廊坊新闻网-主流媒体,廊坊城市门户

快讯:使用GDB调试Linux应用程序

2023-06-27 22:04:25 来源:嵌入式Linux充电站


(资料图片仅供参考)

本篇讲解使用GDB调试Linux应用程序,以下以 hellowld.c为例介绍 GDB 的调试入门:

编写代码

#include < stdio.h >int main(int argc, char **argv){    int i;    int result = 0;    if(1 >= argc)    {        printf("Helloworld.\\n");    }    printf("Hello World %s!\\n",argv[1]);    for(i = 1; i <= 100; i++)  {        result += i;    }    printf("result = %d\\n", result );    return 0;}

编译时加上 -g参数:

gcc helloworld.c -o hellowrld -g

启动调试

$ gdb helloWorldGNU gdb (GDB) Red Hat Enterprise Linux 8.2-12.el8Copyright (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-redhat-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 helloworld...done.(gdb) run                  < ----------------------------- 不带参数运行Starting program: /home/zhuzhg/helloworldMissing separate debuginfos, use: yum debuginfo-install glibc-2.28-101.el8.x86_64helloworld.result = 5050[Inferior 1 (process 1069013) exited normally](gdb) run China            < ----------------------------- 带参数运行Starting program: /home/zhuzhg/helloworld ChinaHello World China!result = 5050[Inferior 1 (process 1071086) exited normally](gdb)

断点

设置断点

文件行号断点:break hellowrld.c:9函数断点:break main条件断点:break helloworld.c:17 if c == 10临时断点, 假设某处的断点只想生效一次,那么可以设置临时断点,这样断点后面就不复存在了:tbreak helleworld.c:9禁用或启动断点:
disable                 # 禁用所有断点  disable bnum            # 禁用标号为bnum的断点  enable                  # 启用所有断点  enable bnum             # 启用标号为bnum的断点  enable delete bnum      # 启动标号为bnum的断点,并且在此之后删除该断点
断点清除:
clear                   # 删除当前行所有breakpoints  clear function          # 删除函数名为function处的断点  clear filename:function # 删除文件filename中函数function处的断点  clear lineNum           # 删除行号为lineNum处的断点  clear f:lename:lineNum  # 删除文件filename中行号为lineNum处的断点  delete                  # 删除所有breakpoints,watchpoints和catchpoints  delete bnum             # 删除断点号为bnum的断点

变量查看

变量查看:最常见的使用便是使用print(可简写为p)打印变量内容。以上述程序为例:

gdb helloworldbreak helloworld.c:17 if i == 0(gdb) runStarting program: /home/book/helloworldhelloworld.Breakpoint 2, main (argc=1, argv=0x7fffffffdca8) at helloworld.c:1717            result += i;(gdb) print i                < ------------------ 查看变量 i 当前的值$1 = 10(gdb) print result           < ------------------ 查看变量 result 当前的值$2 = 45(gdb) print argc             < ------------------ 查看变量 argc 当前的值$3 = 1(gdb) print str$4 = 0x4006c8 "Hello World" < ------------------ 查看变量 str 当前的值

查看内存:examine(简写为x)可以用来查看内存地址中的值。语法如下:

x/[n][f][u] addr

其中:

单元类型常见有如下:

示例:

(gdb) x/4b str0x4006c8:    01001000    01100101    01101100    01101100

可以看到,变量 str 的四个字节都以二进制的方式打印出来了。

b 字节h 半字,即双字节w 字,即四字节g 八字节n 表示要显示的内存单元数,默认值为1f 表示要打印的格式,前面已经提到了格式控制字符u 要打印的单元长度addr 内存地址

查看寄存器内容:info registers

ra             0x3ff7ef2282     0x3ff7ef2282 < __libc_start_main+160 >sp             0x3ffffffaa0     0x3ffffffaa0gp             0x2aaaaac800     0x2aaaaac800tp             0x3ff7fdd250     0x3ff7fdd250t0             0x3ff7ed60b0     274742468784t1             0x3ff7ef21e2     274742583778t2             0x2aaaaac4f0     183251944688fp             0x3ffffffab0     0x3ffffffab0s1             0x0      0a0             0x1      1a1             0x3ffffffc28     274877905960a2             0x3ffffffc38     274877905976a3             0x0      0a4             0x3ffffffad8     274877905624a5             0x0      0a6             0x3ff7fd88a8     274743527592(内容过多未显示完全)

单步调试

单步执行-next:next命令(可简写为n)用于在程序断住后,继续执行下一条语句,假设已经启动调试,并在第12行停住,如果要继续执行,则使用n执行下一条语句,如果后面跟上数字num,则表示执行该命令num次,就达到继续执行n行的效果了:
gdb helloworld                     < ------------------------------- 加载程序   (gdb) break helloworld.c:18        < ------------------------------- 设置断点   (gdb) run                          < ------------------------------- 启动调试   The program being debugged has been started already.   Start it from the beginning? (y or n) y   Starting program: /home/book/helloworld   Helleo World.      Breakpoint 2, main (argc=1, argv=0x7fffffffdca8) at helloworld.c:18         < -------- 程序在 18 行暂停   18            result += i;   Breakpoint 2, main (argc=1, argv=0x7fffffffdca8) at helloworld.c:18   18            result += i;   (gdb) next                                    < --------  单步执行      17        for(i = 1; i <= 100; i++)  {      Breakpoint 2, main (argc=1, argv=0x7fffffffdca8) at helloworld.c:18   18            result += i;   (gdb) next 2                                  < --------  执行两次      Breakpoint 2, main (argc=1, argv=0x7fffffffdca8) at helloworld.c:18   18            result += i;
单步进入-step:如果我们想跟踪函数内部的情况,可以使用step命令(可简写为s),它可以单步跟踪到函数内部,但前提是该函数有调试信息并且有源码信息。断点继续-continue:continue命令(可简写为c),它会继续执行程序,直到再次遇到断点处。

关键词: