[pjmlp]

Because it is touted as an universal truth "Fearless Concurrency" of how Rust beats all languages, when in reality it only applies in a very specific use case, that in the world of distributed systems it isn't even the main one we care about in regards to concurrent and parallel access to data.

So its supremacy above anything else is kind of relative, and always left of out context.

[tialaramex]

See I don't buy that it's not "the main one we care about". What kind of insane software is expecting Sequential Consistency for shared mutable data across processes? That's what I still don't have a clear picture of. I think what I've seen here is merely a race condition, which is just not a big deal.

Humans can't reason about data races because they're contrary to our normal understanding of the world, but an ordinary race condition isn't like that. Earlier I saw there was the nice cheese at the grocery store, but I wasn't sure if they had fresh bread so... I kept walking, when I reached the bread aisle I bought bread and then I went back but nope, somebody else bought the last of the nice cheese. Oh well. Race condition.

[pjmlp]

Well then Fearless Concurrency should be sold in a proper way.

In modern times the network is the computer.

[tialaramex]

But it is fearless Concurrency. If you're worried about race conditions that's not a concurrency problem that's how the universe you were born in works.

Again, no computers involved in my food shopping (well, not the part I described anyway) but there's a race condition, because that's how the universe works. Rust can't magically change how the universe works. Whereas Data Races are something very strange, and Rust can just outlaw those.

[pjmlp]

As long as it is in-process data without external factors changing it, but we are running in circles here.

[tialaramex]

I guess, I just don't buy that it's confusing/ surprising that Rust can't change the laws of physics.

Decades ago a friend wrote a software "Time Machine" (this was long before Apple's backup software) which just buffers all the audio inputs so you could do the same thing with the computer in their studio as on their Sony Mini Disc recorder - if you hit "record" it records the sound you just heard, even though that sound happened before you hit the button, because it's a mains powered piece of kit it can just buffer a few seconds of PCM samples in a loop and so it does.

Sony invented that tech because it's necessary to how the device actually works anyway (it has lossy audio compression inside it, which needs a buffer) and it's useful, so, why not. The "Time Machine" software is of course not actually a time machine, but never did any users or prospective users say "Hey, that's misleading, it's not actually a time machine, those would require a change to the laws of physics". It's just audio software, duh.

The fact fearless concurrency doesn't protect you from the dangers of race conditions is no different from how it doesn't protect you from say mob violence. Those both sound bad, but I wasn't expecting the programming language to magically fix either of them.