gh-111178: fix UBSan failures in `Modules/_sqlite` (GH-129087)

* fix UBSan failures for `pysqlite_Blob`
* fix UBSan failures for `pysqlite_Connection`
* fix UBSan failures for `pysqlite_Cursor`
* fix UBSan failures for `pysqlite_PrepareProtocol`
* fix UBSan failures for `pysqlite_Row`
* fix UBSan failures for `pysqlite_Statement`

* suppress unused return values

1 files changed, 6 insertions, 3 deletions

diff --git a/Modules/_sqlite/statement.c b/Modules/_sqlite/statement.c
index 229bfc3b504..facced0dfbf 100644
--- a/Modules/_sqlite/statement.c
+++ b/Modules/_sqlite/statement.c
@@ -25,6 +25,8 @@
 #include "statement.h"
 #include "util.h"
 
+#define _pysqlite_Statement_CAST(op)    ((pysqlite_Statement *)(op))
+
 /* prototypes */
 static const char *lstrip_sql(const char *sql);
 
@@ -99,10 +101,11 @@ error:
 }
 
 static void
-stmt_dealloc(pysqlite_Statement *self)
+stmt_dealloc(PyObject *op)
 {
+    pysqlite_Statement *self = _pysqlite_Statement_CAST(op);
     PyTypeObject *tp = Py_TYPE(self);
-    PyObject_GC_UnTrack(self);
+    PyObject_GC_UnTrack(op);
     if (self->st) {
         Py_BEGIN_ALLOW_THREADS
         sqlite3_finalize(self->st);
@@ -114,7 +117,7 @@ stmt_dealloc(pysqlite_Statement *self)
 }
 
 static int
-stmt_traverse(pysqlite_Statement *self, visitproc visit, void *arg)
+stmt_traverse(PyObject *self, visitproc visit, void *arg)
 {
     Py_VISIT(Py_TYPE(self));
     return 0;