From 0a5d672e2a539d1a988f5907b3f1541f2271654e Mon Sep 17 00:00:00 2001
From: Crowthebird <78076854+thatbirdguythatuknownot@users.noreply.github.com>
Date: Tue, 8 Mar 2022 13:38:08 +0800
Subject: [PATCH 01/15] bpo-39829: __len__() called twice in the list()
 constructor

---
 Objects/listobject.c | 40 ++++++++++++++++++++--------------------
 1 file changed, 20 insertions(+), 20 deletions(-)

diff --git a/Objects/listobject.c b/Objects/listobject.c
index 783ae88a17f3be..845e27f1bd001c 100644
--- a/Objects/listobject.c
+++ b/Objects/listobject.c
@@ -889,9 +889,16 @@ 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) {
-            Py_DECREF(iterable);
-            return NULL;
+        if (self->ob_item == NULL) {
+            if (list_preallocate_exact(self, n) < 0) {
+                Py_DECREF(iterable);
+                return NULL;
+            }
+        else {
+            if (list_resize(self, m + n) < 0) {
+                Py_DECREF(iterable);
+                return NULL;
+            }
         }
         /* note that we may still have self == iterable here for the
          * situation a.extend(a), but the following code works
@@ -929,10 +936,16 @@ list_extend(PyListObject *self, PyObject *iterable)
          */
     }
     else {
-        mn = m + n;
-        /* Make room. */
-        if (list_resize(self, mn) < 0)
-            goto error;
+        if (self->ob_item == NULL) {
+            if (list_preallocate_exact(self, n) < 0)
+                goto error;
+        }
+        else {
+            mn = m + n;
+            /* Make room. */
+            if (list_resize(self, mn) < 0)
+                goto error;
+        }
         /* Make the list sane again. */
         Py_SET_SIZE(self, m);
     }
@@ -2814,19 +2827,6 @@ 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;

From ac00535bb1ecfcf6fd4566637b08e92eeb76c767 Mon Sep 17 00:00:00 2001
From: Crowthebird <78076854+thatbirdguythatuknownot@users.noreply.github.com>
Date: Tue, 8 Mar 2022 13:44:15 +0800
Subject: [PATCH 02/15] bpo-39829: __len__ called twice in the list()
 constructor

---
 Objects/listobject.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/Objects/listobject.c b/Objects/listobject.c
index 845e27f1bd001c..7fac6ac0d004ac 100644
--- a/Objects/listobject.c
+++ b/Objects/listobject.c
@@ -894,6 +894,7 @@ list_extend(PyListObject *self, PyObject *iterable)
                 Py_DECREF(iterable);
                 return NULL;
             }
+        }
         else {
             if (list_resize(self, m + n) < 0) {
                 Py_DECREF(iterable);

From 12eba0364b67fb0d75d372b2c06ab1126cb79574 Mon Sep 17 00:00:00 2001
From: Crowthebird <78076854+thatbirdguythatuknownot@users.noreply.github.com>
Date: Tue, 8 Mar 2022 13:46:37 +0800
Subject: [PATCH 03/15] bpo-39829: __len__ called twice in the list()
 constructor

---
 Objects/listobject.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/Objects/listobject.c b/Objects/listobject.c
index 7fac6ac0d004ac..004fb2c678a2eb 100644
--- a/Objects/listobject.c
+++ b/Objects/listobject.c
@@ -895,11 +895,9 @@ list_extend(PyListObject *self, PyObject *iterable)
                 return NULL;
             }
         }
-        else {
-            if (list_resize(self, m + n) < 0) {
-                Py_DECREF(iterable);
-                return NULL;
-            }
+        else if (list_resize(self, m + n) < 0) {
+            Py_DECREF(iterable);
+            return NULL;
         }
         /* note that we may still have self == iterable here for the
          * situation a.extend(a), but the following code works

From fc50d3676a2a13dd532036c01f2d6f7300de22c7 Mon Sep 17 00:00:00 2001
From: Crowthebird <78076854+thatbirdguythatuknownot@users.noreply.github.com>
Date: Tue, 8 Mar 2022 14:22:05 +0800
Subject: [PATCH 04/15] bpo-39829: __len__ called twice in the list()
 constructor

