_ob_item, saved_ob_item + saved_ob_size);
+
+    merge_freemem(&ms);
+
+dsu_fail:
+    final_ob_item = self->ob_item;
+    i = Py_SIZE(self);
+    Py_SIZE(self) = saved_ob_size;
+    self->ob_item = saved_ob_item;
+    self->allocated = saved_allocated;
+    if (final_ob_item != NULL) {
+        /* we cannot use list_clear() for this because it does not
+           guarantee that the list is really empty when it returns */
+        while (--i >= 0) {
+            Py_XDECREF(final_ob_item[i]);
+        }
+        PyMem_FREE(final_ob_item);
+    }
+    Py_XDECREF(compare);
+    Py_XINCREF(result);
+    return result;
+}
+#undef IFLT
+#undef ISLT
+
+int
+PyList_Sort(PyObject *v)
+{
+    if (v == NULL || !PyList_Check(v)) {
+        PyErr_BadInternalCall();
+        return -1;
+    }
+    v = listsort((PyListObject *)v, (PyObject *)NULL, (PyObject *)NULL);
+    if (v == NULL)
+        return -1;
+    Py_DECREF(v);
+    return 0;
+}
+
+static PyObject *
+listreverse(PyListObject *self)
+{
+    if (Py_SIZE(self) > 1)
+        reverse_slice(self->ob_item, self->ob_item + Py_SIZE(self));
+    Py_RETURN_NONE;
+}
+
+int
+PyList_Reverse(PyObject *v)
+{
+    PyListObject *self = (PyListObject *)v;
+
+    if (v == NULL || !PyList_Check(v)) {
+        PyErr_BadInternalCall();
+        return -1;
+    }
+    if (Py_SIZE(self) > 1)
+        reverse_slice(self->ob_item, self->ob_item + Py_SIZE(self));
+    return 0;
+}
+
+PyObject *
+PyList_AsTuple(PyObject *v)
+{
+    PyObject *w;
+    PyObject **p, **q;
+    Py_ssize_t n;
+    if (v == NULL || !PyList_Check(v)) {
+        PyErr_BadInternalCall();
+        return NULL;
+    }
+    n = Py_SIZE(v);
+    w = PyTuple_New(n);
+    if (w == NULL)
+        return NULL;
+    p = ((PyTupleObject *)w)->ob_item;
+    q = ((PyListObject *)v)->ob_item;
+    while (--n >= 0) {
+        Py_INCREF(*q);
+        *p = *q;
+        p++;
+        q++;
+    }
+    return w;
+}
+
+static PyObject *
+listindex(PyListObject *self, PyObject *args)
+{
+    Py_ssize_t i, start=0, stop=Py_SIZE(self);
+    PyObject *v, *format_tuple, *err_string;
+    static PyObject *err_format = NULL;
+
+    if (!PyArg_ParseTuple(args, "O|O&O&:index", &v,
+                                _PyEval_SliceIndex, &start,
+                                _PyEval_SliceIndex, &stop))
+        return NULL;
+    if (start < 0) {
+        start += Py_SIZE(self);
+        if (start < 0)
+            start = 0;
+    }
+    if (stop < 0) {
+        stop += Py_SIZE(self);
+        if (stop < 0)
+            stop = 0;
+    }
+    for (i = start; i < stop && i < Py_SIZE(self); i++) {
+        int cmp = PyObject_RichCompareBool(self->ob_item[i], v, Py_EQ);
+        if (cmp > 0)
+            return PyInt_FromSsize_t(i);
+        else if (cmp < 0)
+            return NULL;
+    }
+    if (err_format == NULL) {
+        err_format = PyString_FromString("%r is not in list");
+        if (err_format == NULL)
+            return NULL;
+    }
+    format_tuple = PyTuple_Pack(1, v);
+    if (format_tuple == NULL)
+        return NULL;
+    err_string = PyString_Format(err_format, format_tuple);
+    Py_DECREF(format_tuple);
+    if (err_string == NULL)
+        return NULL;
+    PyErr_SetObject(PyExc_ValueError, err_string);
+    Py_DECREF(err_string);
+    return NULL;
+}
+
+static PyObject *
+listcount(PyListObject *self, PyObject *v)
+{
+    Py_ssize_t count = 0;
+    Py_ssize_t i;
+
+    for (i = 0; i < Py_SIZE(self); i++) {
+        int cmp = PyObject_RichCompareBool(self->ob_item[i], v, Py_EQ);
+        if (cmp > 0)
+            count++;
+        else if (cmp < 0)
+            return NULL;
+    }
+    return PyInt_FromSsize_t(count);
+}
+
+static PyObject *
+listremove(PyListObject *self, PyObject *v)
+{
+    Py_ssize_t i;
+
+    for (i = 0; i < Py_SIZE(self); i++) {
+        int cmp = PyObject_RichCompareBool(self->ob_item[i], v, Py_EQ);
+        if (cmp > 0) {
+            if (list_ass_slice(self, i, i+1,
+                               (PyObject *)NULL) == 0)
+                Py_RETURN_NONE;
+            return NULL;
