BB_C @ BB_C @programming.dev

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2 yr. ago

a better solution would be to add a method called something like ulock that does a combined lock and unwrap.

That's exactly what's done above using an extension trait! You can mutex_val.ulock() with it!

Now that I think about it, I don’t like how unwrap can signal either “I know this can’t fail”, “the possible error states are too rare to care about” or “I can’t be bothered with real error handing right now”.

That's why you're told (clippy does that i think) to use expect instead, so you can signal "whatever string" you want to signal precisely.

• C++ offers no guaranteed memory safety.
• A fictional safe C++ that would inevitably break backwards compatibility might as well be called Noel++, because it's not the same language anymore.
• If that proposal ever gets implemented (it won't), neither the promise of guaranteed memory safety will hold up, nor any big C++ project will adopt it. Big projects don't adopt the (rollingly defined) so-called modern C++ already, and that is something that is a part of the language proper, standardized, and available via multiple implementations.

would you argue that it’s impossible to write a"hello, world" program in C++

bent as expected

This proposal is just a part of a damage control campaign. No (supposedly doable) implementation will ever see the light of day. Ping me when this is proven wrong.

The only (arguably) baseless claim in that quote is this part:

it’s theoretically possible to write memory-safe C++

Maybe try to write more humbly and less fanatically, since you don't seem to be that knowledgable about anything (experienced in other threads too).

It's "theoretically possible" to write memory-safe assembly if we bend contextual meanings enough.

if you're really that bothered..

  rust

    
use std::sync::{Mutex, MutexGuard};

trait ULock<'a> {
    type Guard;
    fn ulock(&'a self) -> Self::Guard;
}

impl<'a, T: 'a> ULock<'a> for Mutex<T> {
    type Guard = MutexGuard<'a, T>;
    fn ulock(&'a self) -> Self::Guard {
      self.lock().unwrap()
    }
}

  

or use a wrapper struct, if you really really want the method to be called exactly lock.

If lock-ergonomics^ⓒ is as relevant to you as indexing, you're doing it wrong.

I would rather take indexing returning Results than the other way around.

One can always wrap any code in {||{ //.. }}() and use question marks liberally anyway (I call them stable try blocks 😉).

I specifically mentioned HTTP/2 because it should have been easy for everyone to both test and find the relevant info.

But anyway, here is a short explanation, and the curl-library thread where the issue was first encountered.

You should also find plenty of blog posts where "unexplainable delay"/"unexplainable slowness"/"something is stuck" is in the premise, and then after a lot of story development and "suspense", the big reveal comes that it was Nagle's fault.

As with many things TCP. A technique that may have been useful once, ends up proving to be counterproductive when used with modern protocols, workflows, and networks.

They don't even run Android TV. They run a modified (normal) Android. This is well known, but the article also mentions it.

You clearly have no idea what ping-pong protocol means.

I already mentioned why! It's common pitfall. For example, try a large HTTP/2 transfer over a socket where TCP_NODELAY is not set (or rather, explicitly unset), and see how the transfer rate would be limited because of it.

A reminder that TCP_NODELAY should be set by default, and you should remember to set it if it's not. Many protocols end up being ping-pong ones. This includes HTTP/2 for example.

..and that's how you drive up metrics.

Never set foot in AU.
I was under the impression that Tasmania doesn't get that cold.
Also, apparently some would rather describe Perth as Mediterranean-SouthAfrican, rather than Mediterranean-Californian 😉

Gross!

Unprofessional.
This is why no one takes Rust seriously.

but futures only execute when polled.

The most interesting part here is the polling only has to take place on the scope itself. That was actually what I wanted to check, but got distracted because all spawns are awaited in the scope in moro's README example.

    
async fn slp() {
    tokio::time::sleep(std::time::Duration::from_millis(1)).await
}

async fn _main() {
    let result_fut = moro::async_scope!(|scope| {
        dbg!("d1");
        scope.spawn(async { 
            dbg!("f1a");
            slp().await;
            slp().await;
            slp().await;
            dbg!("f1b");
        });
        dbg!("d2"); // 11
        scope.spawn(async {
            dbg!("f2a");
            slp().await;
            slp().await;
            dbg!("f2b");
        });
        dbg!("d3"); // 14
        scope.spawn(async {
            dbg!("f3a");
            slp().await;
            dbg!("f3b");
        });
        dbg!("d4");
        async { dbg!("b1"); } // never executes
    });
    slp().await;
    dbg!("o1");
    let _ = result_fut.await;
}

fn main() {
    let rt = tokio::runtime::Builder::new_multi_thread()
        .enable_all()
        .build()
        .unwrap();
    rt.block_on(_main())
}

