Most tricky/useful commands for gdb debugger

Question

Can you post your most tricky and useful commands while you run a debugger like gdb or dbx.

Solution 1

1. backtrace full: Complete backtrace with local variables
2. up, down, frame: Move through frames
3. watch: Suspend the process when a certain condition is met
4. set print pretty on: Prints out prettily formatted C source code
5. set logging on: Log debugging session to show to others for support
6. set print array on: Pretty array printing
7. finish: Continue till end of function
8. enable and disable: Enable/disable breakpoints
9. tbreak: Break once, and then remove the breakpoint
10. where: Line number currently being executed
11. info locals: View all local variables
12. info args: View all function arguments
13. list: view source
14. rbreak: break on function matching regular expression

Solution 2

Start gdb with a textual user interface

gdb -tui

Solution 3

Starting in gdb 7.0, there is reversible debugging, so your new favourite commands are:

* reverse-continue ('rc') -- Continue program being debugged but run it in reverse
* reverse-finish -- Execute backward until just before the selected stack frame is called
* reverse-next ('rn') -- Step program backward, proceeding through subroutine calls.
* reverse-nexti ('rni') -- Step backward one instruction, but proceed through called subroutines.
* reverse-step ('rs') -- Step program backward until it reaches the beginning of a previous source line
* reverse-stepi -- Step backward exactly one instruction
* set exec-direction (forward/reverse) -- Set direction of execution.

Solution 4

Instead of launching GDB with "-tui" param you can also switch to text mode after a while using by typing "wh".

Solution 5

thread apply all bt or thread apply all print $pc: For finding out quickly what all threads are doing.

View more solutions

Comments

[Paul Biggar]

info locals -- View all local variables; list -- view source; rbreak -- break on function matching regular expression.

[DevSolar]

I cannot believe this feature escaped me for all these years. Thank you, thank you, thank you!

[Sudhanshu]

source /path/to/macro/file And all of my nifty macros are there to help me debug in seconds.

[deft_code]

How do you set scheduler locking?

[Ben]

set scheduler-locking on inside gdb

[Kevin]

Ctrl-a a to switch back to 'normal' command line view !

[tothphu]

That was the command I was looking for a long-long time! It is really nasty to check all 30 threads one by one!

[sujin]

Thanks You saved lot of my time.. Wonderfull....

[Kiril Kirov]

set print object on for polymorphic elements and set print elements 0 are two commands I use very often. Pretty useful.

[Kiril Kirov]

Also, t a a bt (meaning thread apply all backtrace). Could be used with (almost) all other commands. Especially useful with bt full.

[Nathan Fellman]

you can change the focus to the command window using focus cmd so that the up/down arrows work. You switch back using focus src.

[Omry Yadan]

how do you make this the default? I tried it .gdbinit but gdb prints /home/omry/.gdbinit:1: Error in sourced command file: Target 'None' cannot support this command.

[raj_gt1]

"-' can be used instaed of 'wh'. shorter the better..:)

[x-yuri]

Ctrl-a a? Is it a joke? Looks more like tmux/screen command. And doesn't work for me. It must be one of as per docs: C-x C-a, C-x a, C-x A.

[SullX]

And another: <minus> RET

[Patryk]

or use cgdb

[doug65536]

You can also use the -iex option to add individual commands on the gdb command line.

[PraveenMax]

very nice features. Missed this so far...

[Sam]

It's actually C-x a. You can also switch views with C-x 1 and C-x 2 when in tui mode to see assembly as well (if need be).

[user28186]

Very useful information received in this thread , thank you all.

[user28186]

Very useful reply