---
 Objects/listobject.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/Objects/listobject.c b/Objects/listobject.c
index 004fb2c678a2eb..653c7fda2e801a 100644
--- a/Objects/listobject.c
+++ b/Objects/listobject.c
@@ -889,7 +889,7 @@ 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 (self->ob_item == NULL) {
+        if (n && self->ob_item == NULL) {
             if (list_preallocate_exact(self, n) < 0) {
                 Py_DECREF(iterable);
                 return NULL;
@@ -935,7 +935,7 @@ list_extend(PyListObject *self, PyObject *iterable)
          */
     }
     else {
-        if (self->ob_item == NULL) {
+        if (n && self->ob_item == NULL) {
             if (list_preallocate_exact(self, n) < 0)
                 goto error;
         }

From 37382e84ea003e73d73c4614ef1d93011f4dec42 Mon Sep 17 00:00:00 2001
From: Crowthebird <78076854+thatbirdguythatuknownot@users.noreply.github.com>
Date: Tue, 8 Mar 2022 20:30:42 +0800
Subject: [PATCH 05/15] bpo-43574 + bpo-39829: Optimize allocations

---
 Objects/listobject.c | 84 +++++++++++---------------------------------
 1 file changed, 21 insertions(+), 63 deletions(-)

diff --git a/Objects/listobject.c b/Objects/listobject.c
index 653c7fda2e801a..61194dce0e55ce 100644
--- a/Objects/listobject.c
+++ b/Objects/listobject.c
@@ -74,8 +74,9 @@ list_resize(PyListObject *self, Py_ssize_t newsize)
     if (newsize - Py_SIZE(self) > (Py_ssize_t)(new_allocated - newsize))
         new_allocated = ((size_t)newsize + 3) & ~(size_t)3;
 
-    if (newsize == 0)
-        new_allocated = 0;
+    /* Don't overallocate for lists that start empty or are set to empty. */
+    if (newsize == 0 || Py_SIZE(self) == 0)
+        new_allocated = newsize;
     num_allocated_bytes = new_allocated * sizeof(PyObject *);
     items = (PyObject **)PyMem_Realloc(self->ob_item, num_allocated_bytes);
     if (items == NULL) {
@@ -218,7 +219,6 @@ valid_index(Py_ssize_t i, Py_ssize_t limit)
 {
     /* The cast to size_t lets us use just a single comparison
        to check whether i is in the range: 0 <= i < limit.
-
        See:  Section 14.2 "Bounds Checking" in the Agner Fog
        optimization manual found at:
        https://www.agner.org/optimize/optimizing_cpp.pdf
@@ -787,11 +787,9 @@ list_ass_item(PyListObject *a, Py_ssize_t i, PyObject *v)
 
 /*[clinic input]
 list.insert
-
     index: Py_ssize_t
     object: object
     /
-
 Insert object before index.
 [clinic start generated code]*/
 
@@ -806,7 +804,6 @@ list_insert_impl(PyListObject *self, Py_ssize_t index, PyObject *object)
 
 /*[clinic input]
 list.clear
-
 Remove all items from list.
 [clinic start generated code]*/
 
@@ -820,7 +817,6 @@ list_clear_impl(PyListObject *self)
 
 /*[clinic input]
 list.copy
-
 Return a shallow copy of the list.
 [clinic start generated code]*/
 
@@ -833,10 +829,8 @@ list_copy_impl(PyListObject *self)
 
 /*[clinic input]
 list.append
-
      object: object
      /
-
 Append object to the end of the list.
 [clinic start generated code]*/
 
@@ -851,10 +845,8 @@ list_append(PyListObject *self, PyObject *object)
 
 /*[clinic input]
 list.extend
-
      iterable: object
      /
-
 Extend list by appending elements from the iterable.
 [clinic start generated code]*/
 
@@ -865,7 +857,6 @@ 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 *);
 
