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Issue #14178: Problem deleting slices with steps != +1 in the _elementtree module.

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Fixed the problem and added some tests. Closes #14178
This commit is contained in:
Eli Bendersky 2012-03-09 13:38:15 +02:00
parent f5a1d76b48
commit 865756a94c
2 changed files with 153 additions and 8 deletions
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70
Modules/_elementtree.c
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@ -1343,9 +1343,74 @@ element_ass_subscr(PyObject* self_, PyObject* item, PyObject* value)
return -1;
}
if (value == NULL)
newlen = 0;
if (value == NULL) {
/* Delete slice */
size_t cur;
Py_ssize_t i;
if (slicelen <= 0)
return 0;
/* Since we're deleting, the direction of the range doesn't matter,
* so for simplicity make it always ascending.
*/
if (step < 0) {
stop = start + 1;
start = stop + step * (slicelen - 1) - 1;
step = -step;
}
assert((size_t)slicelen <= PY_SIZE_MAX / sizeof(PyObject *));
/* recycle is a list that will contain all the children
* scheduled for removal.
*/
if (!(recycle = PyList_New(slicelen))) {
PyErr_NoMemory();
return -1;
}
/* This loop walks over all the children that have to be deleted,
* with cur pointing at them. num_moved is the amount of children
* until the next deleted child that have to be "shifted down" to
* occupy the deleted's places.
* Note that in the ith iteration, shifting is done i+i places down
* because i children were already removed.
*/
for (cur = start, i = 0; cur < (size_t)stop; cur += step, ++i) {
/* Compute how many children have to be moved, clipping at the
* list end.
*/
Py_ssize_t num_moved = step - 1;
if (cur + step >= (size_t)self->extra->length) {
num_moved = self->extra->length - cur - 1;
}
PyList_SET_ITEM(recycle, i, self->extra->children[cur]);
memmove(
self->extra->children + cur - i,
self->extra->children + cur + 1,
num_moved * sizeof(PyObject *));
}
/* Leftover "tail" after the last removed child */
cur = start + (size_t)slicelen * step;
if (cur < (size_t)self->extra->length) {
memmove(
self->extra->children + cur - slicelen,
self->extra->children + cur,
(self->extra->length - cur) * sizeof(PyObject *));
}
self->extra->length -= slicelen;
/* Discard the recycle list with all the deleted sub-elements */
Py_XDECREF(recycle);
return 0;
}
else {
/* A new slice is actually being assigned */
seq = PySequence_Fast(value, "");
if (!seq) {
PyErr_Format(
@ -1367,7 +1432,6 @@ element_ass_subscr(PyObject* self_, PyObject* item, PyObject* value)
return -1;
}
/* Resize before creating the recycle bin, to prevent refleaks. */
if (newlen > slicelen) {
if (element_resize(self, newlen - slicelen) < 0) {