std::time::SystemTime::now() causes panic on wasm32-unknown-unknown. #48564

y-ich · 2018-02-26T23:56:14Z

Hi.
Thank you guys for your great project.

I am trying wasm32-unknown-unknown and got an error(panic) in std::time::SystemTime::now().

Here is a reproduction code.

#[no_mangle]
pub fn test() -> u32 {
    use std::time;
    let now = time::SystemTime::now();
    return 1;
}

<html lang="en">
  <head>
    <meta charset="utf-8">
    <script>
      fetch('wasm_time.wasm')
        .then((response) => response.arrayBuffer())
        .then((bytes) => WebAssembly.instantiate(bytes, {}))
        .then((results) => {
          const instance = results.instance;
          console.log(instance.exports.test());
        });
    </script>
  </head>
  <body>
  </body>
</html>

The error on Chrome on macOS. Similar error on Safari on macOS.

wasm-000873fa-78:2 Uncaught (in promise) RuntimeError: unreachable
    at __rust_start_panic (wasm-function[78]:1)
    at rust_panic (wasm-function[19]:40)
    at _ZN3std9panicking20rust_panic_with_hook17h4d23d2414abbb417E (wasm-function[14]:708)
    at _ZN3std9panicking11begin_panic17ha318dfc1360611dcE (wasm-function[11]:298)
    at _ZN3std3sys4wasm11TimeSysCall7perform17hfcfe4d7cbd5bdf2dE (wasm-function[69]:31)
    at _ZN3std3sys4wasm4time10SystemTime3now17h259757a3c249e0c6E (wasm-function[71]:20)
    at _ZN3std4time10SystemTime3now17hd79e83558f3b295bE (wasm-function[70]:1)
    at test (wasm-function[0]:38)
    at fetch.then.then.then (http://localhost:8000/:10:40)
    at <anonymous>
__rust_start_panic @ wasm-000873fa-78:2
rust_panic @ wasm-000873fa-19:21
_ZN3std9panicking20rust_panic_with_hook17h4d23d2414abbb417E @ wasm-000873fa-14:346
_ZN3std9panicking11begin_panic17ha318dfc1360611dcE @ wasm-000873fa-11:146
_ZN3std3sys4wasm11TimeSysCall7perform17hfcfe4d7cbd5bdf2dE @ wasm-000873fa-69:16
_ZN3std3sys4wasm4time10SystemTime3now17h259757a3c249e0c6E @ wasm-000873fa-71:12
_ZN3std4time10SystemTime3now17hd79e83558f3b295bE @ wasm-000873fa-70:2
test @ wasm-000873fa-0:20
fetch.then.then.then @ (index):10
Promise.then (async)
(anonymous) @ (index):8

My environment is,

OS : macOS 10.13.3
Rust: rustc 1.26.0-nightly (322d7f7 2018-02-25)
Chrome: 64.0.3282.167

Sorry, I have no idea to confirm the version of wasm32-unknown-unknown.

Cheers.

The text was updated successfully, but these errors were encountered:

abonander · 2018-02-27T14:05:50Z

It's weird that it seemingly panics with unreachable!() when, as far as I can tell, that macro was never used even when the time code was stubbed out with panics. Getting the time should actually work now unless the syscall interface is wrong.

alexcrichton · 2018-02-27T19:31:33Z

Thanks for the report! This is unfortunately, for now, an intended implementation detail of the standard library. The unreachable is actually an "illegal instruction" for wasm which is what happens when Rust panics, and Rust currently panics for modules in libstd that don't actually map to wasm (like Instant)

hodlbank · 2018-04-26T19:40:42Z

@alexcrichton , isn't this commit from Jan 30th should have resolved this issue completely?

alexcrichton · 2018-04-26T21:57:47Z

@hodlbank unfortunately that just added the possibility of another backend, but by default this still panics

Kwarrtz · 2018-07-02T03:42:23Z

There is currently an implementation for SystemTime and Instant (which do not panic) in libstd/sys/wasm/time.rs. Shouldn't this suffice?

MaulingMonkey · 2019-06-24T07:37:31Z

Still panics on nightly. Poking at this there's 3 issues, if I'm understanding right:

The wasm_syscall feature is off by default (would require an imports object if enabled, which sounds like a breaking change...?)
wasm32-shim.js isn't distributed with rust installs, nor anything else like wasm-bindgen (but versioning with the rust stdlib seems to make the most sense anyways...?)
Most of the shim syscalls assume a node-like environment and will fail in the browser, although the time one should work.

alexcrichton · 2019-06-24T11:28:04Z

@MaulingMonkey currently things are working as intended today. We're unlikely to ever stabilize the wasm_syscall feature and wasm32-shim.js is only intended for the test suite. Currently it's expected that the standard library's implementation of these primitives panics on the wasm32-unknown-unknown target since there's no way to implement them. For the wasm32-wasi target though they are implemented.

MaulingMonkey · 2019-06-24T17:56:50Z

EDIT (2024-01-15): for anyone stumbling across this comment, consider using the instant crate instead of the below code.

Sweet, I'll try out WASI at some point. For anyone else who stumbles across this issue but isn't quite ready to switch away from wasm32-unknown-unknown yet, here's a quick, poorly tested drop-in replacement for std::time you can plop into your project:

#![allow(dead_code, unused_imports)]

use wasm_bindgen::prelude::*;
use std::convert::{TryInto};
use std::ops::{Add, Sub, AddAssign, SubAssign};

pub use std::time::*;

#[cfg(not(target_arch = "wasm32"))] #[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)] pub struct Instant(std::time::Instant);
#[cfg(not(target_arch = "wasm32"))] impl Instant {
    pub fn now() -> Self { Self(std::time::Instant::now()) }
    pub fn duration_since(&self, earlier: Instant) -> Duration { self.0.duration_since(earlier.0) }
    pub fn elapsed(&self) -> Duration { self.0.elapsed() }
    pub fn checked_add(&self, duration: Duration) -> Option<Self> { self.0.checked_add(duration).map(|i| Self(i)) }
    pub fn checked_sub(&self, duration: Duration) -> Option<Self> { self.0.checked_sub(duration).map(|i| Self(i)) }
}

#[cfg(target_arch = "wasm32")] #[wasm_bindgen] extern "C" { #[wasm_bindgen(js_namespace = Date, js_name = now)] fn date_now() -> f64; }
#[cfg(target_arch = "wasm32")] #[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)] pub struct Instant(u64);
#[cfg(target_arch = "wasm32")] impl Instant {
    pub fn now() -> Self { Self(date_now() as u64) }
    pub fn duration_since(&self, earlier: Instant) -> Duration { Duration::from_millis(self.0 - earlier.0) }
    pub fn elapsed(&self) -> Duration { Self::now().duration_since(*self) }
    pub fn checked_add(&self, duration: Duration) -> Option<Self> {
        match duration.as_millis().try_into() {
            Ok(duration) => self.0.checked_add(duration).map(|i| Self(i)),
            Err(_) => None,
        }
    }
    pub fn checked_sub(&self, duration: Duration) -> Option<Self> {
        match duration.as_millis().try_into() {
            Ok(duration) => self.0.checked_sub(duration).map(|i| