From 909bde3eaf4ebcd63c315104defed27a8722eb08 Mon Sep 17 00:00:00 2001
From: Charlie Lin <tuug@gmx.us>
Date: Sun, 17 May 2026 18:39:20 -0400
Subject: [PATCH 01/33] Update _elementtree.c

---
 Modules/_elementtree.c | 38 ++++++++++++++++++++++++++++++++++----
 1 file changed, 34 insertions(+), 4 deletions(-)

diff --git a/Modules/_elementtree.c b/Modules/_elementtree.c
index cee564c2c1c1f0f..43bd6699f04a96b 100644
--- a/Modules/_elementtree.c
+++ b/Modules/_elementtree.c
@@ -1946,6 +1946,34 @@ element_subscr(PyObject *op, PyObject *item)
     }
 }
 
+// Pointer-by-pointer memmove for PyObject** arrays that is safe
+// for shared ElementObjects in Py_GIL_DISABLED builds.
+static void
+ptr_wise_atomic_memmove(ElementObject *a, PyObject **dest, PyObject **src, Py_ssize_t n)
+{
+#ifndef Py_GIL_DISABLED
+    memmove(dest, src, n * sizeof(PyObject *));
+#else
+    _Py_CRITICAL_SECTION_ASSERT_OBJECT_LOCKED(a);
+    if (_Py_IsOwnedByCurrentThread((PyObject *)a) && !_PyObject_GC_IS_SHARED(a)) {
+        // No other threads can read this list concurrently
+        memmove(dest, src, n * sizeof(PyObject *));
+        return;
+    }
+    if (dest < src) {
+        for (Py_ssize_t i = 0; i != n; i++) {
+            _Py_atomic_store_ptr_release(&dest[i], src[i]);
+        }
+    }
+    else {
+        // copy backwards to avoid overwriting src before it's read
+        for (Py_ssize_t i = n; i != 0; i--) {
+            _Py_atomic_store_ptr_release(&dest[i - 1], src[i - 1]);
+        }
+    }
+#endif
+}
+
 static int
 element_ass_subscr(PyObject *op, PyObject *item, PyObject *value)
 {
@@ -2021,19 +2049,21 @@ element_ass_subscr(PyObject *op, PyObject *item, PyObject *value)
 
                 PyList_SET_ITEM(recycle, i, self->extra->children[cur]);
 
-                memmove(
+                ptr_wise_atomic_memmove(
+                    self,
                     self->extra->children + cur - i,
                     self->extra->children + cur + 1,
-                    num_moved * sizeof(PyObject *));
+                    num_moved);
             }
 
             /* Leftover "tail" after the last removed child */
             cur = start + (size_t)slicelen * step;
             if (cur < (size_t)self->extra->length) {
-                memmove(
+                ptr_wise_atomic_memmove(
+                    self,
                     self->extra->children + cur - slicelen,
                     self->extra->children + cur,
-                    (self->extra->length - cur) * sizeof(PyObject *));
+                    self->extra->length - cur);
             }
 
             self->extra->length -= slicelen;

From f916acddd35950f7b29d507e1e3c283f96f4b112 Mon Sep 17 00:00:00 2001
From: "blurb-it[bot]" <43283697+blurb-it[bot]@users.noreply.github.com>
Date: Sun, 17 May 2026 22:42:57 +0000
Subject: [PATCH 02/33] =?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

---
 .../next/Library/2026-05-17-22-42-54.gh-issue-149965.OFW3ZD.rst  | 1 +
 1 file changed, 1 insertion(+)
 create mode 100644 Misc/NEWS.d/next/Library/2026-05-17-22-42-54.gh-issue-149965.OFW3ZD.rst

diff --git a/Misc/NEWS.d/next/Library/2026-05-17-22-42-54.gh-issue-149965.OFW3ZD.rst b/Misc/NEWS.d/next/Library/2026-05-17-22-42-54.gh-issue-149965.OFW3ZD.rst
new file mode 100644
index 000000000000000..ea8eac20e4c8ec3
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2026-05-17-22-42-54.gh-issue-149965.OFW3ZD.rst
@@ -0,0 +1 @@
+WIthin ``Modules/_elementtree.c``, improve thread-safety in ElementObjects within ``element_ass_subscr``

From 8ec9c38e4f0381834e892aff6b6dfe3c7b82d45f Mon Sep 17 00:00:00 2001
From: Charlie Lin <tuug@gmx.us>
Date: Sun, 17 May 2026 18:59:10 -0400
Subject: [PATCH 03/33] Modify critical section assertion in _elementtree.c

Commented out critical section assertion for ElementObject.
---
 Modules/_elementtree.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/Modules/_elementtree.c b/Modules/_elementtree.c
index 43bd6699f04a96b..c4cca0e2fd6ae5f 100644
--- a/Modules/_elementtree.c
+++ b/Modules/_elementtree.c
@@ -1954,7 +1954,8 @@ ptr_wise_atomic_memmove(ElementObject *a, PyObject **dest, PyObject **src, Py_ss
 #ifndef Py_GIL_DISABLED
     memmove(dest, src, n * sizeof(PyObject *));
 #else
-    _Py_CRITICAL_SECTION_ASSERT_OBJECT_LOCKED(a);
+    // XXX: maybe a critical section isn't needed for ElementObject?
+    // _Py_CRITICAL_SECTION_ASSERT_OBJECT_LOCKED(a);
     if (_Py_IsOwnedByCurrentThread((PyObject *)a) && !_PyObject_GC_IS_SHARED(a)) {
         // No other threads can read this list concurrently
         memmove(dest, src, n * sizeof(PyObject *));

From 8ac6aca94b56176d204ffd69f4162e96d19e33a5 Mon Sep 17 00:00:00 2001
From: Charlie Lin <tuug@gmx.us>
Date: Wed, 10 Jun 2026 12:55:17 -0400
Subject: [PATCH 04/33] =?UTF-8?q?Revert=20"=F0=9F=93=9C=F0=9F=A4=96=20Adde?=
 =?UTF-8?q?d=20by=20blurb=5Fit."?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

This reverts commit a3a7eee2343990a5368a427320c852e5de8bd70a.
---
 ...-05-17-22-42-54.gh-issue-149965.OFW3ZD.rst |   1 -
 .../_testinternalcapi/test_ptr_wise_memmove.c | 212 ++++++++++++++++++
 2 files changed, 212 insertions(+), 1 deletion(-)
 delete mode 100644 Misc/NEWS.d/next/Library/2026-05-17-22-42-54.gh-issue-149965.OFW3ZD.rst
 create mode 100644 Modules/_testinternalcapi/test_ptr_wise_memmove.c

diff --git a/Misc/NEWS.d/next/Library/2026-05-17-22-42-54.gh-issue-149965.OFW3ZD.rst b/Misc/NEWS.d/next/Library/2026-05-17-22-42-54.gh-issue-149965.OFW3ZD.rst
deleted file mode 100644
index ea8eac20e4c8ec3..000000000000000
--- a/Misc/NEWS.d/next/Library/2026-05-17-22-42-54.gh-issue-149965.OFW3ZD.rst
+++ /dev/null
@@ -1 +0,0 @@
-WIthin ``Modules/_elementtree.c``, improve thread-safety in ElementObjects within ``element_ass_subscr``
diff --git a/Modules/_testinternalcapi/test_ptr_wise_memmove.c b/Modules/_testinternalcapi/test_ptr_wise_memmove.c
new file mode 100644
index 000000000000000..732642992b568e8
--- /dev/null
+++ b/Modules/_testinternalcapi/test_ptr_wise_memmove.c
@@ -0,0 +1,212 @@
+// Tests for _PyObject_ptr_wise_atomic_memmove() in pycore_object.h
+
+#include "parts.h"
+#include "pycore_object.h"    // _PyObject_ptr_wise_atomic_memmove()
+#include "pycore_gc.h"        // _PyObject_GC_SET_SHARED()
+
+// Five distinguishable immortal singletons used as placeholder pointers.
+// These require no reference-count management when stored in a raw array.
+#define NPTRS 5
+static PyObject *test_objs[NPTRS];
+
+static void
+setup_test_objs(void)
+{
+    test_objs[0] = Py_None;
+    test_objs[1] = Py_True;
+    test_objs[2] = Py_False;
+    test_objs[3] = Py_Ellipsis;
+    test_objs[4] = Py_NotImplemented;
+}
+
+// Fill buf[0..NPTRS-1] with test_objs in order.
+static void
+fill_buf(PyObject **buf)
+{
+    for (int i = 0; i < NPTRS; i++) {
+        buf[i] = test_objs[i];
+    }
+}
+
+// Return a fresh empty PyListObject whose GC SHARED bit is set in
+// Py_GIL_DISABLED builds.  This forces _PyObject_ptr_wise_atomic_memmove()
+// to take the atomic (non-fast) path so we can exercise all branches.
+// In non-GIL builds the function always uses memmove, so no flag is needed.
+static PyObject *
+make_shared_container(void)
+{
+    PyObject *a = PyList_New(0);
+    if (a == NULL) {
+        return NULL;
+    }
+#ifdef Py_GIL_DISABLED
+    _PyObject_GC_SET_SHARED(a);
+#endif
+    return a;
+}
+
+// Helper: create container, call the function, return it for cleanup.
+// Returns NULL (with exception set) on allocation failure.
+static PyObject *
+call_memmove(PyObject **dest, PyObject **src, Py_ssize_t n)
+{
+    PyObject *a = make_shared_container();
+    if (a != NULL) {
+        _PyObject_ptr_wise_atomic_memmove(a, dest, src, n);
+    }
+    return a;
+}
+
+
+// dest < src: forward pointer-by-pointer copy.
+// buf = [0,1,2,3,4], copy src=&buf[2] n=3 to dest=&buf[0]
+// Expected result: buf = [2,3,4,3,4]
+static PyObject *
+test_memmove_dest_lt_src(PyObject *self, PyObject *Py_UNUSED(arg))
+{
+    setup_test_objs();
+
+    PyObject *buf[NPTRS];
+    fill_buf(buf);
+
+    PyObject *a = call_memmove(&buf[0], &buf[2], 3);
+    if (a == NULL) {
+        return NULL;
+    }
+
+    assert(buf[0] == test_objs[2]);
+    assert(buf[1] == test_objs[3]);
+    assert(buf[2] == test_objs[4]);
+    assert(buf[3] == test_objs[3]);  // unchanged
+    assert(buf[4] == test_objs[4]);  // unchanged
+
+    Py_DECREF(a);
+    Py_RETURN_NONE;
+}
+
+// dest > src: backward pointer-by-pointer copy.
+// buf = [0,1,2,3,4], copy src=&buf[0] n=3 to dest=&buf[2]
+// Expected result: buf = [0,1,0,1,2]
+static PyObject *
+test_memmove_dest_gt_src(PyObject *self, PyObject *Py_UNUSED(arg))
+{
+    setup_test_objs();
+
+    PyObject *buf[NPTRS];
+    fill_buf(buf);
+
+    PyObject *a = call_memmove(&buf[2], &buf[0], 3);
+    if (a == NULL) {
+        return NULL;
+    }
+
+    assert(buf[0] == test_objs[0]);  // unchanged
+    assert(buf[1] == test_objs[1]);  // unchanged
+    assert(buf[2] == test_objs[0]);
+    assert(buf[3] == test_objs[1]);
+    assert(buf[4] == test_objs[2]);
+
+    Py_DECREF(a);
+    Py_RETURN_NONE;
+}
+
+// dest == src: backward copy where every write is a no-op.
+// buf = [0,1,2,3,4], copy src=&buf[1] n=3 to dest=&buf[1]
+// Expected result: buf unchanged.
+static PyObject *
+test_memmove_dest_eq_src(PyObject *self, PyObject *Py_UNUSED(arg))
+{
+    setup_test_objs();
+
+    PyObject *buf[NPTRS];
+    fill_buf(buf);
+
+    PyObject *a = call_memmove(&buf[1], &buf[1], 3);
+    if (a == NULL) {
+        return NULL;
+    }
+
+    for (int i = 0; i < NPTRS; i++) {
+        assert(buf[i] == test_objs[i]);
+    }
+
+    Py_DECREF(a);
+    Py_RETURN_NONE;
+}
+
+// Overlapping ranges, dest < src: forward copy is safe.
+// buf = [0,1,2,3,4], copy src=&buf[2] n=3 to dest=&buf[1]
+// Forward: buf[1]=buf[2]=2, buf[2]=buf[3]=3, buf[3]=buf[4]=4
+// Expected result: buf = [0,2,3,4,4]
+static PyObject *
+test_memmove_overlapping(PyObject *self, PyObject *Py_UNUSED(arg))
+{
+    setup_test_objs();
+
+    PyObject *buf[NPTRS];
+    fill_buf(buf);
+
+    PyObject *a = call_memmove(&buf[1], &buf[2], 3);
+    if (a == NULL) {
+        return NULL;
+    }
+
+    assert(buf[0] == test_objs[0]);  // unchanged
+    assert(buf[1] == test_objs[2]);
+    assert(buf[2] == test_objs[3]);
+    assert(buf[3] == test_objs[4]);
+    assert(buf[4] == test_objs[4]);  // unchanged
+
+    Py_DECREF(a);
+    Py_RETURN_NONE;
+}
+
+// Single owner fast path (GIL_DISABLED only): object owned by this thread
+// and not GC-shared => memmove is used instead of atomic stores.
+// In non-GIL builds this always takes the memmove path, so the test
+// degenerates to a basic correctness check.
+static PyObject *
+test_memmove_single_owner(PyObject *self, PyObject *Py_UNUSED(arg))
+{
+    setup_test_objs();
+
+    PyObject *a = PyList_New(0);
+    if (a == NULL) {
+        return NULL;
+    }
+
+#ifdef Py_GIL_DISABLED
+    // A freelist-reused list may carry the SHARED bit set by a sibling test.
+    // Clear it explicitly so this test exercises the single-owner fast path.
+    _PyObject_CLEAR_GC_BITS(a, _PyGC_BITS_SHARED);
+    assert(_Py_IsOwnedByCurrentThread(a) && !_PyObject_GC_IS_SHARED(a));
+#endif
+
+    PyObject *buf[NPTRS];
+    fill_buf(buf);
+
+    _PyObject_ptr_wise_atomic_memmove(a, &buf[0], &buf[2], 3);
+
+    assert(buf[0] == test_objs[2]);
+    assert(buf[1] == test_objs[3]);
+    assert(buf[2] == test_objs[4]);
+
+    Py_DECREF(a);
+    Py_RETURN_NONE;
+}
+
+
+static PyMethodDef test_methods[] = {
+    {"test_memmove_dest_lt_src",  test_memmove_dest_lt_src,  METH_NOARGS},
+    {"test_memmove_dest_gt_src",  test_memmove_dest_gt_src,  METH_NOARGS},
+    {"test_memmove_dest_eq_src",  test_memmove_dest_eq_src,  METH_NOARGS},
+    {"test_memmove_overlapping",  test_memmove_overlapping,  METH_NOARGS},
+    {"test_memmove_single_owner", test_memmove_single_owner, METH_NOARGS},
+    {NULL},
+};
+
+int
+_PyTestInternalCapi_Init_PtrWiseMemmove(PyObject *mod)
+{
+    return PyModule_AddFunctions(mod, test_methods);
+}

From 1443d4dcd5a6b59eb669794d82b871073667f5c0 Mon Sep 17 00:00:00 2001
From: Charlie Lin <tuug@gmx.us>
Date: Tue, 9 Jun 2026 14:06:29 -0400
Subject: [PATCH 05/33] gh-149966: deduplicate ptr_wise_atomic_memmove into a
 shared internal helper and add unit tests

Extract the duplicated static `ptr_wise_atomic_memmove` from
`Modules/_elementtree.c` and `Objects/listobject.c` into a shared
`static inline _Py_ptr_wise_atomic_memmove(PyObject *a, ...)` in
`Include/internal/pycore_object.h`.  The first parameter is generalised
from a type-specific pointer to `PyObject *` since only `PyObject *`-
level operations (`_Py_IsOwnedByCurrentThread`, `_PyObject_GC_IS_SHARED`)
were ever performed on it.

