6 Linu下gdp调试技术

6-1 学习使用gdb

• 使用gdb命令进入gdb来调试

gdb ./helloworld #或者 gdb helloworld

• 操作过程
  其中，p a表示打印a的值
  
  
  
  
  
• 表示十六进制， d表示整型, u表示无符号整型， f表示浮点型, s表示字符串。
• b(byte)表示1个字节, h（half-word）表示2个字节， w(word)表示4个字节, g(giant)表示8个字节。
  
• 操作过程
  
  

6-2 段错误与内存转储

什么情况下会发生段错误？

使用gdb命令来定位段错误

• 实际操作
  
  
  
• 实际操作

ulimit -c unlimited #shell的路径在main.cpp路径下
./helloworld
gdb helloworld core.*
bt #使用bt查看函数调用栈

gdb的补充说明

• 如何生成带有调试信息的可执行文件？
  
• 如何判断一个程序带有调试信息？
  
• 实验操作，带有调试信息的helloworld

objdump -h helloworld
##生成下面的信息
 0 .interp 0000001c 0000000000400238 0000000000400238 00000238 2**0
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  1 .note.ABI-tag 00000020 0000000000400254 0000000000400254 00000254 2**2
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  2 .note.gnu.build-id 00000024 0000000000400274 0000000000400274 00000274 2**2
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  3 .gnu.hash 00000030 0000000000400298 0000000000400298 00000298 2**3
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  4 .dynsym 00000150 00000000004002c8 00000000004002c8 000002c8 2**3
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  5 .dynstr 00000155 0000000000400418 0000000000400418 00000418 2**0
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  6 .gnu.version 0000001c 000000000040056e 000000000040056e 0000056e 2**1
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  7 .gnu.version_r 00000050 0000000000400590 0000000000400590 00000590 2**3
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  8 .rela.dyn 00000030 00000000004005e0 00000000004005e0 000005e0 2**3
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  9 .rela.plt 000000c0 0000000000400610 0000000000400610 00000610 2**3
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
 10 .init 0000001a 00000000004006d0 00000000004006d0 000006d0 2**2
                  CONTENTS, ALLOC, LOAD, READONLY, CODE
 11 .plt 00000090 00000000004006f0 00000000004006f0 000006f0 2**4
                  CONTENTS, ALLOC, LOAD, READONLY, CODE
 12 .plt.got 00000008 0000000000400780 0000000000400780 00000780 2**3
                  CONTENTS, ALLOC, LOAD, READONLY, CODE
 13 .text 000002b2 0000000000400790 0000000000400790 00000790 2**4
                  CONTENTS, ALLOC, LOAD, READONLY, CODE
 14 .fini 00000009 0000000000400a44 0000000000400a44 00000a44 2**2
                  CONTENTS, ALLOC, LOAD, READONLY, CODE
 15 .rodata 00000004 0000000000400a50 0000000000400a50 00000a50 2**2
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
 16 .eh_frame_hdr 0000005c 0000000000400a54 0000000000400a54 00000a54 2**2
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
 17 .eh_frame 00000194 0000000000400ab0 0000000000400ab0 00000ab0 2**3
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
 18 .init_array 00000018 0000000000600df0 0000000000600df0 00000df0 2**3
                  CONTENTS, ALLOC, LOAD, DATA
 19 .fini_array 00000008 0000000000600e08 0000000000600e08 00000e08 2**3
                  CONTENTS, ALLOC, LOAD, DATA
 20 .jcr 00000008 0000000000600e10 0000000000600e10 00000e10 2**3
                  CONTENTS, ALLOC, LOAD, DATA
 21 .dynamic 000001e0 0000000000600e18 0000000000600e18 00000e18 2**3
                  CONTENTS, ALLOC, LOAD, DATA
 22 .got 00000008 0000000000600ff8 0000000000600ff8 00000ff8 2**3
                  CONTENTS, ALLOC, LOAD, DATA
 23 .got.plt 00000058 0000000000601000 0000000000601000 00001000 2**3
                  CONTENTS, ALLOC, LOAD, DATA
 24 .data 00000010 0000000000601058 0000000000601058 00001058 2**3
                  CONTENTS, ALLOC, LOAD, DATA
 25 .bss 00000118 0000000000601080 0000000000601080 00001068 2**5
                  ALLOC
 26 .comment 0000002d 0000000000000000 0000000000000000 00001068 2**0
                  CONTENTS, READONLY
 27 .debug_aranges 00000060 0000000000000000 0000000000000000 00001095 2**0
                  CONTENTS, READONLY, DEBUGGING
 28 .debug_info 000029d4 0000000000000000 0000000000000000 000010f5 2**0
                  CONTENTS, READONLY, DEBUGGING
 29 .debug_abbrev 00000765 0000000000000000 0000000000000000 00003ac9 2**0
                  CONTENTS, READONLY, DEBUGGING
 30 .debug_line 000004ad 0000000000000000 0000000000000000 0000422e 2**0
                  CONTENTS, READONLY, DEBUGGING
 31 .debug_str 00000d46 0000000000000000 0000000000000000 000046db 2**0

