From 94472946551424b7dc77a5190e6d7f0a6b565020 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?B=C3=A9n=C3=A9dikt=20Tran?=
 <10796600+picnixz@users.noreply.github.com>
Date: Sat, 25 Jan 2025 16:05:02 +0100
Subject: [PATCH 01/10] fix UBSan failures for `PyThreadHandleObject`

---
 Modules/_threadmodule.c | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/Modules/_threadmodule.c b/Modules/_threadmodule.c
index dbc574f7816b85..0db786c310ba10 100644
--- a/Modules/_threadmodule.c
+++ b/Modules/_threadmodule.c
@@ -582,6 +582,8 @@ typedef struct {
     ThreadHandle *handle;
 } PyThreadHandleObject;
 
+#define _PyThreadHandleObject_CAST(op)  ((PyThreadHandleObject *)(op))
+
 static PyThreadHandleObject *
 PyThreadHandleObject_new(PyTypeObject *type)
 {
@@ -609,8 +611,7 @@ PyThreadHandleObject_tp_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
 }
 
 static int
-PyThreadHandleObject_traverse(PyThreadHandleObject *self, visitproc visit,
-                              void *arg)
+PyThreadHandleObject_traverse(PyObject *self, visitproc visit, void *arg)
 {
     Py_VISIT(Py_TYPE(self));
     return 0;
@@ -619,7 +620,7 @@ PyThreadHandleObject_traverse(PyThreadHandleObject *self, visitproc visit,
 static void
 PyThreadHandleObject_dealloc(PyObject *op)
 {
-    PyThreadHandleObject *self = (PyThreadHandleObject*)op;
+    PyThreadHandleObject *self = _PyThreadHandleObject_CAST(op);
     PyObject_GC_UnTrack(self);
     PyTypeObject *tp = Py_TYPE(self);
     ThreadHandle_decref(self->handle);
@@ -630,7 +631,7 @@ PyThreadHandleObject_dealloc(PyObject *op)
 static PyObject *
 PyThreadHandleObject_repr(PyObject *op)
 {
-    PyThreadHandleObject *self = (PyThreadHandleObject*)op;
+    PyThreadHandleObject *self = _PyThreadHandleObject_CAST(op);
     PyThread_ident_t ident = ThreadHandle_ident(self->handle);
     return PyUnicode_FromFormat("<%s object: ident=%" PY_FORMAT_THREAD_IDENT_T ">",
                                 Py_TYPE(self)->tp_name, ident);
@@ -639,14 +640,14 @@ PyThreadHandleObject_repr(PyObject *op)
 static PyObject *
 PyThreadHandleObject_get_ident(PyObject *op, void *Py_UNUSED(ignored))
 {
-    PyThreadHandleObject *self = (PyThreadHandleObject*)op;
+    PyThreadHandleObject *self = _PyThreadHandleObject_CAST(op);
     return PyLong_FromUnsignedLongLong(ThreadHandle_ident(self->handle));
 }
 
 static PyObject *
 PyThreadHandleObject_join(PyObject *op, PyObject *args)
 {
-    PyThreadHandleObject *self = (PyThreadHandleObject*)op;
+    PyThreadHandleObject *self = _PyThreadHandleObject_CAST(op);
 
     PyObject *timeout_obj = NULL;
     if (!PyArg_ParseTuple(args, "|O:join", &timeout_obj)) {
@@ -670,7 +671,7 @@ PyThreadHandleObject_join(PyObject *op, PyObject *args)
 static PyObject *
 PyThreadHandleObject_is_done(PyObject *op, PyObject *Py_UNUSED(ignored))
 {
-    PyThreadHandleObject *self = (PyThreadHandleObject*)op;
+    PyThreadHandleObject *self = _PyThreadHandleObject_CAST(op);
     if (_PyEvent_IsSet(&self->handle->thread_is_exiting)) {
         Py_RETURN_TRUE;
     }
@@ -682,7 +683,7 @@ PyThreadHandleObject_is_done(PyObject *op, PyObject *Py_UNUSED(ignored))
 static PyObject *
 PyThreadHandleObject_set_done(PyObject *op, PyObject *Py_UNUSED(ignored))
 {
-    PyThreadHandleObject *self = (PyThreadHandleObject*)op;
+    PyThreadHandleObject *self = _PyThreadHandleObject_CAST(op);
     if (ThreadHandle_set_done(self->handle) < 0) {
         return NULL;
     }

From 1083c461cb2b00e331dd20b7c721fc2858ea2150 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?B=C3=A9n=C3=A9dikt=20Tran?=
 <10796600+picnixz@users.noreply.github.com>
Date: Sat, 25 Jan 2025 16:08:07 +0100
Subject: [PATCH 02/10] use a macro for casts to `lockobject`

---
 Modules/_threadmodule.c | 19 ++++++++++---------
 1 file changed, 10 insertions(+), 9 deletions(-)

diff --git a/Modules/_threadmodule.c b/Modules/_threadmodule.c
index 0db786c310ba10..6f2e0a3ff774ea 100644
--- a/Modules/_threadmodule.c
+++ b/Modules/_threadmodule.c
@@ -727,6 +727,8 @@ typedef struct {
     PyMutex lock;
 } lockobject;
 
+#define _lockobject_CAST(op)    ((lockobject *)(op))
+
 static int
 lock_traverse(PyObject *self, visitproc visit, void *arg)
 {
@@ -735,13 +737,12 @@ lock_traverse(PyObject *self, visitproc visit, void *arg)
 }
 
 static void
-lock_dealloc(PyObject *op)
+lock_dealloc(PyObject *self)
 {
-    lockobject *self = (lockobject*)op;
     PyObject_GC_UnTrack(self);
-    PyObject_ClearWeakRefs((PyObject *) self);
+    PyObject_ClearWeakRefs(self);
     PyTypeObject *tp = Py_TYPE(self);
-    tp->tp_free((PyObject*)self);
+    tp->tp_free(self);
     Py_DECREF(tp);
 }
 
