目錄
1. GDB簡介
2. GDB安裝教程
1）檢查機器上是否安裝gdb
2) 下載gdb原始碼包
3) 解壓gdb原始碼包
4) 安裝
5) 檢查是否安裝成功
3. GDB入門操作
1）創建測驗代碼
2）啟動gdb
3）斷點
4）運行
5）列印變數的的值
6）退出gdb
參考文章
1. GDB簡介
GDB，全稱 GNU symbolic debugger，簡稱 GDB除錯器，是 Linux 平臺下最常用的一款程式除錯器
2. GDB安裝教程
CentOSx下安裝GDB
1）檢查機器上是否安裝gdb
rpm -qa | grep gdb
[root@]# rpm -qa | grep gdb
gdbm-1.10-8.el7.x86_64
gdbm-devel-1.10-8.el7.x86_64若安裝，則采用以下命令卸載
rpm -e --nodeps [軟體版本]
[root@]# rpm -e --nodeps gdbm-1.10-8.el7.x86_64
[root@]# rpm -e --nodeps gdbm-devel-1.10-8.el7.x86_642) 下載gdb原始碼包
wget http://mirrors.ustc.edu.cn/gnu/gdb/gdb-7.9.1.tar.xz
[root@]# wget http://mirrors.ustc.edu.cn/gnu/gdb/gdb-7.9.1.tar.xz
--2020-10-19 15:05:39-- http://mirrors.ustc.edu.cn/gnu/gdb/gdb-7.9.1.tar.xz
Resolving mirrors.ustc.edu.cn (mirrors.ustc.edu.cn)... 202.141.176.110, 218.104.71.170, 2001:da8:d800:95::110
Connecting to mirrors.ustc.edu.cn (mirrors.ustc.edu.cn)|202.141.176.110|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 17867692 (17M) [application/octet-stream]
Saving to: ‘gdb-7.9.1.tar.xz’
100%[====================================================================================================================================================>] 17,867,692 36.5MB/s in 0.5s
2020-10-19 15:05:39 (36.5 MB/s) - ‘gdb-7.9.1.tar.xz’ saved [17867692/17867692]3) 解壓gdb原始碼包
tar -xf gdb-7.9.1.tar.xz
[root@]# tar -xf gdb-7.9.1.tar.xz4) 安裝
cd gdb-7.9.1
sudo yum install texinfo
./configure
make
sudo make install
[root@]# cd gdb-7.9.1
[root@]# sudo yum install texinfo
.
.
.
Dependency Installed:
perl-Text-Unidecode.noarch 0:0.04-20.el7 perl-libintl.x86_64 0:1.20-12.el7
Complete!
[root@]# ./configure
.
.
.
configure: creating ./config.status
config.status: creating Makefile
[root@]# make
.
.
.
make[1]: Nothing to be done for `all-target'.
make[1]: Leaving directory `/root/.vimplus/gdb-7.9.1'
[root@]# make install
.
.
.
make[1]: Nothing to be done for `install-target'.