@@ -889,13 +880,7 @@ 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 (n && self->ob_item == NULL) {
-            if (list_preallocate_exact(self, n) < 0) {
-                Py_DECREF(iterable);
-                return NULL;
-            }
-        }
-        else if (list_resize(self, m + n) < 0) {
+        if (list_resize(self, m + n) < 0) {
             Py_DECREF(iterable);
             return NULL;
         }
@@ -935,16 +920,13 @@ list_extend(PyListObject *self, PyObject *iterable)
          */
     }
     else {
-        if (n && self->ob_item == NULL) {
+        /* Make room. */
+        if (self->ob_item == NULL) {
             if (list_preallocate_exact(self, n) < 0)
                 goto error;
         }
-        else {
-            mn = m + n;
-            /* Make room. */
-            if (list_resize(self, mn) < 0)
-                goto error;
-        }
+        else if (list_resize(self, m + n) < 0)
+            goto error;
         /* Make the list sane again. */
         Py_SET_SIZE(self, m);
     }
@@ -1009,12 +991,9 @@ list_inplace_concat(PyListObject *self, PyObject *other)
 
 /*[clinic input]
 list.pop
-
     index: Py_ssize_t = -1
     /
-
 Remove and return item at index (default last).
-
 Raises IndexError if list is empty or index is out of range.
 [clinic start generated code]*/
 
@@ -1301,19 +1280,14 @@ binarysort(MergeState *ms, sortslice lo, PyObject **hi, PyObject **start)
 /*
 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
@@ -1355,20 +1329,14 @@ 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
@@ -1449,13 +1417,9 @@ gallop_left(MergeState *ms, PyObject *key, PyObject **a, Py_ssize_t n, Py_ssize_
 /*
 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.
@@ -2286,19 +2250,14 @@ unsafe_tuple_compare(PyObject *v, PyObject *w, MergeState *ms)
  */
 /*[clinic input]
 list.sort
-
     *
     key as keyfunc: object = None
     reverse: bool(accept={int}) = False
-
 Sort the list in ascending order and return None.
-
 The sort is in-place (i.e. the list itself is modified) and stable (i.e. the
 order of two equal elements is maintained).
-
 If a key function is given, apply it once to each list item and sort them,
 ascending or descending, according to their function values.
-
 The reverse flag can be set to sort in descending order.
 [clinic start generated code]*/
 
@@ -2584,7 +2543,6 @@ PyList_Sort(PyObject *v)
 
 /*[clinic input]
 list.reverse
-
 Reverse *IN PLACE*.
 [clinic start generated code]*/
 
@@ -2623,14 +2581,11 @@ PyList_AsTuple(PyObject *v)
 
 /*[clinic input]
 list.index
-
     value: object
     start: slice_index(accept={int}) = 0
     stop: slice_index(accept={int}, c_default="PY_SSIZE_T_MAX") = sys.maxsize
     /
-
 Return first index of value.
-
 Raises ValueError if the value is not present.
 [clinic start generated code]*/
 
@@ -2667,10 +2622,8 @@ list_index_impl(PyListObject *self, PyObject *value, Py_ssize_t start,
 
 /*[clinic input]
 list.count
-
      value: object
      /
-
 Return number of occurrences of value.
 [clinic start generated code]*/
 
@@ -2700,12 +2653,9 @@ list_count(PyListObject *self, PyObject *value)
 
 /*[clinic input]
 list.remove
-
      value: object
      /
-
 Remove first occurrence of value.
-
 Raises ValueError if the value is not present.
 [clinic start generated code]*/
 
@@ -2801,12 +2751,9 @@ list_richcompare(PyObject *v, PyObject *w, int op)
 
 /*[clinic input]
 list.__init__
-
     iterable: object(c_default="NULL") = ()
     /
-
 Built-in mutable sequence.
-
 If no argument is given, the constructor creates a new empty list.
 The argument must be an iterable if specified.
 [clinic start generated code]*/
@@ -2826,6 +2773,19 @@ 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;
@@ -2862,7 +2822,6 @@ list_vectorcall(PyObject *type, PyObject * const*args,
 
 /*[clinic input]
 list.__sizeof__
-
 Return the size of the list in memory, in bytes.
 [clinic start generated code]*/
 
@@ -3390,7 +3349,6 @@ PyTypeObject PyListRevIter_Type = {
 
 /*[clinic input]
 list.__reversed__
-
 Return a reverse iterator over the list.
 [clinic start generated code]*/
 

