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

 ESC-->切到vi窗口
 i -->切到gdb窗口
 - -->减小vi窗口
 = -->增大vi窗口
  shift - -->减小很多vi窗口
  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' set to "$debugdir:$datadir/auto-load".
 To enable execution of this file add   add-auto-load-safe-path /work/ffmpeg/jpeg/jpegc/.gdbinit   line to your configuration file "/home/cong/.gdbinit".
 To completely disable this security protection add    set auto-load safe-path /    line to your configuration file "/home/cong/.gdbinit".
 For more information about this security protection see the  "Auto-loading safe path" section in the 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 <filename>: <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,j,k,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.
 ADDRESS is an expression for the memory address to examine.
 FMT is a repeat count followed by a format letter and a 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),
     s(string)
     z(hex, zero padded on the left).
 Size letters are:                        -->长度类型
     b(byte),
     h(halfword),
     w(word),
     g(giant, 8 bytes).
 The specified number of objects of the specified size are printed
 according to the 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

 (gdb) 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: x/5i $pc
 => 0x1111dc <system_call>:    push %eax
    0x1111dd <system_call+1>:    cld
    0x1111de <system_call+2>:    push %gs
    0x1111e0 <system_call+4>:    push %fs
    0x1111e2 <system_call+6>:    push %es
 (gdb) ni                              --> ni(nexti) 或si(stepi)进行汇编指令级调试
 0x001111dd in system_call ()