+        }
+        else if (cmp < 0)
+            return NULL;
+    }
+    PyErr_SetString(PyExc_ValueError, "list.remove(x): x not in list");
+    return NULL;
+}
+
+static int
+list_traverse(PyListObject *o, visitproc visit, void *arg)
+{
+    Py_ssize_t i;
+
+    for (i = Py_SIZE(o); --i >= 0; )
+        Py_VISIT(o->ob_item[i]);
+    return 0;
+}
+
+static PyObject *
+list_richcompare(PyObject *v, PyObject *w, int op)
+{
+    PyListObject *vl, *wl;
+    Py_ssize_t i;
+
+    if (!PyList_Check(v) || !PyList_Check(w)) {
+        Py_INCREF(Py_NotImplemented);
+        return Py_NotImplemented;
+    }
+
+    vl = (PyListObject *)v;
+    wl = (PyListObject *)w;
+
+    if (Py_SIZE(vl) != Py_SIZE(wl) && (op == Py_EQ || op == Py_NE)) {
+        /* Shortcut: if the lengths differ, the lists differ */
+        PyObject *res;
+        if (op == Py_EQ)
+            res = Py_False;
+        else
+            res = Py_True;
+        Py_INCREF(res);
+        return res;
+    }
+
+    /* Search for the first index where items are different */
+    for (i = 0; i < Py_SIZE(vl) && i < Py_SIZE(wl); i++) {
+        int k = PyObject_RichCompareBool(vl->ob_item[i],
+                                         wl->ob_item[i], Py_EQ);
+        if (k < 0)
+            return NULL;
+        if (!k)
+            break;
+    }
+
+    if (i >= Py_SIZE(vl) || i >= Py_SIZE(wl)) {
+        /* No more items to compare -- compare sizes */
+        Py_ssize_t vs = Py_SIZE(vl);
+        Py_ssize_t ws = Py_SIZE(wl);
+        int cmp;
+        PyObject *res;
+        switch (op) {
+        case Py_LT: cmp = vs <  ws; break;
+        case Py_LE: cmp = vs <= ws; break;
+        case Py_EQ: cmp = vs == ws; break;
+        case Py_NE: cmp = vs != ws; break;
+        case Py_GT: cmp = vs >  ws; break;
+        case Py_GE: cmp = vs >= ws; break;
+        default: return NULL; /* cannot happen */
+        }
+        if (cmp)
+            res = Py_True;
+        else
+            res = Py_False;
+        Py_INCREF(res);
+        return res;
+    }
+
+    /* We have an item that differs -- shortcuts for EQ/NE */
+    if (op == Py_EQ) {
+        Py_INCREF(Py_False);
+        return Py_False;
+    }
+    if (op == Py_NE) {
+        Py_INCREF(Py_True);
+        return Py_True;
+    }
+
+    /* Compare the final item again using the proper operator */
+    return PyObject_RichCompare(vl->ob_item[i], wl->ob_item[i], op);
+}
+
+static int
+list_init(PyListObject *self, PyObject *args, PyObject *kw)
+{
+    PyObject *arg = NULL;
+    static char *kwlist[] = {"sequence", 0};
+
+    if (!PyArg_ParseTupleAndKeywords(args, kw, "|O:list", kwlist, &arg))
+        return -1;
+
+    /* Verify list invariants established by PyType_GenericAlloc() */
+    assert(0 <= Py_SIZE(self));
+    assert(Py_SIZE(self) <= self->allocated || self->allocated == -1);
+    assert(self->ob_item != NULL ||
+           self->allocated == 0 || self->allocated == -1);
+
+    /* Empty previous contents */
+    if (self->ob_item != NULL) {
+        (void)list_clear(self);
+    }
+    if (arg != NULL) {
+        PyObject *rv = listextend(self, arg);
+        if (rv == NULL)
+            return -1;
+        Py_DECREF(rv);
+    }
+    return 0;
+}
+
+static PyObject *
+list_sizeof(PyListObject *self)
+{
+    Py_ssize_t res;
+
+    res = sizeof(PyListObject) + self->allocated * sizeof(void*);
+    return PyInt_FromSsize_t(res);
+}
+
+static PyObject *list_iter(PyObject *seq);
+static PyObject *list_reversed(PyListObject* seq, PyObject* unused);
+
+PyDoc_STRVAR(getitem_doc,
+"x.__getitem__(y) <==> x[y]");
+PyDoc_STRVAR(reversed_doc,
+"L.__reversed__() -- return a reverse iterator over the list");
+PyDoc_STRVAR(sizeof_doc,
+"L.__sizeof__() -- size of L in memory, in bytes");
+PyDoc_STRVAR(append_doc,
+"L.append(object) -- append object to end");
+PyDoc_STRVAR(extend_doc,
+"L.extend(iterable) -- extend list by appending elements from the iterable");
+PyDoc_STRVAR(insert_doc,
+"L.insert(index, object) -- insert object before index");
+PyDoc_STRVAR(pop_doc,
