Introduction to GDB

gcc -g -Wall program.c -o program

“-g” Option is used to add source code information to the executable ,“-Wall” Open all without affecting the behavior of the program warning.

Single process 、 Single thread basic debugging command

start-up 、 sign out 、 Look at the code

• Start and exit

gdb  Executable program 
quit

• Set parameters for the program / Get and set parameters

set args 10 20
show args

• GDB Use the help

help

• View the current file code

list/l    （ Show... From default location ）
list/l     Line number （ Displays... From the specified line ）
list/l     Function name （ Displays... From the specified function ）

• View non current file code

list/l     file name ： Line number 
list/l     file name ： Function name 

• Set the number of rows displayed

show list/listsize
set list/listsize  Row number 

Breakpoint operation

• To set breakpoints

b/break  Line number 
b/break  Function name 
b/break  file name ： Line number 
b/break  file name ： function 

• View breakpoints

i/info b/break

• Delete breakpoints

d/del/delete  Breakpoint number 

• Setting breakpoint is invalid

dis/disable  Breakpoint number 

• Setting breakpoints takes effect

ena/enable  Breakpoint number 

• Set conditional breakpoints （ It is generally used in the position of circulation ）

b/break 10 if i==5

  Debug command

• function GDB Program

start （ The program stops on the first line ）
run （ Stop only when you encounter a breakpoint ）

• Continue operation , Stop at the next breakpoint

c/continue

• One line down （ Will not enter function body ）

n/next

• Variable operating

p/print  Variable name （ Print variable values ）
ptype  Variable name （ Print variable types ）

• Step down debugging （ Encountered a function entering the function body ）

s/step
finish ( Jump out of the body of functions )

• Automatic variable operation

display  Variable name （ Automatically print the value of the specified variable ）
i/info display
undisplay  Number 

• Other operating

set var  Variable name = A variable's value （ More used in the loop ）
until（ Out of the loop , Requires no breakpoints in the loop ）

Multi process debugging command

(gdb) set follow-fork-mode mode

mode You can choose parent perhaps child, namely ： Choose which process to debug

notes ： The process that is not tracked and debugged will end directly

Multithreaded debugging command

1. utilize info threads View thread information
2. thread id Debugging objectives id Specified thread

set scheduler-locking off | on | step

“off” Indicates that no thread is locked ;

“on” Indicates that only the currently debugged thread continues to run ;

“step” When stepping , Only the current thread will execute .