• 实验操作，不带调试信息的helloworld

objdump -h helloworld
## 生成以下信息
 0 .interp 0000001c 0000000000400238 0000000000400238 00000238 2**0
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  1 .note.ABI-tag 00000020 0000000000400254 0000000000400254 00000254 2**2
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  2 .note.gnu.build-id 00000024 0000000000400274 0000000000400274 00000274 2**2
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  3 .gnu.hash 00000030 0000000000400298 0000000000400298 00000298 2**3
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  4 .dynsym 00000150 00000000004002c8 00000000004002c8 000002c8 2**3
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  5 .dynstr 00000155 0000000000400418 0000000000400418 00000418 2**0
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  6 .gnu.version 0000001c 000000000040056e 000000000040056e 0000056e 2**1
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  7 .gnu.version_r 00000050 0000000000400590 0000000000400590 00000590 2**3
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  8 .rela.dyn 00000030 00000000004005e0 00000000004005e0 000005e0 2**3
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  9 .rela.plt 000000c0 0000000000400610 0000000000400610 00000610 2**3
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
 10 .init 0000001a 00000000004006d0 00000000004006d0 000006d0 2**2
                  CONTENTS, ALLOC, LOAD, READONLY, CODE
 11 .plt 00000090 00000000004006f0 00000000004006f0 000006f0 2**4
                  CONTENTS, ALLOC, LOAD, READONLY, CODE
 12 .plt.got 00000008 0000000000400780 0000000000400780 00000780 2**3
                  CONTENTS, ALLOC, LOAD, READONLY, CODE
 13 .text 000002b2 0000000000400790 0000000000400790 00000790 2**4
                  CONTENTS, ALLOC, LOAD, READONLY, CODE
 14 .fini 00000009 0000000000400a44 0000000000400a44 00000a44 2**2
                  CONTENTS, ALLOC, LOAD, READONLY, CODE
 15 .rodata 00000004 0000000000400a50 0000000000400a50 00000a50 2**2
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
 16 .eh_frame_hdr 0000005c 0000000000400a54 0000000000400a54 00000a54 2**2
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
 17 .eh_frame 00000194 0000000000400ab0 0000000000400ab0 00000ab0 2**3
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
 18 .init_array 00000018 0000000000600df0 0000000000600df0 00000df0 2**3
                  CONTENTS, ALLOC, LOAD, DATA
 19 .fini_array 00000008 0000000000600e08 0000000000600e08 00000e08 2**3
                  CONTENTS, ALLOC, LOAD, DATA
 20 .jcr 00000008 0000000000600e10 0000000000600e10 00000e10 2**3
                  CONTENTS, ALLOC, LOAD, DATA
 21 .dynamic 000001e0 0000000000600e18 0000000000600e18 00000e18 2**3
                  CONTENTS, ALLOC, LOAD, DATA
 22 .got 00000008 0000000000600ff8 0000000000600ff8 00000ff8 2**3
                  CONTENTS, ALLOC, LOAD, DATA
 23 .got.plt 00000058 0000000000601000 0000000000601000 00001000 2**3
                  CONTENTS, ALLOC, LOAD, DATA
 24 .data 00000010 0000000000601058 0000000000601058 00001058 2**3
                  CONTENTS, ALLOC, LOAD, DATA
 25 .bss 00000118 0000000000601080 0000000000601080 00001068 2**5
                  ALLOC
 26 .comment 00000035 0000000000000000 0000000000000000 00001068 2**0

• 什么时候使用gdb，是么时候使用打印调试
  

gdb调试 -带有命令行参数参考博客

今天在实现http客户端编程的时候，需要使用命令行参数来输入host的ip地址。但是程序运行的过程中一直报段错误。没办法，只能用gdb进行调试。那么怎样在调试的时候输入我们需要的命令行参数呢。一般有两种方法。

• 进入gdb调试：

gcc -g -Wall httpTest.c -o test  #生成了可调试文件
gdb test 进入调试

• 下面可以使用两种方法输入命令行参数

  • run 命令行参数
  • set args 命令行参数

• 如：我的程序中需要输入的时服务器端ip地址，可以通过以下两种方法输入

  • 如果直接运行程序，run www.baidu.com

  • set args www.baidu.com,后面再继续进行调试

• 实验操作

  • 这里演示调试darknet，我们使用gdb darknet运行gdb，然后添加调试的命令行参数set args detect cfg/yolov2.cfg yolov2.weights data/dog.jpg，最后run运行整个程序。
  • 这里由于运行gdb darknet时没有加sudo，所以报错："darknet" received signal SIGBRT, Aborted.，加上sudo即可正常调试。