gdb调试的基本使用

朱雀 2021-11-22 09:30 320阅读 0赞

原文地址：[https://www.cnblogs.com/HKUI/p/8955443.html][https_www.cnblogs.com_HKUI_p_8955443.html]

GDB调试  
启动程序准备调试  
**GDB yourpram**  
或者  
先输入GDB  
然后输入** file yourpram**

然后使用run或者r命令开始程序的执行,也可以使用 run parameter将参数传递给该程序

**参数列表**

<table> 
 <tbody> 
 <tr> 
 <td> 命令 </td> 
 <td> 命令缩写 </td> 
 <td> 命令说明 </td> 
 </tr> 
 <tr> 
 <td> list </td> 
 <td> l </td> 
 <td> 显示多行源代码 </td> 
 </tr> 
 <tr> 
 <td> break </td> 
 <td> b </td> 
 <td> 设置断点,程序运行到断点的位置会停下来 </td> 
 </tr> 
 <tr> 
 <td> info </td> 
 <td> i </td> 
 <td> 描述程序的状态 </td> 
 </tr> 
 <tr> 
 <td> run </td> 
 <td> r </td> 
 <td> 开始运行程序 </td> 
 </tr> 
 <tr> 
 <td> display </td> 
 <td> disp </td> 
 <td> 跟踪查看某个变量,每次停下来都显示它的值 </td> 
 </tr> 
 <tr> 
 <td> step </td> 
 <td> s </td> 
 <td> 执行下一条语句,如果该语句为函数调用,则进入函数执行其中的第一条语句 </td> 
 </tr> 
 <tr> 
 <td> next </td> 
 <td> n </td> 
 <td> 执行下一条语句,如果该语句为函数调用,不会进入函数内部执行(即不会一步步地调试函数内部语句) </td> 
 </tr> 
 <tr> 
 <td> print </td> 
 <td> p </td> 
 <td> 打印内部变量值 </td> 
 </tr> 
 <tr> 
 <td> continue </td> 
 <td> c </td> 
 <td> 继续程序的运行,直到遇到下一个断点 </td> 
 </tr> 
 <tr> 
 <td> set var name=v </td> 
 <td> &nbsp; </td> 
 <td> 设置变量的值 </td> 
 </tr> 
 <tr> 
 <td> start </td> 
 <td> st </td> 
 <td> 开始执行程序,在main函数的第一条语句前面停下来 </td> 
 </tr> 
 <tr> 
 <td> file </td> 
 <td> &nbsp; </td> 
 <td> 装入需要调试的程序 </td> 
 </tr> 
 <tr> 
 <td> kill </td> 
 <td> k </td> 
 <td> 终止正在调试的程序 </td> 
 </tr> 
 <tr> 
 <td> watch </td> 
 <td> &nbsp; </td> 
 <td> 监视变量值的变化 </td> 
 </tr> 
 <tr> 
 <td> backtrace </td> 
 <td> bt </td> 
 <td> 查看函数调用信息(堆栈) </td> 
 </tr> 
 <tr> 
 <td> frame </td> 
 <td> f </td> 
 <td> 查看栈帧&nbsp; f n 切换到编号为n的栈 </td> 
 </tr> 
 <tr> 
 <td> quit </td> 
 <td> q </td> 
 <td> 退出GDB环境 </td> 
 </tr> 
 </tbody> 
</table>

![复制代码][copycode.gif]

//e.c
 #include <stdio.h>
 void debug(char *str)
 {
 printf("debug info :%s\n",str );
 }
 main(int argc,char *argv[]){
 int i,j;
 j=0;
 for(i=0;i<10;i++){
 j+=5;
 printf("now a=%d\n", j);
 }
 }

![复制代码][copycode.gif]

gcc -g -o e e.c  
调试gdb e  
或者输入gdb  
然后 file e

**list 命令用法**

list命令显示多行源代码,从上次的位置开始显示,默认情况下,一次显示10行,第一次使用时,从代码起始位置显示

![复制代码][copycode.gif]

gdb) list
 1 #include <stdio.h>
 2 void debug(char *str)
 3 {
 4 printf("debug info :%s\n",str );
 5 }
 6 main(int argc,char *argv[]){
 7 int i,j;
 8 j=0;
 9 for(i=0;i<10;i++){
 10 j+=5;
 (gdb)

![复制代码][copycode.gif]

