Debugging with GDB • Hacker News Board

Re: Debugging with GDB

#21

Post by bee_rider » Mon, Mar 21, 2022, 4:31 PM UTC

mixedmath wrote: post #20

bee_rider wrote: post #6

I generally stick pretty close to the classic "old but still good" tools, but GDB is something I really could not get a handle on (probably because it isn't a daily-use tool for me).

What do you use for debugging instead?

Print statements, haha.

My code is for linear algebra stuff, so it is pretty much a straight shot through/filling in some RCI loop most of the time, I usually just have to find which OpenMP or MPI barrier is misbehaving.

Re: Debugging with GDB

#22

Post by havkom » Mon, Mar 21, 2022, 4:33 PM UTC

Have not used gdb for a while but I think a good gdb tip is that you can evaluate functions with the print p command:

> p myfunction()

Re: Debugging with GDB

#23

Post by habibur » Mon, Mar 21, 2022, 4:39 PM UTC

For my 98% of use cases these 3 gdb commands suffices : bt, f, p.

Re: Debugging with GDB

#24

Post by apnsngr » Mon, Mar 21, 2022, 5:05 PM UTC

zebnyc wrote: post #17

Unrelated but does anyone have tips on debugging async code in Nodejs. My work has a gigantic Nodejs monorepo and frankly I am struggling so pointers would be appreciated. There is dependency injection & layers of async / await abstraction. Not fun, when I model my code / unit test against a working sample and some method 25+ layers down does not work as expected as it does not have expected input when the stack fram…

You can use the debugger from Chrome dev tools to debug Node.js. Just run node with the `—-inspect-brk` flag, open `about://inspect` in Chrome, and select your app under remote targets. This has saved me tons of debugging time. See also: https://nodejs.org/en/docs/guides/debugging-getting-started/

Re: Debugging with GDB

#25

Post by edgyquant » Mon, Mar 21, 2022, 5:17 PM UTC

Decabytes wrote: post #11

I learned a lot of debugging using GDB from Greg Laws CPPCon talk https://www.youtube.com/watch?v=-n9Fkq1e6sg . With that being said, one of the things I've heard is that debugging on Linux is a poorer experience than it is on Windows. I believe that RAD Game Tools tried to create a debugger for Linux that was better, but the project failed for some reason. I hope with the increased interest in Linux, GDB or another…

Interesting, the last time GDB hit the front page the consensus seemed to be it was far ahead of all the competition. Having never seriously used a debugger it seems like it’s an opinion to me.

Re: Debugging with GDB

#26

Post by j1elo » Mon, Mar 21, 2022, 5:45 PM UTC

Alekhine wrote: post #16

Are there any easier to use C debuggers than GDB? All I really need to do is watch my variables change with each line.

A nice UI on top of GDB might be all you need. I've used this with some success in the past: https://www.gdbgui.com/

Re: Debugging with GDB

#27

Post by zoomablemind » Mon, Mar 21, 2022, 6:02 PM UTC

Alekhine wrote: post #16

Are there any easier to use C debuggers than GDB? All I really need to do is watch my variables change with each line.

QtCreator has a very capable debug view. No need to have a Qt project, simply start a binary and step-in into it, or attach to a running process.

Most of IDEs have a similar capability to be able to use debug view without setting up a project.

Re: Debugging with GDB

#28

Post by mark_undoio » Mon, Mar 21, 2022, 6:08 PM UTC

Disclaimer: I work for undo.io (see my username) on time travel debugging. We use GDB as the front end but the engine underneath is proprietary.

The GDB Documentation is really nice (as GNU project docs tend to be) and I've made lots of use of them. The fact that they've also documented things like the serial comms protocol is a level further still.

Some related stuff we (Undo) have produced about GDB and might be interesting to the audience here...

Articles about less-known parts of GDB functionality: https://undo.io/resources/gdb-watchpoint/

Greg Law's quick talk on little-known features of GDB: https://undo.io/resources/cppcon-2015-greg-law-give-me-15-mi...

Greg's bigger talk on GDB: https://www.youtube.com/watch?v=-n9Fkq1e6sg

Re: Debugging with GDB

#29

Post by zoomablemind » Mon, Mar 21, 2022, 6:10 PM UTC

jokoon wrote: post #8

How difficult is it to setup an editor like sublime text with gdb? I'm curious if it can be an alternative to visual studio, meaning a window showing the stack, locals, watch, etc?

I used Geany editor (well, it's called a lightweight IDE) with a Debugger plugin. There's also another debug plugin for it, forgot the name, slightly more capable.

All of these are capable of the basic single-threaded debug operations. Multithreaded is not as robust, but it's quite a cookie per se.

For the basics the TUI is very much alright, as long as you remember the hotkeys.

Re: Debugging with GDB

#30

Post by nyanpasu64 » Mon, Mar 21, 2022, 6:11 PM UTC

ho_schi wrote: post #2

Took me some time to get familiar with it but GDB is well documented and fulfills its duty. It looks ancient but it is powerful. Do not underestimate the power of the print command! And the advanced stuff like revers-debugging, multi-threading (all-stop mode - which is the default - and the non-stop mode), binary manipulation (yep, it is possible), and remote debugging. Nowadays accompanied by stuff like debuginfod.…

> Do not underestimate the power of the print command!

Still waiting for it to print the contents of a QList or QString, or pull actual data in cases where I see .