make[1]: Leaving directory `/root/.vimplus/gdb-7.9.1'5) 檢查是否安裝成功
gdb -v
[root@]# gdb -v
GNU gdb (GDB) 7.9.1
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-unknown-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".3. GDB入門操作
命令 簡寫形式 說明
backtrace bt、where 顯示backtrace
break b 設定斷點
continue c、cont 繼續執行
delete d 洗掉斷點
finish 運行到函式結束
info breakpoints 顯示斷點資訊
next n 執行下一行
print p 顯示運算式
run r 運行程式
step s 一次執行一行，包括函式內部
x 顯示記憶體內容
until u 執行到指定行
其他命令
directory dir 插入目錄
disable dis 禁用斷點
down do 在當前呼叫的堆疊幀中選擇要顯示的堆疊幀
edit e 編輯檔案或者函式
frame f 選擇要顯示的堆疊幀
forward-search fo 向前搜索
generate-core-file gcore 生成內核轉存盤
help h 顯示幫助一覽
info i 顯示資訊
list l 顯示函式或行
nexti ni 執行下一行(以匯編代碼為單位)
print-object po 顯示目標資訊
sharelibrary share 加載共享的符號
stepi si 執行下一行
1）創建測驗代碼
vim test.c
gcc -g -o test.exe test.c
關于vim/vi的用法這里不再概述，推薦vim的配置程式vimplus
寫完代碼后，gcc編譯代碼（PS. 如果gcc編譯的時候沒有加上-g引數，那么就不會保留除錯引數，就不能用gdb除錯）
測驗代碼如下：
#include<stdio.h>
#include<stdlib.h>
int main( int argc , char *argv[] )
{
int a = 1;
int i = 0;
int b[3] = {0,1,2};
for(i = 0; i < 3;i++)
b[i] = b[i] + 1;
printf("%d\n",a);
int *p;
p = b;
printf("%d\n",p[0]);
return 0;
}2）啟動gdb
在 Linux 作業系統中，當程式執行發生例外崩潰時，系統可以將發生崩潰時的記憶體資料、呼叫堆疊情況等資訊自動記錄下載，并存盤到一個檔案中，該檔案通常稱為 core 檔案，Linux 系統所具備的這種功能又稱為核心轉儲（core dump），幸運的是，GDB 對 core 檔案的分析和除錯提供有非常強大的功能支持，當程式發生例外崩潰時，通過 GDB 除錯產生的 core 檔案，往往可以更快速的解決問題，
- 查看是否開啟 core dump 這一功能
ulimit -a
[root@]# ulimit -a
core file size (blocks, -c) 0
data seg size (kbytes, -d) unlimited
scheduling priority (-e) 0
file size (blocks, -f) unlimited
pending signals (-i) 7284
max locked memory (kbytes, -l) 64
max memory size (kbytes, -m) unlimited
open files (-n) 65535
pipe size (512 bytes, -p) 8
POSIX message queues (bytes, -q) 819200
real-time priority (-r) 0
stack size (kbytes, -s) 8192
cpu time (seconds, -t) unlimited
max user processes (-u) 7284
virtual memory (kbytes, -v) unlimited
file locks (-x) unlimited如果 core file size（core 檔案大小）對應的值為 0，表示當前系統未開啟 core dump 功能
- 開啟 core dump
ulimit -c unlimited
[root@]# ulimit -c unlimited
[root@]# ulimit -a
core file size (blocks, -c) unlimited
data seg size (kbytes, -d) unlimited
scheduling priority (-e) 0
file size (blocks, -f) unlimited
pending signals (-i) 7284
max locked memory (kbytes, -l) 64
max memory size (kbytes, -m) unlimited
open files (-n) 65535
pipe size (512 bytes, -p) 8
POSIX message queues (bytes, -q) 819200
real-time priority (-r) 0
stack size (kbytes, -s) 8192
cpu time (seconds, -t) unlimited
max user processes (-u) 7284
virtual memory (kbytes, -v) unlimited
file locks (-x) unlimitedunlimited 表示不限制 core 檔案的大小
測驗代碼：
1 #include <stdio.h>
2
3 int main()
4 {
5 char *p = NULL;
6 *p = 123;
7 return 0;
8 }測驗結果：
[root@]# vim main.c
[root@]# gcc -g -o main.exe main.c
[root@]# ls
main.c main.exe test.c test.exe
[root@]# ./main.exe
Segmentation fault (core dumped)
[root@]# ls
core.17313 main.c main.exe test.c test.exe測驗代碼中，發生記憶體訪問錯誤，程式崩潰，崩潰資訊存入core.17313檔案中
- 啟動gdb
gdb test.exe
[root@]# gdb test.exe
GNU gdb (GDB) 7.9.1
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-unknown-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 test.exe...done.
(gdb)_3）斷點
-
根據行號設定斷點
第一種 (gdb) b 5
第二種 (gdb) b test.c:5
-
根據函式設定斷點
(gdb) b main
-
根據條件設定斷點
(gdb) b test.c:10 if a == 1
-
根據偏移量設定斷點
(gdb) b +12
-
根據地址設定斷點
(gdb) b *0x40059b
-
設定臨時斷點
臨時斷點只生效一次
(gdb) tbreak test.c:12
(gdb) b test.c:5
Breakpoint 1 at 0x40053c: file test.c, line 5.
