GDB调试案例

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已于 2024-08-21 16:26:00 修改

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文章标签： c++ 算法开发语言

于 2024-08-21 15:30:51 首次发布

本文链接：https://blog.youkuaiyun.com/xutaoshuaiqi/article/details/141395020

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参考教程：【Linux】GDB保姆级调试指南（什么是GDB？GDB如何使用？）_gdb教程-优快云博客

1、示例代码：

#include <iostream>

void swap(int* x, int* y)
{
    int t = *x;
    *x = *y;
    *y = t;
}
int main()
{
    int a = 10;
    int b = 20;

    std::cout << "a = " << a << ", " << "b = " << b << std::endl;

    swap(&a, &b);

    std::cout << "a = " << a << ", " << "b = " << b << std::endl;

    return 0;
}

2、调试过程

2.1 生成调试文件

g++ -g gcd_test.cpp -o gdb_test

这里需要说明一下，gcd_test.cpp是代码的源文件，gdb_test是生成的debug文件的名字。这是C++文件的编译，对于C文件来说可以使用如下指令：

gcc -g gcd_test.cpp -o gdb_test

2.2 具体调试

进入GDB：

gdb gdb_test

l查看代码，enter键下翻

(gdb) l

第16行设置断点（或者 break 16）

(gdb) b 16
Breakpoint 1 at 0x12b8: file gcd_test.cpp, line 16.

查看断点信息

(gdb) info b
Num     Type           Disp Enb Address            What
1       breakpoint     keep y   0x00000000000012b8 in main() at gcd_test.cpp:16
(gdb) info break
Num     Type           Disp Enb Address            What
1       breakpoint     keep y   0x00000000000012b8 in main() at gcd_test.cpp:16

运行到结束（有断点的话运行到第一个断点处）

(gdb) r
Starting program: /home/xxx/demo/gdb_test 
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
a = 10, b = 20

Breakpoint 1, main () at gcd_test.cpp:16
16	    swap(&a, &b);

查看信息

(gdb) info locals
a = 10
b = 20
(gdb) info args
No arguments.
(gdb) print a
$1 = 10

进入函数

(gdb) s
swap (x=0x7fffffffdbd0, y=0x7fffffffdbd4) at gcd_test.cpp:5
5	    int t = *x;
(gdb) finish
Run till exit from #0  swap (x=0x7fffffffdbd0, y=0x7fffffffdbd4) at gcd_test.cpp:5
main () at gcd_test.cpp:18
18	    std::cout << "a = " << a << ", " << "b = " << b << std::endl;
(gdb) n
a = 20, b = 10
20	    return 0;

进入到swap函数中，此时不想调试，想先立马看看运行结果，但是此时又已经进入调试了，那么我们就可以使用到【finish】来立马执行完这个函数，然后观察一下结果。可以看到，最后打印出结果的时候a和b的值确实发生了交换。

因为提前看了执行结果，所以我们要重新开始调试，按下【r】即可，它会询问你是否需要重新开始调试，选择y之后就可以重新从16行开始进行调试

(gdb) r
The program being debugged has been started already.
Start it from the beginning? (y or n) y
Starting program: /home/xxx/demo/gdb_test 
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
a = 10, b = 20

Breakpoint 1, main () at gcd_test.cpp:16
16	    swap(&a, &b);

追踪a, b的值以及地址

(gdb) display a b &a &b
A syntax error in expression, near `b &a &b'.
(gdb) display a
1: a = 10
(gdb) display b
2: b = 20
(gdb) display &a
3: &a = (int *) 0x7fffffffdbd0
(gdb) display &b
4: &b = (int *) 0x7fffffffdbd4

可以看出不能一次性设置多个。

(gdb) s
swap (x=0x7fffffffdbd0, y=0x7fffffffdbd4) at gcd_test.cpp:5
5	    int t = *x;
(gdb) n
6	    *x = *y;
(gdb) n
7	    *y = t;
(gdb) n
8	}
(gdb) n
main () at gcd_test.cpp:18
18	    std::cout << "a = " << a << ", " << "b = " << b << std::endl;
1: a = 20
2: b = 10
3: &a = (int *) 0x7fffffffdbd0
4: &b = (int *) 0x7fffffffdbd4

结束！