From 4b9631937b98f18d2fcdcacd45902e5b808b5797 Mon Sep 17 00:00:00 2001
From: Crowthebird <78076854+thatbirdguythatuknownot@users.noreply.github.com>
Date: Wed, 9 Mar 2022 08:09:25 +0800
Subject: [PATCH 06/15] bpo-43574 + bpo-39829: Optimize list allocations

---
 Objects/listobject.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/Objects/listobject.c b/Objects/listobject.c
index 61194dce0e55ce..899fd48b9e48a3 100644
--- a/Objects/listobject.c
+++ b/Objects/listobject.c
@@ -68,15 +68,17 @@ list_resize(PyListObject *self, Py_ssize_t newsize)
      *       is PY_SSIZE_T_MAX * (9 / 8) + 6 which always fits in a size_t.
      */
     new_allocated = ((size_t)newsize + (newsize >> 3) + 6) & ~(size_t)3;
-    /* Do not overallocate if the new size is closer to overallocated size
-     * than to the old size.
-     */
-    if (newsize - Py_SIZE(self) > (Py_ssize_t)(new_allocated - newsize))
-        new_allocated = ((size_t)newsize + 3) & ~(size_t)3;
 
     /* Don't overallocate for lists that start empty or are set to empty. */
     if (newsize == 0 || Py_SIZE(self) == 0)
         new_allocated = newsize;
+    else if (newsize - Py_SIZE(self) > (Py_ssize_t)(new_allocated - newsize)) {
+        /* Do not overallocate if the new size is closer to overallocated size
+        * than to the old size.
+        */
+        new_allocated = ((size_t)newsize + 3) & ~(size_t)3;
+    }
+
     num_allocated_bytes = new_allocated * sizeof(PyObject *);
     items = (PyObject **)PyMem_Realloc(self->ob_item, num_allocated_bytes);
     if (items == NULL) {

From ecb8c897d518cffd20bcdb25c6bc9317db50856d Mon Sep 17 00:00:00 2001
From: Crowthebird <78076854+thatbirdguythatuknownot@users.noreply.github.com>
Date: Wed, 9 Mar 2022 09:45:44 +0800
Subject: [PATCH 07/15] bpo-39829: __len__ called twice in the list()
 constructor

---
 Objects/listobject.c | 46 +++++++++++++++++---------------------------
 1 file changed, 18 insertions(+), 28 deletions(-)

diff --git a/Objects/listobject.c b/Objects/listobject.c
index 899fd48b9e48a3..b85d06941e5866 100644
--- a/Objects/listobject.c
+++ b/Objects/listobject.c
@@ -68,17 +68,14 @@ list_resize(PyListObject *self, Py_ssize_t newsize)
      *       is PY_SSIZE_T_MAX * (9 / 8) + 6 which always fits in a size_t.
      */
     new_allocated = ((size_t)newsize + (newsize >> 3) + 6) & ~(size_t)3;
-
-    /* Don't overallocate for lists that start empty or are set to empty. */
-    if (newsize == 0 || Py_SIZE(self) == 0)
-        new_allocated = newsize;
-    else if (newsize - Py_SIZE(self) > (Py_ssize_t)(new_allocated - newsize)) {
-        /* Do not overallocate if the new size is closer to overallocated size
-        * than to the old size.
-        */
+    /* Do not overallocate if the new size is closer to overallocated size
+     * than to the old size.
+     */
+    if (newsize - Py_SIZE(self) > (Py_ssize_t)(new_allocated - newsize))
         new_allocated = ((size_t)newsize + 3) & ~(size_t)3;
-    }
 