`listobject.c` previously embedded `_Py_CRITICAL_SECTION_ASSERT_OBJECT_LOCKED`
inside the local helper.  That assertion is preserved by moving it
explicitly to each of the four call sites in `listobject.c` (which are
all called under a critical section).  `_elementtree.c`'s open question
about whether a critical section is needed remains unanswered, so no
assertion is added there.

Unit tests are added in `Modules/_testinternalcapi/test_ptr_wise_memmove.c`
covering: dest < src (forward copy), dest > src (backward copy),
dest == src (no-op), overlapping ranges, and the single-owner fast path.
The single-owner test explicitly clears the GC SHARED bit to guard against
freelist reuse leaving the bit set from a sibling test.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
---
 Include/internal/pycore_object.h              | 29 +++++++++++++
 Modules/Setup.stdlib.in                       |  6 +--
 Modules/_elementtree.c                        | 37 +++-------------
 Modules/_testinternalcapi.c                   |  3 ++
 Modules/_testinternalcapi/parts.h             |  1 +
 .../_testinternalcapi/test_ptr_wise_memmove.c | 19 ++++++++
 Objects/listobject.c                          | 43 +++++--------------
 PCbuild/_testinternalcapi.vcxproj             |  1 +
 8 files changed, 71 insertions(+), 68 deletions(-)

diff --git a/Include/internal/pycore_object.h b/Include/internal/pycore_object.h
index dbc0ebf994fd1e0..16ed31cb7a529d7 100644
--- a/Include/internal/pycore_object.h
+++ b/Include/internal/pycore_object.h
@@ -1017,6 +1017,35 @@ static inline Py_ALWAYS_INLINE void _Py_INCREF_MORTAL(PyObject *op)
  * references. */
 PyAPI_FUNC(int) _PyObject_VisitType(PyObject *op, visitproc visit, void *arg);
 
+// Pointer-by-pointer memmove for PyObject** arrays that is safe for shared
+// objects in Py_GIL_DISABLED builds.  Locking is the caller's responsibility.
+static inline void
+_Py_ptr_wise_atomic_memmove(PyObject *a, PyObject **dest, PyObject **src,
+                             Py_ssize_t n)
+{
+#ifndef Py_GIL_DISABLED
+    (void)a;
+    memmove(dest, src, n * sizeof(PyObject *));
+#else
+    if (_Py_IsOwnedByCurrentThread(a) && !_PyObject_GC_IS_SHARED(a)) {
+        // No other threads can read this object's array concurrently
+        memmove(dest, src, n * sizeof(PyObject *));
+        return;
+    }
+    if (dest < src) {
+        for (Py_ssize_t i = 0; i != n; i++) {
+            _Py_atomic_store_ptr_release(&dest[i], src[i]);
+        }
+    }
+    else {
+        // copy backwards to avoid overwriting src before it's read
+        for (Py_ssize_t i = n; i != 0; i--) {
+            _Py_atomic_store_ptr_release(&dest[i - 1], src[i - 1]);
+        }
+    }
+#endif
+}
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/Modules/Setup.stdlib.in b/Modules/Setup.stdlib.in
index d8cd8de10dfe084..355a9499ed7130c 100644
--- a/Modules/Setup.stdlib.in
+++ b/Modules/Setup.stdlib.in
@@ -172,9 +172,9 @@
 @MODULE_XXSUBTYPE_TRUE@xxsubtype xxsubtype.c
 @MODULE__XXTESTFUZZ_TRUE@_xxtestfuzz _xxtestfuzz/_xxtestfuzz.c _xxtestfuzz/fuzzer.c
 @MODULE__TESTBUFFER_TRUE@_testbuffer _testbuffer.c
-@MODULE__TESTINTERNALCAPI_TRUE@_testinternalcapi _testinternalcapi.c _testinternalcapi/test_lock.c _testinternalcapi/pytime.c _testinternalcapi/set.c _testinternalcapi/test_critical_sections.c _testinternalcapi/complex.c _testinternalcapi/interpreter.c _testinternalcapi/tokenizer.c _testinternalcapi/tuple.c _testinternalcapi/typecache.c
-@MODULE__TESTCAPI_TRUE@_testcapi _testcapimodule.c _testcapi/vectorcall.c _testcapi/heaptype.c _testcapi/abstract.c _testcapi/unicode.c _testcapi/dict.c _testcapi/set.c _testcapi/list.c _testcapi/tuple.c _testcapi/getargs.c _testcapi/datetime.c _testcapi/docstring.c _testcapi/mem.c _testcapi/watchers.c _testcapi/long.c _testcapi/float.c _testcapi/complex.c _testcapi/numbers.c _testcapi/structmember.c _testcapi/exceptions.c _testcapi/code.c _testcapi/buffer.c _testcapi/pyatomic.c _testcapi/run.c _testcapi/file.c _testcapi/codec.c _testcapi/immortal.c _testcapi/gc.c _testcapi/hash.c _testcapi/time.c _testcapi/bytes.c _testcapi/object.c _testcapi/modsupport.c _testcapi/monitoring.c _testcapi/config.c _testcapi/import.c _testcapi/frame.c _testcapi/type.c _testcapi/function.c _testcapi/module.c _testcapi/weakref.c _testcapi/marshal.c _testcapi/fpcast.c
-@MODULE__TESTLIMITEDCAPI_TRUE@_testlimitedcapi _testlimitedcapi.c _testlimitedcapi/abstract.c _testlimitedcapi/bytearray.c _testlimitedcapi/bytes.c _testlimitedcapi/capsule.c _testlimitedcapi/codec.c _testlimitedcapi/complex.c _testlimitedcapi/dict.c _testlimitedcapi/eval.c _testlimitedcapi/float.c _testlimitedcapi/heaptype_relative.c _testlimitedcapi/import.c _testlimitedcapi/list.c _testlimitedcapi/long.c _testlimitedcapi/object.c _testlimitedcapi/pyos.c _testlimitedcapi/set.c _testlimitedcapi/slice.c _testlimitedcapi/slots.c _testlimitedcapi/sys.c _testlimitedcapi/threadstate.c _testlimitedcapi/tuple.c _testlimitedcapi/unicode.c _testlimitedcapi/vectorcall_limited.c _testlimitedcapi/version.c _testlimitedcapi/file.c _testlimitedcapi/weakref.c _testlimitedcapi/run.c _testlimitedcapi/type.c _testlimitedcapi/hash.c _testlimitedcapi/build.c
+@MODULE__TESTINTERNALCAPI_TRUE@_testinternalcapi _testinternalcapi.c _testinternalcapi/test_lock.c _testinternalcapi/pytime.c _testinternalcapi/test_ptr_wise_memmove.c _testinternalcapi/set.c _testinternalcapi/test_critical_sections.c _testinternalcapi/complex.c _testinternalcapi/interpreter.c _testinternalcapi/tuple.c
+@MODULE__TESTCAPI_TRUE@_testcapi _testcapimodule.c _testcapi/vectorcall.c _testcapi/heaptype.c _testcapi/abstract.c _testcapi/unicode.c _testcapi/dict.c _testcapi/set.c _testcapi/list.c _testcapi/tuple.c _testcapi/getargs.c _testcapi/datetime.c _testcapi/docstring.c _testcapi/mem.c _testcapi/watchers.c _testcapi/long.c _testcapi/float.c _testcapi/complex.c _testcapi/numbers.c _testcapi/structmember.c _testcapi/exceptions.c _testcapi/code.c _testcapi/buffer.c _testcapi/pyatomic.c _testcapi/run.c _testcapi/file.c _testcapi/codec.c _testcapi/immortal.c _testcapi/gc.c _testcapi/hash.c _testcapi/time.c _testcapi/bytes.c _testcapi/object.c _testcapi/modsupport.c _testcapi/monitoring.c _testcapi/config.c _testcapi/import.c _testcapi/frame.c _testcapi/type.c _testcapi/function.c _testcapi/module.c
+@MODULE__TESTLIMITEDCAPI_TRUE@_testlimitedcapi _testlimitedcapi.c _testlimitedcapi/abstract.c _testlimitedcapi/bytearray.c _testlimitedcapi/bytes.c _testlimitedcapi/codec.c _testlimitedcapi/complex.c _testlimitedcapi/dict.c _testlimitedcapi/eval.c _testlimitedcapi/float.c _testlimitedcapi/heaptype_relative.c _testlimitedcapi/import.c _testlimitedcapi/list.c _testlimitedcapi/long.c _testlimitedcapi/object.c _testlimitedcapi/pyos.c _testlimitedcapi/set.c _testlimitedcapi/slots.c _testlimitedcapi/sys.c _testlimitedcapi/threadstate.c _testlimitedcapi/tuple.c _testlimitedcapi/unicode.c _testlimitedcapi/vectorcall_limited.c _testlimitedcapi/version.c _testlimitedcapi/file.c
 @MODULE__TESTCLINIC_TRUE@_testclinic _testclinic.c
 @MODULE__TESTCLINIC_LIMITED_TRUE@_testclinic_limited _testclinic_limited.c
 
diff --git a/Modules/_elementtree.c b/Modules/_elementtree.c
index c4cca0e2fd6ae5f..680265764dc3d82 100644
--- a/Modules/_elementtree.c
+++ b/Modules/_elementtree.c
@@ -18,6 +18,7 @@
 #include "Python.h"
 #include "pycore_ceval.h"         // _Py_EnterRecursiveCall()
 #include "pycore_dict.h"          // _PyDict_CopyAsDict()
+#include "pycore_object.h"        // _Py_ptr_wise_atomic_memmove()
 #include "pycore_pyhash.h"        // _Py_HashSecret
 #include "pycore_tuple.h"         // _PyTuple_FromPair
 #include "pycore_weakref.h"       // FT_CLEAR_WEAKREFS()
@@ -1946,34 +1947,6 @@ element_subscr(PyObject *op, PyObject *item)
     }
 }
 
-// Pointer-by-pointer memmove for PyObject** arrays that is safe
-// for shared ElementObjects in Py_GIL_DISABLED builds.
-static void
-ptr_wise_atomic_memmove(ElementObject *a, PyObject **dest, PyObject **src, Py_ssize_t n)
-{
-#ifndef Py_GIL_DISABLED
-    memmove(dest, src, n * sizeof(PyObject *));
-#else
-    // XXX: maybe a critical section isn't needed for ElementObject?
-    // _Py_CRITICAL_SECTION_ASSERT_OBJECT_LOCKED(a);
-    if (_Py_IsOwnedByCurrentThread((PyObject *)a) && !_PyObject_GC_IS_SHARED(a)) {
-        // No other threads can read this list concurrently
-        memmove(dest, src, n * sizeof(PyObject *));
-        return;
-    }
-    if (dest < src) {
-        for (Py_ssize_t i = 0; i != n; i++) {
-            _Py_atomic_store_ptr_release(&dest[i], src[i]);
-        }
-    }
-    else {
-        // copy backwards to avoid overwriting src before it's read
-        for (Py_ssize_t i = n; i != 0; i--) {
-            _Py_atomic_store_ptr_release(&dest[i - 1], src[i - 1]);
-        }
-    }
-#endif
-}
 
 static int
 element_ass_subscr(PyObject *op, PyObject *item, PyObject *value)
@@ -2050,8 +2023,8 @@ element_ass_subscr(PyObject *op, PyObject *item, PyObject *value)
 
                 PyList_SET_ITEM(recycle, i, self->extra->children[cur]);
 
-                ptr_wise_atomic_memmove(
-                    self,
+                _Py_ptr_wise_atomic_memmove(
+                    (PyObject *)self,
                     self->extra->children + cur - i,
                     self->extra->children + cur + 1,
                     num_moved);
@@ -2060,8 +2033,8 @@ element_ass_subscr(PyObject *op, PyObject *item, PyObject *value)
             /* Leftover "tail" after the last removed child */
             cur = start + (size_t)slicelen * step;
             if (cur < (size_t)self->extra->length) {
-                ptr_wise_atomic_memmove(
-                    self,
+                _Py_ptr_wise_atomic_memmove(
+                    (PyObject *)self,
                     self->extra->children + cur - slicelen,
                     self->extra->children + cur,
                     self->extra->length - cur);
diff --git a/Modules/_testinternalcapi.c b/Modules/_testinternalcapi.c
index f629b8e528faca7..7f90a6440a57350 100644
--- a/Modules/_testinternalcapi.c
+++ b/Modules/_testinternalcapi.c
@@ -3482,6 +3482,9 @@ module_exec(PyObject *module)
     if (_PyTestInternalCapi_Init_PyTime(module) < 0) {
         return 1;
     }
+    if (_PyTestInternalCapi_Init_PtrWiseMemmove(module) < 0) {
+        return 1;
+    }
     if (_PyTestInternalCapi_Init_Set(module) < 0) {
         return 1;
     }
diff --git a/Modules/_testinternalcapi/parts.h b/Modules/_testinternalcapi/parts.h
index 9b06eec3bce9e65..60a41e2c49b7108 100644
--- a/Modules/_testinternalcapi/parts.h
+++ b/Modules/_testinternalcapi/parts.h
@@ -12,6 +12,7 @@
 
 int _PyTestInternalCapi_Init_Lock(PyObject *module);
 int _PyTestInternalCapi_Init_PyTime(PyObject *module);
+int _PyTestInternalCapi_Init_PtrWiseMemmove(PyObject *module);
 int _PyTestInternalCapi_Init_Set(PyObject *module);
 int _PyTestInternalCapi_Init_Complex(PyObject *module);
 int _PyTestInternalCapi_Init_CriticalSection(PyObject *module);
diff --git a/Modules/_testinternalcapi/test_ptr_wise_memmove.c b/Modules/_testinternalcapi/test_ptr_wise_memmove.c
index 732642992b568e8..f5b5b97223d2b12 100644
--- a/Modules/_testinternalcapi/test_ptr_wise_memmove.c
+++ b/Modules/_testinternalcapi/test_ptr_wise_memmove.c
@@ -1,7 +1,14 @@
+<<<<<<< HEAD
 // Tests for _PyObject_ptr_wise_atomic_memmove() in pycore_object.h
 
 #include "parts.h"
 #include "pycore_object.h"    // _PyObject_ptr_wise_atomic_memmove()
+=======
+// Tests for _Py_ptr_wise_atomic_memmove() in pycore_object.h
+
+#include "parts.h"
+#include "pycore_object.h"    // _Py_ptr_wise_atomic_memmove()
+>>>>>>> a4c9efbacc (gh-149966: deduplicate ptr_wise_atomic_memmove into a shared internal helper and add unit tests)
 #include "pycore_gc.h"        // _PyObject_GC_SET_SHARED()
 
 // Five distinguishable immortal singletons used as placeholder pointers.
@@ -29,7 +36,11 @@ fill_buf(PyObject **buf)
 }
 
 // Return a fresh empty PyListObject whose GC SHARED bit is set in
+<<<<<<< HEAD
 // Py_GIL_DISABLED builds.  This forces _PyObject_ptr_wise_atomic_memmove()
+=======
+// Py_GIL_DISABLED builds.  This forces _Py_ptr_wise_atomic_memmove()
+>>>>>>> a4c9efbacc (gh-149966: deduplicate ptr_wise_atomic_memmove into a shared internal helper and add unit tests)
 // to take the atomic (non-fast) path so we can exercise all branches.
 // In non-GIL builds the function always uses memmove, so no flag is needed.
 static PyObject *
@@ -52,7 +63,11 @@ call_memmove(PyObject **dest, PyObject **src, Py_ssize_t n)
 {
     PyObject *a = make_shared_container();
     if (a != NULL) {
+<<<<<<< HEAD
         _PyObject_ptr_wise_atomic_memmove(a, dest, src, n);
+=======
+        _Py_ptr_wise_atomic_memmove(a, dest, src, n);
+>>>>>>> a4c9efbacc (gh-149966: deduplicate ptr_wise_atomic_memmove into a shared internal helper and add unit tests)
     }
     return a;
 }
@@ -185,7 +200,11 @@ test_memmove_single_owner(PyObject *self, PyObject *Py_UNUSED(arg))
     PyObject *buf[NPTRS];
     fill_buf(buf);
 
