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rust-lang
unsafe-code-guidelines
Learning & Reference2019–2026
rust-lang / unsafe-code-guidelines

unsafe-code-guidelines

Forum for discussion about what unsafe code can and can't do

Learning & ReferenceCommunication & Social
Explore on GitHubRead Hacker News discussions
13Distinct people
17Mentions
0Explicit recommenders
756GitHub stars
REPOSITORY AT A GLANCE

What to know before exploring

What it is

Forum for discussion about what unsafe code can and can't do

GitHub

Where it is used

No documented product use was verified in the last source check.

What people are saying

No recommendation phrase was found in the indexed comments.

No classified warning is attached to this page. Read the discussions before treating silence as approval.

Also in these discussions

Mentioned in the same Hacker News threads. That is not proof they are substitutes.

This week on Hacker News

Nov 7–Nov 14 UTC · Direct repository links and separately labeled related project stories. Indexed through 11/14/2026, 6:01:08 PM UTC.

No direct repository links were found in the indexed HN discussions over the past seven days. Older discussions are available below.

Mentions over time

HN mentions by year17 dated mentions

Observed mentions: 2019-08-30 09:11:34 UTC to 2026-10-14 02:47:02 UTC.

012342019-01-01 00:00:00 UTC to 2020-01-01 00:00:00 UTC (exclusive): 1 mentions; 0 submissions, 1 comments20192020-01-01 00:00:00 UTC to 2021-01-01 00:00:00 UTC (exclusive): 3 mentions; 0 submissions, 3 comments2021-01-01 00:00:00 UTC to 2022-01-01 00:00:00 UTC (exclusive): 2 mentions; 0 submissions, 2 comments2022-01-01 00:00:00 UTC to 2023-01-01 00:00:00 UTC (exclusive): 4 mentions; 0 submissions, 4 comments20222023-01-01 00:00:00 UTC to 2024-01-01 00:00:00 UTC (exclusive): 2 mentions; 0 submissions, 2 comments2024-01-01 00:00:00 UTC to 2025-01-01 00:00:00 UTC (exclusive): 2 mentions; 0 submissions, 2 comments2025-01-01 00:00:00 UTC to 2026-01-01 00:00:00 UTC (exclusive): 2 mentions; 0 submissions, 2 comments2026-01-01 00:00:00 UTC to 2027-01-01 00:00:00 UTC (exclusive): 1 mentions; 0 submissions, 1 comments. Incomplete calendar period.2026*

* An incomplete calendar period is marked with an outlined bar. Its count is not directly comparable with a full period.

Counts come from the repository’s dated source evidence. Index cutoff: 2026-11-02 08:16:59 UTC.

View mention counts and date ranges
UTC ranges include their start and exclude their end. Select a period to filter the source evidence.
PeriodStart (UTC)End (exclusive, UTC)MentionsSubmissionsComments
20192019-01-01 00:00:00 UTC2020-01-01 00:00:00 UTC101
20202020-01-01 00:00:00 UTC2021-01-01 00:00:00 UTC303
20212021-01-01 00:00:00 UTC2022-01-01 00:00:00 UTC202
20222022-01-01 00:00:00 UTC2023-01-01 00:00:00 UTC404
20232023-01-01 00:00:00 UTC2024-01-01 00:00:00 UTC202
20242024-01-01 00:00:00 UTC2025-01-01 00:00:00 UTC202
20252025-01-01 00:00:00 UTC2026-01-01 00:00:00 UTC202
2026 (partial)2026-01-01 00:00:00 UTC2027-01-01 00:00:00 UTC101

What Hacker News says

4 sources
nyanpasu64·Jun 27, 2022
To elaborate, there is a recurring trend of sound C programs turning into unsound Rust programs, because shared mutability is often necessary but Stacked Borrows places strict conditions on constructing &mut T (they invalidate some but not all aliasing *const T), and it's less ergonomic to work solely in raw pointers and avoid creating Box<T> or long-lasting &mut T (or for intrusive collections, any &mut T at all). For example, matklad (the author of rust-analyzer, one of the preeminent Rust programmers and someone I'd expect to get code right) made a recent blog post on "Caches In Rust" (https://matklad.github.io/2022/06/11/caches-in-rust.html). The cache is built around https://docs.rs/elsa, which is built around https://docs.rs/stable_deref_trait/latest/stable_deref_trait..., which is unsound for Box and violates stacked borrows in its
Read the rest
current form (https://github.com/Storyyeller/stable_deref_trait/issues/15). However, the rules may be relaxed or more ergonomic alternatives added (https://github.com/rust-lang/unsafe-code-guidelines/issues/3...), it's uncertain right now. (Also I go by "they".)
In Build a PinePhone App with Zig and Zgt
nyanpasu64·Feb 19, 2022
I think it's easier to write correct safe Rust than C, I wouldn't say it's easier to write correct Rust with unsafe blocks than C (many operations strip provenance, you can't free a &UnsafeCell<T> created from a Box<T>, you can't mix &mut and const but you might be able to mix Vec<T> and const (https://github.com/rust-lang/unsafe-code-guidelines/issues/2...), self-referential &mut or Pin<&mut> is likely unsound but undetermined), and it's absolutely more difficult to write sound unsafe Rust than C (sound unsafe Rust must make it impossible for callers to induce UB through any possible set of safe operations including interior mutability, logically inconsistent inputs, and panics).
In ‘Zero-click’ hacks are growing in popularity
DSMan195276·Jan 31, 2022
I feel like you're ignoring the actual history here, these are a few excerpts from right before the 1.0 release of Rust[0]: > Rust has remained true to its goal of providing the safety and convenience of modern programming languages, while still offering the efficiency and low-level control that C and C++ offer. > When used in its own most minimal configuration, it is even possible to write an operating systems kernel in Rust. > The resulting design is not only simpler to learn, but it is also much "closer to the metal" than we ever thought possible before. All Rust language constructs have a very direct mapping to machine operations, and Rust has no required runtime or external dependencies. They do actually have a group working on making `unsafe` better, so they do somewhat recognize the problem (I'm not sure about the results, but the
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last time I looked at it was probably over a year ago): https://github.com/rust-lang/unsafe-code-guidelines Perhaps another catch is that, at least in my experience, the most common situation where `unsafe` can into play is interop with other languages/libraries/etc.. Some of it is avoidable, but a certain amount of it is necessary just be able to interface with existing non-Rust code, so it's not really optional in those situations. Also, just to be clear, I do actually like Rust, and I've written a few different things in it. I just think the state of `unsafe` is poor to the point that it's very hard to determine if you're doing something correctly, which in my opinion makes unsafe unusable for its purpose. [0]: https://blog.rust-lang.org/2014/09/15/Rust-1.0.html Edit: To be clear, I'm not attempting to defend Actix, that was silly. I'm just talking about situations where unsafe is unavoidable, which really covers a lot of potential usages of Rust.
In Uninitialized memory: Unsafe Rust is too hard

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