+    if (newsize == 0)
+        new_allocated = 0;
     num_allocated_bytes = new_allocated * sizeof(PyObject *);
     items = (PyObject **)PyMem_Realloc(self->ob_item, num_allocated_bytes);
     if (items == NULL) {
@@ -882,7 +879,13 @@ 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;
         }
@@ -921,13 +924,13 @@ list_extend(PyListObject *self, PyObject *iterable)
          * eventually run out of memory during the loop.
          */
     }
+    else if (self->ob_item == NULL) {
+        if (list_preallocate_exact(self, n) < 0)
+            goto error;
+    }
     else {
         /* Make room. */
-        if (self->ob_item == NULL) {
-            if (list_preallocate_exact(self, n) < 0)
-                goto error;
-        }
-        else if (list_resize(self, m + n) < 0)
+        if (list_resize(self, m + n) < 0)
             goto error;
         /* Make the list sane again. */
         Py_SET_SIZE(self, m);
@@ -2775,19 +2778,6 @@ 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;

From 66c024686a0ec206eaf3bc21897288dd65b02360 Mon Sep 17 00:00:00 2001
From: Crowthebird <78076854+thatbirdguythatuknownot@users.noreply.github.com>
Date: Wed, 9 Mar 2022 15:10:16 +0800
Subject: [PATCH 08/15] bpo-39829: __len__ called twice in the list()
 constructor

---
 Objects/listobject.c | 45 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 45 insertions(+)

diff --git a/Objects/listobject.c b/Objects/listobject.c
index b85d06941e5866..4da51e907cc6a7 100644
--- a/Objects/listobject.c
+++ b/Objects/listobject.c
@@ -218,6 +218,7 @@ valid_index(Py_ssize_t i, Py_ssize_t limit)
 {
     /* The cast to size_t lets us use just a single comparison
        to check whether i is in the range: 0 <= i < limit.
+
        See:  Section 14.2 "Bounds Checking" in the Agner Fog
        optimization manual found at:
        https://www.agner.org/optimize/optimizing_cpp.pdf
@@ -786,9 +787,11 @@ list_ass_item(PyListObject *a, Py_ssize_t i, PyObject *v)
 
 /*[clinic input]
 list.insert
+
     index: Py_ssize_t
     object: object
     /
+
 Insert object before index.
 [clinic start generated code]*/
 
@@ -803,6 +806,7 @@ list_insert_impl(PyListObject *self, Py_ssize_t index, PyObject *object)
 
 /*[clinic input]
 list.clear
+
 Remove all items from list.
 [clinic start generated code]*/
 
@@ -816,6 +820,7 @@ list_clear_impl(PyListObject *self)
 
 /*[clinic input]
 list.copy
+
 Return a shallow copy of the list.
 [clinic start generated code]*/
 
@@ -828,8 +833,10 @@ list_copy_impl(PyListObject *self)
 
 /*[clinic input]
 list.append
+
      object: object
      /
+
 Append object to the end of the list.
 [clinic start generated code]*/
 
@@ -844,8 +851,10 @@ list_append(PyListObject *self, PyObject *object)
 
 /*[clinic input]
 list.extend
+
      iterable: object
      /
+
 Extend list by appending elements from the iterable.
 [clinic start generated code]*/
 
@@ -996,9 +1005,12 @@ list_inplace_concat(PyListObject *self, PyObject *other)
 
 /*[clinic input]
 list.pop
+
     index: Py_ssize_t = -1
     /
+
 Remove and return item at index (default last).
+
 Raises IndexError if list is empty or index is out of range.
 [clinic start generated code]*/
 
@@ -1285,14 +1297,19 @@ binarysort(MergeState *ms, sortslice lo, PyObject **hi, PyObject **start)
 /*
 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
@@ -1334,14 +1351,20 @@ 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
@@ -1422,9 +1445,13 @@ gallop_left(MergeState *ms, PyObject *key, PyObject **a, Py_ssize_t n, Py_ssize_
 /*
 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.
@@ -2255,14 +2282,19 @@ unsafe_tuple_compare(PyObject *v, PyObject *w, MergeState *ms)
  */
 /*[clinic input]
 list.sort
+
     *
     key as keyfunc: object = None
     reverse: bool(accept={int}) = False
+
 Sort the list in ascending order and return None.
+
 The sort is in-place (i.e. the list itself is modified) and stable (i.e. the
 order of two equal elements is maintained).
+
 If a key function is given, apply it once to each list item and sort them,
 ascending or descending, according to their function values.
+
 The reverse flag can be set to sort in descending order.
 [clinic start generated code]*/
 