@@ -795,7 +796,7 @@ lock_acquire_parse_args(PyObject *args, PyObject *kwds,
 static PyObject *
 lock_PyThread_acquire_lock(PyObject *op, PyObject *args, PyObject *kwds)
 {
-    lockobject *self = (lockobject*)op;
+    lockobject *self = _lockobject_CAST(op);
 
     PyTime_t timeout;
     if (lock_acquire_parse_args(args, kwds, &timeout) < 0) {
@@ -837,7 +838,7 @@ Lock the lock.");
 static PyObject *
 lock_PyThread_release_lock(PyObject *op, PyObject *Py_UNUSED(ignored))
 {
-    lockobject *self = (lockobject*)op;
+    lockobject *self = _lockobject_CAST(op);
     /* Sanity check: the lock must be locked */
     if (_PyMutex_TryUnlock(&self->lock) < 0) {
         PyErr_SetString(ThreadError, "release unlocked lock");
@@ -870,7 +871,7 @@ Release the lock.");
 static PyObject *
 lock_locked_lock(PyObject *op, PyObject *Py_UNUSED(ignored))
 {
-    lockobject *self = (lockobject*)op;
+    lockobject *self = _lockobject_CAST(op);
     return PyBool_FromLong(PyMutex_IsLocked(&self->lock));
 }
 
@@ -889,7 +890,7 @@ An obsolete synonym of locked().");
 static PyObject *
 lock_repr(PyObject *op)
 {
-    lockobject *self = (lockobject*)op;
+    lockobject *self = _lockobject_CAST(op);
     return PyUnicode_FromFormat("<%s %s object at %p>",
         PyMutex_IsLocked(&self->lock) ? "locked" : "unlocked", Py_TYPE(self)->tp_name, self);
 }
@@ -898,7 +899,7 @@ lock_repr(PyObject *op)
 static PyObject *
 lock__at_fork_reinit(PyObject *op, PyObject *Py_UNUSED(args))
 {
-    lockobject *self = (lockobject *)op;
+    lockobject *self = _lockobject_CAST(op);
     _PyMutex_at_fork_reinit(&self->lock);
     Py_RETURN_NONE;
 }

From d7a39aea69ec950ade1332dd52426c43e862df3a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?B=C3=A9n=C3=A9dikt=20Tran?=
 <10796600+picnixz@users.noreply.github.com>
Date: Sat, 25 Jan 2025 16:10:14 +0100
Subject: [PATCH 03/10] fix UBSan failures for `rlockobject`

---
 Modules/_threadmodule.c | 29 +++++++++++++++--------------
 1 file changed, 15 insertions(+), 14 deletions(-)

diff --git a/Modules/_threadmodule.c b/Modules/_threadmodule.c
index 6f2e0a3ff774ea..fd81894f6971e3 100644
--- a/Modules/_threadmodule.c
+++ b/Modules/_threadmodule.c
@@ -991,8 +991,10 @@ typedef struct {
     _PyRecursiveMutex lock;
 } rlockobject;
 
+#define _rlockobject_CAST(op)   ((rlockobject *)(op))
+
 static int
-rlock_traverse(rlockobject *self, visitproc visit, void *arg)
+rlock_traverse(PyObject *self, visitproc visit, void *arg)
 {
     Py_VISIT(Py_TYPE(self));
     return 0;
@@ -1000,11 +1002,10 @@ rlock_traverse(rlockobject *self, visitproc visit, void *arg)
 
 
 static void
-rlock_dealloc(PyObject *op)
+rlock_dealloc(PyObject *self)
 {
-    rlockobject *self = (rlockobject*)op;
     PyObject_GC_UnTrack(self);
-    PyObject_ClearWeakRefs((PyObject *) self);
+    PyObject_ClearWeakRefs(self);
     PyTypeObject *tp = Py_TYPE(self);
     tp->tp_free(self);
     Py_DECREF(tp);
@@ -1014,7 +1015,7 @@ rlock_dealloc(PyObject *op)
 static PyObject *
 rlock_acquire(PyObject *op, PyObject *args, PyObject *kwds)
 {
-    rlockobject *self = (rlockobject*)op;
+    rlockobject *self = _rlockobject_CAST(op);
     PyTime_t timeout;
 
     if (lock_acquire_parse_args(args, kwds, &timeout) < 0) {
@@ -1056,8 +1057,7 @@ Lock the lock.");
 static PyObject *
 rlock_release(PyObject *op, PyObject *Py_UNUSED(ignored))
 {
-    rlockobject *self = (rlockobject*)op;
-
+    rlockobject *self = _rlockobject_CAST(op);
     if (_PyRecursiveMutex_TryUnlock(&self->lock) < 0) {
         PyErr_SetString(PyExc_RuntimeError,
                         "cannot release un-acquired lock");
@@ -1088,7 +1088,7 @@ Release the lock.");
 static PyObject *
 rlock_acquire_restore(PyObject *op, PyObject *args)
 {
-    rlockobject *self = (rlockobject*)op;
+    rlockobject *self = _rlockobject_CAST(op);
     PyThread_ident_t owner;
     Py_ssize_t count;
 