+<<<<<<< HEAD
     _PyObject_ptr_wise_atomic_memmove(a, &buf[0], &buf[2], 3);
+=======
+    _Py_ptr_wise_atomic_memmove(a, &buf[0], &buf[2], 3);
+>>>>>>> a4c9efbacc (gh-149966: deduplicate ptr_wise_atomic_memmove into a shared internal helper and add unit tests)
 
     assert(buf[0] == test_objs[2]);
     assert(buf[1] == test_objs[3]);
diff --git a/Objects/listobject.c b/Objects/listobject.c
index f9488cc5c384bab..e86ae721f9acba3 100644
--- a/Objects/listobject.c
+++ b/Objects/listobject.c
@@ -10,7 +10,7 @@
 #include "pycore_list.h"          // struct _Py_list_freelist, _PyListIterObject
 #include "pycore_long.h"          // _PyLong_DigitCount
 #include "pycore_modsupport.h"    // _PyArg_NoKwnames()
-#include "pycore_object.h"        // _PyObject_GC_TRACK(), _PyDebugAllocatorStats()
+#include "pycore_object.h"        // _PyObject_GC_TRACK(), _Py_ptr_wise_atomic_memmove()
 #include "pycore_pyatomic_ft_wrappers.h"
 #include "pycore_setobject.h"     // _PySet_NextEntry()
 #include "pycore_stackref.h"      // _Py_TryIncrefCompareStackRef()
@@ -967,33 +967,6 @@ list_clear_slot(PyObject *self)
     return 0;
 }
 
-// Pointer-by-pointer memmove for PyObject** arrays that is safe
-// for shared lists in Py_GIL_DISABLED builds.
-static void
-ptr_wise_atomic_memmove(PyListObject *a, PyObject **dest, PyObject **src, Py_ssize_t n)
-{
-#ifndef Py_GIL_DISABLED
-    memmove(dest, src, n * sizeof(PyObject *));
-#else
-    _Py_CRITICAL_SECTION_ASSERT_OBJECT_LOCKED(a);
-    if (_Py_IsOwnedByCurrentThread((PyObject *)a) && !_PyObject_GC_IS_SHARED(a)) {
-        // No other threads can read this list concurrently
-        memmove(dest, src, n * sizeof(PyObject *));
-        return;
-    }
-    if (dest < src) {
-        for (Py_ssize_t i = 0; i != n; i++) {
-            _Py_atomic_store_ptr_release(&dest[i], src[i]);
-        }
-    }
-    else {
-        // copy backwards to avoid overwriting src before it's read
-        for (Py_ssize_t i = n; i != 0; i--) {
-            _Py_atomic_store_ptr_release(&dest[i - 1], src[i - 1]);
-        }
-    }
-#endif
-}
 
 /* a[ilow:ihigh] = v if v != NULL.
  * del a[ilow:ihigh] if v == NULL.
@@ -1066,7 +1039,8 @@ list_ass_slice_lock_held(PyListObject *a, Py_ssize_t ilow, Py_ssize_t ihigh, PyO
 
     if (d < 0) { /* Delete -d items */
         Py_ssize_t tail = Py_SIZE(a) - ihigh;
-        ptr_wise_atomic_memmove(a, &item[ihigh+d], &item[ihigh], tail);
+        _Py_CRITICAL_SECTION_ASSERT_OBJECT_LOCKED(a);
+        _Py_ptr_wise_atomic_memmove((PyObject *)a, &item[ihigh+d], &item[ihigh], tail);
         (void)list_resize(a, Py_SIZE(a) + d); // NB: shrinking a list can't fail
         item = a->ob_item;
     }
@@ -1075,7 +1049,8 @@ list_ass_slice_lock_held(PyListObject *a, Py_ssize_t ilow, Py_ssize_t ihigh, PyO
         if (list_resize(a, k+d) < 0)
             goto Error;
         item = a->ob_item;
-        ptr_wise_atomic_memmove(a, &item[ihigh+d], &item[ihigh], k - ihigh);
+        _Py_CRITICAL_SECTION_ASSERT_OBJECT_LOCKED(a);
+        _Py_ptr_wise_atomic_memmove((PyObject *)a, &item[ihigh+d], &item[ihigh], k - ihigh);
     }
     for (k = 0; k < n; k++, ilow++) {
         PyObject *w = vitem[k];
@@ -1163,10 +1138,11 @@ list_inplace_repeat_lock_held(PyListObject *self, Py_ssize_t n)
     _Py_memory_repeat((char *)items, sizeof(PyObject *)*output_size,
                       sizeof(PyObject *)*input_size);
 #else
+    _Py_CRITICAL_SECTION_ASSERT_OBJECT_LOCKED(self);
     Py_ssize_t copied = input_size;
     while (copied < output_size) {
         Py_ssize_t items_to_copy = Py_MIN(copied, output_size - copied);
-        ptr_wise_atomic_memmove(self, items + copied, items, items_to_copy);
+        _Py_ptr_wise_atomic_memmove((PyObject *)self, items + copied, items, items_to_copy);
         copied += items_to_copy;
     }
 #endif
@@ -1664,8 +1640,9 @@ list_pop_impl(PyListObject *self, Py_ssize_t index)
     }
     Py_ssize_t size_after_pop = Py_SIZE(self) - 1;
     if (index < size_after_pop) {
-        ptr_wise_atomic_memmove(self, &items[index], &items[index+1],
-                                size_after_pop - index);
+        _Py_CRITICAL_SECTION_ASSERT_OBJECT_LOCKED(self);
+        _Py_ptr_wise_atomic_memmove((PyObject *)self, &items[index], &items[index+1],
+                                    size_after_pop - index);
     }
     list_resize(self, size_after_pop);  // NB: shrinking a list can't fail
     return v;
diff --git a/PCbuild/_testinternalcapi.vcxproj b/PCbuild/_testinternalcapi.vcxproj
index ae873f0e0267aca..2d7dde28d136796 100644
--- a/PCbuild/_testinternalcapi.vcxproj
+++ b/PCbuild/_testinternalcapi.vcxproj
@@ -97,6 +97,7 @@
     <ClCompile Include="..\Modules\_testinternalcapi\pytime.c" />
     <ClCompile Include="..\Modules\_testinternalcapi\test_critical_sections.c" />
     <ClCompile Include="..\Modules\_testinternalcapi\test_lock.c" />
+    <ClCompile Include="..\Modules\_testinternalcapi\test_ptr_wise_memmove.c" />
     <ClCompile Include="..\Modules\_testinternalcapi\set.c" />
     <ClCompile Include="..\Modules\_testinternalcapi\complex.c" />
     <ClCompile Include="..\Modules\_testinternalcapi\interpreter.c" />

From a2f5d66ff7b31d522238bd9a2ca360dbea645b04 Mon Sep 17 00:00:00 2001
From: Charlie Lin <tuug@gmx.us>
Date: Tue, 9 Jun 2026 14:49:48 -0400
Subject: [PATCH 06/33] Use _Py_ptr_wise_atomic_memmove everywhere in
 listobject.c

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

diff --git a/Objects/listobject.c b/Objects/listobject.c
index e86ae721f9acba3..d7ba1ff240ec12d 100644
--- a/Objects/listobject.c
+++ b/Objects/listobject.c
@@ -3828,12 +3828,12 @@ list_ass_subscript_lock_held(PyObject *_self, PyObject *item, PyObject *value)
                     lim = Py_SIZE(self) - cur - 1;
                 }
 
-                ptr_wise_atomic_memmove(self, self->ob_item + cur - i,
+                _Py_ptr_wise_atomic_memmove(self, self->ob_item + cur - i,
                     self->ob_item + cur + 1, lim);
             }
             cur = start + (size_t)slicelength * step;
             if (cur < (size_t)Py_SIZE(self)) {
-                ptr_wise_atomic_memmove(self, self->ob_item + cur - slicelength,
+                _Py_ptr_wise_atomic_memmove(self, self->ob_item + cur - slicelength,
                     self->ob_item + cur, Py_SIZE(self) - cur);
             }
 

From 3305b86f5c50b2c176c85dba76e7dceb1f909819 Mon Sep 17 00:00:00 2001
From: Charlie Lin <tuug@gmx.us>
Date: Tue, 9 Jun 2026 14:58:19 -0400
Subject: [PATCH 07/33] Keep _testlimitedcapi/weakref.c in Setup.stdlib.in

---
 Modules/Setup.stdlib.in | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/Modules/Setup.stdlib.in b/Modules/Setup.stdlib.in
index 355a9499ed7130c..db81e482405b9d7 100644
--- a/Modules/Setup.stdlib.in
+++ b/Modules/Setup.stdlib.in
@@ -173,8 +173,8 @@
 @MODULE__XXTESTFUZZ_TRUE@_xxtestfuzz _xxtestfuzz/_xxtestfuzz.c _xxtestfuzz/fuzzer.c
 @MODULE__TESTBUFFER_TRUE@_testbuffer _testbuffer.c
 @MODULE__TESTINTERNALCAPI_TRUE@_testinternalcapi _testinternalcapi.c _testinternalcapi/test_lock.c _testinternalcapi/pytime.c _testinternalcapi/test_ptr_wise_memmove.c _testinternalcapi/set.c _testinternalcapi/test_critical_sections.c _testinternalcapi/complex.c _testinternalcapi/interpreter.c _testinternalcapi/tuple.c
-@MODULE__TESTCAPI_TRUE@_testcapi _testcapimodule.c _testcapi/vectorcall.c _testcapi/heaptype.c _testcapi/abstract.c _testcapi/unicode.c _testcapi/dict.c _testcapi/set.c _testcapi/list.c _testcapi/tuple.c _testcapi/getargs.c _testcapi/datetime.c _testcapi/docstring.c _testcapi/mem.c _testcapi/watchers.c _testcapi/long.c _testcapi/float.c _testcapi/complex.c _testcapi/numbers.c _testcapi/structmember.c _testcapi/exceptions.c _testcapi/code.c _testcapi/buffer.c _testcapi/pyatomic.c _testcapi/run.c _testcapi/file.c _testcapi/codec.c _testcapi/immortal.c _testcapi/gc.c _testcapi/hash.c _testcapi/time.c _testcapi/bytes.c _testcapi/object.c _testcapi/modsupport.c _testcapi/monitoring.c _testcapi/config.c _testcapi/import.c _testcapi/frame.c _testcapi/type.c _testcapi/function.c _testcapi/module.c
-@MODULE__TESTLIMITEDCAPI_TRUE@_testlimitedcapi _testlimitedcapi.c _testlimitedcapi/abstract.c _testlimitedcapi/bytearray.c _testlimitedcapi/bytes.c _testlimitedcapi/codec.c _testlimitedcapi/complex.c _testlimitedcapi/dict.c _testlimitedcapi/eval.c _testlimitedcapi/float.c _testlimitedcapi/heaptype_relative.c _testlimitedcapi/import.c _testlimitedcapi/list.c _testlimitedcapi/long.c _testlimitedcapi/object.c _testlimitedcapi/pyos.c _testlimitedcapi/set.c _testlimitedcapi/slots.c _testlimitedcapi/sys.c _testlimitedcapi/threadstate.c _testlimitedcapi/tuple.c _testlimitedcapi/unicode.c _testlimitedcapi/vectorcall_limited.c _testlimitedcapi/version.c _testlimitedcapi/file.c
+@MODULE__TESTCAPI_TRUE@_testcapi _testcapimodule.c _testcapi/vectorcall.c _testcapi/heaptype.c _testcapi/abstract.c _testcapi/unicode.c _testcapi/dict.c _testcapi/set.c _testcapi/list.c _testcapi/tuple.c _testcapi/getargs.c _testcapi/datetime.c _testcapi/docstring.c _testcapi/mem.c _testcapi/watchers.c _testcapi/long.c _testcapi/float.c _testcapi/complex.c _testcapi/numbers.c _testcapi/structmember.c _testcapi/exceptions.c _testcapi/code.c _testcapi/buffer.c _testcapi/pyatomic.c _testcapi/run.c _testcapi/file.c _testcapi/codec.c _testcapi/immortal.c _testcapi/gc.c _testcapi/hash.c _testcapi/time.c _testcapi/bytes.c _testcapi/object.c _testcapi/modsupport.c _testcapi/monitoring.c _testcapi/config.c _testcapi/import.c _testcapi/frame.c _testcapi/type.c _testcapi/function.c _testcapi/module.c _testcapi/weakref.c
+@MODULE__TESTLIMITEDCAPI_TRUE@_testlimitedcapi _testlimitedcapi.c _testlimitedcapi/abstract.c _testlimitedcapi/bytearray.c _testlimitedcapi/bytes.c _testlimitedcapi/codec.c _testlimitedcapi/complex.c _testlimitedcapi/dict.c _testlimitedcapi/eval.c _testlimitedcapi/float.c _testlimitedcapi/heaptype_relative.c _testlimitedcapi/import.c _testlimitedcapi/list.c _testlimitedcapi/long.c _testlimitedcapi/object.c _testlimitedcapi/pyos.c _testlimitedcapi/set.c _testlimitedcapi/slots.c _testlimitedcapi/sys.c _testlimitedcapi/threadstate.c _testlimitedcapi/tuple.c _testlimitedcapi/unicode.c _testlimitedcapi/vectorcall_limited.c _testlimitedcapi/version.c _testlimitedcapi/file.c _testlimitedcapi/weakref.c
 @MODULE__TESTCLINIC_TRUE@_testclinic _testclinic.c
 @MODULE__TESTCLINIC_LIMITED_TRUE@_testclinic_limited _testclinic_limited.c
 

From 73a8c67cc33a9549275351f1f6ccf306439c4cb0 Mon Sep 17 00:00:00 2001
From: Charlie Lin <tuug@gmx.us>
Date: Tue, 9 Jun 2026 15:07:54 -0400
Subject: [PATCH 08/33] Cast 1st arg of all calls to
 _Py_ptr_wise_atomic_memmove to PyObject*

---
 Objects/listobject.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/Objects/listobject.c b/Objects/listobject.c
index d7ba1ff240ec12d..c0a847ccfdf5004 100644
--- a/Objects/listobject.c
+++ b/Objects/listobject.c
@@ -3828,12 +3828,14 @@ list_ass_subscript_lock_held(PyObject *_self, PyObject *item, PyObject *value)
                     lim = Py_SIZE(self) - cur - 1;
                 }
 
-                _Py_ptr_wise_atomic_memmove(self, self->ob_item + cur - i,
+                _Py_CRITICAL_SECTION_ASSERT_OBJECT_LOCKED(self);
+                _Py_ptr_wise_atomic_memmove((PyObject *)self, self->ob_item + cur - i,
                     self->ob_item + cur + 1, lim);
             }
             cur = start + (size_t)slicelength * step;
             if (cur < (size_t)Py_SIZE(self)) {
-                _Py_ptr_wise_atomic_memmove(self, self->ob_item + cur - slicelength,
+                _Py_CRITICAL_SECTION_ASSERT_OBJECT_LOCKED(self);
+                _Py_ptr_wise_atomic_memmove((PyObject *)self, self->ob_item + cur - slicelength,
                     self->ob_item + cur, Py_SIZE(self) - cur);
             }
 

From 0b804bbae1fa4d563904c34e6f797cf5a8af36bd Mon Sep 17 00:00:00 2001
From: Charlie Lin <tuug@gmx.us>
Date: Tue, 9 Jun 2026 15:49:05 -0400
Subject: [PATCH 09/33] Make test shut up check-c-globals.py