@@ -2548,6 +2580,7 @@ PyList_Sort(PyObject *v)
 
 /*[clinic input]
 list.reverse
+
 Reverse *IN PLACE*.
 [clinic start generated code]*/
 
@@ -2586,11 +2619,14 @@ PyList_AsTuple(PyObject *v)
 
 /*[clinic input]
 list.index
+
     value: object
     start: slice_index(accept={int}) = 0
     stop: slice_index(accept={int}, c_default="PY_SSIZE_T_MAX") = sys.maxsize
     /
+
 Return first index of value.
+
 Raises ValueError if the value is not present.
 [clinic start generated code]*/
 
@@ -2627,8 +2663,10 @@ list_index_impl(PyListObject *self, PyObject *value, Py_ssize_t start,
 
 /*[clinic input]
 list.count
+
      value: object
      /
+
 Return number of occurrences of value.
 [clinic start generated code]*/
 
@@ -2658,9 +2696,12 @@ list_count(PyListObject *self, PyObject *value)
 
 /*[clinic input]
 list.remove
+
      value: object
      /
+
 Remove first occurrence of value.
+
 Raises ValueError if the value is not present.
 [clinic start generated code]*/
 
@@ -2756,8 +2797,10 @@ list_richcompare(PyObject *v, PyObject *w, int op)
 
 /*[clinic input]
 list.__init__
+
     iterable: object(c_default="NULL") = ()
     /
+
 Built-in mutable sequence.
 If no argument is given, the constructor creates a new empty list.
 The argument must be an iterable if specified.
@@ -2814,6 +2857,7 @@ list_vectorcall(PyObject *type, PyObject * const*args,
 
 /*[clinic input]
 list.__sizeof__
+
 Return the size of the list in memory, in bytes.
 [clinic start generated code]*/
 
@@ -3341,6 +3385,7 @@ PyTypeObject PyListRevIter_Type = {
 
 /*[clinic input]
 list.__reversed__
+
 Return a reverse iterator over the list.
 [clinic start generated code]*/
 

From 1f706b4f85ecdab3cd88f04720be3db292bd4c6f Mon Sep 17 00:00:00 2001
From: Crowthebird <78076854+thatbirdguythatuknownot@users.noreply.github.com>
Date: Wed, 9 Mar 2022 15:10:50 +0800
Subject: [PATCH 09/15] bpo-39829: __len__ called twice in the list()
 constructor

---
 Objects/listobject.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/Objects/listobject.c b/Objects/listobject.c
index 4da51e907cc6a7..d94f339f292103 100644
--- a/Objects/listobject.c
+++ b/Objects/listobject.c
@@ -2802,6 +2802,7 @@ list.__init__
     /
 
 Built-in mutable sequence.
+
 If no argument is given, the constructor creates a new empty list.
 The argument must be an iterable if specified.
 [clinic start generated code]*/

From 75ec222c2ec82b1b1928e5ccadd651960d8dbe9c Mon Sep 17 00:00:00 2001
From: Crowthebird <78076854+thatbirdguythatuknownot@users.noreply.github.com>
Date: Thu, 10 Mar 2022 08:34:30 +0800
Subject: [PATCH 10/15] bpo-39829: __len__() called twice when constructing a
 list

---
 Objects/listobject.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Objects/listobject.c b/Objects/listobject.c
index d94f339f292103..f7ccec94a7ec4c 100644
--- a/Objects/listobject.c
+++ b/Objects/listobject.c
@@ -933,7 +933,7 @@ list_extend(PyListObject *self, PyObject *iterable)
          * eventually run out of memory during the loop.
          */
     }
-    else if (self->ob_item == NULL) {
+    else if (n && self->ob_item == NULL) {
         if (list_preallocate_exact(self, n) < 0)
             goto error;
     }

From b5841b9010429c6f435504a10c80c8c15c88cc89 Mon Sep 17 00:00:00 2001
From: Crowthebird <78076854+thatbirdguythatuknownot@users.noreply.github.com>
Date: Thu, 10 Mar 2022 19:04:42 +0800
Subject: [PATCH 11/15] bpo-39829: __len__ called twice in the list()
 constructor

