traverseda
/
cpython
1
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity

bpo-27660: remove unnecessary overflow checks in list_resize (GH-189)

This commit is contained in:
Xiang Zhang 2017-02-22 12:32:30 +08:00 committed by GitHub
parent 3e8d6cb189
commit 4cee049f5b
1 changed files with 7 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

19
Objects/listobject.c
View File

@ -26,7 +26,7 @@ static int
list_resize(PyListObject *self, Py_ssize_t newsize)
{
PyObject **items;
size_t new_allocated;
size_t new_allocated, num_allocated_bytes;
Py_ssize_t allocated = self->allocated;
/* Bypass realloc() when a previous overallocation is large enough
@ -45,24 +45,19 @@ list_resize(PyListObject *self, Py_ssize_t newsize)
* 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, ...
* Note: new_allocated won't overflow because the largest possible value
* is PY_SSIZE_T_MAX * (9 / 8) + 6 which always fits in a size_t.
*/
new_allocated = (newsize >> 3) + (newsize < 9 ? 3 : 6);
/* check for integer overflow */
if (new_allocated > SIZE_MAX - newsize) {
new_allocated = (size_t)newsize + (newsize >> 3) + (newsize < 9 ? 3 : 6);
if (new_allocated > (size_t)PY_SSIZE_T_MAX / sizeof(PyObject *)) {
PyErr_NoMemory();
return -1;
} else {
new_allocated += newsize;
}
if (newsize == 0)
new_allocated = 0;
items = self->ob_item;
if (new_allocated <= (SIZE_MAX / sizeof(PyObject *)))
PyMem_RESIZE(items, PyObject *, new_allocated);
else
items = NULL;
num_allocated_bytes = new_allocated * sizeof(PyObject *);
items = (PyObject **)PyMem_Realloc(self->ob_item, num_allocated_bytes);
if (items == NULL) {
PyErr_NoMemory();
return -1;