GDB调试

一 GDB调试Core_dump

　1 设置core文件大小为无限制：

ulimit -c unlimited

2 使用gcc -g 编译程序（-g 编译器将符号表（对应于程序的变量和代码行的内存地址列表）保存在生成的可执行文件中）：

gcc -g ./test.c

　2 运行程序 ./a.out，产生段错误，生成core文件。

3 使用gdb查看core文件：

　　gdb ./a.out ./core

　　输出如下：

GNU gdb (Ubuntu 7.9-1ubuntu1) 7.9
Copyright (C) 2015 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-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 ./a.out...done.
[New LWP 3115]
Core was generated by `./a.out'.
Program terminated with signal SIGSEGV, Segmentation fault.
#0  0x000000000040051b in do_it () at ./test.c:11
11        *p = 'a';

　　如果只想显示错误所在行，使用where：

(gdb) where
#0  0x000000000040051b in do_it () at ./test.c:11
#1  0x0000000000400504 in main () at ./test.c:4

二 GDB插入断点

　　1）使用gcc -g 编译源代码得到可执行文件 b

　gcc btest.c -g -o b.out

　　2）进入gdb模式，file b 加载可执行文件b

　　(gdb) file b.out

　　Reading symbols from b.out

　　...done.

　　3）run 执行

(gdb) r
Starting program: /home/lijinxu/UNIX/Gdb/b.out 
n = 1, nGlobalVar = 88 /ntempFunction is called, a = 1, b = 2 /nn = 3[Inferior 1 (process 3240) exited normally]

　　4) 在主函数入口处插入断点然后run

(gdb) b main
Breakpoint 2 at 0x40056d: file btest.c, line 14.
(gdb) r
Starting program: /home/lijinxu/UNIX/Gdb/b.out 
Breakpoint 2, main () at btest.c:14
14        n = 1;

　　上面信息表示下面将要执行的语句是第14行： n=1；

　　5）step 执行下一条：

(gdb) s
15        n++;

　　6）print 查看变量的值：

(gdb) p n
$1 = 1

　　横插一脚：在vi中显示行号：

：set nu  #全部显示行号
：nu       #显示当前行号

　　7）按照函数名和行号分别插入断点：

(gdb) break 26
Breakpoint 3 at 0x4005da: file btest.c, line 26.
(gdb) b tempFunction 
Breakpoint 4 at 0x400544: file btest.c, line 7.

　　8）continue命令继续执行：

(gdb) c
Continuing.
n = 1, nGlobalVar = 88 

Breakpoint 4, tempFunction (a=1, b=2) at btest.c:7
7        printf("tempFunction is called, a = %d, b = %d 
", a, b);

三查看汇编代码

(gdb) display /i $pc

　　以后再进行到断点处就会显示相应的汇编代码了。

四删除断点

五查看寄存器

　　information register

(gdb) b *main
Breakpoint 1 at 0x400565: file btest.c, line 12.
(gdb) r
Starting program: /home/lijinxu/UNIX/Gdb/b.out 

Breakpoint 1, main () at btest.c:12
12    {
(gdb) i r
rax            0x400565    4195685
rbx            0x0    0
rcx            0x0    0
rdx            0x7fffffffdf18    140737488346904
rsi            0x7fffffffdf08    140737488346888
rdi            0x1    1
rbp            0x4005f0    0x4005f0 <__libc_csu_init>
rsp            0x7fffffffde28    0x7fffffffde28
r8             0x7ffff7dd4dd0    140737351863760
r9             0x7ffff7de99d0    140737351948752
r10            0x833    2099
r11            0x7ffff7a2f950    140737348041040
r12            0x400440    4195392
r13            0x7fffffffdf00    140737488346880
r14            0x0    0
r15            0x0    0
rip            0x400565    0x400565 <main>
eflags         0x246    [ PF ZF IF ]
cs             0x33    51
ss             0x2b    43
ds             0x0    0
es             0x0    0
fs             0x0    0

　　显示指定寄存器：

(gdb) i r eax

六退出