---
 Objects/listobject.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/Objects/listobject.c b/Objects/listobject.c
index f7ccec94a7ec4c..95fe3153984d72 100644
--- a/Objects/listobject.c
+++ b/Objects/listobject.c
@@ -933,8 +933,9 @@ list_extend(PyListObject *self, PyObject *iterable)
          * eventually run out of memory during the loop.
          */
     }
-    else if (n && self->ob_item == NULL) {
-        if (list_preallocate_exact(self, n) < 0)
+    else if (self->ob_item == NULL) {
+        /* We have to rely on n being correct in this case. */
+        if (n && list_preallocate_exact(self, n) < 0)
             goto error;
     }
     else {

From e08c4263c2d0f43498a76acf4f892d1595da1bae Mon Sep 17 00:00:00 2001
From: "blurb-it[bot]" <43283697+blurb-it[bot]@users.noreply.github.com>
Date: Fri, 11 Mar 2022 09:39:02 +0000
Subject: [PATCH 12/15] =?UTF-8?q?=F0=9F=93=9C=F0=9F=A4=96=20Added=20by=20b?=
 =?UTF-8?q?lurb=5Fit.?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 .../Core and Builtins/2022-03-11-09-39-01.bpo-39829.mlW3Su.rst   | 1 +
 1 file changed, 1 insertion(+)
 create mode 100644 Misc/NEWS.d/next/Core and Builtins/2022-03-11-09-39-01.bpo-39829.mlW3Su.rst

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 00000000000000..1f3d945188a32a
--- /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.

From 0eb28714c459b9212e91f3edf735586c5ce93478 Mon Sep 17 00:00:00 2001
From: Crowthebird <78076854+thatbirdguythatuknownot@users.noreply.github.com>
Date: Fri, 11 Mar 2022 17:40:33 +0800
Subject: [PATCH 13/15] bpo-39829: __len__ called twice in the list()
 constructor

---
 Misc/ACKS | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Misc/ACKS b/Misc/ACKS
index df851bb834cd4e..e202b4439b994c 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -1335,6 +1335,7 @@ William Park
 Claude Paroz
 Heikki Partanen
 Harri Pasanen
+Jeremiah Pascual
 Gaël Pasgrimaud
 Feanil Patel
 Ashish Nitin Patil
@@ -1863,7 +1864,6 @@ Kurt Vile
 Norman Vine
 Pauli Virtanen
 Frank Visser
-Jeremiah Vivian (Pascual)
 Johannes Vogel
 Michael Vogt
 Radu Voicilas

From 39b88e3ddf5fbd29791a758b5ffcda7f29cea326 Mon Sep 17 00:00:00 2001
From: Crowthebird <78076854+thatbirdguythatuknownot@users.noreply.github.com>
Date: Sat, 12 Mar 2022 06:06:18 +0800
Subject: [PATCH 14/15] bpo-39829: __len__() called twice in the list()
 constructor

---
 Objects/listobject.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/Objects/listobject.c b/Objects/listobject.c
index 95fe3153984d72..d50633d2b31321 100644
--- a/Objects/listobject.c
+++ b/Objects/listobject.c
@@ -934,7 +934,6 @@ list_extend(PyListObject *self, PyObject *iterable)
          */
     }
     else if (self->ob_item == NULL) {
-        /* We have to rely on n being correct in this case. */
         if (n && list_preallocate_exact(self, n) < 0)
             goto error;
     }

From ad547f539539e2695ebc81df7010a72d9b71f1c9 Mon Sep 17 00:00:00 2001
From: Crowthebird <78076854+thatbirdguythatuknownot@users.noreply.github.com>
Date: Sun, 13 Mar 2022 22:34:09 +0800
Subject: [PATCH 15/15] bpo-39829: __len__ called twice in the list()
 constructor

---
 Misc/ACKS | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Misc/ACKS b/Misc/ACKS
index e202b4439b994c..45573bd96c1435 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -1335,7 +1335,7 @@ William Park
 Claude Paroz
 Heikki Partanen
 Harri Pasanen
-Jeremiah Pascual
+Jeremiah Gabriel Pascual
 Gaël Pasgrimaud
 Feanil Patel
 Ashish Nitin Patil