gdb 調試程序

要調試生成的可執行程序，必須在生成的時候加入-g選項，生成能夠調試的代碼

例如：gcc -o test a.c b.c -g

這樣gcc就會在連接的時候加入一些用於調試的符號

 

在生成能夠調試的可執行程序後，使用gdb命令進入調試模式

 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) 

此時，程序並無開始運行，在運行程序以前，能夠作一些準備工做

1. 設置運行參數

(gdb) set args 5 設置第一個參數爲5

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

2. 設置斷點，break命令，簡寫b

在指定行數設置斷點

(gdb) b 8 在第8行設置斷點 Breakpoint 1 at 0x4004f0: file main.cpp, line 8. (gdb) 

爲指定函數設置斷點

 

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

 

在指定行數或函數設置條件變量

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

 

查看斷點

 

(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

 

禁用斷點 disable b 4，禁用4號斷點

啓動斷點 enable b 4，啓用4號斷點

刪除斷點 clear 51 刪除51行的斷點

 

3. 查看源文件，list命令，簡寫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) 

也能夠指定查看的行數list 5,,10，查看從5到10行的源代碼

作好準備工做以後，就能夠真正運行程序了

4. 運行程序，run命令，簡寫r

(gdb) b 8 Breakpoint 1 at 0x4004f0: file main.cpp, line 8. (gdb) run 5 能夠直接在run後面能夠跟運行參數，也能夠用set設置運行參數 Starting program: /home/leo/test/project/classes/test 5 Breakpoint 1, main (argc=2, argv=0x7fffffffe018) at main.cpp:8
8 { (gdb) 

5. 查看變量，display命令。在使用斷點命令後，在運行到斷點處，就能夠使用此命令查看變量得值了

(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 查看運行參數個數 1: argc = 2 (gdb) display argv[1] 查看第一個運行參數的值 2: argv[1] = 0x7fffffffe38b "5"  (gdb) 

6. 繼續執行，continue命令，簡寫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. 修改變量的值，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" 將第一個運行參數的值從字符串「7」改成「8」 (gdb) c Continuing. Leo is here 8 . result is 3 6.800000.

[Inferior 1 (process 4009) exited normally]

8. 退出調試，q命令

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

 9. 查看變量類型，whatis命令

(gdb) whatis num1 type = int (gdb) 

10. 查看結構詳細定義，ptype命令

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

10. 進入函數體（step，簡寫s）和單步調試命令（next，簡寫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. 查看調用堆棧（backtrace，簡寫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. 獲取當前斷點下的運行狀況（info）

13.  多線程調試

　　info thread: 獲取當前進程中全部線程信息；

　　thread thread_id: 進入指定的線程進行調試；

14. 打印指定函數的彙編代碼

　　disassamble sum

15.  幫助信息

　　help