Personal experiences of Rust rewrites

[aidanhs]

ayzim, a conversion of the emscripten asm.js optimizer (C++) to Rust.

~7.5k lines of fairly dense code, it was a pretty harrowing experience at times as the rewrite also involved some data structures redesign for efficiency. rustc also strongly disagreed with g++ at times about what 'valid code' means. Completed it successfully (submitting fixes for some bugs I found along the way), I now use it for all of my emscripten work and it's a serious QoL improvement. Probably would have given up if it was in C and used pointers instead of references.

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machroot, a rewrite and re-purposing of bubblewrap (basically docker minus the daemon) to just deal with mounts (so a chroot on steroids).

I was going to leave it as C, stripping out the parts I didn't need and adding new bits, but didn't really like how part of it was quite weakly typed so I rewrote half of it in Rust, finding some bugs on the way (submitted fixes to the original project). I then stopped because the other half seems to work fine as C and it's easy to call from Rust. Completed successfully, I use it every day as a better chroot for a dev environment.

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A rewrite of the owntracks recorder. Started as a project to learn Rust (after grokking some of the source and finding some segfaults, would never expose the C version as-is). Unfinished and stalled while I do other things.

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In summary, would RIIR again if itch-scratching, and apparently rewriting in Rust helps find bugs (unsure if this is unique to Rust). Would not recommend porting

• >2k dense lines at a time
• pointer heavy code
• if I didn't know Rust
• code that interacts heavily with libc and syscalls and uses pointers a lot

If C and C++ came with language-level ADTs (very useful for ayzim and machroot) and a decent package manager, none of the rewrites above would have started.

[rivertam]

Thanks for sharing!

[KellerFuchs]

Rewrote pam_setquota in Rust, after attempting to clean up the original C version. It turned out that the rewrite took me less time (and resulted in more readable/maintainable code) than I spent fixing the original C version; moreover, despite the time I spent on cleaning up the C version, I would still be uncomfortable deploying it to production.

Currently working on a bunch of new PAM modules, and I might perhaps also RIIR pam_namespaces as I ran into bugs there that would likely require large refactors to fix in a clean way.

[poucet]

Great article! While I have nothing against or for rust and totally believe that people should feel free to rewrite things in Rust. I think your article rightfully elucidates that you shouldn't expect others to follow your choices.

I also like your strategy on comments.

[ssokolow]

While I've had to put the project on hold for the moment, I'm in the process of rewriting the backend portion of this experiment in Rust as I refactor it to something maintainable before working to complete it any further.

The partially-complete rewrite of the frontend portion uses PyQt+rust-cpython... though, technically, it's more that it's a single PyQt project where Rust is replacing Python function-by-function, to ensure it remains functional at every step along the way.

(The end goal being a backend that can have bindings written for use by projects like Lutris and GNOME Games and a Qt frontend I can use to experiment with UI/UX improvements I haven't seen others trying.)

[aidanhs]

I've started another one - taking small parts of bup (written mostly in Python) and implementing them in Rust to reduce memory usage (4x) and increase speed (2x). I use these bits in combination with the rest of bup as part of my overall backup strategy.

I've submitted patches for a few bugs I found during my rewrite (supporting my "rewriting in Rust helps find bugs" discovery from the original post). I've started exploring upstreaming my work at https://groups.google.com/d/msg/bup-list/DhCakXUkHjI/tNaazL30BwAJ