Why Rewriting Emacs Is Hard

https://kyo.iroiro.party/en/posts/why-rewriting-emacs-is-hard/

70•signa11•5mo ago

Comments

WantonQuantum•5mo ago

That's quite a read! Looks like emacs has done an amazing job of handling text correctly in the face of quite a few challenges. Including cases where there perhaps is no "correct" choice.

Now, I'm certainly not in the "all C code must be rewritten in Rust because security" camp but it does raise the question: With all this complexity how do I know that pasting text from a web page into emacs (or any editor really) isn't going to trigger an undiscovered vulnerability?

Edit: I guess that's rhetorical question because of course the answer is "you don't".

Suzuran•5mo ago

The answer isn't material; You just rewrite it in Rust, and then if anything goes wrong it's not your fault because you did The Right Thing. Rust cannot fail, it can only be failed.

_mlbt•5mo ago

C style null terminated strings were a mistake. They are almost never the right answer. Even C itself should start transitioning to length prefixed strings instead.

Suzuran•5mo ago

It's worse than that; Null-terminated strings both predate C and were considered harmful when C was created.

iLemming•5mo ago

IMO the only/main reason to rewrite C-parts in Rust is to refactor and untagle the code to generate better incentive for people to work on it, because from what I heard - some C parts of Emacs are of nightmarish complexity, and there are literally only a few on this planet who even want to deal with it.

And the same time, I don't think there's enough people who can be persuaded to think that in a decade or two those Rust-rewritten parts wouldn't become problematic either - who can promise today that Zig for example isn't a better choice for that? Or maybe even some close-to-metal Lisp variant?

celeritascelery•5mo ago

This was a great post that really gets into a lot of the details. As the author of one of the Emacs "clones" I wrote a detailed comment about some of this over on Reddit that might be of interest to readers here.

https://www.reddit.com/r/emacs/comments/1n7i586/comment/ncbc...

mdaniel•5mo ago

> Because of IRC's scandanavian origin, the characters {}| are considered to be the lower case equivalents of the characters []\, respectively

/me facepalms

Text rendering hates you (2019) - https://news.ycombinator.com/item?id=36478892 - June, 2023 (119 comments)

et al, as there was a follow-up posted in the top comment of that thread

I thought there was an "Falsehoods Programmers Believe About Text" but between that link and <https://github.com/kdeldycke/awesome-falsehood#international...> it's close enough for the point

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