bpo-43083: Fix error handling in _sqlite3 (GH-24395)

(cherry picked from commit 9073180)

Co-authored-by: Serhiy Storchaka <[email protected]>

Author: miss-islington

Modules/_sqlite/connection.c

@@ -1704,7 +1704,11 @@ pysqlite_connection_create_collation(pysqlite_Connection* self, PyObject* args)
                                   (callable != Py_None) ? callable : NULL,
                                   (callable != Py_None) ? pysqlite_collation_callback : NULL);
     if (rc != SQLITE_OK) {
-        PyDict_DelItem(self->collations, uppercase_name);
+        if (callable != Py_None) {
+            if (PyDict_DelItem(self->collations, uppercase_name) < 0) {
+                PyErr_Clear();
+            }
+        }
         _pysqlite_seterror(self->db, NULL);
         goto finally;
     }

Modules/_sqlite/cursor.c

@@ -569,11 +569,13 @@ _pysqlite_query_execute(pysqlite_Cursor* self, int multiple, PyObject* args)
         }
 
         if (!multiple) {
-            Py_DECREF(self->lastrowid);
             Py_BEGIN_ALLOW_THREADS
             lastrowid = sqlite3_last_insert_rowid(self->connection->db);
             Py_END_ALLOW_THREADS
-            self->lastrowid = PyLong_FromLongLong(lastrowid);
+            Py_SETREF(self->lastrowid, PyLong_FromLongLong(lastrowid));
+            if (self->lastrowid == NULL) {
+                goto error;
+            }
         }
 
         if (rc == SQLITE_ROW) {
@@ -802,8 +804,11 @@ PyObject* pysqlite_cursor_fetchmany(pysqlite_Cursor* self, PyObject* args, PyObj
     }
 
     while ((row = pysqlite_cursor_iternext(self))) {
-        PyList_Append(list, row);
-        Py_XDECREF(row);
+        if (PyList_Append(list, row) < 0) {
+            Py_DECREF(row);
+            break;
+        }
+        Py_DECREF(row);
 
         if (++counter == maxrows) {
             break;
@@ -829,8 +834,11 @@ PyObject* pysqlite_cursor_fetchall(pysqlite_Cursor* self, PyObject* args)
     }
 
     while ((row = pysqlite_cursor_iternext(self))) {
-        PyList_Append(list, row);
-        Py_XDECREF(row);
+        if (PyList_Append(list, row) < 0) {
+            Py_DECREF(row);
+            break;
+        }
+        Py_DECREF(row);
     }
 
     if (PyErr_Occurred()) {