---
 .../_testinternalcapi/test_ptr_wise_memmove.c | 20 +++----------------
 1 file changed, 3 insertions(+), 17 deletions(-)

diff --git a/Modules/_testinternalcapi/test_ptr_wise_memmove.c b/Modules/_testinternalcapi/test_ptr_wise_memmove.c
index f5b5b97223d2b12..9d548af1a9ee2b4 100644
--- a/Modules/_testinternalcapi/test_ptr_wise_memmove.c
+++ b/Modules/_testinternalcapi/test_ptr_wise_memmove.c
@@ -14,18 +14,9 @@
 // Five distinguishable immortal singletons used as placeholder pointers.
 // These require no reference-count management when stored in a raw array.
 #define NPTRS 5
-static PyObject *test_objs[NPTRS];
-
-static void
-setup_test_objs(void)
-{
-    test_objs[0] = Py_None;
-    test_objs[1] = Py_True;
-    test_objs[2] = Py_False;
-    test_objs[3] = Py_Ellipsis;
-    test_objs[4] = Py_NotImplemented;
-}
-
+const static PyObject *test_objs[NPTRS] = {
+    Py_None, Py_True, Py_False, Py_Ellipsis, Py_NotImplemented
+};
 // Fill buf[0..NPTRS-1] with test_objs in order.
 static void
 fill_buf(PyObject **buf)
@@ -79,7 +70,6 @@ call_memmove(PyObject **dest, PyObject **src, Py_ssize_t n)
 static PyObject *
 test_memmove_dest_lt_src(PyObject *self, PyObject *Py_UNUSED(arg))
 {
-    setup_test_objs();
 
     PyObject *buf[NPTRS];
     fill_buf(buf);
@@ -105,7 +95,6 @@ test_memmove_dest_lt_src(PyObject *self, PyObject *Py_UNUSED(arg))
 static PyObject *
 test_memmove_dest_gt_src(PyObject *self, PyObject *Py_UNUSED(arg))
 {
-    setup_test_objs();
 
     PyObject *buf[NPTRS];
     fill_buf(buf);
@@ -131,7 +120,6 @@ test_memmove_dest_gt_src(PyObject *self, PyObject *Py_UNUSED(arg))
 static PyObject *
 test_memmove_dest_eq_src(PyObject *self, PyObject *Py_UNUSED(arg))
 {
-    setup_test_objs();
 
     PyObject *buf[NPTRS];
     fill_buf(buf);
@@ -156,7 +144,6 @@ test_memmove_dest_eq_src(PyObject *self, PyObject *Py_UNUSED(arg))
 static PyObject *
 test_memmove_overlapping(PyObject *self, PyObject *Py_UNUSED(arg))
 {
-    setup_test_objs();
 
     PyObject *buf[NPTRS];
     fill_buf(buf);
@@ -183,7 +170,6 @@ test_memmove_overlapping(PyObject *self, PyObject *Py_UNUSED(arg))
 static PyObject *
 test_memmove_single_owner(PyObject *self, PyObject *Py_UNUSED(arg))
 {
-    setup_test_objs();
 
     PyObject *a = PyList_New(0);
     if (a == NULL) {

From d3fc80b86826cab73a237ad3f90ddfb801fbe4b2 Mon Sep 17 00:00:00 2001
From: Charlie Lin <tuug@gmx.us>
Date: Tue, 9 Jun 2026 16:02:38 -0400
Subject: [PATCH 10/33] Drop const in test_objs

---
 Modules/_testinternalcapi/test_ptr_wise_memmove.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Modules/_testinternalcapi/test_ptr_wise_memmove.c b/Modules/_testinternalcapi/test_ptr_wise_memmove.c
index 9d548af1a9ee2b4..480a5d19363e9ef 100644
--- a/Modules/_testinternalcapi/test_ptr_wise_memmove.c
+++ b/Modules/_testinternalcapi/test_ptr_wise_memmove.c
@@ -14,7 +14,7 @@
 // Five distinguishable immortal singletons used as placeholder pointers.
 // These require no reference-count management when stored in a raw array.
 #define NPTRS 5
-const static PyObject *test_objs[NPTRS] = {
+static PyObject *test_objs[NPTRS] = {
     Py_None, Py_True, Py_False, Py_Ellipsis, Py_NotImplemented
 };
 // Fill buf[0..NPTRS-1] with test_objs in order.

From e2d17d263d0da1f94ba69ef98b1ec78dee505212 Mon Sep 17 00:00:00 2001
From: Charlie Lin <tuug@gmx.us>
Date: Tue, 9 Jun 2026 16:13:45 -0400
Subject: [PATCH 11/33] Revert previous changes

---
 .../_testinternalcapi/test_ptr_wise_memmove.c | 20 ++++++++++++++++---
 1 file changed, 17 insertions(+), 3 deletions(-)

diff --git a/Modules/_testinternalcapi/test_ptr_wise_memmove.c b/Modules/_testinternalcapi/test_ptr_wise_memmove.c
index 480a5d19363e9ef..f5b5b97223d2b12 100644
--- a/Modules/_testinternalcapi/test_ptr_wise_memmove.c
+++ b/Modules/_testinternalcapi/test_ptr_wise_memmove.c
@@ -14,9 +14,18 @@
 // Five distinguishable immortal singletons used as placeholder pointers.
 // These require no reference-count management when stored in a raw array.
 #define NPTRS 5
-static PyObject *test_objs[NPTRS] = {
-    Py_None, Py_True, Py_False, Py_Ellipsis, Py_NotImplemented
-};
+static PyObject *test_objs[NPTRS];
+
+static void
+setup_test_objs(void)
+{
+    test_objs[0] = Py_None;
+    test_objs[1] = Py_True;
+    test_objs[2] = Py_False;
+    test_objs[3] = Py_Ellipsis;
+    test_objs[4] = Py_NotImplemented;
+}
+
 // Fill buf[0..NPTRS-1] with test_objs in order.
 static void
 fill_buf(PyObject **buf)
@@ -70,6 +79,7 @@ call_memmove(PyObject **dest, PyObject **src, Py_ssize_t n)
 static PyObject *
 test_memmove_dest_lt_src(PyObject *self, PyObject *Py_UNUSED(arg))
 {
+    setup_test_objs();
 
     PyObject *buf[NPTRS];
     fill_buf(buf);
@@ -95,6 +105,7 @@ test_memmove_dest_lt_src(PyObject *self, PyObject *Py_UNUSED(arg))
 static PyObject *
 test_memmove_dest_gt_src(PyObject *self, PyObject *Py_UNUSED(arg))
 {
+    setup_test_objs();
 
     PyObject *buf[NPTRS];
     fill_buf(buf);
@@ -120,6 +131,7 @@ test_memmove_dest_gt_src(PyObject *self, PyObject *Py_UNUSED(arg))
 static PyObject *
 test_memmove_dest_eq_src(PyObject *self, PyObject *Py_UNUSED(arg))
 {
+    setup_test_objs();
 
     PyObject *buf[NPTRS];
     fill_buf(buf);
@@ -144,6 +156,7 @@ test_memmove_dest_eq_src(PyObject *self, PyObject *Py_UNUSED(arg))
 static PyObject *
 test_memmove_overlapping(PyObject *self, PyObject *Py_UNUSED(arg))
 {
+    setup_test_objs();
 
     PyObject *buf[NPTRS];
     fill_buf(buf);
@@ -170,6 +183,7 @@ test_memmove_overlapping(PyObject *self, PyObject *Py_UNUSED(arg))
 static PyObject *
 test_memmove_single_owner(PyObject *self, PyObject *Py_UNUSED(arg))
 {
+    setup_test_objs();
 
     PyObject *a = PyList_New(0);
     if (a == NULL) {

From 50d71cfb7b523aa38fc6e111665056a8541e8131 Mon Sep 17 00:00:00 2001
From: "blurb-it[bot]" <43283697+blurb-it[bot]@users.noreply.github.com>
Date: Wed, 10 Jun 2026 14:01:16 +0000
Subject: [PATCH 12/33] =?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

---
 .../2026-06-10-14-01-11.gh-issue-149965.edk2ut.rst               | 1 +
 1 file changed, 1 insertion(+)
 create mode 100644 Misc/NEWS.d/next/Core_and_Builtins/2026-06-10-14-01-11.gh-issue-149965.edk2ut.rst

diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2026-06-10-14-01-11.gh-issue-149965.edk2ut.rst b/Misc/NEWS.d/next/Core_and_Builtins/2026-06-10-14-01-11.gh-issue-149965.edk2ut.rst
new file mode 100644
index 000000000000000..17f62e95c43758d
--- /dev/null
+++ b/Misc/NEWS.d/next/Core_and_Builtins/2026-06-10-14-01-11.gh-issue-149965.edk2ut.rst
@@ -0,0 +1 @@
+Promote ``ptr_wise_atomic_memmove`` to internal header

From ab0750e90b8c994cb37d50614a7f56772092cf7b Mon Sep 17 00:00:00 2001
From: Charlie Lin <tuug@gmx.us>
Date: Wed, 10 Jun 2026 12:39:50 -0400
Subject: [PATCH 13/33] Delete
 Misc/NEWS.d/next/Core_and_Builtins/2026-06-10-14-01-11.gh-issue-149965.edk2ut.rst

---
 .../2026-06-10-14-01-11.gh-issue-149965.edk2ut.rst               | 1 -
 1 file changed, 1 deletion(-)
 delete mode 100644 Misc/NEWS.d/next/Core_and_Builtins/2026-06-10-14-01-11.gh-issue-149965.edk2ut.rst

diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2026-06-10-14-01-11.gh-issue-149965.edk2ut.rst b/Misc/NEWS.d/next/Core_and_Builtins/2026-06-10-14-01-11.gh-issue-149965.edk2ut.rst
deleted file mode 100644
index 17f62e95c43758d..000000000000000
--- a/Misc/NEWS.d/next/Core_and_Builtins/2026-06-10-14-01-11.gh-issue-149965.edk2ut.rst
+++ /dev/null
@@ -1 +0,0 @@
-Promote ``ptr_wise_atomic_memmove`` to internal header

From 44c5f6cc0c33a92eeaa9d7a5f9de6792fb88d45a Mon Sep 17 00:00:00 2001
From: Charlie Lin <tuug@gmx.us>
Date: Wed, 10 Jun 2026 16:21:49 -0400
Subject: [PATCH 14/33] Drop unit tests for now

---
 Modules/Setup.stdlib.in                       |   6 +-
 Modules/_testinternalcapi.c                   |   3 -
 Modules/_testinternalcapi/parts.h             |   1 -
 .../_testinternalcapi/test_ptr_wise_memmove.c | 231 ------------------
 PCbuild/_testinternalcapi.vcxproj             |   1 -
 5 files changed, 3 insertions(+), 239 deletions(-)
 delete mode 100644 Modules/_testinternalcapi/test_ptr_wise_memmove.c

diff --git a/Modules/Setup.stdlib.in b/Modules/Setup.stdlib.in
index db81e482405b9d7..c3dd47a5e40a675 100644
--- a/Modules/Setup.stdlib.in
+++ b/Modules/Setup.stdlib.in
@@ -172,9 +172,9 @@
 @MODULE_XXSUBTYPE_TRUE@xxsubtype xxsubtype.c
 @MODULE__XXTESTFUZZ_TRUE@_xxtestfuzz _xxtestfuzz/_xxtestfuzz.c _xxtestfuzz/fuzzer.c
 @MODULE__TESTBUFFER_TRUE@_testbuffer _testbuffer.c
-@MODULE__TESTINTERNALCAPI_TRUE@_testinternalcapi _testinternalcapi.c _testinternalcapi/test_lock.c _testinternalcapi/pytime.c _testinternalcapi/test_ptr_wise_memmove.c _testinternalcapi/set.c _testinternalcapi/test_critical_sections.c _testinternalcapi/complex.c _testinternalcapi/interpreter.c _testinternalcapi/tuple.c
-@MODULE__TESTCAPI_TRUE@_testcapi _testcapimodule.c _testcapi/vectorcall.c _testcapi/heaptype.c _testcapi/abstract.c _testcapi/unicode.c _testcapi/dict.c _testcapi/set.c _testcapi/list.c _testcapi/tuple.c _testcapi/getargs.c _testcapi/datetime.c _testcapi/docstring.c _testcapi/mem.c _testcapi/watchers.c _testcapi/long.c _testcapi/float.c _testcapi/complex.c _testcapi/numbers.c _testcapi/structmember.c _testcapi/exceptions.c _testcapi/code.c _testcapi/buffer.c _testcapi/pyatomic.c _testcapi/run.c _testcapi/file.c _testcapi/codec.c _testcapi/immortal.c _testcapi/gc.c _testcapi/hash.c _testcapi/time.c _testcapi/bytes.c _testcapi/object.c _testcapi/modsupport.c _testcapi/monitoring.c _testcapi/config.c _testcapi/import.c _testcapi/frame.c _testcapi/type.c _testcapi/function.c _testcapi/module.c _testcapi/weakref.c
-@MODULE__TESTLIMITEDCAPI_TRUE@_testlimitedcapi _testlimitedcapi.c _testlimitedcapi/abstract.c _testlimitedcapi/bytearray.c _testlimitedcapi/bytes.c _testlimitedcapi/codec.c _testlimitedcapi/complex.c _testlimitedcapi/dict.c _testlimitedcapi/eval.c _testlimitedcapi/float.c _testlimitedcapi/heaptype_relative.c _testlimitedcapi/import.c _testlimitedcapi/list.c _testlimitedcapi/long.c _testlimitedcapi/object.c _testlimitedcapi/pyos.c _testlimitedcapi/set.c _testlimitedcapi/slots.c _testlimitedcapi/sys.c _testlimitedcapi/threadstate.c _testlimitedcapi/tuple.c _testlimitedcapi/unicode.c _testlimitedcapi/vectorcall_limited.c _testlimitedcapi/version.c _testlimitedcapi/file.c _testlimitedcapi/weakref.c
+@MODULE__TESTINTERNALCAPI_TRUE@_testinternalcapi _testinternalcapi.c _testinternalcapi/test_lock.c _testinternalcapi/pytime.c _testinternalcapi/set.c _testinternalcapi/test_critical_sections.c _testinternalcapi/complex.c _testinternalcapi/interpreter.c _testinternalcapi/tuple.c
+@MODULE__TESTCAPI_TRUE@_testcapi _testcapimodule.c _testcapi/vectorcall.c _testcapi/heaptype.c _testcapi/abstract.c _testcapi/unicode.c _testcapi/dict.c _testcapi/set.c _testcapi/list.c _testcapi/tuple.c _testcapi/getargs.c _testcapi/datetime.c _testcapi/docstring.c _testcapi/mem.c _testcapi/watchers.c _testcapi/long.c _testcapi/float.c _testcapi/complex.c _testcapi/numbers.c _testcapi/structmember.c _testcapi/exceptions.c _testcapi/code.c _testcapi/buffer.c _testcapi/pyatomic.c _testcapi/run.c _testcapi/file.c _testcapi/codec.c _testcapi/immortal.c _testcapi/gc.c _testcapi/hash.c _testcapi/time.c _testcapi/bytes.c _testcapi/object.c _testcapi/modsupport.c _testcapi/monitoring.c _testcapi/config.c _testcapi/import.c _testcapi/frame.c _testcapi/type.c _testcapi/function.c _testcapi/module.c
+@MODULE__TESTLIMITEDCAPI_TRUE@_testlimitedcapi _testlimitedcapi.c _testlimitedcapi/abstract.c _testlimitedcapi/bytearray.c _testlimitedcapi/bytes.c _testlimitedcapi/codec.c _testlimitedcapi/complex.c _testlimitedcapi/dict.c _testlimitedcapi/eval.c _testlimitedcapi/float.c _testlimitedcapi/heaptype_relative.c _testlimitedcapi/import.c _testlimitedcapi/list.c _testlimitedcapi/long.c _testlimitedcapi/object.c _testlimitedcapi/pyos.c _testlimitedcapi/set.c _testlimitedcapi/slots.c _testlimitedcapi/sys.c _testlimitedcapi/threadstate.c _testlimitedcapi/tuple.c _testlimitedcapi/unicode.c _testlimitedcapi/vectorcall_limited.c _testlimitedcapi/version.c _testlimitedcapi/file.c
 @MODULE__TESTCLINIC_TRUE@_testclinic _testclinic.c
 @MODULE__TESTCLINIC_LIMITED_TRUE@_testclinic_limited _testclinic_limited.c
 
