开发过程中的一次GDB调试

 

1. 程序运行过程中偶尔出现段错误如下：

[Thread debugging using libthread_db enabled]LogMemoryStatus=DISABLED, WarnMemoryGrain=104857600[New Thread 0xb7621710 (LWP 4115)][New Thread 0xb7620b90 (LWP 4116)][New Thread 0xb6e1fb90 (LWP 4117)][New Thread 0xb661eb90 (LWP 4118)]<-1226703984:4115> 10:12:31.813 [00001] in get event thread! Connected to Asterisk Call Manager v1.1<-1235096688:4115> 10:12:31.813 [00001] in get event thread! <-1218311280:4115> 10:12:31.812 [00001] in get record thread! <-1218308336:4115> 10:12:31.813 [00001] Handle queue size is 0.Program received signal SIGSEGV, Segmentation fault.[Switching to Thread 0xb661eb90 (LWP 4118)]0xb7e9d9a0 in pthread_mutex_lock () from /lib/i686/cmov/libpthread.so.0(gdb) bt#0 0xb7e9d9a0 in pthread_mutex_lock () from /lib/i686/cmov/libpthread.so.0#1 0xb5ccd2e0 in SQLGetEnvAttr () from /usr/lib/odbc/psqlodbcw.so#2 0xb78bcef7 in ?? () from /usr/lib/libodbc.so.1#3 0x00000000 in ?? ()(gdb)  

2.对生成的 core 文件的大小不进行限制

ulimit – c unlimited

3.添加g++中的调试选项，ggdb3用于输出调试信息，其中3标识调试级别，调试级别越高输出的冗余信息越多。

4. 重新段错误生成core文件，由于是偶尔发生段错误，所以得多运行几次才行：

LogMemoryStatus=DISABLED, WarnMemoryGrain=104857600<-1218303088:4982> 11:46:31.916 [00001] in get record thread! <-1226695792:4982> 11:46:31.916 [00001] in get event thread! Connected to Asterisk Call Manager v1.1<-1235088496:4982> 11:46:31.917 [00001] in get event thread! <-1218300144:4982> 11:46:31.917 [00001] Handle queue size is 0.Segmentation fault (core dumped) 

生成了core文件名称为：core.4982，其中4982是进出的PID值。

5. 调试core文件

# gdb --core=core.4982 GNU gdb 6.8-debianCopyright (C) 2008 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.There is NO WARRANTY, to the extent permitted by law. Type "show copying"and "show warranty" for details.This GDB was configured as "i486-linux-gnu".(no debugging symbols found)Core was generated by `./confcontroltest'.Program terminated with signal 11, Segmentation fault.[New process 4983][New process 4985][New process 4984][New process 4982]#0 0xb7e9f9a0 in ?? ()(gdb) bt#0 0xb7e9f9a0 in ?? ()(gdb)  

gdb没有找到调试符号信息。于是需要加入符号信息。

(gdb) file ./confcontroltestReading symbols from /home/gz/work/cvscode/ap/conferencecall/inconference/confcontroltest...done.(gdb) bt#0 0xb7e9f9a0 in ?? ()#1 0xb7911cc4 in ?? ()#2 0xb7eadff4 in ?? ()#3 0xb7911cc4 in ?? ()#4 0xb7ea00c4 in ?? ()#5 0xb7fa385b in ?? ()#6 0x000009d8 in ?? ()#7 0x00000139 in ?? ()#8 0x00000001 in ?? ()#9 0x00000005 in ?? ()#10 0x00001377 in ?? ()#11 0xb78b3c1e in ?? ()#12 0x00000039 in ?? ()#13 0xb78b2000 in ?? ()#14 0x00001377 in ?? ()#15 0xb5cf2520 in ?? ()#16 0x000000c8 in ?? ()#17 0x00000000 in ?? ()(gdb) 

下面拿到了符号信息，但是对解决问题没有帮助。 

(gdb) l4 #include "common/base_func.h"5 #include "common/compile.h"6 #include "common/uniconfig.h"7 #include "common/unilog.h"89 #include "logger.h"10 #include "parseconfig.h"11 #include "database.h"12 int main(){13 CFCR::TParseConfig config("confcontrol.conf");(gdb) 14 config.loadConfig();15 if(config.getLoaded()){16 std::cout << config.getAmiHost()<< " " << config.getAmiUser() << " " << config.getAmiPassword() << std::endl;17 std::cout << config.getDbName() << " " << config.getDbUser() << " " << config.getDbPassword() << std::endl;18 CFCR::TDatabase hd(config.getDbUser(),config.getDbPassword(),config.getDbName(),config.getAmiHost(),config.getAmiUser(),config.getAmiPassword());19 hd.handleRequestRecord();20 }21 return 0;22 }(gdb)  

于是再运行了几次，终于爆出了问题的提示。

*** glibc detected *** ./confcontroltest: double free or corruption (out): 0xb5d1e4d8 ***======= Backtrace: =========/lib/i686/cmov/libc.so.6[0xb7bea624]/lib/i686/cmov/libc.so.6(cfree+0x96)[0xb7bec826]/usr/lib/libodbc.so.1[0xb78e7c2d]/usr/lib/libodbc.so.1(SQLFreeStmt+0x39)[0xb78beef9]/home/TDCISREL/lib/libdbconn.so(_ZN15TODBCConnection10disconnectEv+0x26)[0xb7eb950c]libconfcontrol.so(_ZN4CFCR9TDatabase18disconnectDatabaseEv+0x20)[0xb7e1192e]libconfcontrol.so(_ZN4CFCR9TDatabase18handleAfterMeetingEv+0x3d)[0xb7e11afd]libconfcontrol.so(_ZN4CFCR9TDatabase21setAfterMeetingThreadEPv+0x4c)[0xb7e11b6e]/lib/i686/cmov/libpthread.so.0[0xb7e934c0]/lib/i686/cmov/libc.so.6(clone+0x5e)[0xb7c5c6de]======= Memory map: ========08048000-08052000 r-xp 00000000 08:05 386020 /home/gz/work/cvscode/ap/conferencecall/inconference/confcontroltest08052000-08053000 rw-p 00009000 08:05 386020 /home/gz/work/cvscode/ap/conferencecall/inconference/confcontroltest0856c000-085cd000 rw-p 0856c000 00:00 0 [heap] 

 

两次释放内存的错误，而且_ZN4CFCR9TDatabase18disconnectDatabaseEv+0x20给出了提示，连接了一次数据库，却释放了两次。无意中的错误啊。