[Python-checkins] bpo-39829: Fix `__len__()` is called twice in list() constructor (GH-31816)
methane
webhook-mailer at python.org
Wed May 18 00:17:33 EDT 2022
https://github.com/python/cpython/commit/009aeb6bb689aadf954d8bebaba4c78acd571cbe
commit: 009aeb6bb689aadf954d8bebaba4c78acd571cbe
branch: 3.10
author: Miss Islington (bot) <31488909+miss-islington at users.noreply.github.com>
committer: methane <songofacandy at gmail.com>
date: 2022-05-18T13:16:58+09:00
summary:
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 at users.noreply.github.com>
files:
A Misc/NEWS.d/next/Core and Builtins/2022-03-11-09-39-01.bpo-39829.mlW3Su.rst
M Misc/ACKS
M Objects/listobject.c
diff --git a/Misc/ACKS b/Misc/ACKS
index 889bf8aeaea1a..b83f99956de0b 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -1332,6 +1332,7 @@ William Park
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 0000000000000..1f3d945188a32
--- /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 d3bc5766df7a0..7f37b7386051d 100644
--- a/Objects/listobject.c
+++ b/Objects/listobject.c
@@ -863,7 +863,6 @@ list_extend(PyListObject *self, PyObject *iterable)
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 @@ list_extend(PyListObject *self, PyObject *iterable)
/* 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 @@ list_extend(PyListObject *self, PyObject *iterable)
* 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 @@ list___init___impl(PyListObject *self, PyObject *iterable)
(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;
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