diff --git a/Modules/_testinternalcapi.c b/Modules/_testinternalcapi.c
index 7f90a6440a57350..f629b8e528faca7 100644
--- a/Modules/_testinternalcapi.c
+++ b/Modules/_testinternalcapi.c
@@ -3482,9 +3482,6 @@ module_exec(PyObject *module)
     if (_PyTestInternalCapi_Init_PyTime(module) < 0) {
         return 1;
     }
-    if (_PyTestInternalCapi_Init_PtrWiseMemmove(module) < 0) {
-        return 1;
-    }
     if (_PyTestInternalCapi_Init_Set(module) < 0) {
         return 1;
     }
diff --git a/Modules/_testinternalcapi/parts.h b/Modules/_testinternalcapi/parts.h
index 60a41e2c49b7108..9b06eec3bce9e65 100644
--- a/Modules/_testinternalcapi/parts.h
+++ b/Modules/_testinternalcapi/parts.h
@@ -12,7 +12,6 @@
 
 int _PyTestInternalCapi_Init_Lock(PyObject *module);
 int _PyTestInternalCapi_Init_PyTime(PyObject *module);
-int _PyTestInternalCapi_Init_PtrWiseMemmove(PyObject *module);
 int _PyTestInternalCapi_Init_Set(PyObject *module);
 int _PyTestInternalCapi_Init_Complex(PyObject *module);
 int _PyTestInternalCapi_Init_CriticalSection(PyObject *module);
diff --git a/Modules/_testinternalcapi/test_ptr_wise_memmove.c b/Modules/_testinternalcapi/test_ptr_wise_memmove.c
deleted file mode 100644
index f5b5b97223d2b12..000000000000000
--- a/Modules/_testinternalcapi/test_ptr_wise_memmove.c
+++ /dev/null
@@ -1,231 +0,0 @@
-<<<<<<< HEAD
-// Tests for _PyObject_ptr_wise_atomic_memmove() in pycore_object.h
-
-#include "parts.h"
-#include "pycore_object.h"    // _PyObject_ptr_wise_atomic_memmove()
-=======
-// Tests for _Py_ptr_wise_atomic_memmove() in pycore_object.h
-
-#include "parts.h"
-#include "pycore_object.h"    // _Py_ptr_wise_atomic_memmove()
->>>>>>> a4c9efbacc (gh-149966: deduplicate ptr_wise_atomic_memmove into a shared internal helper and add unit tests)
-#include "pycore_gc.h"        // _PyObject_GC_SET_SHARED()
-
-// Five distinguishable immortal singletons used as placeholder pointers.
-// These require no reference-count management when stored in a raw array.
-#define NPTRS 5
-static PyObject *test_objs[NPTRS];
-
-static void
-setup_test_objs(void)
-{
-    test_objs[0] = Py_None;
-    test_objs[1] = Py_True;
-    test_objs[2] = Py_False;
-    test_objs[3] = Py_Ellipsis;
-    test_objs[4] = Py_NotImplemented;
-}
-
-// Fill buf[0..NPTRS-1] with test_objs in order.
-static void
-fill_buf(PyObject **buf)
-{
-    for (int i = 0; i < NPTRS; i++) {
-        buf[i] = test_objs[i];
-    }
-}
-
-// Return a fresh empty PyListObject whose GC SHARED bit is set in
-<<<<<<< HEAD
-// Py_GIL_DISABLED builds.  This forces _PyObject_ptr_wise_atomic_memmove()
-=======
-// Py_GIL_DISABLED builds.  This forces _Py_ptr_wise_atomic_memmove()
->>>>>>> a4c9efbacc (gh-149966: deduplicate ptr_wise_atomic_memmove into a shared internal helper and add unit tests)
-// to take the atomic (non-fast) path so we can exercise all branches.
-// In non-GIL builds the function always uses memmove, so no flag is needed.
-static PyObject *
-make_shared_container(void)
-{
-    PyObject *a = PyList_New(0);
-    if (a == NULL) {
-        return NULL;
-    }
-#ifdef Py_GIL_DISABLED
-    _PyObject_GC_SET_SHARED(a);
-#endif
-    return a;
-}
-
-// Helper: create container, call the function, return it for cleanup.
-// Returns NULL (with exception set) on allocation failure.
-static PyObject *
-call_memmove(PyObject **dest, PyObject **src, Py_ssize_t n)
-{
-    PyObject *a = make_shared_container();
-    if (a != NULL) {
-<<<<<<< HEAD
-        _PyObject_ptr_wise_atomic_memmove(a, dest, src, n);
-=======
-        _Py_ptr_wise_atomic_memmove(a, dest, src, n);
->>>>>>> a4c9efbacc (gh-149966: deduplicate ptr_wise_atomic_memmove into a shared internal helper and add unit tests)
-    }
-    return a;
-}
-
-
-// dest < src: forward pointer-by-pointer copy.
-// buf = [0,1,2,3,4], copy src=&buf[2] n=3 to dest=&buf[0]
-// Expected result: buf = [2,3,4,3,4]
-static PyObject *
-test_memmove_dest_lt_src(PyObject *self, PyObject *Py_UNUSED(arg))
-{
-    setup_test_objs();
-
-    PyObject *buf[NPTRS];
-    fill_buf(buf);
-
-    PyObject *a = call_memmove(&buf[0], &buf[2], 3);
-    if (a == NULL) {
-        return NULL;
-    }
-
-    assert(buf[0] == test_objs[2]);
-    assert(buf[1] == test_objs[3]);
-    assert(buf[2] == test_objs[4]);
-    assert(buf[3] == test_objs[3]);  // unchanged
-    assert(buf[4] == test_objs[4]);  // unchanged
-
-    Py_DECREF(a);
-    Py_RETURN_NONE;
-}
-
-// dest > src: backward pointer-by-pointer copy.
-// buf = [0,1,2,3,4], copy src=&buf[0] n=3 to dest=&buf[2]
-// Expected result: buf = [0,1,0,1,2]
-static PyObject *
-test_memmove_dest_gt_src(PyObject *self, PyObject *Py_UNUSED(arg))
-{
-    setup_test_objs();
-
-    PyObject *buf[NPTRS];
-    fill_buf(buf);
-
-    PyObject *a = call_memmove(&buf[2], &buf[0], 3);
-    if (a == NULL) {
-        return NULL;
-    }
-
-    assert(buf[0] == test_objs[0]);  // unchanged
-    assert(buf[1] == test_objs[1]);  // unchanged
-    assert(buf[2] == test_objs[0]);
-    assert(buf[3] == test_objs[1]);
-    assert(buf[4] == test_objs[2]);
-
-    Py_DECREF(a);
-    Py_RETURN_NONE;
-}
-
-// dest == src: backward copy where every write is a no-op.
-// buf = [0,1,2,3,4], copy src=&buf[1] n=3 to dest=&buf[1]
-// Expected result: buf unchanged.
-static PyObject *
-test_memmove_dest_eq_src(PyObject *self, PyObject *Py_UNUSED(arg))
-{
-    setup_test_objs();
-
-    PyObject *buf[NPTRS];
-    fill_buf(buf);
-
-    PyObject *a = call_memmove(&buf[1], &buf[1], 3);
-    if (a == NULL) {
-        return NULL;
-    }
-
-    for (int i = 0; i < NPTRS; i++) {
-        assert(buf[i] == test_objs[i]);
-    }
-
-    Py_DECREF(a);
-    Py_RETURN_NONE;
-}
-
-// Overlapping ranges, dest < src: forward copy is safe.
-// buf = [0,1,2,3,4], copy src=&buf[2] n=3 to dest=&buf[1]
-// Forward: buf[1]=buf[2]=2, buf[2]=buf[3]=3, buf[3]=buf[4]=4
-// Expected result: buf = [0,2,3,4,4]
-static PyObject *
-test_memmove_overlapping(PyObject *self, PyObject *Py_UNUSED(arg))
-{
-    setup_test_objs();
-
-    PyObject *buf[NPTRS];
-    fill_buf(buf);
-
-    PyObject *a = call_memmove(&buf[1], &buf[2], 3);
-    if (a == NULL) {
-        return NULL;
-    }
-
-    assert(buf[0] == test_objs[0]);  // unchanged
-    assert(buf[1] == test_objs[2]);
-    assert(buf[2] == test_objs[3]);
-    assert(buf[3] == test_objs[4]);
-    assert(buf[4] == test_objs[4]);  // unchanged
-
-    Py_DECREF(a);
-    Py_RETURN_NONE;
-}
-
-// Single owner fast path (GIL_DISABLED only): object owned by this thread
-// and not GC-shared => memmove is used instead of atomic stores.
-// In non-GIL builds this always takes the memmove path, so the test
-// degenerates to a basic correctness check.
-static PyObject *
-test_memmove_single_owner(PyObject *self, PyObject *Py_UNUSED(arg))
-{
-    setup_test_objs();
-
-    PyObject *a = PyList_New(0);
-    if (a == NULL) {
-        return NULL;
-    }
-
-#ifdef Py_GIL_DISABLED
-    // A freelist-reused list may carry the SHARED bit set by a sibling test.
-    // Clear it explicitly so this test exercises the single-owner fast path.
-    _PyObject_CLEAR_GC_BITS(a, _PyGC_BITS_SHARED);
-    assert(_Py_IsOwnedByCurrentThread(a) && !_PyObject_GC_IS_SHARED(a));
-#endif
-
-    PyObject *buf[NPTRS];
-    fill_buf(buf);
-
-<<<<<<< HEAD
-    _PyObject_ptr_wise_atomic_memmove(a, &buf[0], &buf[2], 3);
-=======
-    _Py_ptr_wise_atomic_memmove(a, &buf[0], &buf[2], 3);
->>>>>>> a4c9efbacc (gh-149966: deduplicate ptr_wise_atomic_memmove into a shared internal helper and add unit tests)
-
-    assert(buf[0] == test_objs[2]);
-    assert(buf[1] == test_objs[3]);
-    assert(buf[2] == test_objs[4]);
-
-    Py_DECREF(a);
-    Py_RETURN_NONE;
-}
-
-
-static PyMethodDef test_methods[] = {
-    {"test_memmove_dest_lt_src",  test_memmove_dest_lt_src,  METH_NOARGS},
-    {"test_memmove_dest_gt_src",  test_memmove_dest_gt_src,  METH_NOARGS},
-    {"test_memmove_dest_eq_src",  test_memmove_dest_eq_src,  METH_NOARGS},
-    {"test_memmove_overlapping",  test_memmove_overlapping,  METH_NOARGS},
-    {"test_memmove_single_owner", test_memmove_single_owner, METH_NOARGS},
-    {NULL},
-};
-
-int
-_PyTestInternalCapi_Init_PtrWiseMemmove(PyObject *mod)
-{
-    return PyModule_AddFunctions(mod, test_methods);
-}
diff --git a/PCbuild/_testinternalcapi.vcxproj b/PCbuild/_testinternalcapi.vcxproj
index 2d7dde28d136796..ae873f0e0267aca 100644
--- a/PCbuild/_testinternalcapi.vcxproj
+++ b/PCbuild/_testinternalcapi.vcxproj
@@ -97,7 +97,6 @@
     <ClCompile Include="..\Modules\_testinternalcapi\pytime.c" />
     <ClCompile Include="..\Modules\_testinternalcapi\test_critical_sections.c" />
     <ClCompile Include="..\Modules\_testinternalcapi\test_lock.c" />
-    <ClCompile Include="..\Modules\_testinternalcapi\test_ptr_wise_memmove.c" />
     <ClCompile Include="..\Modules\_testinternalcapi\set.c" />
     <ClCompile Include="..\Modules\_testinternalcapi\complex.c" />
     <ClCompile Include="..\Modules\_testinternalcapi\interpreter.c" />

From c4db78564b94ea8da8f03f2b9b0e0f9678f02696 Mon Sep 17 00:00:00 2001
From: Charlie Lin <tuug@gmx.us>
Date: Wed, 10 Jun 2026 16:29:03 -0400
Subject: [PATCH 15/33] Don't exclude weakref for testing

---
 Modules/Setup.stdlib.in | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/Modules/Setup.stdlib.in b/Modules/Setup.stdlib.in
index c3dd47a5e40a675..db81e482405b9d7 100644
--- a/Modules/Setup.stdlib.in
+++ b/Modules/Setup.stdlib.in
@@ -172,9 +172,9 @@
 @MODULE_XXSUBTYPE_TRUE@xxsubtype xxsubtype.c
 @MODULE__XXTESTFUZZ_TRUE@_xxtestfuzz _xxtestfuzz/_xxtestfuzz.c _xxtestfuzz/fuzzer.c
 @MODULE__TESTBUFFER_TRUE@_testbuffer _testbuffer.c
-@MODULE__TESTINTERNALCAPI_TRUE@_testinternalcapi _testinternalcapi.c _testinternalcapi/test_lock.c _testinternalcapi/pytime.c _testinternalcapi/set.c _testinternalcapi/test_critical_sections.c _testinternalcapi/complex.c _testinternalcapi/interpreter.c _testinternalcapi/tuple.c
-@MODULE__TESTCAPI_TRUE@_testcapi _testcapimodule.c _testcapi/vectorcall.c _testcapi/heaptype.c _testcapi/abstract.c _testcapi/unicode.c _testcapi/dict.c _testcapi/set.c _testcapi/list.c _testcapi/tuple.c _testcapi/getargs.c _testcapi/datetime.c _testcapi/docstring.c _testcapi/mem.c _testcapi/watchers.c _testcapi/long.c _testcapi/float.c _testcapi/complex.c _testcapi/numbers.c _testcapi/structmember.c _testcapi/exceptions.c _testcapi/code.c _testcapi/buffer.c _testcapi/pyatomic.c _testcapi/run.c _testcapi/file.c _testcapi/codec.c _testcapi/immortal.c _testcapi/gc.c _testcapi/hash.c _testcapi/time.c _testcapi/bytes.c _testcapi/object.c _testcapi/modsupport.c _testcapi/monitoring.c _testcapi/config.c _testcapi/import.c _testcapi/frame.c _testcapi/type.c _testcapi/function.c _testcapi/module.c
-@MODULE__TESTLIMITEDCAPI_TRUE@_testlimitedcapi _testlimitedcapi.c _testlimitedcapi/abstract.c _testlimitedcapi/bytearray.c _testlimitedcapi/bytes.c _testlimitedcapi/codec.c _testlimitedcapi/complex.c _testlimitedcapi/dict.c _testlimitedcapi/eval.c _testlimitedcapi/float.c _testlimitedcapi/heaptype_relative.c _testlimitedcapi/import.c _testlimitedcapi/list.c _testlimitedcapi/long.c _testlimitedcapi/object.c _testlimitedcapi/pyos.c _testlimitedcapi/set.c _testlimitedcapi/slots.c _testlimitedcapi/sys.c _testlimitedcapi/threadstate.c _testlimitedcapi/tuple.c _testlimitedcapi/unicode.c _testlimitedcapi/vectorcall_limited.c _testlimitedcapi/version.c _testlimitedcapi/file.c
+@MODULE__TESTINTERNALCAPI_TRUE@_testinternalcapi _testinternalcapi.c _testinternalcapi/test_lock.c _testinternalcapi/pytime.c _testinternalcapi/test_ptr_wise_memmove.c _testinternalcapi/set.c _testinternalcapi/test_critical_sections.c _testinternalcapi/complex.c _testinternalcapi/interpreter.c _testinternalcapi/tuple.c
+@MODULE__TESTCAPI_TRUE@_testcapi _testcapimodule.c _testcapi/vectorcall.c _testcapi/heaptype.c _testcapi/abstract.c _testcapi/unicode.c _testcapi/dict.c _testcapi/set.c _testcapi/list.c _testcapi/tuple.c _testcapi/getargs.c _testcapi/datetime.c _testcapi/docstring.c _testcapi/mem.c _testcapi/watchers.c _testcapi/long.c _testcapi/float.c _testcapi/complex.c _testcapi/numbers.c _testcapi/structmember.c _testcapi/exceptions.c _testcapi/code.c _testcapi/buffer.c _testcapi/pyatomic.c _testcapi/run.c _testcapi/file.c _testcapi/codec.c _testcapi/immortal.c _testcapi/gc.c _testcapi/hash.c _testcapi/time.c _testcapi/bytes.c _testcapi/object.c _testcapi/modsupport.c _testcapi/monitoring.c _testcapi/config.c _testcapi/import.c _testcapi/frame.c _testcapi/type.c _testcapi/function.c _testcapi/module.c _testcapi/weakref.c
+@MODULE__TESTLIMITEDCAPI_TRUE@_testlimitedcapi _testlimitedcapi.c _testlimitedcapi/abstract.c _testlimitedcapi/bytearray.c _testlimitedcapi/bytes.c _testlimitedcapi/codec.c _testlimitedcapi/complex.c _testlimitedcapi/dict.c _testlimitedcapi/eval.c _testlimitedcapi/float.c _testlimitedcapi/heaptype_relative.c _testlimitedcapi/import.c _testlimitedcapi/list.c _testlimitedcapi/long.c _testlimitedcapi/object.c _testlimitedcapi/pyos.c _testlimitedcapi/set.c _testlimitedcapi/slots.c _testlimitedcapi/sys.c _testlimitedcapi/threadstate.c _testlimitedcapi/tuple.c _testlimitedcapi/unicode.c _testlimitedcapi/vectorcall_limited.c _testlimitedcapi/version.c _testlimitedcapi/file.c _testlimitedcapi/weakref.c
 @MODULE__TESTCLINIC_TRUE@_testclinic _testclinic.c
 @MODULE__TESTCLINIC_LIMITED_TRUE@_testclinic_limited _testclinic_limited.c
 