@@ -1111,7 +1111,7 @@ For internal use by `threading.Condition`.");
 static PyObject *
 rlock_release_save(PyObject *op, PyObject *Py_UNUSED(ignored))
 {
-    rlockobject *self = (rlockobject*)op;
+    rlockobject *self = _rlockobject_CAST(op);
 
     if (!_PyRecursiveMutex_IsLockedByCurrentThread(&self->lock)) {
         PyErr_SetString(PyExc_RuntimeError,
@@ -1135,7 +1135,7 @@ For internal use by `threading.Condition`.");
 static PyObject *
 rlock_recursion_count(PyObject *op, PyObject *Py_UNUSED(ignored))
 {
-    rlockobject *self = (rlockobject*)op;
+    rlockobject *self = _rlockobject_CAST(op);
     if (_PyRecursiveMutex_IsLockedByCurrentThread(&self->lock)) {
         return PyLong_FromSize_t(self->lock.level + 1);
     }
@@ -1151,7 +1151,7 @@ For internal use by reentrancy checks.");
 static PyObject *
 rlock_is_owned(PyObject *op, PyObject *Py_UNUSED(ignored))
 {
-    rlockobject *self = (rlockobject*)op;
+    rlockobject *self = _rlockobject_CAST(op);
     long owned = _PyRecursiveMutex_IsLockedByCurrentThread(&self->lock);
     return PyBool_FromLong(owned);
 }
@@ -1176,7 +1176,7 @@ rlock_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
 static PyObject *
 rlock_repr(PyObject *op)
 {
-    rlockobject *self = (rlockobject*)op;
+    rlockobject *self = _rlockobject_CAST(op);
     PyThread_ident_t owner = self->lock.thread;
     size_t count = self->lock.level + 1;
     return PyUnicode_FromFormat(
@@ -1189,8 +1189,9 @@ rlock_repr(PyObject *op)
 
 #ifdef HAVE_FORK
 static PyObject *
-rlock__at_fork_reinit(rlockobject *self, PyObject *Py_UNUSED(args))
+rlock__at_fork_reinit(PyObject *op, PyObject *Py_UNUSED(args))
 {
+    rlockobject *self = _rlockobject_CAST(op);
     self->lock = (_PyRecursiveMutex){0};
     Py_RETURN_NONE;
 }
@@ -1215,7 +1216,7 @@ static PyMethodDef rlock_methods[] = {
     {"__exit__",    rlock_release,
      METH_VARARGS, rlock_exit_doc},
 #ifdef HAVE_FORK
-    {"_at_fork_reinit",    (PyCFunction)rlock__at_fork_reinit,
+    {"_at_fork_reinit", rlock__at_fork_reinit,
      METH_NOARGS, NULL},
 #endif
     {NULL,           NULL}              /* sentinel */

From 557dbd002bd5a2fe1d27a5728291ae0e5cef0b9c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?B=C3=A9n=C3=A9dikt=20Tran?=
 <10796600+picnixz@users.noreply.github.com>
Date: Sat, 25 Jan 2025 16:11:09 +0100
Subject: [PATCH 04/10] fix UBSan failures for `localdummyobject`

---
 Modules/_threadmodule.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/Modules/_threadmodule.c b/Modules/_threadmodule.c
index fd81894f6971e3..728e675dfdb1c8 100644
--- a/Modules/_threadmodule.c
+++ b/Modules/_threadmodule.c
@@ -1313,14 +1313,17 @@ typedef struct {
     PyObject *weakreflist;      /* List of weak references to self */
 } localdummyobject;
 
+#define _localdummyobject_CAST(op)  ((localdummyobject *)(op))
+
 static void
 localdummy_dealloc(PyObject *op)
 {
-    localdummyobject *self = (localdummyobject*)op;
-    if (self->weakreflist != NULL)
-        PyObject_ClearWeakRefs((PyObject *) self);
+    localdummyobject *self = _localdummyobject_CAST(op);
+    if (self->weakreflist != NULL) {
+        PyObject_ClearWeakRefs(op);
+    }
     PyTypeObject *tp = Py_TYPE(self);
-    tp->tp_free((PyObject*)self);
+    tp->tp_free(self);
     Py_DECREF(tp);
 }
 

From a96a296863e74c4500d19817034d8369cc6a133f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?B=C3=A9n=C3=A9dikt=20Tran?=
 <10796600+picnixz@users.noreply.github.com>
Date: Sat, 25 Jan 2025 16:16:53 +0100
Subject: [PATCH 05/10] fix UBSan failures for `localobject`

---
 Modules/_threadmodule.c | 49 +++++++++++++++++++++--------------------
 1 file changed, 25 insertions(+), 24 deletions(-)

diff --git a/Modules/_threadmodule.c b/Modules/_threadmodule.c
index 728e675dfdb1c8..64bbc9308eccaf 100644
--- a/Modules/_threadmodule.c
+++ b/Modules/_threadmodule.c
@@ -1359,6 +1359,8 @@ typedef struct {
     PyObject *thread_watchdogs;
 } localobject;
 
+#define _localobject_CAST(op)   ((localobject *)(op))
+
 /* Forward declaration */
 static int create_localsdict(localobject *self, thread_module_state *state,
                              PyObject **localsdict, PyObject **sentinel_wr);
@@ -1369,7 +1371,7 @@ static PyObject *
 create_sentinel_wr(localobject *self)
 {
     static PyMethodDef wr_callback_def = {
-        "clear_locals", (PyCFunction) clear_locals, METH_O
+        "clear_locals", clear_locals, METH_O
     };
 
     PyThreadState *tstate = PyThreadState_Get();
@@ -1461,8 +1463,9 @@ local_new(PyTypeObject *type, PyObject *args, PyObject *kw)
 }
 
 static int
-local_traverse(localobject *self, visitproc visit, void *arg)
+local_traverse(PyObject *op, visitproc visit, void *arg)
 {
+    localobject *self = _localobject_CAST(op);
     Py_VISIT(Py_TYPE(self));
     Py_VISIT(self->args);
     Py_VISIT(self->kw);
@@ -1472,8 +1475,9 @@ local_traverse(localobject *self, visitproc visit, void *arg)
 }
 
 static int
-local_clear(localobject *self)
+local_clear(PyObject *op)
 {
+    localobject *self = _localobject_CAST(op);
     Py_CLEAR(self->args);
     Py_CLEAR(self->kw);
     Py_CLEAR(self->localdicts);
@@ -1482,20 +1486,18 @@ local_clear(localobject *self)
 }
 
 static void
-local_dealloc(localobject *self)
+local_dealloc(PyObject *op)
 {
+    localobject *self = _localobject_CAST(op);
     /* Weakrefs must be invalidated right now, otherwise they can be used
        from code called below, which is very dangerous since Py_REFCNT(self) == 0 */
     if (self->weakreflist != NULL) {
-        PyObject_ClearWeakRefs((PyObject *) self);
+        PyObject_ClearWeakRefs(op);
     }
-
     PyObject_GC_UnTrack(self);
-
-    local_clear(self);
-
+    (void)local_clear(op);
     PyTypeObject *tp = Py_TYPE(self);
-    tp->tp_free((PyObject*)self);
+    tp->tp_free(self);
     Py_DECREF(tp);
 }
 
