如何调试崩溃的程序

[weijiz]

在程序开发中经常会遇到这样的问题，对于C或C++的程序有时程序崩溃不能获得有效的调试信息
Segmentation fault
Core dump
这样的程序如何进行调试呢？
我们可以利用gdb去调试崩溃程序。

首先开启core dump文件。在开启之后，当程序崩溃的时候操作系统会自动的把崩溃信息存储到core文件里面。
在终端输入

ulimit -c unlimited

这样就打开core dump 功能了。

下面是一个崩溃的实际例子

randoms@nowhere:~/ramdisk$ /home/randoms/Documents/ros/workspace/devel/lib/orb_slam2/mono /home/randoms/Documents/ros/workspace/src/ORB_SLAM2/Examples/ROS/orb_slam2/Data/ORBvoc.bin /home/randoms/Documents/ros/workspace/src/ORB_SLAM2/Examples/ROS/orb_slam2/Data/setting4.yaml /camera/image_raw:=/camera_node/image_raw /Pose2D:=/xqserial_server/Pose2D > orb.log 
mono: ../nptl/pthread_mutex_lock.c:350: __pthread_mutex_lock_full: Assertion `(-(e)) != 3 || !robust' failed.
Aborted (core dumped)
randoms@nowhere:~/ramdisk$ ls
2.bag  core  KeyFrameTrajectory.txt  orb.log

可以看到在程序崩溃后创建了一个core文件，在终端输入下面的指令开始调试

randoms@nowhere:~/ramdisk$ gdb /home/randoms/Documents/ros/workspace/devel/lib/orb_slam2/mono core

gdb的指令格式是 gdb EXE_FILE_PATH CORE_FILE_PATH

等待载入完成

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Reading symbols from /home/randoms/Documents/ros/workspace/devel/lib/orb_slam2/mono...(no debugging symbols found)...done.
[New LWP 14392]
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[New LWP 14376]
[New LWP 14391]
[New LWP 14407]
[New LWP 14406]
[New LWP 14408]
[New LWP 14377]
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[New LWP 14387]
[New LWP 14409]
[New LWP 14412]
[New LWP 14390]
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
Core was generated by `/home/randoms/Documents/ros/workspace/devel/lib/orb_slam2/mono /home/randoms/Do'.
Program terminated with signal SIGABRT, Aborted.
#0  0x00007fe6ca6ecc37 in __GI_raise (sig=sig@entry=6)
    at ../nptl/sysdeps/unix/sysv/linux/raise.c:56
56	../nptl/sysdeps/unix/sysv/linux/raise.c: No such file or directory.

gdb在终端中输入

bt

可以显示出崩溃时的堆栈信息

#0  0x00007fe6ca6ecc37 in __GI_raise (sig=sig@entry=6)
    at ../nptl/sysdeps/unix/sysv/linux/raise.c:56
#1  0x00007fe6ca6f0028 in __GI_abort () at abort.c:89
#2  0x00007fe6ca6e5bf6 in __assert_fail_base (
    fmt=0x7fe6ca8363b8 "%s%s%s:%u: %s%sAssertion `%s' failed.\n%n", 
    assertion=assertion@entry=0x7fe6c9bb6a25 "(-(e)) != 3 || !robust", 
    file=file@entry=0x7fe6c9bb6a08 "../nptl/pthread_mutex_lock.c", 
    line=line@entry=350, 
    function=function@entry=0x7fe6c9bb6b20 <__PRETTY_FUNCTION__.8695> "__pthread_mutex_lock_full") at assert.c:92
#3  0x00007fe6ca6e5ca2 in __GI___assert_fail (
    assertion=assertion@entry=0x7fe6c9bb6a25 "(-(e)) != 3 || !robust", 
    file=file@entry=0x7fe6c9bb6a08 "../nptl/pthread_mutex_lock.c", 
    line=line@entry=350, 
    function=function@entry=0x7fe6c9bb6b20 <__PRETTY_FUNCTION__.8695> "__pthread_mutex_lock_full") at assert.c:101
#4  0x00007fe6c9ba9ce1 in __pthread_mutex_lock_full (mutex=0x9643740)
    at ../nptl/pthread_mutex_lock.c:350
#5  0x00007fe6cb03403a in __gthread_mutex_lock (__mutex=0x9643740)
    at /usr/include/x86_64-linux-gnu/c++/4.8/bits/gthr-default.h:748
#6  lock (this=0x9643740) at /usr/include/c++/4.8/mutex:134
#7  lock (this=0x7fe694ed5a10) at /usr/include/c++/4.8/mutex:511
#8  unique_lock (__m=..., this=0x7fe694ed5a10)
---Type <return> to continue, or q <return> to quit---
    at /usr/include/c++/4.8/mutex:443
#9  ORB_SLAM2::MapPoint::isBad (this=0x96434c0)
    at /home/randoms/Documents/ros/workspace/src/ORB_SLAM2/src/MapPoint.cc:272
#10 0x00007fe6cb03c957 in ORB_SLAM2::KeyFrame::RemoveBadPoints (this=0xa33f510)
    at /home/randoms/Documents/ros/workspace/src/ORB_SLAM2/src/KeyFrame.cc:1155
#11 0x00007fe6caff8b5a in ORB_SLAM2::Tracking::GC (this=0x711d310)
    at /home/randoms/Documents/ros/workspace/src/ORB_SLAM2/src/Tracking.cc:311
#12 0x00007fe6cb0baef2 in ORB_SLAM2::GC::Run (this=0x7157fe0)
    at /home/randoms/Documents/ros/workspace/src/ORB_SLAM2/src/GC.cc:37
#13 0x00007fe6cad42a60 in ?? () from /usr/lib/x86_64-linux-gnu/libstdc++.so.6
#14 0x00007fe6c9bac184 in start_thread (arg=0x7fe694ed6700)
    at pthread_create.c:312
#15 0x00007fe6ca7b037d in clone ()
    at ../sysdeps/unix/sysv/linux/x86_64/clone.S:111

这样我们就可以定位到具体在哪一个语句崩溃的。可以看出这次的崩溃是一个锁的问题。在MapPoint.cc文件里面。