How To Debug

debug:产生调试信息.
首先需要满足编译的时候带有-g标识.(这个不用管.现在编译的配置文件都是打开的-g)
然后运行

$gdb pidgin
会有如图的消息:

GNU gdb (Ubuntu/Linaro 7.4-2012.04-0ubuntu2) 7.4-2012.04
Copyright (C) 2012 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.<br>
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"<br>
and "show warranty" for details.<br>
This GDB was configured as "x86_64-linux-gnu".<br>
For bug reporting instructions, please see:<br>
<http://bugs.launchpad.net/gdb-linaro/>...<br>
Reading symbols from /usr/bin/pidgin...Reading symbols from /usr/lib/debug/usr/bin/pidgin...done.<br>
done.<br>
(gdb)

此时输入run (r)回车

(gdb) r

就会开始运行pidgin了.

其中控制台会出现许多信息.不用管它.

[Sep  9 09:18:48] DEBUG[18627]: /home/xiehuc/PROJECT/pidgin-lwqq/src/liblwqq/info.c:1210     lwqq_info_get_friend_detail_info: in function.hi
r={"to":2505299203,"face":0,"content":"[\"hi\",[\"font\",{\"name\":\"宋体\",\"size\":\"13\",\"style\": [0,0,0],\"color\":\"000000\"}]]","msg_id":3310000,"clientid":"84684545","psessionid":"8368046764001f636f6e6e7365727665725f7765627171403137322e32332e3133342e323136000055cb00000ce1016e04009563e4146d0000000a40744f4462614167355a6d00000028f74c3012cadb51c60b55ab412e8d1dd7070b0ce4bb78d5f2acf877a6afa94b3ee508bc7e56de8383"}&clientid=84684545&psessionid=8368046764001f636f6e6e7365727665725f7765627171403137322e32332e3133342e323136000055cb00000ce1016e04009563e4146d0000000a40744f4462614167355a6d00000028f74c3012cadb51c60b55ab412e8d1dd7070b0ce4bb78d5f2acf877a6afa94b3ee508bc7e56de8383
{"retcode":0,"result":"ok"}

你有兴趣的话可以看一下.大部分是POST消息.
然后运行操作让它崩溃.

Program received signal SIGINT, Interrupt.
0x00007ffff46afb03 in __GI___poll (fds=<optimized out>, nfds=<optimized out>, 
    timeout=<optimized out>) at ../sysdeps/unix/sysv/linux/poll.c:87
87	../sysdeps/unix/sysv/linux/poll.c: 没有那个文件或目录.
(gdb) 

现在已经在gdb里面了.当然这些信息还根本没有什么作用.
运行(gdb) bt可以查看系统调用栈,如下:

(gdb) bt
#0  qq_send_im (gc=0x5555565f20c0, who=0x555555e15e00 "2505299203", 
    what=0x555555dcff60 "hi", UNUSED_flags=PURPLE_MESSAGE_SEND)
    at /home/xiehuc/PROJECT/pidgin-lwqq/src/webqq.c:771
#1  0x00007ffff4d0fb94 in serv_send_im (gc=0x5555565f20c0, 
    name=0x555555e15e00 "2505299203", message=0x555555dcff60 "hi", 
    flags=PURPLE_MESSAGE_SEND)
    at /build/buildd/pidgin-2.10.3/./libpurple/server.c:145
#2  0x00007ffff4cdeb9f in common_send (conv=0x555556655440, 
    message=<optimized out>, msgflags=PURPLE_MESSAGE_SEND)
    at /build/buildd/pidgin-2.10.3/./libpurple/conversation.c:182
#3  0x00005555555b5065 in send_cb (widget=<optimized out>, 
    gtkconv=0x5555566efe00)
    at /build/buildd/pidgin-2.10.3/./pidgin/gtkconv.c:612
#4  0x00007ffff52b6ca2 in g_closure_invoke ()
   from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#5  0x00007ffff52c7fdd in ?? ()
   from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#6  0x00007ffff52cf289 in g_signal_emitv ()
   from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#7  0x00007ffff617380a in ?? ()
   from /usr/lib/x86_64-linux-gnu/libgtk-x11-2.0.so.0
#8  0x00007ffff6173d68 in ?? ()
   from /usr/lib/x86_64-linux-gnu/libgtk-x11-2.0.so.0

其中可以看到是在qq_send_im这个函数挂调的(我这里是设置的断点,其实没有问题)
而且提示是在771行,因为不同的版本行肯定会改变的.
(你用的是19日编译版本,我用的是29日编译版本,中间添加了这么多代码,肯定会造成行移位)
所以使用(gdb) l可以查看代码.中间一行就是出错的位置. (gdb) l 766 767 768 //send a message to a friend. 769 //called by purple 770 static int qq_send_im(PurpleConnection gc, const gchar who, const gchar what, PurpleMessageFlags UNUSED(flags)) 771 { 772 qq_account ac = (qq_account)purple_connection_get_protocol_data(gc); 773 LwqqClient lc = ac->qq; 774 char nick[32],gname[32]; 775 const char* pos;

(我这里是加的断点,所以是函数一开始).
有了具体的位置了.调试起来就容易了.