@@ -1634,8 +1636,9 @@ _ldict(localobject *self, thread_module_state *state)
 }
 
 static int
-local_setattro(localobject *self, PyObject *name, PyObject *v)
+local_setattro(PyObject *op, PyObject *name, PyObject *v)
 {
+    localobject *self = _localobject_CAST(op);
     PyObject *module = PyType_GetModuleByDef(Py_TYPE(self), &thread_module);
     assert(module != NULL);
     thread_module_state *state = get_thread_state(module);
@@ -1656,8 +1659,7 @@ local_setattro(localobject *self, PyObject *name, PyObject *v)
         goto err;
     }
 
-    int st =
-        _PyObject_GenericSetAttrWithDict((PyObject *)self, name, v, ldict);
+    int st = _PyObject_GenericSetAttrWithDict(op, name, v, ldict);
     Py_DECREF(ldict);
     return st;
 
@@ -1666,7 +1668,7 @@ local_setattro(localobject *self, PyObject *name, PyObject *v)
     return -1;
 }
 
-static PyObject *local_getattro(localobject *, PyObject *);
+static PyObject *local_getattro(PyObject *, PyObject *);
 
 static PyMemberDef local_type_members[] = {
     {"__weaklistoffset__", Py_T_PYSSIZET, offsetof(localobject, weakreflist), Py_READONLY},
@@ -1674,12 +1676,12 @@ static PyMemberDef local_type_members[] = {
 };
 
 static PyType_Slot local_type_slots[] = {
-    {Py_tp_dealloc, (destructor)local_dealloc},
-    {Py_tp_getattro, (getattrofunc)local_getattro},
-    {Py_tp_setattro, (setattrofunc)local_setattro},
+    {Py_tp_dealloc, local_dealloc},
+    {Py_tp_getattro, local_getattro},
+    {Py_tp_setattro, local_setattro},
     {Py_tp_doc, "_local()\n--\n\nThread-local data"},
-    {Py_tp_traverse, (traverseproc)local_traverse},
-    {Py_tp_clear, (inquiry)local_clear},
+    {Py_tp_traverse, local_traverse},
+    {Py_tp_clear, local_clear},
     {Py_tp_new, local_new},
     {Py_tp_members, local_type_members},
     {0, 0}
@@ -1694,8 +1696,9 @@ static PyType_Spec local_type_spec = {
 };
 
 static PyObject *
-local_getattro(localobject *self, PyObject *name)
+local_getattro(PyObject *op, PyObject *name)
 {
+    localobject *self = _localobject_CAST(op);
     PyObject *module = PyType_GetModuleByDef(Py_TYPE(self), &thread_module);
     assert(module != NULL);
     thread_module_state *state = get_thread_state(module);
@@ -1715,8 +1718,7 @@ local_getattro(localobject *self, PyObject *name)
 
     if (!Py_IS_TYPE(self, state->local_type)) {
         /* use generic lookup for subtypes */
-        PyObject *res =
-            _PyObject_GenericGetAttrWithDict((PyObject *)self, name, ldict, 0);
+        PyObject *res = _PyObject_GenericGetAttrWithDict(op, name, ldict, 0);
         Py_DECREF(ldict);
         return res;
     }
@@ -1730,8 +1732,7 @@ local_getattro(localobject *self, PyObject *name)
     }
 
     /* Fall back on generic to get __class__ and __dict__ */
-    PyObject *res =
-        _PyObject_GenericGetAttrWithDict((PyObject *)self, name, ldict, 0);
+    PyObject *res = _PyObject_GenericGetAttrWithDict(op, name, ldict, 0);
     Py_DECREF(ldict);
     return res;
 }

From 339a4164cf9940c01e72d0efb5996d55eb388875 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?B=C3=A9n=C3=A9dikt=20Tran?=
 <10796600+picnixz@users.noreply.github.com>
Date: Sat, 25 Jan 2025 16:17:15 +0100
Subject: [PATCH 06/10] add safe casts

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

diff --git a/Modules/_threadmodule.c b/Modules/_threadmodule.c
index 64bbc9308eccaf..3511f19432ad8e 100644
--- a/Modules/_threadmodule.c
+++ b/Modules/_threadmodule.c
@@ -1743,7 +1743,7 @@ static PyObject *
 clear_locals(PyObject *locals_and_key, PyObject *dummyweakref)
 {
     PyObject *localweakref = PyTuple_GetItem(locals_and_key, 0);
-    localobject *self = (localobject *)_PyWeakref_GET_REF(localweakref);
+    localobject *self = _localobject_CAST(_PyWeakref_GET_REF(localweakref));
     if (self == NULL) {
         Py_RETURN_NONE;
     }

From 17ba46108afccfd7a154fe13e74f92ed608895d6 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?B=C3=A9n=C3=A9dikt=20Tran?=
 <10796600+picnixz@users.noreply.github.com>
Date: Sat, 25 Jan 2025 16:18:50 +0100
Subject: [PATCH 07/10] cleanup module functions

