linux調(diào)試工具gdb具體步驟（GDB調(diào)試入門）

本篇講解使用GDB調(diào)試Linux應(yīng)用程序，下面以?hellowld.c?為例，簡單介紹一下 GDB 的調(diào)試入門。

1、編寫代碼

#include?

int?main(int?argc,?char?**argv)
{
????int?i;
????int?result?=?0;

????if(1?>=?argc)
????{
????????printf("Helloworld.
");
????}
????printf("Hello World?%s!
",argv[1]);

????for(i?=?1;?i?<=?100;?i++)??{
????????result?+=?i;
????}

????printf("result?=?%d
",?result?);

????return?0;
}

編譯時(shí)加上?-g?參數(shù)：

gcc helloworld.c?-o hellowrld?-g

2、啟動(dòng)調(diào)試

$?gdb helloWorld
GNU gdb?(GDB)?Red Hat Enterprise Linux 8.2-12.el8
Copyright?(C)?2018 Free Software Foundation,?Inc.
License GPLv3+:?GNU GPL version 3 or later?
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".
Type?"show configuration"?for?configuration details.
For bug reporting instructions,?please see:
.
Find the GDB manual and other documentation resources online at:
????.

For?help,?type?"help".
Type?"apropos word"?to search?for?commands related to?"word"...
Reading symbols from helloworld...done.
(gdb)?run??????????????????<-----------------------------?不帶參數(shù)運(yùn)行
Starting program:?/home/zhuzhg/helloworld
Missing separate debuginfos,?use:?yum debuginfo-install glibc-2.28-101.el8.x86_64
helloworld.
result?=?5050
[Inferior 1?(process 1069013)?exited normally]
(gdb)?run China????????????<-----------------------------?帶參數(shù)運(yùn)行
Starting program:?/home/zhuzhg/helloworld China
Hello World China!
result?=?5050
[Inferior 1?(process 1071086)?exited normally]
(gdb)

3、斷點(diǎn)

設(shè)置斷點(diǎn)

文件行號(hào)斷點(diǎn)：break hellowrld.c:9

函數(shù)斷點(diǎn)：break main

條件斷點(diǎn)：break helloworld.c:17 if c == 10

臨時(shí)斷點(diǎn), 假設(shè)某處的斷點(diǎn)只想生效一次，那么可以設(shè)置臨時(shí)斷點(diǎn)，這樣斷點(diǎn)后面就不復(fù)存在了：tbreak helleworld.c:9

禁用或啟動(dòng)斷點(diǎn)：

??disable?????????????????#?禁用所有斷點(diǎn)
??disable bnum????????????#?禁用標(biāo)號(hào)為bnum的斷點(diǎn)
??enable??????????????????#?啟用所有斷點(diǎn)
??enable bnum?????????????#?啟用標(biāo)號(hào)為bnum的斷點(diǎn)
??enable?delete?bnum??????#?啟動(dòng)標(biāo)號(hào)為bnum的斷點(diǎn)，并且在此之后刪除該斷點(diǎn)

斷點(diǎn)清除：

??clear???????????????????#?刪除當(dāng)前行所有breakpoints
??clear function??????????#?刪除函數(shù)名為function處的斷點(diǎn)
??clear filename:function?#?刪除文件filename中函數(shù)function處的斷點(diǎn)
??clear lineNum???????????#?刪除行號(hào)為lineNum處的斷點(diǎn)
??clear flineNum??#?刪除文件filename中行號(hào)為lineNum處的斷點(diǎn)
??delete??????????????????#?刪除所有breakpoints,watchpoints和catchpoints
??delete?bnum?????????????#?刪除斷點(diǎn)號(hào)為bnum的斷點(diǎn)

4、變量查看

b 字節(jié)

h 半字，即雙字節(jié)

w 字，即四字節(jié)

g 八字節(jié)

n 表示要顯示的內(nèi)存單元數(shù)，默認(rèn)值為1

f 表示要打印的格式，前面已經(jīng)提到了格式控制字符

u 要打印的單元長度

addr 內(nèi)存地址

變量查看:?最常見的使用便是使用print（可簡寫為p）打印變量內(nèi)容。

以上述程序?yàn)槔?/p>

gdb helloworld
break?helloworld.c:17?if?i?==?0
(gdb)?run
Starting program:?/home/book/helloworld
helloworld.