**list n显示已第n行未中心的10行代码**

![复制代码][copycode.gif]

(gdb) list 8
 3 {
 4 printf("debug info :%s\n",str );
 5 }
 6 main(int argc,char *argv[]){
 7 int i,j;
 8 j=0;
 9 for(i=0;i<10;i++){
 10 j+=5;
 11 printf("now a=%d\n", j);
 12 }
 (gdb)

![复制代码][copycode.gif]

**list functionname显示以functionname的函数为中心的10行代码**

![复制代码][copycode.gif]

(gdb) list main
 1 #include <stdio.h>
 2 void debug(char *str)
 3 {
 4 printf("debug info :%s\n",str );
 5 }
 6 main(int argc,char *argv[]){
 7 int i,j;
 8 j=0;
 9 for(i=0;i<10;i++){
 10 j+=5;
 (gdb)

![复制代码][copycode.gif]

**list - 显示刚才打印过的源代码之前的代码**

![复制代码][copycode.gif]

(gdb) list 10
 5 }
 6 main(int argc,char *argv[]){
 7 int i,j;
 8 j=0;
 9 for(i=0;i<10;i++){
 10 j+=5;
 11 printf("now a=%d\n", j);
 12 }
 13 }(gdb) list -
 1 #include <stdio.h>
 2 void debug(char *str)
 3 {
 4 printf("debug info :%s\n",str );
 (gdb)

![复制代码][copycode.gif]

断点命令break  
break location:在location位置设置断点,该位置可以为某一行,某函数名或者其它结构的地址  
GDB会在执行该位置的代码之前停下来

![ContractedBlock.gif][]

使用delete breakpoints 断点号 删除断点  
这里的断点号表示的是第几个断点,刚才执行break 10返回 reakpoint 1 at 0x40050a: file e.c, line 10.  
中的1表示该断点的标号，因此使用 delete breakpoints 1表示删除第10行所定义的断点  
clear n表示清除第n行的断点,因此clear 10等同于delete breakpoints 1  
disable/enable n表示使得编号为n的断点暂时失效或有效  
可使用info查看断点相关的信息  
**info breakpoints**

![复制代码][copycode.gif]

gdb) info breakpoints
    No breakpoints or watchpoints.
    (gdb) break 10
    Breakpoint 2 at 0x40050a: file e.c, line 10.
    (gdb) break 9
    Breakpoint 3 at 0x400501: file e.c, line 9.
    (gdb) info breakpoints
    Num     Type           Disp Enb Address            What
    2       breakpoint     keep y   0x000000000040050a in main at e.c:10
    3       breakpoint     keep y   0x0000000000400501 in main at e.c:9

![复制代码][copycode.gif]

**display命令**  
**查看参数的值**

![ExpandedBlockStart.gif][]

![复制代码][copycode.gif]

(gdb) break 10
    Breakpoint 1 at 0x40050a: file e.c, line 10.
    (gdb) r
    Starting program: /mnt/hgfs/www/c/gcc/e 
    
    Breakpoint 1, main (argc=1, argv=0x7fffffffe548) at e.c:10
    10            j+=5;
    (gdb) display j
    1: j = 0
    (gdb) c
    Continuing.
    now a=5
    
    Breakpoint 1, main (argc=1, argv=0x7fffffffe548) at e.c:10
    10            j+=5;
    1: j = 5
    (gdb) display
    1: j = 5
    (gdb) display i
    2: i = 1
    (gdb) display j
    3: j = 5
    (gdb) display j*2
    4: j*2 = 10
    (gdb) info display
    Auto-display expressions now in effect:
    Num Enb Expression
    4:   y  j*2
    3:   y  j
    2:   y  i
    1:   y  j

![复制代码][copycode.gif]

也可以使用disable,enable,delete,info命令修改及查看其状态,用法与对断点的一样

**step及next命令**  
step可使得程序逐条执行,即执行完一条语句然后在吓一跳语句前停下来,等待用户的命令  
一般使用step命令是，可使用display或者watch命令查看变量的变化,从而判断程序行为是否符合要求  
当下一条指令为函数时,s进入函数内部,在其第一条语句前停下来  
step n,next n 表示连续但不执行n条指令,如果期间遇到断点,则停下来

![ExpandedBlockStart.gif][]

![复制代码][copycode.gif]