+"L.pop([index]) -> item -- remove and return item at index (default last).\n"
+"Raises IndexError if list is empty or index is out of range.");
+PyDoc_STRVAR(remove_doc,
+"L.remove(value) -- remove first occurrence of value.\n"
+"Raises ValueError if the value is not present.");
+PyDoc_STRVAR(index_doc,
+"L.index(value, [start, [stop]]) -> integer -- return first index of value.\n"
+"Raises ValueError if the value is not present.");
+PyDoc_STRVAR(count_doc,
+"L.count(value) -> integer -- return number of occurrences of value");
+PyDoc_STRVAR(reverse_doc,
+"L.reverse() -- reverse *IN PLACE*");
+PyDoc_STRVAR(sort_doc,
+"L.sort(cmp=None, key=None, reverse=False) -- stable sort *IN PLACE*;\n\
+cmp(x, y) -> -1, 0, 1");
+
+static PyObject *list_subscript(PyListObject*, PyObject*);
+
+static PyMethodDef list_methods[] = {
+    {"__getitem__", (PyCFunction)list_subscript, METH_O|METH_COEXIST, getitem_doc},
+    {"__reversed__",(PyCFunction)list_reversed, METH_NOARGS, reversed_doc},
+    {"__sizeof__",  (PyCFunction)list_sizeof, METH_NOARGS, sizeof_doc},
+    {"append",          (PyCFunction)listappend,  METH_O, append_doc},
+    {"insert",          (PyCFunction)listinsert,  METH_VARARGS, insert_doc},
+    {"extend",      (PyCFunction)listextend,  METH_O, extend_doc},
+    {"pop",             (PyCFunction)listpop,     METH_VARARGS, pop_doc},
+    {"remove",          (PyCFunction)listremove,  METH_O, remove_doc},
+    {"index",           (PyCFunction)listindex,   METH_VARARGS, index_doc},
+    {"count",           (PyCFunction)listcount,   METH_O, count_doc},
+    {"reverse",         (PyCFunction)listreverse, METH_NOARGS, reverse_doc},
+    {"sort",            (PyCFunction)listsort,    METH_VARARGS | METH_KEYWORDS, sort_doc},
+    {NULL,              NULL}           /* sentinel */
+};
+
+static PySequenceMethods list_as_sequence = {
+    (lenfunc)list_length,                       /* sq_length */
+    (binaryfunc)list_concat,                    /* sq_concat */
+    (ssizeargfunc)list_repeat,                  /* sq_repeat */
+    (ssizeargfunc)list_item,                    /* sq_item */
+    (ssizessizeargfunc)list_slice,              /* sq_slice */
+    (ssizeobjargproc)list_ass_item,             /* sq_ass_item */
+    (ssizessizeobjargproc)list_ass_slice,       /* sq_ass_slice */
+    (objobjproc)list_contains,                  /* sq_contains */
+    (binaryfunc)list_inplace_concat,            /* sq_inplace_concat */
+    (ssizeargfunc)list_inplace_repeat,          /* sq_inplace_repeat */
+};
+
+PyDoc_STRVAR(list_doc,
+"list() -> new empty list\n"
+"list(iterable) -> new list initialized from iterable's items");
+
+
+static PyObject *
+list_subscript(PyListObject* self, PyObject* item)
+{
+    if (PyIndex_Check(item)) {
+        Py_ssize_t i;
+        i = PyNumber_AsSsize_t(item, PyExc_IndexError);
+        if (i == -1 && PyErr_Occurred())
+            return NULL;
+        if (i < 0)
+            i += PyList_GET_SIZE(self);
+        return list_item(self, i);
+    }
+    else if (PySlice_Check(item)) {
+        Py_ssize_t start, stop, step, slicelength, cur, i;
+        PyObject* result;
+        PyObject* it;
+        PyObject **src, **dest;
+
+        if (PySlice_GetIndicesEx((PySliceObject*)item, Py_SIZE(self),
+                         &start, &stop, &step, &slicelength) < 0) {
+            return NULL;
+        }
+
+        if (slicelength <= 0) {
+            return PyList_New(0);
+        }
+        else if (step == 1) {
+            return list_slice(self, start, stop);
+        }
+        else {
+            result = PyList_New(slicelength);
+            if (!result) return NULL;
+
+            src = self->ob_item;
+            dest = ((PyListObject *)result)->ob_item;
+            for (cur = start, i = 0; i < slicelength;
+                 cur += step, i++) {
+                it = src[cur];
+                Py_INCREF(it);
+                dest[i] = it;
+            }
+
+            return result;
+        }
+    }
+    else {
+        PyErr_Format(PyExc_TypeError,