Breakpoint?2,?main?(argc=1,?argv=0x7fffffffdca8)?at helloworld.c:17
17????????????result?+=?i;
(gdb)?print i????????????????<------------------?查看變量?i?當(dāng)前的值
$1?=?10
(gdb)?print result???????????<------------------?查看變量?result?當(dāng)前的值
$2?=?45
(gdb)?print argc?????????????<------------------?查看變量?argc?當(dāng)前的值
$3?=?1
(gdb)?print str
$4?=?0x4006c8?"Hello World"?<------------------?查看變量?str?當(dāng)前的值

查看內(nèi)存：?examine(簡寫為x)可以用來查看內(nèi)存地址中的值。語法如下：

x/[n][f][u]?addr

其中：

單元類型常見有如下：

示例：

(gdb)?x/4b?str
0x4006c8:????01001000????01100101????01101100????01101100

可以看到，變量 str 的四個(gè)字節(jié)都以二進(jìn)制的方式打印出來了。

查看寄存器內(nèi)容：info registers

ra?????????????0x3ff7ef2282?????0x3ff7ef2282?<__libc_start_main+160>
sp?????????????0x3ffffffaa0?????0x3ffffffaa0
gp?????????????0x2aaaaac800?????0x2aaaaac800
tp?????????????0x3ff7fdd250?????0x3ff7fdd250
t0?????????????0x3ff7ed60b0?????274742468784
t1?????????????0x3ff7ef21e2?????274742583778
t2?????????????0x2aaaaac4f0?????183251944688
fp?????????????0x3ffffffab0?????0x3ffffffab0
s1?????????????0x0??????0
a0?????????????0x1??????1
a1?????????????0x3ffffffc28?????274877905960
a2?????????????0x3ffffffc38?????274877905976
a3?????????????0x0??????0
a4?????????????0x3ffffffad8?????274877905624
a5?????????????0x0??????0
a6?????????????0x3ff7fd88a8?????274743527592
(內(nèi)容過多未顯示完全)

5、單步調(diào)試

單步執(zhí)行-next：

next命令（可簡寫為n）用于在程序斷住后，繼續(xù)執(zhí)行下一條語句，假設(shè)已經(jīng)啟動(dòng)調(diào)試，并在第12行停住，如果要繼續(xù)執(zhí)行，則使用n執(zhí)行下一條語句，如果后面跟上數(shù)字num，則表示執(zhí)行該命令num次，就達(dá)到繼續(xù)執(zhí)行n行的效果了：

???gdb helloworld?????????????????????<-------------------------------?加載程序
???(gdb)?break?helloworld.c:18????????<-------------------------------?設(shè)置斷點(diǎn)
???(gdb)?run??????????????????????????<-------------------------------?啟動(dòng)調(diào)試
???The program being debugged has been started already.
???Start it from the beginning??(y?or?n)?y
???Starting program:?/home/book/helloworld
???Helleo World.
???
???Breakpoint?2,?main?(argc=1,?argv=0x7fffffffdca8)?at helloworld.c:18?????????<--------?程序在?18?行暫停
???18????????????result?+=?i;
???Breakpoint?2,?main?(argc=1,?argv=0x7fffffffdca8)?at helloworld.c:18
???18????????????result?+=?i;
???(gdb)?next????????????????????????????????????<--------??單步執(zhí)行
???
???17????????for(i?=?1;?i?<=?100;?i++)??{
???
???Breakpoint?2,?main?(argc=1,?argv=0x7fffffffdca8)?at helloworld.c:18
???18????????????result?+=?i;
???(gdb)?next?2??????????????????????????????????<--------??執(zhí)行兩次
???
???Breakpoint?2,?main?(argc=1,?argv=0x7fffffffdca8)?at helloworld.c:18
???18????????????result?+=?i;

單步進(jìn)入-step：

如果我們想跟蹤函數(shù)內(nèi)部的情況，可以使用step命令（可簡寫為s），它可以單步跟蹤到函數(shù)內(nèi)部，但前提是該函數(shù)有調(diào)試信息并且有源碼信息。

斷點(diǎn)繼續(xù)-continue：

continue命令（可簡寫為c），它會(huì)繼續(xù)執(zhí)行程序，直到再次遇到斷點(diǎn)處。

編輯：黃飛

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