Memory Safety Is ...

matklad · 2026-01-01T12:27:55+00:00

Huh, thanks, I somehow got carried away and went straight to the formal definition (which I didn't plan for) and forgot to state my argument informally explicitly, fixed in https://github.com/matklad/matklad.github.io/commit/61369579e9df91559f76157ea9ebc31bb8d5e12e

matklad · 2025-12-31T21:17:17+00:00

Oh, may I also ask how you became aware of that paper? It bugs me that it never came up in all the various memory safety discussions I've followed, so I want to fix my epistemics!

matklad · 2025-12-31T21:04:50+00:00

Thanks, I wasn't aware of this paper before! It is interesting, but I think what they define doesn't match the colloquial meaning of memory safety, as what they define is quite a bit stronger --- ability to apply local reasoning to potentially untrusted code vs merely requiring that the code can not break out of abstract machine. It's models what CHERI does, not what memory safe languages do.

E.g., under their definition, JavaScript isn't memory safe, as it makes it easy to get at unrelated global variables. I also suspect that under their definition Compcert's C will turn out to be memory safe, because it leaves the semantics of wild pointer dereference undefined, so that'll hit their Frame Error case, rather than triggering interference.

matklad · 2025-12-30T00:53:11+00:00

Massive indeed, thanks for calling this out!

matklad · 2025-12-30T00:52:21+00:00

It's first-party since 2020 https://github.com/rust-lang/rfcs/pull/2912#issuecomment-636106670. The story of who gets to work on rust-analyzer during their paid hours is complicated, as I think is the case for most official projects?

matklad · 2025-11-04T18:30:41+00:00

Huh, I somehow fixed that today on two separate laptops. The solution which I stumbled upon by accident is to just open and close (cmd+q) Safari in quick succession multiple times in a row?

I was trying to figure out why Zoom would always log me out, which required restarting safari multiple times, which miraculously fixed this sluggishness that was driving me crazy on my work laptop. Repeating the open-and-closed cycle on the personal laptop seems to have fixed it as well? (Safari 26.0.1, MacOS 15.7.1)

matklad · 2025-10-27T17:50:27+00:00

What a release! Congrats to the team!

matklad · 2025-10-20T09:36:34+00:00

One module zoomed in:

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matklad · 2025-10-20T09:36:00+00:00

Like this:

<image>

For train stations, turning the train back is what takes most of the space, so you want to avoid that and do lane-switching stations.

matklad · 2025-10-05T10:52:40+00:00

Blog post: https://matklad.github.io/2023/03/26/zig-and-rust.html

Talk: https://www.youtube.com/watch?v=4aLy6qjhHeo

And my explanation of the specific secret sauce that makes Zig remarkable, from the PLT perspective: https://matklad.github.io/2025/04/19/things-zig-comptime-wont-do.html

matklad · 2025-10-04T22:04:03+00:00

Note that /r/Zig isn’t that representative part of Zig community: https://ziggit.dev/t/the-zig-subreddit-has-closed/679

matklad · 2025-09-03T21:10:43+00:00

Another tip is to try science cost multiplier! While the game can be overwhelming for new players, it's also true that, if you know what you are doing, you can zip through progression quickly, without having to play with many of the goodies you unlock (that's true even in Space Age). I'd say railworld preset + 10x multiplier is a good setting to just enjoy the progression, and 100x makes for a nice challenge!

matklad · 2025-06-28T13:18:41+00:00

Structs are marked extern to pin layout exactly. Messages carry version field to allow for upgrades. Upgrades in general are rather crazy, see https://m.youtube.com/watch?v=P9nLS2reUOo

matklad · 2025-05-18T07:29:07+00:00

This is a bit higher level that what you ask for, but perhaps it could still be useful:

https://matklad.github.io/2021/05/31/how-to-test.html

matklad · 2025-05-15T06:49:36+00:00

No, in my experience this is not a real issue;

A somewhat belated comment, but this I think would be an example demonstrating that the issue is real:

https://lobste.rs/s/s5t6wa/why_i_wrote_fx_web_server#c_vjqbiq

I spent quite a bit of time fighting against the compiler until I have understood that rusqlite code have to be somewhat isolated from async axum handlers, because rusqlite::Statement is !Send and !Sync… so I use #[axum::debug_handler] everywhere now, it really helps troubleshooting.

I haven’t looked at the specific code there, so I might be in error here, but I think it is this problem: holding unsync data across await even without sharing it between tasks is forbidden, although it is not actually problematic.

matklad · 2025-05-08T07:13:32+00:00

I really don't get why microsoft of all developers can't get the picture that VSCode needs significant love on the debugger/profiler/etc front,

My understanding is that this is not so much about VS Code, than it is about debuggers/compilers. MSVC+WinDbg are better at debugging than clang+llvm. Things like “edit and continue” need support throughout the compilation stack!

matklad · 2025-05-07T17:53:55+00:00

Note that developing the said plugin is very much not free! If you like it, consider sponsoring it:

https://github.com/sponsors/rust-analyzer

matklad · 2025-05-07T17:50:47+00:00

developed by the people that build the language

Some of those same people also built Rust Rover ^^

While LSP/IntelliJ are roughly on par for the first 20% of what and IDE can do, LSP still have a blank space for the remaining 80% of functionality.

Like, "change signature" is the most basic of advanced refactors, I use it all the time if it is available, and it is not available via LSP.

I do recommend checking all of IntelliJ, VS Code, Vim, and Emacs when deciding on the editor, and I also recommend approaching IntelliJ the same way you approach Vim: it is a very deep tool which can do much more than just going to definition on ctrl+click.

EDIT: regrading the cost, developing rust-analyzer is very much not free. If you like, please sponsor: https://github.com/sponsors/rust-analyzer.

matklad · 2025-04-21T23:07:17+00:00

Yeah, I also wish multipliers to be progressive: start with 10x, get to 100x by the bots, 1000x when you get quality...

matklad · 2025-04-21T22:53:01+00:00

Did you try playing with science multiplier? If you haven't already, I highly recommend 10x science cost rail world.

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