+                     "list indices must be integers, not %.200s",
+                     item->ob_type->tp_name);
+        return NULL;
+    }
+}
+
+static int
+list_ass_subscript(PyListObject* self, PyObject* item, PyObject* value)
+{
+    if (PyIndex_Check(item)) {
+        Py_ssize_t i = PyNumber_AsSsize_t(item, PyExc_IndexError);
+        if (i == -1 && PyErr_Occurred())
+            return -1;
+        if (i < 0)
+            i += PyList_GET_SIZE(self);
+        return list_ass_item(self, i, value);
+    }
+    else if (PySlice_Check(item)) {
+        Py_ssize_t start, stop, step, slicelength;
+
+        if (PySlice_GetIndicesEx((PySliceObject*)item, Py_SIZE(self),
+                         &start, &stop, &step, &slicelength) < 0) {
+            return -1;
+        }
+
+        if (step == 1)
+            return list_ass_slice(self, start, stop, value);
+
+        /* Make sure s[5:2] = [..] inserts at the right place:
+           before 5, not before 2. */
+        if ((step < 0 && start < stop) ||
+            (step > 0 && start > stop))
+            stop = start;
+
+        if (value == NULL) {
+            /* delete slice */
+            PyObject **garbage;
+            size_t cur;
+            Py_ssize_t i;
+
+            if (slicelength <= 0)
+                return 0;
+
+            if (step < 0) {
+                stop = start + 1;
+                start = stop + step*(slicelength - 1) - 1;
+                step = -step;
+            }
+
+            assert((size_t)slicelength <=
+                   PY_SIZE_MAX / sizeof(PyObject*));
+
+            garbage = (PyObject**)
+                PyMem_MALLOC(slicelength*sizeof(PyObject*));
+            if (!garbage) {
+                PyErr_NoMemory();
+                return -1;
+            }
+
+            /* drawing pictures might help understand these for
+               loops. Basically, we memmove the parts of the
+               list that are *not* part of the slice: step-1
+               items for each item that is part of the slice,
+               and then tail end of the list that was not
+               covered by the slice */
+            for (cur = start, i = 0;
+                 cur < (size_t)stop;
+                 cur += step, i++) {
+                Py_ssize_t lim = step - 1;
+
+                garbage[i] = PyList_GET_ITEM(self, cur);
+
+                if (cur + step >= (size_t)Py_SIZE(self)) {
+                    lim = Py_SIZE(self) - cur - 1;
+                }
+
+                memmove(self->ob_item + cur - i,
+                    self->ob_item + cur + 1,
+                    lim * sizeof(PyObject *));
+            }
+            cur = start + slicelength*step;
+            if (cur < (size_t)Py_SIZE(self)) {
+                memmove(self->ob_item + cur - slicelength,
+                    self->ob_item + cur,
+                    (Py_SIZE(self) - cur) *
+                     sizeof(PyObject *));
+            }
+
+            Py_SIZE(self) -= slicelength;
+            list_resize(self, Py_SIZE(self));
+
+            for (i = 0; i < slicelength; i++) {
+                Py_DECREF(garbage[i]);
+            }
+            PyMem_FREE(garbage);
+
+            return 0;
+        }
+        else {
+            /* assign slice */
+            PyObject *ins, *seq;
+            PyObject **garbage, **seqitems, **selfitems;
+            Py_ssize_t cur, i;
+
+            /* protect against a[::-1] = a */
+            if (self == (PyListObject*)value) {
+                seq = list_slice((PyListObject*)value, 0,
+                                   PyList_GET_SIZE(value));
+            }
+            else {
+                seq = PySequence_Fast(value,
+                                      "must assign iterable "
+                                      "to extended slice");
+            }
+            if (!seq)
+                return -1;
+
+            if (PySequence_Fast_GET_SIZE(seq) != slicelength) {
+                PyErr_Format(PyExc_ValueError,
+                    "attempt to assign sequence of "
+                    "size %zd to extended slice of "
