diff --git a/tests/100_extras2.py b/tests/100_extras2.py
new file mode 100644
index 00000000..659e03f2
--- /dev/null
+++ b/tests/100_extras2.py
@@ -0,0 +1,94 @@
+''' 
+========= src/common/algorithm.c =========
+'''
+
+# 该函数的return false没有被覆盖
+# bool c11__stable_sort(void* ptr_,
+#                       int length,
+#                       int elem_size,
+#                       int (*f_lt)(const void* a, const void* b, void* extra),
+#                       void* extra) {
+#     // merge sort
+#     char *ptr = ptr_, *tmp = PK_MALLOC(length * elem_size);
+#     for(int seg = 1; seg < length; seg *= 2) {
+#         for(char* a = ptr; a < ptr + (length - seg) * elem_size; a += 2 * seg * elem_size) {
+#             char *b = a + seg * elem_size, *a_end = b, *b_end = b + seg * elem_size;
+#             if(b_end > ptr + length * elem_size) b_end = ptr + length * elem_size;
+#             bool ok = _stable_sort_merge(a, a_end, b, b_end, tmp, elem_size, f_lt, extra);
+#             if(!ok) {
+#                 PK_FREE(tmp);
+# ---->           return false;  
+#             }
+#             memcpy(a, tmp, b_end - a);
+#         }
+#     }
+#     PK_FREE(tmp);
+#     return true;
+# }
+
+
+# 调查得知只要触发bool ok = pk_stack_binaryop(vm, __lt__, __gt__)的return false即可
+# bool pk_stack_binaryop(VM* self, py_Name op, py_Name rop) {
+#     // [a, b]
+#     py_Ref magic = py_tpfindmagic(SECOND()->type, op);
+#     if(magic) {
+#         bool ok = py_call(magic, 2, SECOND());
+# ---->   if(!ok) return false;
+#         if(self->last_retval.type != tp_NotImplementedType) return true;
+#     }
+#     // try reverse operation
+#     if(rop) {
+#         // [a, b] -> [b, a]
+#         py_TValue tmp = *TOP();
+#         *TOP() = *SECOND();
+#         *SECOND() = tmp;
+#         magic = py_tpfindmagic(SECOND()->type, rop);
+#         if(magic) {
+#             bool ok = py_call(magic, 2, SECOND());
+# ---->       if(!ok) return false;
+#             if(self->last_retval.type != tp_NotImplementedType) return true;
+#         }
+#     }
+#     // eq/ne op never fails
+#     bool res = py_isidentical(SECOND(), TOP());
+#     if(op == __eq__) {
+#         py_newbool(py_retval(), res);
+#         return true;
+#     }
+#     if(op == __ne__) {
+#         py_newbool(py_retval(), !res);
+#         return true;
+#     }
+
+#     py_Type lhs_t = rop ? TOP()->type : SECOND()->type;
+#     py_Type rhs_t = rop ? SECOND()->type : TOP()->type;
+#     return TypeError("unsupported operand type(s) for '%s': '%t' and '%t'",
+#                      pk_op2str(op),
+#                      lhs_t,
+#                      rhs_t);
+# }
+
+# 
+# 调查得知只要触发bool ok = py_call(py_tpfindmagic(SECOND()->type, __lt__/__gt__), 2, SECOND())的return false即可
+# bool py_call(py_Ref f, int argc, py_Ref argv) {
+#     if(f->type == tp_nativefunc) {
+#         return py_callcfunc(f->_cfunc, argc, argv);
+#     } else {
+#         py_push(f);
+#         py_pushnil();
+#         for(int i = 0; i < argc; i++)
+#             py_push(py_offset(argv, i));
+#         bool ok = py_vectorcall(argc, 0);
+#         return ok;
+#     }
+# }
+
+class A():
+    def __lt__(self, other:int=1):
+        return True
+
+
+try:
+    [A(), 1111].sort()
+except TypeError:
+    pass
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