Data walker extension

Hi there,


I've written an extension for gdb in python so you can walk over data 
structures (similar to mdb ::walk).

The principle of the thing is

pipe <for each element in a data structure> | if <element is 
interesting> | show <do some gdb command>

and variations thereon.


As an example, printing at all elements that have value 100 in a 
hypothetical list starting at `mylist_head` and is NULL terminated

pipe follow-until mylist_head; {} == 0; ((mylist_T *){})->next | if 
((mylist_T *){})->value == 100 | show print *(mylist_T *){}


I was hoping people could try it out and give me some feedback. It's a 
bit raw at the moment (most error messages come with a stack trace and 
suchlike) but I'm finding it pretty useful already.


More complicated walkers can be written for specific applications, I've 
written some for neovim data structures in the bundled_walkers/ directory.

If people want to add or request specific walkers I'd like to hear that too.


The repo is here https://github.com/hardenedapple/gdb-walkers/


Thank you,

Matthew Malcomson