+                    "size %zd",
+                         PySequence_Fast_GET_SIZE(seq),
+                         slicelength);
+                Py_DECREF(seq);
+                return -1;
+            }
+
+            if (!slicelength) {
+                Py_DECREF(seq);
+                return 0;
+            }
+
+            garbage = (PyObject**)
+                PyMem_MALLOC(slicelength*sizeof(PyObject*));
+            if (!garbage) {
+                Py_DECREF(seq);
+                PyErr_NoMemory();
+                return -1;
+            }
+
+            selfitems = self->ob_item;
+            seqitems = PySequence_Fast_ITEMS(seq);
+            for (cur = start, i = 0; i < slicelength;
+                 cur += step, i++) {
+                garbage[i] = selfitems[cur];
+                ins = seqitems[i];
+                Py_INCREF(ins);
+                selfitems[cur] = ins;
+            }
+
+            for (i = 0; i < slicelength; i++) {
+                Py_DECREF(garbage[i]);
+            }
+
+            PyMem_FREE(garbage);
+            Py_DECREF(seq);
+
+            return 0;
+        }
+    }
+    else {
+        PyErr_Format(PyExc_TypeError,
+                     "list indices must be integers, not %.200s",
+                     item->ob_type->tp_name);
+        return -1;
+    }
+}
+
+static PyMappingMethods list_as_mapping = {
+    (lenfunc)list_length,
+    (binaryfunc)list_subscript,
+    (objobjargproc)list_ass_subscript
+};
+
+PyTypeObject PyList_Type = {
+    PyVarObject_HEAD_INIT(&PyType_Type, 0)
+    "list",
+    sizeof(PyListObject),
+    0,
+    (destructor)list_dealloc,                   /* tp_dealloc */
+    (printfunc)list_print,                      /* tp_print */
+    0,                                          /* tp_getattr */
+    0,                                          /* tp_setattr */
+    0,                                          /* tp_compare */
+    (reprfunc)list_repr,                        /* tp_repr */
+    0,                                          /* tp_as_number */
+    &list_as_sequence,                          /* tp_as_sequence */
+    &list_as_mapping,                           /* tp_as_mapping */
+    (hashfunc)PyObject_HashNotImplemented,      /* tp_hash */
+    0,                                          /* tp_call */
+    0,                                          /* tp_str */
+    PyObject_GenericGetAttr,                    /* tp_getattro */
+    0,                                          /* tp_setattro */
+    0,                                          /* tp_as_buffer */
+    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC |
+        Py_TPFLAGS_BASETYPE | Py_TPFLAGS_LIST_SUBCLASS,         /* tp_flags */
+    list_doc,                                   /* tp_doc */
+    (traverseproc)list_traverse,                /* tp_traverse */
+    (inquiry)list_clear,                        /* tp_clear */
+    list_richcompare,                           /* tp_richcompare */
+    0,                                          /* tp_weaklistoffset */
+    list_iter,                                  /* tp_iter */
+    0,                                          /* tp_iternext */
+    list_methods,                               /* tp_methods */
+    0,                                          /* tp_members */
+    0,                                          /* tp_getset */
+    0,                                          /* tp_base */
+    0,                                          /* tp_dict */
+    0,                                          /* tp_descr_get */
+    0,                                          /* tp_descr_set */
+    0,                                          /* tp_dictoffset */
+    (initproc)list_init,                        /* tp_init */
+    PyType_GenericAlloc,                        /* tp_alloc */
+    PyType_GenericNew,                          /* tp_new */
+    PyObject_GC_Del,                            /* tp_free */
+};
+
+
+/*********************** List Iterator **************************/