From cf79ca0f1011e9fdc06fca28af1b8077cc2f639b Mon Sep 17 00:00:00 2001
From: Charlie Lin <tuug@gmx.us>
Date: Wed, 10 Jun 2026 16:38:57 -0400
Subject: [PATCH 16/33] Actually drop unit test

---
 Modules/Setup.stdlib.in | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Modules/Setup.stdlib.in b/Modules/Setup.stdlib.in
index db81e482405b9d7..8efea27824f0e88 100644
--- a/Modules/Setup.stdlib.in
+++ b/Modules/Setup.stdlib.in
@@ -172,7 +172,7 @@
 @MODULE_XXSUBTYPE_TRUE@xxsubtype xxsubtype.c
 @MODULE__XXTESTFUZZ_TRUE@_xxtestfuzz _xxtestfuzz/_xxtestfuzz.c _xxtestfuzz/fuzzer.c
 @MODULE__TESTBUFFER_TRUE@_testbuffer _testbuffer.c
-@MODULE__TESTINTERNALCAPI_TRUE@_testinternalcapi _testinternalcapi.c _testinternalcapi/test_lock.c _testinternalcapi/pytime.c _testinternalcapi/test_ptr_wise_memmove.c _testinternalcapi/set.c _testinternalcapi/test_critical_sections.c _testinternalcapi/complex.c _testinternalcapi/interpreter.c _testinternalcapi/tuple.c
+@MODULE__TESTINTERNALCAPI_TRUE@_testinternalcapi _testinternalcapi.c _testinternalcapi/test_lock.c _testinternalcapi/pytime.c _testinternalcapi/set.c _testinternalcapi/test_critical_sections.c _testinternalcapi/complex.c _testinternalcapi/interpreter.c _testinternalcapi/tuple.c
 @MODULE__TESTCAPI_TRUE@_testcapi _testcapimodule.c _testcapi/vectorcall.c _testcapi/heaptype.c _testcapi/abstract.c _testcapi/unicode.c _testcapi/dict.c _testcapi/set.c _testcapi/list.c _testcapi/tuple.c _testcapi/getargs.c _testcapi/datetime.c _testcapi/docstring.c _testcapi/mem.c _testcapi/watchers.c _testcapi/long.c _testcapi/float.c _testcapi/complex.c _testcapi/numbers.c _testcapi/structmember.c _testcapi/exceptions.c _testcapi/code.c _testcapi/buffer.c _testcapi/pyatomic.c _testcapi/run.c _testcapi/file.c _testcapi/codec.c _testcapi/immortal.c _testcapi/gc.c _testcapi/hash.c _testcapi/time.c _testcapi/bytes.c _testcapi/object.c _testcapi/modsupport.c _testcapi/monitoring.c _testcapi/config.c _testcapi/import.c _testcapi/frame.c _testcapi/type.c _testcapi/function.c _testcapi/module.c _testcapi/weakref.c
 @MODULE__TESTLIMITEDCAPI_TRUE@_testlimitedcapi _testlimitedcapi.c _testlimitedcapi/abstract.c _testlimitedcapi/bytearray.c _testlimitedcapi/bytes.c _testlimitedcapi/codec.c _testlimitedcapi/complex.c _testlimitedcapi/dict.c _testlimitedcapi/eval.c _testlimitedcapi/float.c _testlimitedcapi/heaptype_relative.c _testlimitedcapi/import.c _testlimitedcapi/list.c _testlimitedcapi/long.c _testlimitedcapi/object.c _testlimitedcapi/pyos.c _testlimitedcapi/set.c _testlimitedcapi/slots.c _testlimitedcapi/sys.c _testlimitedcapi/threadstate.c _testlimitedcapi/tuple.c _testlimitedcapi/unicode.c _testlimitedcapi/vectorcall_limited.c _testlimitedcapi/version.c _testlimitedcapi/file.c _testlimitedcapi/weakref.c
 @MODULE__TESTCLINIC_TRUE@_testclinic _testclinic.c

From 98a544bc2327fc07d75f46a6450f460859492930 Mon Sep 17 00:00:00 2001
From: Charlie Lin <tuug@gmx.us>
Date: Thu, 11 Jun 2026 16:28:13 -0400
Subject: [PATCH 17/33] Rename to _PyObject_ptr_wise_atomic_memmove

---
 Include/internal/pycore_object.h |  4 +++-
 Modules/_elementtree.c           | 10 +++++-----
 Objects/listobject.c             | 14 +++++++-------
 3 files changed, 15 insertions(+), 13 deletions(-)

diff --git a/Include/internal/pycore_object.h b/Include/internal/pycore_object.h
index 16ed31cb7a529d7..984b95c4bdd5983 100644
--- a/Include/internal/pycore_object.h
+++ b/Include/internal/pycore_object.h
@@ -1020,7 +1020,7 @@ PyAPI_FUNC(int) _PyObject_VisitType(PyObject *op, visitproc visit, void *arg);
 // Pointer-by-pointer memmove for PyObject** arrays that is safe for shared
 // objects in Py_GIL_DISABLED builds.  Locking is the caller's responsibility.
 static inline void
-_Py_ptr_wise_atomic_memmove(PyObject *a, PyObject **dest, PyObject **src,
+_PyObject_ptr_wise_atomic_memmove(PyObject *a, PyObject **dest, PyObject **src,
                              Py_ssize_t n)
 {
 #ifndef Py_GIL_DISABLED
@@ -1046,6 +1046,8 @@ _Py_ptr_wise_atomic_memmove(PyObject *a, PyObject **dest, PyObject **src,
 #endif
 }
 
+#define _PyObject_ptr_wise_atomic_memmove(a, dest, src, n) _PyObject_ptr_wise_atomic_memmove(_PyObject_CAST(a), dest, src, n)
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/Modules/_elementtree.c b/Modules/_elementtree.c
index 680265764dc3d82..13299a1cf0751ec 100644
--- a/Modules/_elementtree.c
+++ b/Modules/_elementtree.c
@@ -18,7 +18,7 @@
 #include "Python.h"
 #include "pycore_ceval.h"         // _Py_EnterRecursiveCall()
 #include "pycore_dict.h"          // _PyDict_CopyAsDict()
-#include "pycore_object.h"        // _Py_ptr_wise_atomic_memmove()
+#include "pycore_object.h"        // _PyObject_ptr_wise_atomic_memmove()
 #include "pycore_pyhash.h"        // _Py_HashSecret
 #include "pycore_tuple.h"         // _PyTuple_FromPair
 #include "pycore_weakref.h"       // FT_CLEAR_WEAKREFS()
@@ -2023,8 +2023,8 @@ element_ass_subscr(PyObject *op, PyObject *item, PyObject *value)
 
                 PyList_SET_ITEM(recycle, i, self->extra->children[cur]);
 
-                _Py_ptr_wise_atomic_memmove(
-                    (PyObject *)self,
+                _PyObject_ptr_wise_atomic_memmove(
+                    self,
                     self->extra->children + cur - i,
                     self->extra->children + cur + 1,
                     num_moved);
@@ -2033,8 +2033,8 @@ element_ass_subscr(PyObject *op, PyObject *item, PyObject *value)
             /* Leftover "tail" after the last removed child */
             cur = start + (size_t)slicelen * step;
             if (cur < (size_t)self->extra->length) {
-                _Py_ptr_wise_atomic_memmove(
-                    (PyObject *)self,
+                _PyObject_ptr_wise_atomic_memmove(
+                    self,
                     self->extra->children + cur - slicelen,
                     self->extra->children + cur,
                     self->extra->length - cur);
diff --git a/Objects/listobject.c b/Objects/listobject.c
index c0a847ccfdf5004..03fedc491f33a19 100644
--- a/Objects/listobject.c
+++ b/Objects/listobject.c
@@ -10,7 +10,7 @@
 #include "pycore_list.h"          // struct _Py_list_freelist, _PyListIterObject
 #include "pycore_long.h"          // _PyLong_DigitCount
 #include "pycore_modsupport.h"    // _PyArg_NoKwnames()
-#include "pycore_object.h"        // _PyObject_GC_TRACK(), _Py_ptr_wise_atomic_memmove()
+#include "pycore_object.h"        // _PyObject_GC_TRACK(), _PyObject_ptr_wise_atomic_memmove()
 #include "pycore_pyatomic_ft_wrappers.h"
 #include "pycore_setobject.h"     // _PySet_NextEntry()
 #include "pycore_stackref.h"      // _Py_TryIncrefCompareStackRef()
@@ -1040,7 +1040,7 @@ list_ass_slice_lock_held(PyListObject *a, Py_ssize_t ilow, Py_ssize_t ihigh, PyO
     if (d < 0) { /* Delete -d items */
         Py_ssize_t tail = Py_SIZE(a) - ihigh;
         _Py_CRITICAL_SECTION_ASSERT_OBJECT_LOCKED(a);
-        _Py_ptr_wise_atomic_memmove((PyObject *)a, &item[ihigh+d], &item[ihigh], tail);
+        _PyObject_ptr_wise_atomic_memmove(a, &item[ihigh+d], &item[ihigh], tail);
         (void)list_resize(a, Py_SIZE(a) + d); // NB: shrinking a list can't fail
         item = a->ob_item;
     }
@@ -1050,7 +1050,7 @@ list_ass_slice_lock_held(PyListObject *a, Py_ssize_t ilow, Py_ssize_t ihigh, PyO
             goto Error;
         item = a->ob_item;
         _Py_CRITICAL_SECTION_ASSERT_OBJECT_LOCKED(a);
-        _Py_ptr_wise_atomic_memmove((PyObject *)a, &item[ihigh+d], &item[ihigh], k - ihigh);
+        _PyObject_ptr_wise_atomic_memmove(a, &item[ihigh+d], &item[ihigh], k - ihigh);
     }
     for (k = 0; k < n; k++, ilow++) {
         PyObject *w = vitem[k];
@@ -1142,7 +1142,7 @@ list_inplace_repeat_lock_held(PyListObject *self, Py_ssize_t n)
     Py_ssize_t copied = input_size;
     while (copied < output_size) {
         Py_ssize_t items_to_copy = Py_MIN(copied, output_size - copied);
-        _Py_ptr_wise_atomic_memmove((PyObject *)self, items + copied, items, items_to_copy);
+        _PyObject_ptr_wise_atomic_memmove(self, items + copied, items, items_to_copy);
         copied += items_to_copy;
     }
 #endif
@@ -1641,7 +1641,7 @@ list_pop_impl(PyListObject *self, Py_ssize_t index)
     Py_ssize_t size_after_pop = Py_SIZE(self) - 1;
     if (index < size_after_pop) {
         _Py_CRITICAL_SECTION_ASSERT_OBJECT_LOCKED(self);
-        _Py_ptr_wise_atomic_memmove((PyObject *)self, &items[index], &items[index+1],
+        _PyObject_ptr_wise_atomic_memmove(self, &items[index], &items[index+1],
                                     size_after_pop - index);
     }
     list_resize(self, size_after_pop);  // NB: shrinking a list can't fail
@@ -3829,13 +3829,13 @@ list_ass_subscript_lock_held(PyObject *_self, PyObject *item, PyObject *value)
                 }
 
                 _Py_CRITICAL_SECTION_ASSERT_OBJECT_LOCKED(self);
-                _Py_ptr_wise_atomic_memmove((PyObject *)self, self->ob_item + cur - i,
+                _PyObject_ptr_wise_atomic_memmove(self, self->ob_item + cur - i,
                     self->ob_item + cur + 1, lim);
             }
             cur = start + (size_t)slicelength * step;
             if (cur < (size_t)Py_SIZE(self)) {
                 _Py_CRITICAL_SECTION_ASSERT_OBJECT_LOCKED(self);
-                _Py_ptr_wise_atomic_memmove((PyObject *)self, self->ob_item + cur - slicelength,
+                _PyObject_ptr_wise_atomic_memmove(self, self->ob_item + cur - slicelength,
                     self->ob_item + cur, Py_SIZE(self) - cur);
             }
 

From d079b0df3eb5ca2bb964783683d11997ec8a99d9 Mon Sep 17 00:00:00 2001
From: "blurb-it[bot]" <43283697+blurb-it[bot]@users.noreply.github.com>
Date: Fri, 12 Jun 2026 19:38:32 +0000
Subject: [PATCH 18/33] =?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

---
 .../2026-06-12-19-38-28.gh-issue-149965.w5eiS4.rst               | 1 +
 1 file changed, 1 insertion(+)
 create mode 100644 Misc/NEWS.d/next/Core_and_Builtins/2026-06-12-19-38-28.gh-issue-149965.w5eiS4.rst

diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2026-06-12-19-38-28.gh-issue-149965.w5eiS4.rst b/Misc/NEWS.d/next/Core_and_Builtins/2026-06-12-19-38-28.gh-issue-149965.w5eiS4.rst
new file mode 100644
index 000000000000000..2e0745c63688397
--- /dev/null
+++ b/Misc/NEWS.d/next/Core_and_Builtins/2026-06-12-19-38-28.gh-issue-149965.w5eiS4.rst
@@ -0,0 +1 @@
+Use :c:func:``_PyObject_ptr_wise_atomic_memmove`` in ``_elementtree``

From 5944e34d5a346f884c685c3704d1081fc57f7880 Mon Sep 17 00:00:00 2001
From: Charlie Lin <tuug@gmx.us>
Date: Sun, 11 Oct 2026 08:05:33 -0400
Subject: [PATCH 19/33] Backtick

---
 .../2026-06-12-19-38-28.gh-issue-149965.w5eiS4.rst              | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2026-06-12-19-38-28.gh-issue-149965.w5eiS4.rst b/Misc/NEWS.d/next/Core_and_Builtins/2026-06-12-19-38-28.gh-issue-149965.w5eiS4.rst
index 2e0745c63688397..45a1456984372da 100644
--- a/Misc/NEWS.d/next/Core_and_Builtins/2026-06-12-19-38-28.gh-issue-149965.w5eiS4.rst
+++ b/Misc/NEWS.d/next/Core_and_Builtins/2026-06-12-19-38-28.gh-issue-149965.w5eiS4.rst
@@ -1 +1 @@
-Use :c:func:``_PyObject_ptr_wise_atomic_memmove`` in ``_elementtree``
+Use :c:func:`_PyObject_ptr_wise_atomic_memmove` in ``_elementtree``

From f526c6033f13da447fd3d9aa939a3988e78e86cd Mon Sep 17 00:00:00 2001
From: Charlie Lin <tuug@gmx.us>
Date: Sun, 11 Oct 2026 08:10:28 -0400
Subject: [PATCH 20/33] Rebase mishaps

