fix clearing of final bit

Author: kumaraditya303

Modules/_ctypes/_ctypes.c

@@ -716,7 +716,7 @@ StructUnionType_init(PyObject *self, PyObject *args, PyObject *kwds, int isStruc
         /* copy base info */
         ret = PyCStgInfo_clone(info, baseinfo);
         if (ret >= 0) {
-            assert(stginfo_get_dict_final(info) == 0);
+            stginfo_clear_dict_final_lock_held(info);
             stginfo_set_dict_final_lock_held(baseinfo);
         }
         STGINFO_UNLOCK2();

Modules/_ctypes/ctypes.h

@@ -436,6 +436,13 @@ stginfo_set_dict_final(StgInfo *info)
     STGINFO_UNLOCK();
 }
 
+static inline void
+stginfo_clear_dict_final_lock_held(StgInfo *info)
+{
+    _Py_CRITICAL_SECTION_ASSERT_MUTEX_LOCKED(&info->mutex);
+    FT_ATOMIC_STORE_INT(info->dict_final, 0);
+}
+
 extern int PyCStgInfo_clone(StgInfo *dst_info, StgInfo *src_info);
 extern void ctype_clear_stginfo(StgInfo *info);