---
 Modules/_threadmodule.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/Modules/_threadmodule.c b/Modules/_threadmodule.c
index 3511f19432ad8e..ef377d8f0df972 100644
--- a/Modules/_threadmodule.c
+++ b/Modules/_threadmodule.c
@@ -2521,13 +2521,13 @@ _thread_set_name_impl(PyObject *module, PyObject *name_obj)
 
 
 static PyMethodDef thread_methods[] = {
-    {"start_new_thread",        (PyCFunction)thread_PyThread_start_new_thread,
+    {"start_new_thread",        thread_PyThread_start_new_thread,
      METH_VARARGS, start_new_thread_doc},
-    {"start_new",               (PyCFunction)thread_PyThread_start_new_thread,
+    {"start_new",               thread_PyThread_start_new_thread,
      METH_VARARGS, start_new_doc},
     {"start_joinable_thread",   _PyCFunction_CAST(thread_PyThread_start_joinable_thread),
      METH_VARARGS | METH_KEYWORDS, start_joinable_doc},
-    {"daemon_threads_allowed",  (PyCFunction)thread_daemon_threads_allowed,
+    {"daemon_threads_allowed",  thread_daemon_threads_allowed,
      METH_NOARGS, daemon_threads_allowed_doc},
     {"allocate_lock",           thread_PyThread_allocate_lock,
      METH_NOARGS, allocate_lock_doc},
@@ -2537,7 +2537,7 @@ static PyMethodDef thread_methods[] = {
      METH_NOARGS, exit_thread_doc},
     {"exit",                    thread_PyThread_exit_thread,
      METH_NOARGS, exit_doc},
-    {"interrupt_main",          (PyCFunction)thread_PyThread_interrupt_main,
+    {"interrupt_main",          thread_PyThread_interrupt_main,
      METH_VARARGS, interrupt_doc},
     {"get_ident",               thread_get_ident,
      METH_NOARGS, get_ident_doc},
@@ -2547,7 +2547,7 @@ static PyMethodDef thread_methods[] = {
 #endif
     {"_count",                  thread__count,
      METH_NOARGS, _count_doc},
-    {"stack_size",              (PyCFunction)thread_stack_size,
+    {"stack_size",              thread_stack_size,
      METH_VARARGS, stack_size_doc},
     {"_excepthook",             thread_excepthook,
      METH_O, excepthook_doc},
@@ -2719,7 +2719,7 @@ thread_module_clear(PyObject *module)
 static void
 thread_module_free(void *module)
 {
-    thread_module_clear((PyObject *)module);
+    (void)thread_module_clear((PyObject *)module);
 }
 
 

From 4b3e706dc0cff7f4d1597986898183a5741f8cad Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?B=C3=A9n=C3=A9dikt=20Tran?=
 <10796600+picnixz@users.noreply.github.com>
Date: Thu, 6 Feb 2025 18:04:42 +0100
Subject: [PATCH 08/10] use semantically correct parameter names

---
 Modules/_threadmodule.c | 22 +++++++++++-----------
 1 file changed, 11 insertions(+), 11 deletions(-)

diff --git a/Modules/_threadmodule.c b/Modules/_threadmodule.c
index ef377d8f0df972..e45789435576ba 100644
--- a/Modules/_threadmodule.c
+++ b/Modules/_threadmodule.c
@@ -638,7 +638,7 @@ PyThreadHandleObject_repr(PyObject *op)
 }
 
 static PyObject *
-PyThreadHandleObject_get_ident(PyObject *op, void *Py_UNUSED(ignored))
+PyThreadHandleObject_get_ident(PyObject *op, void *Py_UNUSED(closure))
 {
     PyThreadHandleObject *self = _PyThreadHandleObject_CAST(op);
     return PyLong_FromUnsignedLongLong(ThreadHandle_ident(self->handle));
@@ -669,7 +669,7 @@ PyThreadHandleObject_join(PyObject *op, PyObject *args)
 }
 
 static PyObject *
-PyThreadHandleObject_is_done(PyObject *op, PyObject *Py_UNUSED(ignored))
+PyThreadHandleObject_is_done(PyObject *op, PyObject *Py_UNUSED(dummy))
 {
     PyThreadHandleObject *self = _PyThreadHandleObject_CAST(op);
     if (_PyEvent_IsSet(&self->handle->thread_is_exiting)) {
@@ -681,7 +681,7 @@ PyThreadHandleObject_is_done(PyObject *op, PyObject *Py_UNUSED(ignored))
 }
 
 static PyObject *
-PyThreadHandleObject_set_done(PyObject *op, PyObject *Py_UNUSED(ignored))
+PyThreadHandleObject_set_done(PyObject *op, PyObject *Py_UNUSED(dummy))
 {
     PyThreadHandleObject *self = _PyThreadHandleObject_CAST(op);
     if (ThreadHandle_set_done(self->handle) < 0) {
@@ -836,7 +836,7 @@ PyDoc_STRVAR(enter_doc,
 Lock the lock.");
 
 static PyObject *
-lock_PyThread_release_lock(PyObject *op, PyObject *Py_UNUSED(ignored))
+lock_PyThread_release_lock(PyObject *op, PyObject *Py_UNUSED(dummy))
 {
     lockobject *self = _lockobject_CAST(op);
     /* Sanity check: the lock must be locked */
@@ -869,7 +869,7 @@ PyDoc_STRVAR(lock_exit_doc,
 Release the lock.");
 
 static PyObject *
-lock_locked_lock(PyObject *op, PyObject *Py_UNUSED(ignored))
+lock_locked_lock(PyObject *op, PyObject *Py_UNUSED(dummy))
 {
     lockobject *self = _lockobject_CAST(op);
     return PyBool_FromLong(PyMutex_IsLocked(&self->lock));
@@ -897,7 +897,7 @@ lock_repr(PyObject *op)
 
