cgdb---ubuntu14.04下安装cgdb及gdb的使用

一. ubuntu 14.04 下安装cgdb
1.ubuntun14.04下安装cgdb
cong@msi:~$ sudo apt-get install cgdb

2. 使用:cgdb ./hello就可以了
a. cgdb分为上面的vi窗口与下面的gdb窗口

1. ESC->切到vi窗口
   
2. i>切到gdb窗口
   
3. >减小vi窗口
   
4. =>增大vi窗口
   
5. shift>减小很多vi窗口
   
6. shift>增大很多vi窗口

b.断点
空格添加/删除断点
c. gdbinit脚本不能用

warning:File"/work/ffmpeg/jpeg/jpegc/.gdbinit"auto-loading has been declined by your `auto-load safe-path'setto"$debugdir:$datadir/auto-load".

Toenable execution of this file addadd-autoloadsafepath/workffmpegjpegjpegc/.gdbinitlinetoyour configuration file"/home/cong/.gdbinit"Tocompletely disable this security protection add setload safe/ lineFormore information about this security protection see the "Auto-loading safe path"sectioninthe GDB manual.E.g.,run from the shell:

info"(gdb)Auto-loading safe path"

临时的方法:在gdb的命令行里面 source .gdbinit
永久的方法:cong@msi:~$ cat .gdbinit
set auto-load safe-path /

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二. gdb的使用
1. 断点
a. 在指定文件中指定函数处设断点

b<filename>:<func_name>

b<line_num> --> 例:break mm/slab.c:673

2. 打印
2.1
p {i,j,k,l} -->打印多个变量
display {i,l} --> 每执行一次都打印这几个变量
undisplay --> 去掉display

3.2 打印某个地址处的数据

(gdb)help x

examine memory:x/FMT ADDRESS.

ADDRESSisan expressionforthe memory addresstoexamine.

FMTisa repeat count followed by a format letteranda size letter.-->显示格式用两部分表示

Format letters are: -->格式类型

o(octal),

x(hex

d(decimal

u(unsigned decimal

t(binary

f(float

a(address

i(instruction

c(char

sstring)

zontheleft.

Size letters are: -->长度类型

b(byte

h(halfword

w(word

g(giant.

The specified number of objects of the specified size are printed

accordingtothe format.

例如要按16进制显示类型为short的inode->i_zone
(gdb) x /20xh inode->i_zone
0x2cb92 : 0xbbc7 0xbbc8 0xbbc9 0xbbca 0xbbcb 0xbbcc 0xbbcd 0xbbce
0x2cba2 : 0x0000 0x0000 0x0000 0x0000 0x0000 0x0b6b 0x9bdc 0x0000
0x2cbb2 : 0x0000 0x0301 0x0931 0x0001

注: 要用display自动显示--> display /40wx 0xc0101f80

2.3 gdb汇编级调试

)display/5i $pc -->pc是gdb的一个内部变量,打印当前的5条汇编指令

1/5i $pc

>0x1111dc<system_call:push%eax

0x1111dd+1:cld

0x1111de+2%gs

0x1111e0+4%fs

0x1111e2+6%es

)ni --> ni(nexti) 或si(stepi)进行汇编指令级调试

0x001111ddinsystem_call()