---
 Modules/Setup.stdlib.in | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/Modules/Setup.stdlib.in b/Modules/Setup.stdlib.in
index 8efea27824f0e88..50db569eba2e5dd 100644
--- a/Modules/Setup.stdlib.in
+++ b/Modules/Setup.stdlib.in
@@ -172,9 +172,9 @@
 @MODULE_XXSUBTYPE_TRUE@xxsubtype xxsubtype.c
 @MODULE__XXTESTFUZZ_TRUE@_xxtestfuzz _xxtestfuzz/_xxtestfuzz.c _xxtestfuzz/fuzzer.c
 @MODULE__TESTBUFFER_TRUE@_testbuffer _testbuffer.c
-@MODULE__TESTINTERNALCAPI_TRUE@_testinternalcapi _testinternalcapi.c _testinternalcapi/test_lock.c _testinternalcapi/pytime.c _testinternalcapi/set.c _testinternalcapi/test_critical_sections.c _testinternalcapi/complex.c _testinternalcapi/interpreter.c _testinternalcapi/tuple.c
-@MODULE__TESTCAPI_TRUE@_testcapi _testcapimodule.c _testcapi/vectorcall.c _testcapi/heaptype.c _testcapi/abstract.c _testcapi/unicode.c _testcapi/dict.c _testcapi/set.c _testcapi/list.c _testcapi/tuple.c _testcapi/getargs.c _testcapi/datetime.c _testcapi/docstring.c _testcapi/mem.c _testcapi/watchers.c _testcapi/long.c _testcapi/float.c _testcapi/complex.c _testcapi/numbers.c _testcapi/structmember.c _testcapi/exceptions.c _testcapi/code.c _testcapi/buffer.c _testcapi/pyatomic.c _testcapi/run.c _testcapi/file.c _testcapi/codec.c _testcapi/immortal.c _testcapi/gc.c _testcapi/hash.c _testcapi/time.c _testcapi/bytes.c _testcapi/object.c _testcapi/modsupport.c _testcapi/monitoring.c _testcapi/config.c _testcapi/import.c _testcapi/frame.c _testcapi/type.c _testcapi/function.c _testcapi/module.c _testcapi/weakref.c
-@MODULE__TESTLIMITEDCAPI_TRUE@_testlimitedcapi _testlimitedcapi.c _testlimitedcapi/abstract.c _testlimitedcapi/bytearray.c _testlimitedcapi/bytes.c _testlimitedcapi/codec.c _testlimitedcapi/complex.c _testlimitedcapi/dict.c _testlimitedcapi/eval.c _testlimitedcapi/float.c _testlimitedcapi/heaptype_relative.c _testlimitedcapi/import.c _testlimitedcapi/list.c _testlimitedcapi/long.c _testlimitedcapi/object.c _testlimitedcapi/pyos.c _testlimitedcapi/set.c _testlimitedcapi/slots.c _testlimitedcapi/sys.c _testlimitedcapi/threadstate.c _testlimitedcapi/tuple.c _testlimitedcapi/unicode.c _testlimitedcapi/vectorcall_limited.c _testlimitedcapi/version.c _testlimitedcapi/file.c _testlimitedcapi/weakref.c
+@MODULE__TESTINTERNALCAPI_TRUE@_testinternalcapi _testinternalcapi.c _testinternalcapi/test_lock.c _testinternalcapi/pytime.c _testinternalcapi/set.c _testinternalcapi/test_critical_sections.c _testinternalcapi/complex.c _testinternalcapi/interpreter.c _testinternalcapi/tokenizer.c _testinternalcapi/tuple.c _testinternalcapi/typecache.c
+@MODULE__TESTCAPI_TRUE@_testcapi _testcapimodule.c _testcapi/vectorcall.c _testcapi/heaptype.c _testcapi/abstract.c _testcapi/unicode.c _testcapi/dict.c _testcapi/set.c _testcapi/list.c _testcapi/tuple.c _testcapi/getargs.c _testcapi/datetime.c _testcapi/docstring.c _testcapi/mem.c _testcapi/watchers.c _testcapi/long.c _testcapi/float.c _testcapi/complex.c _testcapi/numbers.c _testcapi/structmember.c _testcapi/exceptions.c _testcapi/code.c _testcapi/buffer.c _testcapi/pyatomic.c _testcapi/run.c _testcapi/file.c _testcapi/codec.c _testcapi/immortal.c _testcapi/gc.c _testcapi/hash.c _testcapi/time.c _testcapi/bytes.c _testcapi/object.c _testcapi/modsupport.c _testcapi/monitoring.c _testcapi/config.c _testcapi/import.c _testcapi/frame.c _testcapi/type.c _testcapi/function.c _testcapi/module.c _testcapi/weakref.c _testcapi/marshal.c _testcapi/fpcast.c
+@MODULE__TESTLIMITEDCAPI_TRUE@_testlimitedcapi _testlimitedcapi.c _testlimitedcapi/abstract.c _testlimitedcapi/bytearray.c _testlimitedcapi/bytes.c  _testlimitedcapi/capsule.c _testlimitedcapi/codec.c _testlimitedcapi/complex.c _testlimitedcapi/dict.c _testlimitedcapi/eval.c _testlimitedcapi/float.c _testlimitedcapi/heaptype_relative.c _testlimitedcapi/import.c _testlimitedcapi/list.c _testlimitedcapi/long.c _testlimitedcapi/object.c _testlimitedcapi/pyos.c _testlimitedcapi/set.c _testlimitedcapi/slice.c _testlimitedcapi/slots.c  _testlimitedcapi/sys.c _testlimitedcapi/threadstate.c _testlimitedcapi/tuple.c _testlimitedcapi/unicode.c _testlimitedcapi/vectorcall_limited.c _testlimitedcapi/version.c _testlimitedcapi/file.c _testlimitedcapi/weakref.c _testlimitedcapi/run.c _testlimitedcapi/type.c _testlimitedcapi/hash.c _testlimitedcapi/build.c
 @MODULE__TESTCLINIC_TRUE@_testclinic _testclinic.c
 @MODULE__TESTCLINIC_LIMITED_TRUE@_testclinic_limited _testclinic_limited.c
 

From 0daec9c0564264c59ac7d737244548a57dbb8b32 Mon Sep 17 00:00:00 2001
From: Charlie Lin <tuug@gmx.us>
Date: Sun, 11 Oct 2026 08:23:38 -0400
Subject: [PATCH 21/33] Backtick

---
 .../2026-06-12-19-38-28.gh-issue-149965.w5eiS4.rst              | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2026-06-12-19-38-28.gh-issue-149965.w5eiS4.rst b/Misc/NEWS.d/next/Core_and_Builtins/2026-06-12-19-38-28.gh-issue-149965.w5eiS4.rst
index 45a1456984372da..fe6a6a01705f84a 100644
--- a/Misc/NEWS.d/next/Core_and_Builtins/2026-06-12-19-38-28.gh-issue-149965.w5eiS4.rst
+++ b/Misc/NEWS.d/next/Core_and_Builtins/2026-06-12-19-38-28.gh-issue-149965.w5eiS4.rst
@@ -1 +1 @@
-Use :c:func:`_PyObject_ptr_wise_atomic_memmove` in ``_elementtree``
+Use ``_PyObject_ptr_wise_atomic_memmove`` in ``_elementtree``

From 1535db6c545d9dd7355161bd901ee435faf585be Mon Sep 17 00:00:00 2001
From: Charlie Lin <tuug@gmx.us>
Date: Sun, 11 Oct 2026 08:30:20 -0400
Subject: [PATCH 22/33] Finally use func declaration in internal header

---
 Objects/listobject.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/Objects/listobject.c b/Objects/listobject.c
index 03fedc491f33a19..9dc1d98e940d56c 100644
--- a/Objects/listobject.c
+++ b/Objects/listobject.c
@@ -499,15 +499,13 @@ end:;
     return ret;
 }
 
-static void ptr_wise_atomic_memmove(PyListObject *a, PyObject **dest,
-                                    PyObject **src, Py_ssize_t n);
-
 static inline void
 list_shift_items_right_lock_held(PyListObject *self, Py_ssize_t first,
                                  Py_ssize_t last)
 {
 #ifdef Py_GIL_DISABLED
-    ptr_wise_atomic_memmove(self, &self->ob_item[first + 1],
+       _Py_CRITICAL_SECTION_ASSERT_OBJECT_LOCKED(self);
+    _PyObject_ptr_wise_atomic_memmove(self, &self->ob_item[first + 1],
                             &self->ob_item[first], last - first);
 #else
     PyObject **items = self->ob_item;
@@ -522,7 +520,8 @@ list_shift_items_left_lock_held(PyListObject *self, Py_ssize_t first,
                                 Py_ssize_t last)
 {
 #ifdef Py_GIL_DISABLED
-    ptr_wise_atomic_memmove(self, &self->ob_item[first],
+       _Py_CRITICAL_SECTION_ASSERT_OBJECT_LOCKED(self);
+    _PyObject_ptr_wise_atomic_memmove(self, &self->ob_item[first],
                             &self->ob_item[first + 1], last - first);
 #else
     PyObject **items = self->ob_item;

From 31298e01305dd5b3a6860c78992dad1656a5e3a6 Mon Sep 17 00:00:00 2001
From: Charlie Lin <tuug@gmx.us>
Date: Tue, 13 Oct 2026 08:39:24 -0400
Subject: [PATCH 23/33] Update 2026-06-12-19-38-28.gh-issue-149965.w5eiS4.rst

---
 .../2026-06-12-19-38-28.gh-issue-149965.w5eiS4.rst              | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2026-06-12-19-38-28.gh-issue-149965.w5eiS4.rst b/Misc/NEWS.d/next/Core_and_Builtins/2026-06-12-19-38-28.gh-issue-149965.w5eiS4.rst
index fe6a6a01705f84a..416c7451b19810a 100644
--- a/Misc/NEWS.d/next/Core_and_Builtins/2026-06-12-19-38-28.gh-issue-149965.w5eiS4.rst
+++ b/Misc/NEWS.d/next/Core_and_Builtins/2026-06-12-19-38-28.gh-issue-149965.w5eiS4.rst
@@ -1 +1 @@
-Use ``_PyObject_ptr_wise_atomic_memmove`` in ``_elementtree``
+Fix thread-safety issues in ``xml.etree``

From 4d1ca96b78e3d4684d5050d173a71f1e3a395454 Mon Sep 17 00:00:00 2001
From: Charlie Lin <tuug@gmx.us>
Date: Tue, 13 Oct 2026 08:40:16 -0400
Subject: [PATCH 24/33] Update comments and formatting in Setup.stdlib.in

---
 Modules/Setup.stdlib.in | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/Modules/Setup.stdlib.in b/Modules/Setup.stdlib.in
index 50db569eba2e5dd..7730aa85159dc37 100644
--- a/Modules/Setup.stdlib.in
+++ b/Modules/Setup.stdlib.in
@@ -5,20 +5,20 @@
 
 # The file is not used by default yet. For testing do:
 #
-#     ln -sfr Modules/Setup.stdlib Modules/Setup.local
+#   ln -sfr Modules/Setup.stdlib Modules/Setup.local
 #
 
 # * @MODULE_{NAME}_TRUE@ is removed when configure detects all build
-#   dependencies for a module. Otherwise the template variable is replaced
-#   by a comment "#" and the module is skipped.
+#  dependencies for a module. Otherwise the template variable is replaced
+#  by a comment "#" and the module is skipped.
 # * Module lines without any compiler and linker flags automatically use
-#   $(MODULE_{NAME}_CFLAGS) and $(MODULE_{NAME}_LDFLAGS). These flags are
-#   generated by PY_STDLIB_MOD macro.
+#  $(MODULE_{NAME}_CFLAGS) and $(MODULE_{NAME}_LDFLAGS). These flags are
+#  generated by PY_STDLIB_MOD macro.
 # * All source files automatically depend on $(PYTHON_HEADERS) and
-#   $(MODULE_{NAME}_DEPS).
+#  $(MODULE_{NAME}_DEPS).
 # * ${NAME}$(EXT_SUFFIX) rules automatically depend on $(MODULE_{NAME}_LDEPS),
-#   thus $(MODULE_{NAME}_LDEPS) must only contain Makefile rule names. To pass
-#   specific values to the linker, use $(MODULE_{NAME}_LDFLAGS) instead.
+#  thus $(MODULE_{NAME}_LDEPS) must only contain Makefile rule names. To pass
+#  specific values to the linker, use $(MODULE_{NAME}_LDFLAGS) instead.
 #
 # See Modules/Setup and Modules/makesetup
 #
@@ -174,7 +174,7 @@
 @MODULE__TESTBUFFER_TRUE@_testbuffer _testbuffer.c
 @MODULE__TESTINTERNALCAPI_TRUE@_testinternalcapi _testinternalcapi.c _testinternalcapi/test_lock.c _testinternalcapi/pytime.c _testinternalcapi/set.c _testinternalcapi/test_critical_sections.c _testinternalcapi/complex.c _testinternalcapi/interpreter.c _testinternalcapi/tokenizer.c _testinternalcapi/tuple.c _testinternalcapi/typecache.c
 @MODULE__TESTCAPI_TRUE@_testcapi _testcapimodule.c _testcapi/vectorcall.c _testcapi/heaptype.c _testcapi/abstract.c _testcapi/unicode.c _testcapi/dict.c _testcapi/set.c _testcapi/list.c _testcapi/tuple.c _testcapi/getargs.c _testcapi/datetime.c _testcapi/docstring.c _testcapi/mem.c _testcapi/watchers.c _testcapi/long.c _testcapi/float.c _testcapi/complex.c _testcapi/numbers.c _testcapi/structmember.c _testcapi/exceptions.c _testcapi/code.c _testcapi/buffer.c _testcapi/pyatomic.c _testcapi/run.c _testcapi/file.c _testcapi/codec.c _testcapi/immortal.c _testcapi/gc.c _testcapi/hash.c _testcapi/time.c _testcapi/bytes.c _testcapi/object.c _testcapi/modsupport.c _testcapi/monitoring.c _testcapi/config.c _testcapi/import.c _testcapi/frame.c _testcapi/type.c _testcapi/function.c _testcapi/module.c _testcapi/weakref.c _testcapi/marshal.c _testcapi/fpcast.c
-@MODULE__TESTLIMITEDCAPI_TRUE@_testlimitedcapi _testlimitedcapi.c _testlimitedcapi/abstract.c _testlimitedcapi/bytearray.c _testlimitedcapi/bytes.c  _testlimitedcapi/capsule.c _testlimitedcapi/codec.c _testlimitedcapi/complex.c _testlimitedcapi/dict.c _testlimitedcapi/eval.c _testlimitedcapi/float.c _testlimitedcapi/heaptype_relative.c _testlimitedcapi/import.c _testlimitedcapi/list.c _testlimitedcapi/long.c _testlimitedcapi/object.c _testlimitedcapi/pyos.c _testlimitedcapi/set.c _testlimitedcapi/slice.c _testlimitedcapi/slots.c  _testlimitedcapi/sys.c _testlimitedcapi/threadstate.c _testlimitedcapi/tuple.c _testlimitedcapi/unicode.c _testlimitedcapi/vectorcall_limited.c _testlimitedcapi/version.c _testlimitedcapi/file.c _testlimitedcapi/weakref.c _testlimitedcapi/run.c _testlimitedcapi/type.c _testlimitedcapi/hash.c _testlimitedcapi/build.c
+@MODULE__TESTLIMITEDCAPI_TRUE@_testlimitedcapi _testlimitedcapi.c _testlimitedcapi/abstract.c _testlimitedcapi/bytearray.c _testlimitedcapi/bytes.c _testlimitedcapi/capsule.c _testlimitedcapi/codec.c _testlimitedcapi/complex.c _testlimitedcapi/dict.c _testlimitedcapi/eval.c _testlimitedcapi/float.c _testlimitedcapi/heaptype_relative.c _testlimitedcapi/import.c _testlimitedcapi/list.c _testlimitedcapi/long.c _testlimitedcapi/object.c _testlimitedcapi/pyos.c _testlimitedcapi/set.c _testlimitedcapi/slice.c _testlimitedcapi/slots.c _testlimitedcapi/sys.c _testlimitedcapi/threadstate.c _testlimitedcapi/tuple.c _testlimitedcapi/unicode.c _testlimitedcapi/vectorcall_limited.c _testlimitedcapi/version.c _testlimitedcapi/file.c _testlimitedcapi/weakref.c _testlimitedcapi/run.c _testlimitedcapi/type.c _testlimitedcapi/hash.c _testlimitedcapi/build.c
 @MODULE__TESTCLINIC_TRUE@_testclinic _testclinic.c
 @MODULE__TESTCLINIC_LIMITED_TRUE@_testclinic_limited _testclinic_limited.c
 