 #ifdef HAVE_FORK
 static PyObject *
-lock__at_fork_reinit(PyObject *op, PyObject *Py_UNUSED(args))
+lock__at_fork_reinit(PyObject *op, PyObject *Py_UNUSED(dummy))
 {
     lockobject *self = _lockobject_CAST(op);
     _PyMutex_at_fork_reinit(&self->lock);
@@ -1055,7 +1055,7 @@ PyDoc_STRVAR(rlock_enter_doc,
 Lock the lock.");
 
 static PyObject *
-rlock_release(PyObject *op, PyObject *Py_UNUSED(ignored))
+rlock_release(PyObject *op, PyObject *Py_UNUSED(dummy))
 {
     rlockobject *self = _rlockobject_CAST(op);
     if (_PyRecursiveMutex_TryUnlock(&self->lock) < 0) {
@@ -1109,7 +1109,7 @@ PyDoc_STRVAR(rlock_acquire_restore_doc,
 For internal use by `threading.Condition`.");
 
 static PyObject *
-rlock_release_save(PyObject *op, PyObject *Py_UNUSED(ignored))
+rlock_release_save(PyObject *op, PyObject *Py_UNUSED(dummy))
 {
     rlockobject *self = _rlockobject_CAST(op);
 
@@ -1133,7 +1133,7 @@ PyDoc_STRVAR(rlock_release_save_doc,
 For internal use by `threading.Condition`.");
 
 static PyObject *
-rlock_recursion_count(PyObject *op, PyObject *Py_UNUSED(ignored))
+rlock_recursion_count(PyObject *op, PyObject *Py_UNUSED(dummy))
 {
     rlockobject *self = _rlockobject_CAST(op);
     if (_PyRecursiveMutex_IsLockedByCurrentThread(&self->lock)) {
@@ -1149,7 +1149,7 @@ PyDoc_STRVAR(rlock_recursion_count_doc,
 For internal use by reentrancy checks.");
 
 static PyObject *
-rlock_is_owned(PyObject *op, PyObject *Py_UNUSED(ignored))
+rlock_is_owned(PyObject *op, PyObject *Py_UNUSED(dummy))
 {
     rlockobject *self = _rlockobject_CAST(op);
     long owned = _PyRecursiveMutex_IsLockedByCurrentThread(&self->lock);
@@ -1189,7 +1189,7 @@ rlock_repr(PyObject *op)
 
 #ifdef HAVE_FORK
 static PyObject *
-rlock__at_fork_reinit(PyObject *op, PyObject *Py_UNUSED(args))
+rlock__at_fork_reinit(PyObject *op, PyObject *Py_UNUSED(dummy))
 {
     rlockobject *self = _rlockobject_CAST(op);
     self->lock = (_PyRecursiveMutex){0};

From 7a5ed410e0c27c3868d550f7662fa0d2c03cb3a0 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?B=C3=A9n=C3=A9dikt=20Tran?=
 <10796600+picnixz@users.noreply.github.com>
Date: Sat, 8 Feb 2025 10:18:03 +0100
Subject: [PATCH 09/10] Do Do not use `_` + capital letter in new code as it is
 also UB.

---
 Modules/_threadmodule.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/Modules/_threadmodule.c b/Modules/_threadmodule.c
index 1b32277ebf09ad..bd16cccdc7d622 100644
--- a/Modules/_threadmodule.c
+++ b/Modules/_threadmodule.c
@@ -582,7 +582,7 @@ typedef struct {
     ThreadHandle *handle;
 } PyThreadHandleObject;
 
-#define _PyThreadHandleObject_CAST(op)  ((PyThreadHandleObject *)(op))
+#define PyThreadHandleObject_CAST(op)   ((PyThreadHandleObject *)(op))
 
 static PyThreadHandleObject *
 PyThreadHandleObject_new(PyTypeObject *type)
@@ -620,7 +620,7 @@ PyThreadHandleObject_traverse(PyObject *self, visitproc visit, void *arg)
 static void
 PyThreadHandleObject_dealloc(PyObject *op)
 {
-    PyThreadHandleObject *self = _PyThreadHandleObject_CAST(op);
+    PyThreadHandleObject *self = PyThreadHandleObject_CAST(op);
     PyObject_GC_UnTrack(self);
     PyTypeObject *tp = Py_TYPE(self);
     ThreadHandle_decref(self->handle);
@@ -631,7 +631,7 @@ PyThreadHandleObject_dealloc(PyObject *op)
 static PyObject *
 PyThreadHandleObject_repr(PyObject *op)
 {
-    PyThreadHandleObject *self = _PyThreadHandleObject_CAST(op);
+    PyThreadHandleObject *self = PyThreadHandleObject_CAST(op);
     PyThread_ident_t ident = ThreadHandle_ident(self->handle);
     return PyUnicode_FromFormat("<%s object: ident=%" PY_FORMAT_THREAD_IDENT_T ">",
                                 Py_TYPE(self)->tp_name, ident);
@@ -640,14 +640,14 @@ PyThreadHandleObject_repr(PyObject *op)
 static PyObject *
 PyThreadHandleObject_get_ident(PyObject *op, void *Py_UNUSED(closure))
 {
-    PyThreadHandleObject *self = _PyThreadHandleObject_CAST(op);
+    PyThreadHandleObject *self = PyThreadHandleObject_CAST(op);
     return PyLong_FromUnsignedLongLong(ThreadHandle_ident(self->handle));
 }
 
 static PyObject *
 PyThreadHandleObject_join(PyObject *op, PyObject *args)
 {
-    PyThreadHandleObject *self = _PyThreadHandleObject_CAST(op);
+    PyThreadHandleObject *self = PyThreadHandleObject_CAST(op);
 