**watch**  
**watch可设置观察点(watchpoint)。使用观察点可以使得当某表达式的值发生变化时,程序暂停执行。**  
执行该命令前，必须保证程序已经运行

![ExpandedBlockStart.gif][]

![复制代码][copycode.gif]

**print命令**

![ExpandedBlockStart.gif][]

![复制代码][copycode.gif]

**set var name=value**

**set args 可指定运行时参数(当main函数需要参数时 如:set args 10 20 30 40 50)**

**show args 命令可以查看设置好的运行参数**

在程序运行中动态改变变量的值

![ExpandedBlockStart.gif][]

![复制代码][copycode.gif]

(gdb) list
 1 #include <stdio.h>
 2 void debug(char *str)
 3 {
 4 printf("debug info :%s\n",str );
 5 }
 6 
 7 main(int argc,char *argv[]){
 8 int i,j;
 9 j=0;
 10 for(i=0;i<10;i++){
 (gdb) 
 11 j+=5;
 12 printf("now j=%d\n", j);
 13 debug("x=======x");
 14 }
 15 }(gdb) 
 Line number 16 out of range; e.c has 15 lines.
 (gdb) break main
 Breakpoint 1 at 0x4004fa: file e.c, line 9.
 (gdb) r
 Starting program: /mnt/hgfs/www/c/gcc/e1 
 
 Breakpoint 1, main (argc=1, argv=0x7fffffffe538) at e.c:9
 9 j=0;
 (gdb) watch i
 Hardware watchpoint 2: i
 (gdb) watch j
 Hardware watchpoint 3: j
 (gdb) c
 Continuing.
 Hardware watchpoint 3: j
 
 Old value = 0
 New value = 5
 main (argc=1, argv=0x7fffffffe538) at e.c:12
 12 printf("now j=%d\n", j);
 (gdb) c
 Continuing.
 now j=5
 debug info :x=======x
 Hardware watchpoint 2: i
 
 Old value = 0
 New value = 1
 0x0000000000400533 in main (argc=1, argv=0x7fffffffe538) at e.c:10
 10 for(i=0;i<10;i++){
 (gdb) c
 Continuing.
 Hardware watchpoint 3: j
 
 Old value = 5
 New value = 10
 main (argc=1, argv=0x7fffffffe538) at e.c:12
 12 printf("now j=%d\n", j);
 (gdb) c
 Continuing.
 now j=10
 debug info :x=======x
 Hardware watchpoint 2: i
 
 Old value = 1
 New value = 2
 0x0000000000400533 in main (argc=1, argv=0x7fffffffe538) at e.c:10
 10 for(i=0;i<10;i++){
 (gdb) c
 Continuing.
 Hardware watchpoint 3: j
 
 Old value = 10
 New value = 15
 main (argc=1, argv=0x7fffffffe538) at e.c:12
 12 printf("now j=%d\n", j);
 (gdb) c
 Continuing.
 now j=15
 debug info :x=======x
 Hardware watchpoint 2: i
 
 Old value = 2
 New value = 3
 0x0000000000400533 in main (argc=1, argv=0x7fffffffe538) at e.c:10
 10 for(i=0;i<10;i++){
 (gdb) c
 Continuing.
 Hardware watchpoint 3: j
 
 Old value = 15
 New value = 20
 main (argc=1, argv=0x7fffffffe538) at e.c:12
 12 printf("now j=%d\n", j);
 (gdb) c
 Continuing.
 now j=20
 debug info :x=======x
 Hardware watchpoint 2: i
 
 Old value = 3
 New value = 4
 0x0000000000400533 in main (argc=1, argv=0x7fffffffe538) at e.c:10
 10 for(i=0;i<10;i++){
 (gdb) set var i=8
 (gdb) c
 Continuing.
 Hardware watchpoint 3: j
 
 Old value = 20
 New value = 25
 main (argc=1, argv=0x7fffffffe538) at e.c:12
 12 printf("now j=%d\n", j);
 (gdb) c
 Continuing.
 now j=25
 debug info :x=======x
 Hardware watchpoint 2: i
 
 Old value = 8
 New value = 9
 0x0000000000400533 in main (argc=1, argv=0x7fffffffe538) at e.c:10
 10 for(i=0;i<10;i++){
 (gdb) c
 Continuing.
 Hardware watchpoint 3: j
 
 Old value = 25
 New value = 30
 main (argc=1, argv=0x7fffffffe538) at e.c:12
 12 printf("now j=%d\n", j);
 (gdb) c
 Continuing.
 now j=30
 debug info :x=======x
 Hardware watchpoint 2: i
 
 Old value = 9
 New value = 10
 0x0000000000400533 in main (argc=1, argv=0x7fffffffe538) at e.c:10
 10 for(i=0;i<10;i++){
 (gdb) c
 Continuing.
 