(gdb) b main
Note: breakpoint 1 also set at pc 0x40053c.
Breakpoint 2 at 0x40053c: file test.c, line 6.
(gdb) b test.c:10 if a == 1
Breakpoint 3 at 0x400568: file test.c, line 10.
(gdb) b +12
Breakpoint 4 at 0x40059b: file test.c, line 13.
(gdb) b *0x40059b
Note: breakpoint 4 also set at pc 0x40059b.
Breakpoint 5 at 0x40059b: file test.c, line 13.
(gdb) tbreak test.c:12
Note: breakpoints 4 and 5 also set at pc 0x40059b.
Temporary breakpoint 6 at 0x40059b: file test.c, line 12.-
顯示所有斷點
(gdb) info break
(gdb) info break
Num Type Disp Enb Address What
1 breakpoint keep y 0x000000000040053c in main at test.c:5
2 breakpoint keep y 0x000000000040053c in main at test.c:6
3 breakpoint keep y 0x0000000000400568 in main at test.c:10
stop only if a == 1
4 breakpoint keep y 0x000000000040059b in main at test.c:13
5 breakpoint keep y 0x000000000040059b in main at test.c:13
6 breakpoint del y 0x000000000040059b in main at test.c:12-
清除斷點
清除某個斷點 (gdb) delete 4
清除所有斷點 (gdb) delete
(gdb) delete 4
(gdb) delete
Delete all breakpoints? (y or n) y
(gdb) info break
No breakpoints or watchpoints.清除當前行斷點 (gdb) clear
Breakpoint 3, main (argc=1, argv=0x7fffffffe508) at test.c:13
13 p = b;
(gdb) clear
Deleted breakpoint 3 4）運行
- 運行和繼續
運行 r
繼續單步除錯 n
繼續執行到下一個斷點 c
-
查看原始碼和行號
l
(gdb) l
1 #include <stdio.h>
2 #include <stdlib.h>
3
4 int main( int argc, char *argv[])
5 {
6 int a = 1;
7 int i = 0;
8 int b[3] = {0, 1, 2};
9 for (i = 0; i < 3; i++)
10 b[i] = b[i] + 1;
(gdb) l
11 printf("%d\n", a);
12 int *p;
13 p = b;
14 printf("%d\n", p[0]);
15 return 0;
16 }
(gdb) l
Line number 17 out of range; test.c has 16 lines.5）列印變數的的值
- 列印變數
p a
- 列印指標
p p
- 列印main函式中的變數a
p 'main'::a
- 列印指標指向的內容，@后面跟的是列印的長度
p *p@3
(gdb) run
Starting program: /root/daizhh/test.exe
Breakpoint 1, main (argc=1, argv=0x7fffffffe508) at test.c:11
11 printf("%d\n", a);
(gdb) p a
$1 = 1
(gdb) p b
$2 = {1, 2, 3}
(gdb) n
1
13 p = b;
(gdb) c
Continuing.
Breakpoint 2, main (argc=1, argv=0x7fffffffe508) at test.c:14
14 printf("%d\n", p[0]);
(gdb) p p
$3 = (int *) 0x7fffffffe400
(gdb) p 'main'::a
$4 = 1
(gdb) p *p@3
$5 = {1, 2, 3}- 設定變數列印
set $index = 0
p p[$index]
(gdb) set $index = 0
(gdb) p p[$index]
$6 = 1- 設定列印格式
- x 按十六進制格式顯示變數
- d 按十進制格式顯示變數
- u 按十六進制格式顯示無符號整型
- o 按八進制格式顯示變數
- t 按二進制格式顯示變數
- a 按十六進制格式顯示變數
- c 按字符格式顯示變數
- f 按浮點數格式顯示變數
(gdb) p/x a（按十六進制格式顯示變數）
(gdb) p/x a
$7 = 0x16）退出gdb
q
參考文章
http://c.biancheng.net/gdb/
https://blog.csdn.net/wh_computers/article/details/94618240
https://blog.csdn.net/andrewgithub/article/details/88210949
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