c++ list index out of range 错误

Question

程序在linux下core dump掉，gdb调试core文件

Python Exception <class 'IndexError'> list index out of range

整个程序并没有用python开发
定位到的错误是在respRoomInit函数调用SnakesBroadMessage函数过程中变量SFSessionIDList SIDL在传递函数引用参数的过程中出现的，下图是两个函数的内容

分别定位到两个函数输出SFSessionIDList的值，在调用SnakesBroadMessage之前list里面是有一个值的，而进入该函数之后list就为空了，所以估计根本问题不在这里，再别的地方，请问该怎么找？

(gdb) f 9
#9  0x00000000004a186d in SnakeScene::respRoomInit (this=0x7f735800ee90, nSID=...)
    at /home/jjq/svn/Snake/SnakesGame/GmScene/GmSceneType/SnakeScene.cpp:983
983    /home/jjq/svn/Snake/SnakesGame/GmScene/GmSceneType/SnakeScene.cpp: No such file or directory.
(gdb) p nSID
$12 = {mSocketId = 16, mSeqId = 18}
(gdb) f 8
Python Exception <class 'IndexError'> list index out of range: 
#8  0x00000000004cde44 in SnakesBroadMessage (sids=std::list, cmdId=3, msg=0x7f7379ffaa30, uid=0)
    at /home/jjq/svn/Snake/SnakesGame/SnakesActionChain.cpp:47
47    /home/jjq/svn/Snake/SnakesGame/SnakesActionChain.cpp: No such file or directory.
(gdb) p sids
Python Exception <class 'IndexError'> list index out of range: 
$13 = std::list

Answer 1

用gdb给你的那个变量打一个watch，看看进入前后有什么线程访问修改了它