     PyObject *timeout_obj = NULL;
     if (!PyArg_ParseTuple(args, "|O:join", &timeout_obj)) {
@@ -671,7 +671,7 @@ PyThreadHandleObject_join(PyObject *op, PyObject *args)
 static PyObject *
 PyThreadHandleObject_is_done(PyObject *op, PyObject *Py_UNUSED(dummy))
 {
-    PyThreadHandleObject *self = _PyThreadHandleObject_CAST(op);
+    PyThreadHandleObject *self = PyThreadHandleObject_CAST(op);
     if (_PyEvent_IsSet(&self->handle->thread_is_exiting)) {
         Py_RETURN_TRUE;
     }
@@ -683,7 +683,7 @@ PyThreadHandleObject_is_done(PyObject *op, PyObject *Py_UNUSED(dummy))
 static PyObject *
 PyThreadHandleObject_set_done(PyObject *op, PyObject *Py_UNUSED(dummy))
 {
-    PyThreadHandleObject *self = _PyThreadHandleObject_CAST(op);
+    PyThreadHandleObject *self = PyThreadHandleObject_CAST(op);
     if (ThreadHandle_set_done(self->handle) < 0) {
         return NULL;
     }

From ce0eb112f17d5678ca1e5a8347a6b3696fb94e43 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?B=C3=A9n=C3=A9dikt=20Tran?=
 <10796600+picnixz@users.noreply.github.com>
Date: Sat, 8 Feb 2025 10:18:39 +0100
Subject: [PATCH 10/10] Do not add an underscore to the macro if none is
 needed.

---
 Modules/_threadmodule.c | 48 ++++++++++++++++++++---------------------
 1 file changed, 24 insertions(+), 24 deletions(-)

diff --git a/Modules/_threadmodule.c b/Modules/_threadmodule.c
index bd16cccdc7d622..eb06d711057ea0 100644
--- a/Modules/_threadmodule.c
+++ b/Modules/_threadmodule.c
@@ -727,7 +727,7 @@ typedef struct {
     PyMutex lock;
 } lockobject;
 
-#define _lockobject_CAST(op)    ((lockobject *)(op))
+#define lockobject_CAST(op) ((lockobject *)(op))
 
 static int
 lock_traverse(PyObject *self, visitproc visit, void *arg)
@@ -796,7 +796,7 @@ lock_acquire_parse_args(PyObject *args, PyObject *kwds,
 static PyObject *
 lock_PyThread_acquire_lock(PyObject *op, PyObject *args, PyObject *kwds)
 {
-    lockobject *self = _lockobject_CAST(op);
+    lockobject *self = lockobject_CAST(op);
 
     PyTime_t timeout;
     if (lock_acquire_parse_args(args, kwds, &timeout) < 0) {
@@ -838,7 +838,7 @@ Lock the lock.");
 static PyObject *
 lock_PyThread_release_lock(PyObject *op, PyObject *Py_UNUSED(dummy))
 {
-    lockobject *self = _lockobject_CAST(op);
+    lockobject *self = lockobject_CAST(op);
     /* Sanity check: the lock must be locked */
     if (_PyMutex_TryUnlock(&self->lock) < 0) {
         PyErr_SetString(ThreadError, "release unlocked lock");
@@ -871,7 +871,7 @@ Release the lock.");
 static PyObject *
 lock_locked_lock(PyObject *op, PyObject *Py_UNUSED(dummy))
 {
-    lockobject *self = _lockobject_CAST(op);
+    lockobject *self = lockobject_CAST(op);
     return PyBool_FromLong(PyMutex_IsLocked(&self->lock));
 }
 
@@ -890,7 +890,7 @@ An obsolete synonym of locked().");
 static PyObject *
 lock_repr(PyObject *op)
 {
-    lockobject *self = _lockobject_CAST(op);
+    lockobject *self = lockobject_CAST(op);
     return PyUnicode_FromFormat("<%s %s object at %p>",
         PyMutex_IsLocked(&self->lock) ? "locked" : "unlocked", Py_TYPE(self)->tp_name, self);
 }
@@ -899,7 +899,7 @@ lock_repr(PyObject *op)
 static PyObject *
 lock__at_fork_reinit(PyObject *op, PyObject *Py_UNUSED(dummy))
 {
-    lockobject *self = _lockobject_CAST(op);
+    lockobject *self = lockobject_CAST(op);
     _PyMutex_at_fork_reinit(&self->lock);
     Py_RETURN_NONE;
 }
@@ -991,7 +991,7 @@ typedef struct {
     _PyRecursiveMutex lock;
 } rlockobject;
 
-#define _rlockobject_CAST(op)   ((rlockobject *)(op))
+#define rlockobject_CAST(op)    ((rlockobject *)(op))
 
 static int
 rlock_traverse(PyObject *self, visitproc visit, void *arg)
@@ -1015,7 +1015,7 @@ rlock_dealloc(PyObject *self)
 static PyObject *
 rlock_acquire(PyObject *op, PyObject *args, PyObject *kwds)
 {
-    rlockobject *self = _rlockobject_CAST(op);
+    rlockobject *self = rlockobject_CAST(op);
     PyTime_t timeout;
 
     if (lock_acquire_parse_args(args, kwds, &timeout) < 0) {
@@ -1057,7 +1057,7 @@ Lock the lock.");
 static PyObject *
 rlock_release(PyObject *op, PyObject *Py_UNUSED(dummy))
 {
-    rlockobject *self = _rlockobject_CAST(op);
+    rlockobject *self = rlockobject_CAST(op);
     if (_PyRecursiveMutex_TryUnlock(&self->lock) < 0) {
         PyErr_SetString(PyExc_RuntimeError,
                         "cannot release un-acquired lock");
@@ -1088,7 +1088,7 @@ Release the lock.");
 static PyObject *
 rlock_acquire_restore(PyObject *op, PyObject *args)
 {
-    rlockobject *self = _rlockobject_CAST(op);
+    rlockobject *self = rlockobject_CAST(op);
     PyThread_ident_t owner;
     Py_ssize_t count;
 
