Drgn: A programmable C debugger, scriptable from Python | Hacker News Reader

Drgn: A programmable C debugger, scriptable from Python

github.com

147 pointspizza11 comments

Drgn: How the Linux kernel team at Facebook debugs the kernel at scale - https://news.ycombinator.com/item?id=29537594 - Dec 2021 (125 comments)

Interesting, apparently drgn doesn't even depend on existing debuggers like gdb or lldb. And since drgn uses debug information, it doesn't need any boilerplate to integrate with C code and data structures, which makes for even easier language integration than pybind11. Perhaps drgn could eventually become a replacement for pybind11?

This talk has a very good hands-on demo of investigating a kernel bug with drgn: https://www.youtube.com/watch?v=ukxH_55BiQE

I'm building a crash-like environment on top of drgn: https://codeberg.org/pf-kernel/crush

this is pretty amazing tbh. scripting debuggers can be so tedious. i havemt tried it yet but this looks really sane and nice. thanks!

`lldb` also uses Python, and it’s insane. Nobody wants a language where whitespace is significant as a debugging extension language! It’s verbose and unpleasant and fiddly to write in a REPL.

> Nobody wants a language where whitespace is significant as a debugging extension language! It’s verbose and unpleasant and fiddly to write in a REPL.

You are correct about it being fiddly to write multi-line Python scripts at the REPL.

However:

- Modern python REPLs are really good. They auto-complete very well and suggest indentation when they recognise the syntax of the previous line:

```

$ python3

>>> for x in range(1, 10):<user presses enter key>

....<indentation is provided by REPL, note the "....">

```

- Python indentation rules are quite simple once you get the hang of it

- The issue with typing at the REPL is really more about remembering the syntax of various language statements rather than the white space rules of Python. This is a problem with using any (other language) like, say, Lua/Javascript at the REPL.

- Most "scripts" at the REPL tend to be just a single line where you don't need to worry about whitespace indentation. When you have a long script then you simply run a program directly

- Yes, Python scripting at the REPL is a bit more verbose than Javascript (for example). But most people can live with the extra characters and the verbosity makes it easier to understand what you meant a few REPL commands ago

- The reason to use Python generally its insanely large ecosystem of software. The inconvenience of the white-space-significant aspect of language at the REPL is totally offset by that.

> Nobody wants a language where whitespace is significant as a debugging extension language!

Nobody just not true, and also overdramatizing at the whitespaces, lol. Taking the expressiveness over C anytime, and also over Javascrpt's uglyness and insanities. What's your fav then?

GDB also uses Python for scripting, and Python is the official scripting language for the VFX and games industry (in what concerns tooling), all major products support it.

A newcomer will have a hard time replacing it.

Because Python has a long experience with REPL, the experience ends up being awesome.

If you try iPython + a PYTHONSTARTUP script, it will be very hard to use anything else.

And ipdb is a very good example of using a debugger that fully benefit from that.

So it is entirely possible to have an exceptionnally good experience in a Python REPL, despite the significant whitespaces, but it does depend of the implementation.

GDB also uses Python

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