c++如何解决段错误 (核心已转储)
在后端优化中遇到了段错误 (核心已转储)问题，寻求解决方法。
首先通过不断的注释部分代码，运行，注释，运行，找到一个大概的范围是错在哪一块。
这类问题只能说根本原因是内存的非法操作。建议生成内存段错误转储文件，发生段错误后用gdb分析该文件定位到发生段错误的代码上，这样才能确定导致段错误的直接原因。 -国庆
GDB大法好，直接定位到相关的信息上去，使用gdb ggoLearning 进入调试界面
gdb ggoLearning
GNU gdb (Ubuntu 8.1-0ubuntu3.2) 8.1.0.20180409-git
Copyright (C) 2018 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
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and "show warranty" for details.
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Type "show configuration" for configuration details.
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<http://www.gnu.org/software/gdb/bugs/>.
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Reading symbols from ggoLearning...done.
进入（gdb）调试界面，输入r,可以运行程序，可以看到程序在运行的时候，出现了Program received signal SIGSEGV, Segmentation fault.错误。
当程序出现异常时通常伴随着会收到一个由内核发过来的异常信号，如当对内存出现非法访问时将收到段错误信号SIGSEGV，然后才退出。利用这一点，当我们在收到异常信号后将程序的调用栈进行输出，它通常是利用signal()函数，关于系统信号的
(gdb) r
Starting program: /home/user/work/x/rgbd-slam-tutorial-gx/partI/bin/ggoLearning
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
RMSE for the structure is: 0.00825072
RMSE for the rotation of camera is: 0.0478788
RMSE for the translation of camera is: 0.0220988
Program received signal SIGSEGV, Segmentation fault.
0x00007ffff75e6267 in g2o::BaseVertex<6, g2o::SE3Quat>::pop() ()
from /home/user/work/x/rgbd-slam-tutorial-gx/partI/include/g2o/lib/libg2o.so
bt可以看到程序的好几层，使用backtrace回溯定位问题。这里有一个例子：在Linux中如何利用backtrace信息解决程序崩溃的问题
(gdb) bt
#0 0x00007ffff75e6267 in g2o::BaseVertex<6, g2o::SE3Quat>::pop() ()
from /home/user/work/x/rgbd-slam-tutorial-gx/partI/include/g2o/lib/libg2o.so
#1 0x00007ffff7620a78 in g2o::SparseOptimizer::pop(std::vector >&) ()
from /home/user/work//rgbd-slam-tutorial-gx/partI/include/g2o/lib/libg2o.so
#2 0x00007ffff7629be2 in g2o::OptimizationAlgorithmLevenberg::solve(int, bool)
()
from /home/user/work/x/rgbd-slam-tutorial-gx/partI/include/g2o/lib/libg2o.so
#3 0x00007ffff76219cd in g2o::SparseOptimizer::optimize(int, bool) ()
from /home/user/work/xio/rgbd-slam-tutorial-gx/partI/include/g2o/lib/libg2o.so
#4 0x000055555581f5a0 in SolveBA (
vNoisyCameras=std::vector of length 3, capacity 3 = {...},
vpNoiseGeometryFeatures=std::vector of length 2, capacity 2 = {...})
at /home/user/work/x/rgbd-slam-tutorial-gx/partI/src/ggoLearning.cpp:477
#5 0x000055555581c4bd in main (argc=1, argv=0x7fffffffdd18)
at /home/user/work/x/rgbd-slam-tutorial-gx/partI/src/ggoLearning.cpp:123
(gdb) frame 5
#5 0x000055555581c4bd in main (argc=1, argv=0x7fffffffdd18)
at /home/user/work/x/rgbd-slam-tutorial-gx/partI/src/ggoLearning.cpp:123
warning: Source file is more recent than executable.
123 SolveBA(vNoisyCameras,vNoisyGeomeryPlaneFeatures);
我们一般使用各类的库
(gdb) frame 4
#4 0x000055555581f5a0 in SolveBA (
vNoisyCameras=std::vector of length 3, capacity 3 = {...},
vpNoiseGeometryFeatures=std::vector of length 2, capacity 2 = {...})
at /home/user/work/xinguo/rgbd-slam-tutorial-gx/partI/src/ggoLearning.cpp:477
477 optimizer.optimize(10);
(gdb)
输入quit或者按下Ctrl-d退出
调试到后面发现进入了汇编语言界面，。。。
HLT 使 CPU 进入这么一个状态：既不取指令，也不读写数据，总线上“静悄悄”的。这条指令
用的地方不多，一般用于等外部中断。