@@ -1111,7 +1111,7 @@ For internal use by `threading.Condition`.");
 static PyObject *
 rlock_release_save(PyObject *op, PyObject *Py_UNUSED(dummy))
 {
-    rlockobject *self = _rlockobject_CAST(op);
+    rlockobject *self = rlockobject_CAST(op);
 
     if (!_PyRecursiveMutex_IsLockedByCurrentThread(&self->lock)) {
         PyErr_SetString(PyExc_RuntimeError,
@@ -1135,7 +1135,7 @@ For internal use by `threading.Condition`.");
 static PyObject *
 rlock_recursion_count(PyObject *op, PyObject *Py_UNUSED(dummy))
 {
-    rlockobject *self = _rlockobject_CAST(op);
+    rlockobject *self = rlockobject_CAST(op);
     if (_PyRecursiveMutex_IsLockedByCurrentThread(&self->lock)) {
         return PyLong_FromSize_t(self->lock.level + 1);
     }
@@ -1151,7 +1151,7 @@ For internal use by reentrancy checks.");
 static PyObject *
 rlock_is_owned(PyObject *op, PyObject *Py_UNUSED(dummy))
 {
-    rlockobject *self = _rlockobject_CAST(op);
+    rlockobject *self = rlockobject_CAST(op);
     long owned = _PyRecursiveMutex_IsLockedByCurrentThread(&self->lock);
     return PyBool_FromLong(owned);
 }
@@ -1176,7 +1176,7 @@ rlock_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
 static PyObject *
 rlock_repr(PyObject *op)
 {
-    rlockobject *self = _rlockobject_CAST(op);
+    rlockobject *self = rlockobject_CAST(op);
     PyThread_ident_t owner = self->lock.thread;
     size_t count = self->lock.level + 1;
     return PyUnicode_FromFormat(
@@ -1191,7 +1191,7 @@ rlock_repr(PyObject *op)
 static PyObject *
 rlock__at_fork_reinit(PyObject *op, PyObject *Py_UNUSED(dummy))
 {
-    rlockobject *self = _rlockobject_CAST(op);
+    rlockobject *self = rlockobject_CAST(op);
     self->lock = (_PyRecursiveMutex){0};
     Py_RETURN_NONE;
 }
@@ -1313,12 +1313,12 @@ typedef struct {
     PyObject *weakreflist;      /* List of weak references to self */
 } localdummyobject;
 
-#define _localdummyobject_CAST(op)  ((localdummyobject *)(op))
+#define localdummyobject_CAST(op)   ((localdummyobject *)(op))
 
 static void
 localdummy_dealloc(PyObject *op)
 {
-    localdummyobject *self = _localdummyobject_CAST(op);
+    localdummyobject *self = localdummyobject_CAST(op);
     if (self->weakreflist != NULL) {
         PyObject_ClearWeakRefs(op);
     }
@@ -1359,7 +1359,7 @@ typedef struct {
     PyObject *thread_watchdogs;
 } localobject;
 
-#define _localobject_CAST(op)   ((localobject *)(op))
+#define localobject_CAST(op)    ((localobject *)(op))
 
 /* Forward declaration */
 static int create_localsdict(localobject *self, thread_module_state *state,
@@ -1465,7 +1465,7 @@ local_new(PyTypeObject *type, PyObject *args, PyObject *kw)
 static int
 local_traverse(PyObject *op, visitproc visit, void *arg)
 {
-    localobject *self = _localobject_CAST(op);
+    localobject *self = localobject_CAST(op);
     Py_VISIT(Py_TYPE(self));
     Py_VISIT(self->args);
     Py_VISIT(self->kw);
@@ -1477,7 +1477,7 @@ local_traverse(PyObject *op, visitproc visit, void *arg)
 static int
 local_clear(PyObject *op)
 {
-    localobject *self = _localobject_CAST(op);
+    localobject *self = localobject_CAST(op);
     Py_CLEAR(self->args);
     Py_CLEAR(self->kw);
     Py_CLEAR(self->localdicts);
@@ -1488,7 +1488,7 @@ local_clear(PyObject *op)
 static void
 local_dealloc(PyObject *op)
 {
-    localobject *self = _localobject_CAST(op);
+    localobject *self = localobject_CAST(op);
     /* Weakrefs must be invalidated right now, otherwise they can be used
        from code called below, which is very dangerous since Py_REFCNT(self) == 0 */
     if (self->weakreflist != NULL) {
@@ -1646,7 +1646,7 @@ _ldict(localobject *self, thread_module_state *state)
 static int
 local_setattro(PyObject *op, PyObject *name, PyObject *v)
 {
-    localobject *self = _localobject_CAST(op);
+    localobject *self = localobject_CAST(op);
     PyObject *module = PyType_GetModuleByDef(Py_TYPE(self), &thread_module);
     assert(module != NULL);
     thread_module_state *state = get_thread_state(module);
@@ -1706,7 +1706,7 @@ static PyType_Spec local_type_spec = {
 static PyObject *
 local_getattro(PyObject *op, PyObject *name)
 {
-    localobject *self = _localobject_CAST(op);
+    localobject *self = localobject_CAST(op);
     PyObject *module = PyType_GetModuleByDef(Py_TYPE(self), &thread_module);
     assert(module != NULL);
     thread_module_state *state = get_thread_state(module);
@@ -1751,7 +1751,7 @@ static PyObject *
 clear_locals(PyObject *locals_and_key, PyObject *dummyweakref)
 {
     PyObject *localweakref = PyTuple_GetItem(locals_and_key, 0);
-    localobject *self = _localobject_CAST(_PyWeakref_GET_REF(localweakref));
+    localobject *self = localobject_CAST(_PyWeakref_GET_REF(localweakref));
     if (self == NULL) {
         Py_RETURN_NONE;
     }