gdb 调试程序

要调试生成的可执行程序，必须在生成的时候加入-g选项，生成能够调试的代码

例如：gcc -o test a.c b.c -g

这样gcc就会在连接的时候加入一些用于调试的符号

 

在生成能够调试的可执行程序后，使用gdb命令进入调试模式

 1 root@ubuntu:/home/leo/test/project/classes# gdb test  2 GNU gdb (Ubuntu 7.10-1ubuntu2) 7.10
 3 Copyright (C) 2015 Free Software Foundation, Inc.  4 License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
 5 This is free software: you are free to change and redistribute it.  6 There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
 7 and "show warranty" for details.  8 This GDB was configured as "x86_64-linux-gnu".  9 Type "show configuration" for configuration details. 10 For bug reporting instructions, please see: 11 <http://www.gnu.org/software/gdb/bugs/>.
12 Find the GDB manual and other documentation resources online at: 13 <http://www.gnu.org/software/gdb/documentation/>.
14 For help, type "help". 15 Type "apropos word" to search for commands related to "word"... 16 Reading symbols from test...done. 17 (gdb) 

此时，程序并无开始运行，在运行程序以前，能够作一些准备工做

1. 设置运行参数

(gdb) set args 5 设置第一个参数为5

(gdb) show args
Argument list to give program being debugged when it is started is "5".

2. 设置断点，break命令，简写b

在指定行数设置断点

(gdb) b 8 在第8行设置断点 Breakpoint 1 at 0x4004f0: file main.cpp, line 8. (gdb) 

为指定函数设置断点

 

(gdb) b add_int
Breakpoint 3 at 0x400660: file math/add_int.cpp, line 5.

 

在指定行数或函数设置条件变量

(gdb) b add_int if num1 == 1 Breakpoint 4 at 0x400660: file math/add_int.cpp, line 5.

 

查看断点

 

(gdb) info breakpoints 
Num     Type           Disp Enb Address            What
4       breakpoint     keep y   0x0000000000400660 in add_int(int, int) 
                                                   at math/add_int.cpp:5
    stop only if num1 == 1
    breakpoint already hit 1 time

 

禁用断点 disable b 4，禁用4号断点

启动断点 enable b 4，启用4号断点

删除断点 clear 51 删除51行的断点

 

3. 查看源文件，list命令，简写l

(gdb) list 1    #include "stdlib.h"
2    #include "stdio.h"
3    
4    int add_int(int, int); 5    float add_float(float, float); 6    
7    int main(int argc, char *argv[]) 8 { 9        int value = (*argv[1]) - '0'; 10        printf("Leo is here %d . \n", value); (gdb) list 11    
12        int num1 = add_int(1, 2); 13        float num2 = add_float(2.3, 4.5); 14        printf("result is %d %f.", num1, num2); 15    
16 getchar(); 17    
18        return 0; 19 } (gdb) list Line number 20 out of range; main.cpp has 19 lines. (gdb) 

也能够指定查看的行数list 5,,10，查看从5到10行的源代码

作好准备工做以后，就能够真正运行程序了

4. 运行程序，run命令，简写r

(gdb) b 8 Breakpoint 1 at 0x4004f0: file main.cpp, line 8. (gdb) run 5 能够直接在run后面能够跟运行参数，也能够用set设置运行参数 Starting program: /home/leo/test/project/classes/test 5 Breakpoint 1, main (argc=2, argv=0x7fffffffe018) at main.cpp:8
8 { (gdb) 

5. 查看变量，display命令。在使用断点命令后，在运行到断点处，就能够使用此命令查看变量得值了

(gdb) b 8 Breakpoint 1 at 0x4004f0: file main.cpp, line 8. (gdb) run 5 Starting program: /home/leo/test/project/classes/test 5 Breakpoint 1, main (argc=2, argv=0x7fffffffe018) at main.cpp:8
8 { (gdb) display argc 查看运行参数个数 1: argc = 2 (gdb) display argv[1] 查看第一个运行参数的值 2: argv[1] = 0x7fffffffe38b "5"  (gdb) 

6. 继续执行，continue命令，简写c

(gdb) b 8 Breakpoint 1 at 0x4004f0: file main.cpp, line 8. (gdb) run 5 Starting program: /home/leo/test/project/classes/test 5 Breakpoint 1, main (argc=2, argv=0x7fffffffe018) at main.cpp:8
8 { (gdb) c Continuing. Leo is here 5 . result is 3 6.800000.

[Inferior 1 (process 4009) exited normally]

7. 修改变量的值，set命令

(gdb) b 8 Breakpoint 1 at 0x4004f0: file main.cpp, line 8. (gdb) run 7 Starting program: /home/leo/test/project/classes/test 7 Breakpoint 1, main (argc=2, argv=0x7fffffffe018) at main.cpp:8
8 { (gdb) display argv[1] 1: argv[1] = 0x7fffffffe38b "7" (gdb) set argv[1] = "8" 将第一个运行参数的值从字符串“7”改成“8” (gdb) c Continuing. Leo is here 8 . result is 3 6.800000.

[Inferior 1 (process 4009) exited normally]

8. 退出调试，q命令

(gdb) q A debugging session is active. Inferior 1 [process 3997] will be killed. Quit anyway? (y or n) y

 9. 查看变量类型，whatis命令

(gdb) whatis num1 type = int (gdb) 

10. 查看结构详细定义，ptype命令

(gdb) ptype u type = struct User { int id char name[20] }

10. 进入函数体（step，简写s）和单步调试命令（next，简写n）

(gdb) s 6    }2: num2 = 2
1: num1 = 1 (gdb) n main (argc=<optimized out>, argv=<optimized out>) at main.cpp:13
13        float num2 = add_float(2.3, 4.5); (gdb) 

11. 查看调用堆栈（backtrace，简写bt）

(gdb) bt #0  add_int (num1=num1@entry=1, num2=num2@entry=2) at math/add_int.cpp:6 #1  0x000000000040051b in main (argc=<optimized out>, argv=<optimized out>) at main.cpp:12 (gdb) 

12. 获取当前断点下的运行状况（info）

13.  多线程调试

　　info thread: 获取当前进程中全部线程信息；

　　thread thread_id: 进入指定的线程进行调试；

14. 打印指定函数的汇编代码

　　disassamble sum

15.  帮助信息

　　help