bpo-39829: Fix `__len__()` is called twice in list() constructor (GH-31816)
(cherry picked from commit 2153daf0a02a598ed5df93f2f224c1ab2a2cca0d)
This patch fixes gh-87740 too.
Co-authored-by: Crowthebird <78076854+thatbirdguythatuknownot@users.noreply.github.com>
diff --git a/Misc/ACKS b/Misc/ACKS
index 889bf8a..b83f999 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -1332,6 +1332,7 @@
Claude Paroz
Heikki Partanen
Harri Pasanen
+Jeremiah Gabriel Pascual
Gaël Pasgrimaud
Feanil Patel
Ashish Nitin Patil
diff --git a/Misc/NEWS.d/next/Core and Builtins/2022-03-11-09-39-01.bpo-39829.mlW3Su.rst b/Misc/NEWS.d/next/Core and Builtins/2022-03-11-09-39-01.bpo-39829.mlW3Su.rst
new file mode 100644
index 0000000..1f3d945
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2022-03-11-09-39-01.bpo-39829.mlW3Su.rst
@@ -0,0 +1 @@
+Removed the ``__len__()`` call when initializing a list and moved initializing to ``list_extend``. Patch by Jeremiah Pascual.
diff --git a/Objects/listobject.c b/Objects/listobject.c
index d3bc576..7f37b73 100644
--- a/Objects/listobject.c
+++ b/Objects/listobject.c
@@ -863,7 +863,6 @@
PyObject *it; /* iter(v) */
Py_ssize_t m; /* size of self */
Py_ssize_t n; /* guess for size of iterable */
- Py_ssize_t mn; /* m + n */
Py_ssize_t i;
PyObject *(*iternext)(PyObject *);
@@ -887,7 +886,13 @@
/* It should not be possible to allocate a list large enough to cause
an overflow on any relevant platform */
assert(m < PY_SSIZE_T_MAX - n);
- if (list_resize(self, m + n) < 0) {
+ if (self->ob_item == NULL) {
+ if (list_preallocate_exact(self, n) < 0) {
+ return NULL;
+ }
+ Py_SET_SIZE(self, n);
+ }
+ else if (list_resize(self, m + n) < 0) {
Py_DECREF(iterable);
return NULL;
}
@@ -926,10 +931,13 @@
* eventually run out of memory during the loop.
*/
}
+ else if (self->ob_item == NULL) {
+ if (n && list_preallocate_exact(self, n) < 0)
+ goto error;
+ }
else {
- mn = m + n;
/* Make room. */
- if (list_resize(self, mn) < 0)
+ if (list_resize(self, m + n) < 0)
goto error;
/* Make the list sane again. */
Py_SET_SIZE(self, m);
@@ -2717,19 +2725,6 @@
(void)_list_clear(self);
}
if (iterable != NULL) {
- if (_PyObject_HasLen(iterable)) {
- Py_ssize_t iter_len = PyObject_Size(iterable);
- if (iter_len == -1) {
- if (!PyErr_ExceptionMatches(PyExc_TypeError)) {
- return -1;
- }
- PyErr_Clear();
- }
- if (iter_len > 0 && self->ob_item == NULL
- && list_preallocate_exact(self, iter_len)) {
- return -1;
- }
- }
PyObject *rv = list_extend(self, iterable);
if (rv == NULL)
return -1;