+
+typedef struct {
+    PyObject_HEAD
+    long it_index;
+    PyListObject *it_seq; /* Set to NULL when iterator is exhausted */
+} listiterobject;
+
+static PyObject *list_iter(PyObject *);
+static void listiter_dealloc(listiterobject *);
+static int listiter_traverse(listiterobject *, visitproc, void *);
+static PyObject *listiter_next(listiterobject *);
+static PyObject *listiter_len(listiterobject *);
+
+PyDoc_STRVAR(length_hint_doc, "Private method returning an estimate of len(list(it)).");
+
+static PyMethodDef listiter_methods[] = {
+    {"__length_hint__", (PyCFunction)listiter_len, METH_NOARGS, length_hint_doc},
+    {NULL,              NULL}           /* sentinel */
+};
+
+PyTypeObject PyListIter_Type = {
+    PyVarObject_HEAD_INIT(&PyType_Type, 0)
+    "listiterator",                             /* tp_name */
+    sizeof(listiterobject),                     /* tp_basicsize */
+    0,                                          /* tp_itemsize */
+    /* methods */
+    (destructor)listiter_dealloc,               /* tp_dealloc */
+    0,                                          /* tp_print */
+    0,                                          /* tp_getattr */
+    0,                                          /* tp_setattr */
+    0,                                          /* tp_compare */
+    0,                                          /* tp_repr */
+    0,                                          /* tp_as_number */
+    0,                                          /* tp_as_sequence */
+    0,                                          /* tp_as_mapping */
+    0,                                          /* tp_hash */
+    0,                                          /* tp_call */
+    0,                                          /* tp_str */
+    PyObject_GenericGetAttr,                    /* tp_getattro */
+    0,                                          /* tp_setattro */
+    0,                                          /* tp_as_buffer */
+    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC,/* tp_flags */
+    0,                                          /* tp_doc */
+    (traverseproc)listiter_traverse,            /* tp_traverse */
+    0,                                          /* tp_clear */
+    0,                                          /* tp_richcompare */
+    0,                                          /* tp_weaklistoffset */
+    PyObject_SelfIter,                          /* tp_iter */
+    (iternextfunc)listiter_next,                /* tp_iternext */
+    listiter_methods,                           /* tp_methods */
+    0,                                          /* tp_members */
+};
+
+
+static PyObject *
+list_iter(PyObject *seq)
+{
+    listiterobject *it;
+
+    if (!PyList_Check(seq)) {
+        PyErr_BadInternalCall();
+        return NULL;
+    }
+    it = PyObject_GC_New(listiterobject, &PyListIter_Type);
+    if (it == NULL)
+        return NULL;
+    it->it_index = 0;
+    Py_INCREF(seq);
+    it->it_seq = (PyListObject *)seq;
+    _PyObject_GC_TRACK(it);
+    return (PyObject *)it;
+}
+
+static void
+listiter_dealloc(listiterobject *it)
+{
+    _PyObject_GC_UNTRACK(it);
+    Py_XDECREF(it->it_seq);
+    PyObject_GC_Del(it);
+}
+
+static int
+listiter_traverse(listiterobject *it, visitproc visit, void *arg)
+{
+    Py_VISIT(it->it_seq);
+    return 0;
+}
+
+static PyObject *
+listiter_next(listiterobject *it)
+{
+    PyListObject *seq;
+    PyObject *item;
+
+    assert(it != NULL);
+    seq = it->it_seq;
+    if (seq == NULL)
+        return NULL;
+    assert(PyList_Check(seq));
+
+    if (it->it_index < PyList_GET_SIZE(seq)) {
+        item = PyList_GET_ITEM(seq, it->it_index);
+        ++it->it_index;
+        Py_INCREF(item);
+        return item;
+    }
+
+    Py_DECREF(seq);
+    it->it_seq = NULL;
+    return NULL;
+}
+
+static PyObject *
+listiter_len(listiterobject *it)
+{
+    Py_ssize_t len;
+    if (it->it_seq) {
+        len = PyList_GET_SIZE(it->it_seq) - it->it_index;
+        if (len >= 0)
+            return PyInt_FromSsize_t(len);