  

    
[src/main.rs:32:5] "o1" = "o1"
[src/main.rs:7:9] "d1" = "d1"
[src/main.rs:15:9] "d2" = "d2"
[src/main.rs:22:9] "d3" = "d3"
[src/main.rs:28:9] "d4" = "d4"
[src/main.rs:9:13] "f1a" = "f1a"
[src/main.rs:17:13] "f2a" = "f2a"
[src/main.rs:24:13] "f3a" = "f3a"
[src/main.rs:26:13] "f3b" = "f3b"
[src/main.rs:20:13] "f2b" = "f2b"
[src/main.rs:13:13] "f1b" = "f1b"

  

The non-awaited jobs are run concurrently as the moro docs say. But what if we immediately await f2?

    
[src/main.rs:32:5] "o1" = "o1"
[src/main.rs:7:9] "d1" = "d1"
[src/main.rs:15:9] "d2" = "d2"
[src/main.rs:9:13] "f1a" = "f1a"
[src/main.rs:17:13] "f2a" = "f2a"
[src/main.rs:20:13] "f2b" = "f2b"
[src/main.rs:22:9] "d3" = "d3"
[src/main.rs:28:9] "d4" = "d4"
[src/main.rs:24:13] "f3a" = "f3a"
[src/main.rs:13:13] "f1b" = "f1b"
[src/main.rs:26:13] "f3b" = "f3b"

  

f1 and f2 are run concurrently, f3 is run after f2 finishes, but doesn't have to wait for f1 to finish, which is maybe obvious, but... (see below).

So two things here:

1. Re-using the spawn terminology here irks me for some reason. I don't know what would be better though. Would defer_to_scope() be confusing if the job is awaited in the scope?
2. Even if assumed obvious, a note about execution order when there is a mix of awaited and non-awaited jobs is worth adding to the documentation IMHO.

I skimmed the latter parts of this post since I felt like I read it all before, but I think moro is new to me. I was intrigued to find out how scoped span exactly behaves.

  rust

    
async fn slp() {
    tokio::time::sleep(std::time::Duration::from_millis(1)).await
}

async fn _main() {
    let value = 22;
    let result_fut = moro::async_scope!(|scope| {
        dbg!(); // line 8
        let future1 = scope.spawn(async {
            slp().await;
            dbg!(); // line 11
            let future2 = scope.spawn(async {
                slp().await;
                dbg!(); // line 14
                value // access stack values that outlive scope
            });
            slp().await;
            dbg!(); // line 18

            let v = future2.await * 2;
            v
        });

        slp().await;
        dbg!(); // line 25
        let v = future1.await * 2;
        slp().await;
        dbg!(); // line 28
        v
    });
    slp().await;
    dbg!(); // line 32
    let result = result_fut.await;
    eprintln!("{result}"); // prints 88
}

fn main() {
    // same output with `new_current_thread()` of course
    let rt = tokio::runtime::Builder::new_multi_thread()
        .enable_all()
        .build()
        .unwrap();
    rt.block_on(_main())
}

  

This prints:

    
[src/main.rs:32:5]
[src/main.rs:8:9]
[src/main.rs:25:9]
[src/main.rs:11:13]
[src/main.rs:18:13]
[src/main.rs:14:17]
[src/main.rs:28:9]
88

  

So scoped spawn doesn't really spawn tasks as one might mistakenly think!

Because non-open ones are not available, even for a price. Unless you buy something bigger than the "standard" itself of course, like a company that is responsible for it or having access to it.

There is also the process of standardization itself, with committees, working groups, public proposals, ..etc involved.

Anyway, we can't backtrack on calling ISO standards and their likes "open" on the global level, hence my suggestion to use more precise language (“publicly available and sharable”) when talking about truly open standards.

The term open-standard does not cut it. People should start using "publicly available and sharable" instead (maybe there is a better name for it).

ISO standards for example are technically "open". But how relevant is that to a curious individual developer when anything you need to implement would require access to multiple "open" standards, each coming with a (monetary) price, with some extra shenanigans ^[archived] on top.

IETF standards however are actually truly open, as in publicly available and sharable.

It implies that the value of their policy work is significantly below...

It's always safe to assume that value to be negative unless proven otherwise actually.

The LARPing levels in moronix comments are higher than usual, but the comedic value is still not lost.

Monthly Reminder: High or low, all Linux usage stats are fake.