 Watchpoint 2 deleted because the program has left the block in
 which its expression is valid.
 
 Watchpoint 3 deleted because the program has left the block in
 which its expression is valid.
 __libc_start_main (main=0x4004eb <main>, argc=1, ubp_av=0x7fffffffe538, init=<value optimized out>, fini=<value optimized out>, rtld_fini=<value optimized out>, 
 stack_end=0x7fffffffe528) at libc-start.c:258
 258 exit (result);
 (gdb) c
 Continuing.
 
 Program exited with code 026.

![复制代码][copycode.gif]

函数调用相关的  
**backtrace**  
**可使用frame 查看堆栈中某一帧的信息**

![ExpandedBlockStart.gif][]

![复制代码][copycode.gif]

** GDB段错误调试**

所谓段错误就是对内存的非法访问  
采用GDB调试段错误有2种方法  
1.在GDB中运行目标程序,当发生段错误时,GDB中运行的程序会自动停下来  
2.直接运行目标程序,使其在发生段错误时产生内存转储(core dump)文件,GDB对该文件进行调试

abort.c

![复制代码][copycode.gif]

#include <stdio.h>
 #include <stdlib.h>
 
 void recurse(void)
 {
 static int i;
 if( ++i == 3)
 abort();
 else
 recurse();
 }
 int main(int argc,char ** argv){
 recurse();
 }

![复制代码][copycode.gif]

gcc -g -o abort abort.c
    使用gdb调试
    Line number 15 out of range; abort.c has 14 lines.
    (gdb) r
    Starting program: /mnt/hgfs/www/c/gcc/abort 
    
    Program received signal SIGABRT, Aborted.
    0x000000333a232495 in raise (sig=6) at ../nptl/sysdeps/unix/sysv/linux/raise.c:64
    64      return INLINE_SYSCALL (tgkill, 3, pid, selftid, sig);
    (gdb) bt
    #0  0x000000333a232495 in raise (sig=6) at ../nptl/sysdeps/unix/sysv/linux/raise.c:64
    #1  0x000000333a233c75 in abort () at abort.c:92
    #2  0x00000000004004e7 in recurse () at abort.c:8
    #3  0x00000000004004ec in recurse () at abort.c:10
    #4  0x00000000004004ec in recurse () at abort.c:10
    #5  0x0000000000400502 in main (argc=1, argv=0x7fffffffe528) at abort.c:13
    显示在recurse函数调用了3次后调用了abort函数,产生段错误

![复制代码][copycode.gif]

**使用内存转储文件**

**ulimit -a **

![复制代码][copycode.gif]

[root@centos1 gcc]# 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) 7331
    max locked memory       (kbytes, -l) 64
    max memory size         (kbytes, -m) unlimited
    open files                      (-n) 1024
    pipe size            (512 bytes, -p) 8
    POSIX message queues     (bytes, -q) 819200
    real-time priority              (-r) 0
    stack size              (kbytes, -s) 10240
    cpu time               (seconds, -t) unlimited
    max user processes              (-u) 7331
    virtual memory          (kbytes, -v) unlimited
    file locks                      (-x) unlimited
    core file size 此时是0

![复制代码][copycode.gif]

**ulimit -c unlimited  设置为不受限制**

执行 ./abort 产生内存转储文件  
ls 可看到一个名为core且以进程号为后缀的文件

core.6289  
**gdb abort core.6289**  
bt  
方法同上一个gdb调试

转载于:https://www.cnblogs.com/guochaoxxl/p/10941727.html

[https_www.cnblogs.com_HKUI_p_8955443.html]: https://www.cnblogs.com/HKUI/p/8955443.html
[copycode.gif]: /images/20211122/d05358a5405d4bde9a52320e4978e8f2.png
[ContractedBlock.gif]: /images/20211122/b82cee14141846ceb512956e210d2a8e.png
[ExpandedBlockStart.gif]: /images/20211122/c4669f88ac3c4c2185baec6dedf4d114.png