GDB usage

请设置文章作者

发布于：Feb 25, 2020

次浏览

Basic Usage

• Make sure compile file with -g option, which mean turn on debugging with gdb
  • like this: gcc -g main.cpp -o main

Debugging with GDB

• Open file
  • here are two way
  • gdb <file>
    • gdb path/to/main
  • gdb -> file path/to/main
• Show list
  • use l command to show source code with line number
• breakpoint
  • use b <LINENUM> to add breakpoint, such as b 1 add breakpoint at line 1
  • or use b <FUNCTIONNAME> to add breakpoint, such as b main add breakpoint at main function
  • b <[file:]linenum|[file:]funciont>
  • tb[reak] for a temporary breakpoint
• Show breakpoint information
  • i b i for information, b for breakpoint
  • clear [[file:]function|[file:]lennum] to clean all breakpoint
  • rb[reak] REGEXP set breakpoint for all function matching REGEXP
  • ignore N COUNT ignore bp 1 for COUNT times
• Inspect
  • use print, inspect or p [OPTION...] [EXP] to print value of expression EXP
    • use p a will show information of variable a
    • p [/FMT] print with specified format
    • p ARRAY[@len] print arrary with len element
    • p ['file'::]var print var in specified file
• Delete breakpoint
  • d <BREAKPOINTNUM> break point num from i b
  • i b info of breakpoint, information will be like a order list. If delete a pointid in the previous, the next point will just add in the end of the idlist.
• Run debug
  • r [args...]
• Gdb controler
  • n [N] for next line, one step debugging
  • s for step into(one step)
  • u|until [LINENUM|FUNC|ADDR|if condition]
  • set args [parameter] for command line args
  • return <value> finish function and return <value>
  • call <function> call specified function
• Finish function and continue
  • finish for finish function
  • c for continue until program exit or breakpoint
• Quit gdb
  • q

Tips

• You can write shell script in gdb
  • (gdb) shell <cmd>
• Set log
  • set logging on, which will copy output to file gdb.txt
• Watchpoints, Catchpoint… and so on
  • You can use a watchpoint to stop execution whenever the value of an expression changes.
  • watch *<addr> or watch <value>
  • info watchpoints to print info of watchpoints
• Debug a running program
  • gdb -p <pid>
• Debug a core file
  • gdb <binary file> <core file>
  • System will no generate a core file by default. Because typically core files are very big. You can use ulimit command to set unset the limit.
• 自定义脚本

1
2
3
4
5
6
7
8

define print_list
set $list=$arg0
while($list)
printf "%d\n",$list->val
set $list=$list->next
end
printf "\n"
end