GDB

I wrote these notes when debugging my router for my networking course (CSC458)

Yashar Ganjali is a great prof

This was moved over from my notes repo because having it on my blog makes it more searchable

• https://github.com/Fullchee/progress/blob/master/gdb_notes.md

Get GDB to look like an IDE debugger

• GDB Text User Interface
• Ctrl-x-a
• or type tui

How to refresh the display?

• ctrl l

Scroll through previous commands?

• ctrl-p: back
• ctrl-n: forwards
• not arrow keys anymore!
• Ctrl-b: back
• Ctrl-f: forward

Python in GDB?

• type python
• and then a new prompt will appear
• type end to end the python

Example of usefulness of Python in GDB?

python print (gdb.breakpoints()[0].location) -> cars.c:car_arrive

After a seg fault, what do you do to find more info?

• bt
  • stands for backtrace, looks at the stack trace

Run a command automatically at a given breakpoint

1. command 1
2. run

3. end

4. this will execute run on breakpoint 1

   • (could have multiple commands!)
5. Enable Reverse debugging ???????? command 2
6. breakpoint for main record continue end
7. command 3
8. the run end

Create a watchpoint

• watch
• reverse-continue

Print all the local variable info

info locals

2 ways to add arguments to an executable

Option 1

gdb --args ./traffic schedule.txt
gdb --args ./executable -arg1 -arg2

• the args have to go in front of everything

Option 2

gdb ./file
in GDB: run arg1 arg2 ...

How to temporarily remove your breakpoints?

disable

How to print a char array as a string?

instead of print char_arr x/s char_arr

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Last update: 2023-04-24