From 85454966b57c3063fc0c9a142e6ae4c2e692ea7f Mon Sep 17 00:00:00 2001
From: Charlie Lin <tuug@gmx.us>
Date: Tue, 13 Oct 2026 08:41:10 -0400
Subject: [PATCH 25/33] Comment out lines in Setup.stdlib.in for clarity

---
 Modules/Setup.stdlib.in | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/Modules/Setup.stdlib.in b/Modules/Setup.stdlib.in
index 7730aa85159dc37..0a7691abeb97b8b 100644
--- a/Modules/Setup.stdlib.in
+++ b/Modules/Setup.stdlib.in
@@ -5,20 +5,20 @@
 
 # The file is not used by default yet. For testing do:
 #
-#   ln -sfr Modules/Setup.stdlib Modules/Setup.local
+#    ln -sfr Modules/Setup.stdlib Modules/Setup.local
 #
 
 # * @MODULE_{NAME}_TRUE@ is removed when configure detects all build
-#  dependencies for a module. Otherwise the template variable is replaced
-#  by a comment "#" and the module is skipped.
+#   dependencies for a module. Otherwise the template variable is replaced
+#   by a comment "#" and the module is skipped.
 # * Module lines without any compiler and linker flags automatically use
-#  $(MODULE_{NAME}_CFLAGS) and $(MODULE_{NAME}_LDFLAGS). These flags are
-#  generated by PY_STDLIB_MOD macro.
+#   $(MODULE_{NAME}_CFLAGS) and $(MODULE_{NAME}_LDFLAGS). These flags are
+#   generated by PY_STDLIB_MOD macro.
 # * All source files automatically depend on $(PYTHON_HEADERS) and
-#  $(MODULE_{NAME}_DEPS).
+#   $(MODULE_{NAME}_DEPS).
 # * ${NAME}$(EXT_SUFFIX) rules automatically depend on $(MODULE_{NAME}_LDEPS),
-#  thus $(MODULE_{NAME}_LDEPS) must only contain Makefile rule names. To pass
-#  specific values to the linker, use $(MODULE_{NAME}_LDFLAGS) instead.
+#   thus $(MODULE_{NAME}_LDEPS) must only contain Makefile rule names. To pass
+#   specific values to the linker, use $(MODULE_{NAME}_LDFLAGS) instead.
 #
 # See Modules/Setup and Modules/makesetup
 #

From a2f13f188603e76077c8e27fb91e1d956d57364f Mon Sep 17 00:00:00 2001
From: Charlie Lin <tuug@gmx.us>
Date: Tue, 13 Oct 2026 08:41:32 -0400
Subject: [PATCH 26/33] Fix comment formatting in Setup.stdlib.in

---
 Modules/Setup.stdlib.in | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Modules/Setup.stdlib.in b/Modules/Setup.stdlib.in
index 0a7691abeb97b8b..d8cd8de10dfe084 100644
--- a/Modules/Setup.stdlib.in
+++ b/Modules/Setup.stdlib.in
@@ -5,7 +5,7 @@
 
 # The file is not used by default yet. For testing do:
 #
-#    ln -sfr Modules/Setup.stdlib Modules/Setup.local
+#     ln -sfr Modules/Setup.stdlib Modules/Setup.local
 #
 
 # * @MODULE_{NAME}_TRUE@ is removed when configure detects all build

From 1e8267c7fb0b1427e5e30a4d2640a5213d41e8ed Mon Sep 17 00:00:00 2001
From: Charlie Lin <tuug@gmx.us>
Date: Tue, 13 Oct 2026 08:43:47 -0400
Subject: [PATCH 27/33] Update _elementtree.c

---
 Modules/_elementtree.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/Modules/_elementtree.c b/Modules/_elementtree.c
index 13299a1cf0751ec..d2cd040ce1e30ba 100644
--- a/Modules/_elementtree.c
+++ b/Modules/_elementtree.c
@@ -1947,7 +1947,6 @@ element_subscr(PyObject *op, PyObject *item)
     }
 }
 
-
 static int
 element_ass_subscr(PyObject *op, PyObject *item, PyObject *value)
 {

From bdb231c576a1b97b63491429a3320faa1dbeb3ad Mon Sep 17 00:00:00 2001
From: Charlie Lin <tuug@gmx.us>
Date: Tue, 13 Oct 2026 08:47:13 -0400
Subject: [PATCH 28/33] Remove lock assertions in listobject functions

Removed assertions for object lock in list operations.
---
 Objects/listobject.c | 8 --------
 1 file changed, 8 deletions(-)

diff --git a/Objects/listobject.c b/Objects/listobject.c
index 9dc1d98e940d56c..d7f06a76383d7a8 100644
--- a/Objects/listobject.c
+++ b/Objects/listobject.c
@@ -504,7 +504,6 @@ list_shift_items_right_lock_held(PyListObject *self, Py_ssize_t first,
                                  Py_ssize_t last)
 {
 #ifdef Py_GIL_DISABLED
-       _Py_CRITICAL_SECTION_ASSERT_OBJECT_LOCKED(self);
     _PyObject_ptr_wise_atomic_memmove(self, &self->ob_item[first + 1],
                             &self->ob_item[first], last - first);
 #else
@@ -520,7 +519,6 @@ list_shift_items_left_lock_held(PyListObject *self, Py_ssize_t first,
                                 Py_ssize_t last)
 {
 #ifdef Py_GIL_DISABLED
-       _Py_CRITICAL_SECTION_ASSERT_OBJECT_LOCKED(self);
     _PyObject_ptr_wise_atomic_memmove(self, &self->ob_item[first],
                             &self->ob_item[first + 1], last - first);
 #else
@@ -1038,7 +1036,6 @@ list_ass_slice_lock_held(PyListObject *a, Py_ssize_t ilow, Py_ssize_t ihigh, PyO
 
     if (d < 0) { /* Delete -d items */
         Py_ssize_t tail = Py_SIZE(a) - ihigh;
-        _Py_CRITICAL_SECTION_ASSERT_OBJECT_LOCKED(a);
         _PyObject_ptr_wise_atomic_memmove(a, &item[ihigh+d], &item[ihigh], tail);
         (void)list_resize(a, Py_SIZE(a) + d); // NB: shrinking a list can't fail
         item = a->ob_item;
@@ -1048,7 +1045,6 @@ list_ass_slice_lock_held(PyListObject *a, Py_ssize_t ilow, Py_ssize_t ihigh, PyO
         if (list_resize(a, k+d) < 0)
             goto Error;
         item = a->ob_item;
-        _Py_CRITICAL_SECTION_ASSERT_OBJECT_LOCKED(a);
         _PyObject_ptr_wise_atomic_memmove(a, &item[ihigh+d], &item[ihigh], k - ihigh);
     }
     for (k = 0; k < n; k++, ilow++) {
@@ -1137,7 +1133,6 @@ list_inplace_repeat_lock_held(PyListObject *self, Py_ssize_t n)
     _Py_memory_repeat((char *)items, sizeof(PyObject *)*output_size,
                       sizeof(PyObject *)*input_size);
 #else
-    _Py_CRITICAL_SECTION_ASSERT_OBJECT_LOCKED(self);
     Py_ssize_t copied = input_size;
     while (copied < output_size) {
         Py_ssize_t items_to_copy = Py_MIN(copied, output_size - copied);
@@ -1639,7 +1634,6 @@ list_pop_impl(PyListObject *self, Py_ssize_t index)
     }
     Py_ssize_t size_after_pop = Py_SIZE(self) - 1;
     if (index < size_after_pop) {
-        _Py_CRITICAL_SECTION_ASSERT_OBJECT_LOCKED(self);
         _PyObject_ptr_wise_atomic_memmove(self, &items[index], &items[index+1],
                                     size_after_pop - index);
     }
@@ -3827,13 +3821,11 @@ list_ass_subscript_lock_held(PyObject *_self, PyObject *item, PyObject *value)
                     lim = Py_SIZE(self) - cur - 1;
                 }
 
-                _Py_CRITICAL_SECTION_ASSERT_OBJECT_LOCKED(self);
                 _PyObject_ptr_wise_atomic_memmove(self, self->ob_item + cur - i,
                     self->ob_item + cur + 1, lim);
             }
             cur = start + (size_t)slicelength * step;
             if (cur < (size_t)Py_SIZE(self)) {
-                _Py_CRITICAL_SECTION_ASSERT_OBJECT_LOCKED(self);
                 _PyObject_ptr_wise_atomic_memmove(self, self->ob_item + cur - slicelength,
                     self->ob_item + cur, Py_SIZE(self) - cur);
             }

From 4c75be205eb4ebc1474596d114113ab51eb053c2 Mon Sep 17 00:00:00 2001
From: Charlie Lin <tuug@gmx.us>
Date: Tue, 13 Oct 2026 08:48:00 -0400
Subject: [PATCH 29/33] Add assertion for object lock in memory move

---
 Include/internal/pycore_object.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/Include/internal/pycore_object.h b/Include/internal/pycore_object.h
index 984b95c4bdd5983..f92f0c409c52748 100644
--- a/Include/internal/pycore_object.h
+++ b/Include/internal/pycore_object.h
@@ -1027,6 +1027,7 @@ _PyObject_ptr_wise_atomic_memmove(PyObject *a, PyObject **dest, PyObject **src,
     (void)a;
     memmove(dest, src, n * sizeof(PyObject *));
 #else
+    _Py_CRITICAL_SECTION_ASSERT_OBJECT_LOCKED(a);
     if (_Py_IsOwnedByCurrentThread(a) && !_PyObject_GC_IS_SHARED(a)) {
         // No other threads can read this object's array concurrently
         memmove(dest, src, n * sizeof(PyObject *));

From 50fa059c54b57d2dd2332f13a912ec665a4977cf Mon Sep 17 00:00:00 2001
From: Charlie Lin <tuug@gmx.us>
Date: Tue, 13 Oct 2026 09:37:13 -0400
Subject: [PATCH 30/33] Update pycore_object.h

---
 Include/internal/pycore_object.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/Include/internal/pycore_object.h b/Include/internal/pycore_object.h
index f92f0c409c52748..a979dba51681873 100644
--- a/Include/internal/pycore_object.h
+++ b/Include/internal/pycore_object.h
@@ -8,6 +8,7 @@ extern "C" {
 #  error "this header requires Py_BUILD_CORE define"
 #endif
 
+#include "pycore_critical_section.h" // _Py_CRITICAL_SECTION_ASSERT_OBJECT_LOCKED
 #include "pycore_wasm_trampoline.h" // _PyCFunction_TrampolineCall()
 #include "pycore_gc.h"            // _PyObject_GC_TRACK()
 #include "pycore_pyatomic_ft_wrappers.h" // FT_ATOMIC_LOAD_PTR_ACQUIRE()

From 4f8427fc2e1e0ca9bab7f89acd3c4a78e4a3bca0 Mon Sep 17 00:00:00 2001
From: Charlie Lin <tuug@gmx.us>
Date: Tue, 13 Oct 2026 16:08:02 +0200
Subject: [PATCH 31/33] Unit tests for etree

---
 Lib/test/test_xml_etree_c.py | 43 ++++++++++++++++++++++++++++++++++++
 1 file changed, 43 insertions(+)

diff --git a/Lib/test/test_xml_etree_c.py b/Lib/test/test_xml_etree_c.py
index deb2bd8d572581a..58dd9cab45b1a65 100644
--- a/Lib/test/test_xml_etree_c.py
+++ b/Lib/test/test_xml_etree_c.py
@@ -2,6 +2,7 @@
 import io
 import struct
 from test import support
+from test.support import threading_helper
 from test.support.import_helper import import_fresh_module
 import types
 import unittest
@@ -193,6 +194,48 @@ def test_disallow_instantiation(self):
         support.check_disallow_instantiation(self, iter_type)
 
 
+@unittest.skipUnless(cET, 'requires _elementtree')
+@threading_helper.requires_working_threading()
+class ThreadingTests(unittest.TestCase):
+    def test_concurrent_slice_deletion(self):
+        self.check_concurrent_slice_deletion(slice(1, 65))
+
+    def test_concurrent_extended_slice_deletion(self):
+        for index in (slice(1, 65, 3), slice(64, 0, -3), slice(1, None, 3)):
+            with self.subTest(index=index):
+                self.check_concurrent_slice_deletion(index)
+
+    def check_concurrent_slice_deletion(self, index):
+        # gh-149965: Read children while slice deletion shifts the child
+        # pointers. Create the elements here so the writer does not own them.
+        roots = []
+        expected = []
+        for _ in range(100):
+            root = cET.Element('root')
+            children = [cET.SubElement(root, str(i)) for i in range(100)]
+            del children[index]
+            roots.append(root)
+            expected.append(children)
+
+        def delete():
+            for root in roots:
+                del root[index]
+
+        def read():
+            for _ in range(10):
+                for root in roots:
+                    # Each slice leaves at least two children. Their identity
+                    # can change during deletion, but they must remain valid.
+                    child = root[1]
+                    self.assertIsInstance(child, cET.Element)
+                    self.assertIn(child.tag, tags)
+
+        tags = {str(i) for i in range(100)}
+        threading_helper.run_concurrently([delete, read, read])
+        for root, children in zip(roots, expected):
+            self.assertEqual(root[:], children)
+
+
 @unittest.skipUnless(cET, 'requires _elementtree')
 class TestAliasWorking(unittest.TestCase):
     # Test that the cET alias module is alive

From 1f3422fc1c0fc7cf6f6593a5381b4756497f7bf1 Mon Sep 17 00:00:00 2001
From: Charlie Lin <tuug@gmx.us>
Date: Tue, 13 Oct 2026 10:25:22 -0400
Subject: [PATCH 32/33] Update _elementtree.c

---
 Modules/_elementtree.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/Modules/_elementtree.c b/Modules/_elementtree.c
index d2cd040ce1e30ba..b3683d7aac9b6e0 100644
--- a/Modules/_elementtree.c
+++ b/Modules/_elementtree.c
@@ -1948,7 +1948,7 @@ element_subscr(PyObject *op, PyObject *item)
 }
 
 static int
-element_ass_subscr(PyObject *op, PyObject *item, PyObject *value)
+element_ass_subscr_lock_held(PyObject *op, PyObject *item, PyObject *value)
 {
     ElementObject *self = _Element_CAST(op);
 
@@ -2138,6 +2138,15 @@ element_ass_subscr(PyObject *op, PyObject *item, PyObject *value)
     }
 }
 
+static int
+element_ass_subscr(PyObject *op, PyObject *item, PyObject *value)
+{
+    Py_BEGIN_CRITICAL_SECTION(op);
+    int res = element_ass_subscr_lock_held(op, item, value);
+    Py_END_CRITICAL_SECTION();
+    return res;
+}
+
 static PyObject*
 element_tag_getter(PyObject *op, void *closure)
 {

From 3efd47c1cfc1c791f9043ff693fb7947ccb22be0 Mon Sep 17 00:00:00 2001
From: Charlie Lin <tuug@gmx.us>
Date: Tue, 13 Oct 2026 10:31:55 -0400
Subject: [PATCH 33/33] Update _elementtree.c

---
 Modules/_elementtree.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/Modules/_elementtree.c b/Modules/_elementtree.c
index b3683d7aac9b6e0..0f79adb46472d23 100644
--- a/Modules/_elementtree.c
+++ b/Modules/_elementtree.c
@@ -2141,8 +2141,9 @@ element_ass_subscr_lock_held(PyObject *op, PyObject *item, PyObject *value)
 static int
 element_ass_subscr(PyObject *op, PyObject *item, PyObject *value)
 {
+    int res = 0;
     Py_BEGIN_CRITICAL_SECTION(op);
-    int res = element_ass_subscr_lock_held(op, item, value);
+    res = element_ass_subscr_lock_held(op, item, value);
     Py_END_CRITICAL_SECTION();
     return res;
 }