[[email protected] share]# gdb test        >>>>>>>>>>>>>>>啟動gdb時直接指定可執行檔案

GNU gdb (GDB) Red Hat Enterprise Linux  (7.0.1-32.el5)

Copyright (C) 2009 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".

For bug reporting instructions, please  see:

<http://www.gnu.org/software/gdb/bugs/>...

Reading symbols from  /data/yinsy/share/test...done.

(gdb) l               >>>>>>>>>>>>>>>顯示（預設10行）原始碼

1        #include<stdio.h>

2        #include<stdlib.h>

3        #include <string.h>

4

5        int main()

6        {

7           char* a=malloc(3);

8           char* b=malloc(5);

9

10          printf("please enter a string  for b:");

(gdb)                >>>>>>>>>>>>>>>直接按enter，重複上一條子命令

11          scanf("%s",b);

12          printf("please enter a string  for a:");

13           scanf("%s",a);

14          printf("address:  a=%p,b=%p\n",a,b);

15          printf("strlen :  a=%d,b=%d\n",strlen(a),strlen(b));

16          printf("content:  a=%s,b=%s\n",a,b);

17

18          free(a);

19          free(b);

20       }

(gdb) b 9            >>>>>>>>>>>>>>>在第9行設定斷點

Breakpoint 1 at 0x40058c: file test.c,  line 9.

(gdb) b 17            >>>>>>>>>>>>>>>在第17行設定斷點

Breakpoint 2 at 0x400657: file test.c,  line 17.

(gdb) i b              >>>>>>>>>>>>>>>顯示已經設定的斷點資訊

Num      Type           Disp Enb  Address            What

1        breakpoint     keep y   0x000000000040058c in main at test.c:9

2        breakpoint     keep y   0x0000000000400657 in main at test.c:17

(gdb) r               >>>>>>>>>>>>>>>開始執行可執行檔案

Starting program: /data/yinsy/share/test

Breakpoint 1, main () at test.c:10         >>>>>>>>>>>>>>>在第一個斷點出停下來，等待命令

10          printf("please enter a string  for b:");

(gdb) p a             >>>>>>>>>>>>>>>列印指標a的值，以及其指向地址的內容，當前為空

$1 = 0x601010 ""

(gdb) p b            >>>>>>>>>>>>>>>列印指標b的值，以及其指向地址的內容，當前為空

$2 = 0x601030 ""

(gdb) s              >>>>>>>>>>>>>>>單步執行

11          scanf("%s",b);

(gdb)               >>>>>>>>>>>>>>>繼續單步執行，給b賦值“01234”

please enter a string for b:01234

12          printf("please enter a string  for a:");

(gdb)

13          scanf("%s",a);

(gdb) p b           >>>>>>>>>>>>>>>給a賦值前，列印b指標及其指向地址的內容，仍為“01234”

$3 = 0x601030 "01234"

(gdb) s

please enter a string for  a:abcdefghijklmnopqrstuvwxyzabcdefghijk

14          printf("address:  a=%p,b=%p\n",a,b);

(gdb) p a

$4 = 0x601010 "abcdefghijklmnopqrstuvwxyzabcdefghijk"

(gdb) p b           >>>>>>>>>>>>>>>給a賦值後，b指標指向地址的內容也發生變化，變為“ghijk”

$5 = 0x601030 "ghijk"

(gdb) c             >>>>>>>>>>>>>>>繼續執行程式，直到遇到第二個斷點暫停

Continuing.

address: a=0x601010,b=0x601030

strlen : a=37,b=5

content: a=abcdefghijklmnopqrstuvwxyzabcdefghijk,b=ghijk

Breakpoint 2, main () at test.c:18

18          free(a);

(gdb) s             >>>>>>>>>>>>>>>繼續單步執行free(a)操作，程式出現錯誤，glibc提示invalid next size

*** glibc detected ***  /data/yinsy/share/test: free(): invalid next size (fast): 0x0000000000601010  ***

======= Backtrace: =========

/lib64/libc.so.6[0x3e13c7245f]

/lib64/libc.so.6(cfree+0x4b)[0x3e13c728bb]

/data/yinsy/share/test[0x400660]

/lib64/libc.so.6(__libc_start_main+0xf4)[0x3e13c1d994]

/data/yinsy/share/test[0x4004b9]

======= Memory map: ========

00400000-00401000 r-xp 00000000 08:06  674109                              /data/yinsy/share/test

00600000-00601000 rw-p 00000000 08:06  674109                              /data/yinsy/share/test

00601000-00622000 rw-p 00601000 00:00  0                                   [heap]

3893600000-389360d000 r-xp 00000000 08:05 278756                          /lib64/libgcc_s-4.1.2-20080825.so.1

389360d000-389380d000 ---p 0000d000 08:05 278756                          /lib64/libgcc_s-4.1.2-20080825.so.1

389380d000-389380e000 rw-p 0000d000 08:05 278756                          /lib64/libgcc_s-4.1.2-20080825.so.1

3e13800000-3e1381c000 r-xp 00000000 08:05  278556                          /lib64/ld-2.5.so

3e13a1b000-3e13a1c000 r--p 0001b000 08:05  278556                         /lib64/ld-2.5.so

3e13a1c000-3e13a1d000 rw-p 0001c000 08:05  278556                          /lib64/ld-2.5.so

3e13c00000-3e13d4e000 r-xp 00000000 08:05  283255                          /lib64/libc-2.5.so

3e13d4e000-3e13f4e000 ---p 0014e000 08:05  283255                          /lib64/libc-2.5.so

3e13f4e000-3e13f52000 r--p 0014e000 08:05  283255                          /lib64/libc-2.5.so

3e13f52000-3e13f53000 rw-p 00152000 08:05  283255                          /lib64/libc-2.5.so

3e13f53000-3e13f58000 rw-p 3e13f53000  00:00 0

2aaaaaaab000-2aaaaaaaf000 r-xp  2aaaaaaab000 00:00 0                       [vdso]

2aaaaaaaf000-2aaaaaab3000 rw-p  2aaaaaaaf000 00:00 0

2aaaaaade000-2aaaaaadf000 rw-p  2aaaaaade000 00:00 0

7ffffffea000-7ffffffff000 rw-p 7ffffffe9000  00:00 0                      [stack]

ffffffffff600000-ffffffffffe00000 ---p  00000000 00:00 0                   [vsyscall]

Program received signal SIGABRT, Aborted.

0x0000003e13c30265 in raise () from  /lib64/libc.so.6

(gdb) s

Single stepping until exit from function  raise,

which has no line number information.

Program terminated with signal SIGABRT,  Aborted.

The program no longer exists.

(gdb) q             >>>>>>>>>>>>>>>退出gdb除錯