TIL also - until today, I thought it was just "mercaptan". Turns out there are actually two variants of that:

> Ethanethiol (EM), commonly known as ethyl mercaptan is used in liquefied petroleum gas (LPG) and resembles odor of leeks, onions, durian, or cooked cabbage

Methanethiol, commonly known as methyl mercaptan, is added to natural gas as an odorant, usually in mixtures containing methane. Its smell is reminiscent of rotten eggs or cabbage.

...but you can still call it "mercaptan" and be ~ correct in most cases.

TIL!

Note that that is a doubly linked list, because it is a "soup of ownership" data structure. A singly linked list has clear ownership so it can be modelled in safe Rust.

On modern aschitectures you shouldn't use either unless you have an extremely niche use-case. They are not general use data structures anymore in a world where cache locality is a thing.

No you don’t. You can use the standard linked list that is already included in the standard library.

Coming up with these niche examples of things you need unsafe for in order to discredit rust’s safety guarantees is just not interesting. What fraction of programmer time is spent writing custom linked lists? Surely way less than 1%. In most of the other 99%, Rust is very helpful.

I love how the most common negative thing I hear about rust is how a really uncommon data structure no one should write by hand and should almost always import can be written using the unsafe rust language feature. Meanwhile rust application s tend to in most cases be considerably faster, more correct and more enjoyable to maintain than other languages. Must be a really awesome technology.

This is far less of a problem than it would be in a C-like language, though.

You can implement that linked list just once, audit the unsafe parts extensively, provide a fully safe API to clients, and then just use that safe API in many different places. You don't need thousands of project-specific linked list reimplementations.

Doesn’t Arc and Weak work for doubly linked lists? Rust docs recommend Weak as a way to break pointer cycles: https://doc.rust-lang.org/std/sync/struct.Arc.html#breaking-...

I assume GP was referring to mercaptan, or similar. i.e. Something with a distinctive bad smell.

https://en.m.wikipedia.org/wiki/Methanethiol

> Hydrogen sulfide is highly toxic (it's comparable to carbon monoxide)

It's a bad comparison since CO doesn't smell, which is what makes it dangerous, while H2S is detected by our sense of smell at concentrations much lower than the toxic dose (in fact, its biggest dangers comes from the fact that at dangerous concentration it doesn't even smell anything due to our receptors being saturated).

It's not what's being put in natural gas, but it wouldn't be that dangerous if we did.

By your line of reasoning, SIMD intrinsics functions should not be marked as unsafe in the first place. Then why are they marked as unsafe?

SIMD intrinsics are unsafe because they are available only under some CPU features.

I don't read any moralizing in my previous comment. And it seems to mirror the relevant section in the book:

"People are fallible, and mistakes will happen, but by requiring these five unsafe operations to be inside blocks annotated with unsafe you’ll know that any errors related to memory safety must be within an unsafe block. Keep unsafe blocks small; you’ll be thankful later when you investigate memory bugs."

I hope the SIMD intrinsics make it to stable soon so folks can ditch unnecessary unsafes if that's the only issue.

They add mercaptan which is like 1000x the rotten egg smell of H2S.

you are lucky to not have smelled metacarpan (which is what is actually put in). Much much worse than H2S