From 6d0d8d2a04b3509d589cb18bf632278ce113cd77 Mon Sep 17 00:00:00 2001
From: flizzywine <1041958497@qq.com>
Date: Mon, 2 Apr 2018 13:12:48 +0800
Subject: [PATCH] fix a list infinite loop bug

imagine such code:
list_t ls1 = alloc_object(1);
cons(2, ls1);
these code will make an infinite loop, because NEXT(NEXT(ls1) ) == ls.
to avoid this bug, fix the alloc_object() function, add some statements.
---
 C10-Elementary-Data-Structures/exercise_code/af-obj.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/C10-Elementary-Data-Structures/exercise_code/af-obj.c b/C10-Elementary-Data-Structures/exercise_code/af-obj.c
index 9bb7f4fb..2047f0f7 100644
--- a/C10-Elementary-Data-Structures/exercise_code/af-obj.c
+++ b/C10-Elementary-Data-Structures/exercise_code/af-obj.c
@@ -31,6 +31,8 @@ list_t allocate_object() {
     
     list_t new = free_list;
     free_list = NEXT(free_list);
+    NEXT(new_obj) = empty_list;
+    PREV(new_obj) = empty_list;
     return new;
 }