+    }
+    return PyInt_FromLong(0);
+}
+/*********************** List Reverse Iterator **************************/
+
+typedef struct {
+    PyObject_HEAD
+    Py_ssize_t it_index;
+    PyListObject *it_seq; /* Set to NULL when iterator is exhausted */
+} listreviterobject;
+
+static PyObject *list_reversed(PyListObject *, PyObject *);
+static void listreviter_dealloc(listreviterobject *);
+static int listreviter_traverse(listreviterobject *, visitproc, void *);
+static PyObject *listreviter_next(listreviterobject *);
+static PyObject *listreviter_len(listreviterobject *);
+
+static PyMethodDef listreviter_methods[] = {
+    {"__length_hint__", (PyCFunction)listreviter_len, METH_NOARGS, length_hint_doc},
+    {NULL,              NULL}           /* sentinel */
+};
+
+PyTypeObject PyListRevIter_Type = {
+    PyVarObject_HEAD_INIT(&PyType_Type, 0)
+    "listreverseiterator",                      /* tp_name */
+    sizeof(listreviterobject),                  /* tp_basicsize */
+    0,                                          /* tp_itemsize */
+    /* methods */
+    (destructor)listreviter_dealloc,            /* tp_dealloc */
+    0,                                          /* tp_print */
+    0,                                          /* tp_getattr */
+    0,                                          /* tp_setattr */
+    0,                                          /* tp_compare */
+    0,                                          /* tp_repr */
+    0,                                          /* tp_as_number */
+    0,                                          /* tp_as_sequence */
+    0,                                          /* tp_as_mapping */
+    0,                                          /* tp_hash */
+    0,                                          /* tp_call */
+    0,                                          /* tp_str */
+    PyObject_GenericGetAttr,                    /* tp_getattro */
+    0,                                          /* tp_setattro */
+    0,                                          /* tp_as_buffer */
+    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC,/* tp_flags */
+    0,                                          /* tp_doc */
+    (traverseproc)listreviter_traverse,         /* tp_traverse */
+    0,                                          /* tp_clear */
+    0,                                          /* tp_richcompare */
+    0,                                          /* tp_weaklistoffset */
+    PyObject_SelfIter,                          /* tp_iter */
+    (iternextfunc)listreviter_next,             /* tp_iternext */
+    listreviter_methods,                /* tp_methods */
+    0,
+};
+
+static PyObject *
+list_reversed(PyListObject *seq, PyObject *unused)
+{
+    listreviterobject *it;
+
+    it = PyObject_GC_New(listreviterobject, &PyListRevIter_Type);
+    if (it == NULL)
+        return NULL;
+    assert(PyList_Check(seq));
+    it->it_index = PyList_GET_SIZE(seq) - 1;
+    Py_INCREF(seq);
+    it->it_seq = seq;
+    PyObject_GC_Track(it);
+    return (PyObject *)it;
+}
+
+static void
+listreviter_dealloc(listreviterobject *it)
+{
+    PyObject_GC_UnTrack(it);
+    Py_XDECREF(it->it_seq);
+    PyObject_GC_Del(it);
+}
+
+static int
+listreviter_traverse(listreviterobject *it, visitproc visit, void *arg)
+{
+    Py_VISIT(it->it_seq);
+    return 0;
+}
+
+static PyObject *
+listreviter_next(listreviterobject *it)
+{
+    PyObject *item;
+    Py_ssize_t index = it->it_index;
+    PyListObject *seq = it->it_seq;
+
+    if (index>=0 && index < PyList_GET_SIZE(seq)) {
+        item = PyList_GET_ITEM(seq, index);
+        it->it_index--;
+        Py_INCREF(item);
+        return item;
+    }
+    it->it_index = -1;
+    if (seq != NULL) {
+        it->it_seq = NULL;
+        Py_DECREF(seq);
+    }
+    return NULL;
+}
+
+static PyObject *
+listreviter_len(listreviterobject *it)
+{
+    Py_ssize_t len = it->it_index + 1;
+    if (it->it_seq == NULL || PyList_GET_SIZE(it->it_seq) < len)
+        len = 0;
+    return PyLong_FromSsize_t(len);
+}