【Linux】coredump 文件的例子分析

最新推荐文章于 2024-08-06 21:52:00 发布

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最新推荐文章于 2024-08-06 21:52:00 发布 · 887 阅读

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#linux #服务器

文章介绍了如何临时开启并设置core文件生成，修改配置使其保存到特定位置，通过示例演示了编译运行时coredump的触发和使用GDB进行分析的过程，以及如何通过-g选项进行更详细的debug。

1. 生成 core 文件

网上很多教程，我这里举一种

临时开启生成 core 文件

# 0 就是没有开 coredump 功能
root@swd-Lenovo-G40-80:/home/swd/pros/c--learn/0.test_codes/demos# ulimit -c
0
# 设置值临时为 unlimited
root@swd-Lenovo-G40-80:/home/swd/pros/c--learn/0.test_codes/demos# ulimit -c unlimited
# 检查值为 unlimited
root@swd-Lenovo-G40-80:/home/swd/pros/c--learn/0.test_codes/demos# ulimit -c
unlimited
# 可以看到下面的字段 core file size 的值为 unlimited
root@swd-Lenovo-G40-80:/home/swd/pros/c--learn/0.test_codes/demos# ulimit -a
core file size          (blocks, -c) unlimited
data seg size           (kbytes, -d) unlimited
scheduling priority             (-e) 0
file size               (blocks, -f) unlimited
pending signals                 (-i) 31282
max locked memory       (kbytes, -l) 65536
max memory size         (kbytes, -m) unlimited
open files                      (-n) 1024
pipe size            (512 bytes, -p) 8
POSIX message queues     (bytes, -q) 819200
real-time priority              (-r) 0
stack size              (kbytes, -s) 8192
cpu time               (seconds, -t) unlimited
max user processes              (-u) 31282
virtual memory          (kbytes, -v) unlimited
file locks                      (-x) unlimited

修改保存的文件位置

vim /etc/sysctl.conf

# 添加下面两行

kernel.core_pattern=/var/core/core_%e_%p
kernel.core_uses_pid=0

# 使修改生效
sysctl -p /etc/sysctl.conf

# 创建文件夹 /var/core
mkdir -p /var/core

2. 创建一个例子

// demo1.cc 
#include <iostream>
using namespace std;

int main()
{
   
   
    int *p = nullptr;
    cout << *p << endl;
    return 0;
}

编译、运行，会报 (core dumped)

g++ -o demo1 demo1.cc
./demo1
Segmentation fault (core dumped)

查看生成的 core_dump 文件：

# 拷到当前目录
cp /var/core/core_demo1_5392 .
# 查看文件
ls
core_demo1_5392   demo1  demo1.cc

使用 gdb 分析，可以看到直接报 Segmentation fault。

gdb demo1 core_demo1_5392
GNU gdb (Ubuntu 8.1.1-0ubuntu1) 8.1.1
Copyright (C) 2018 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 "x86_64-linux-gnu".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>.
Find the GDB manual and other documentation resources online at:
<http://www.gnu.org/software/gdb/documentation/>.
For help, type "help".
Type "apropos word" to search for commands related to "word"...
Reading symbols from demo1...(no debugging symbols found)

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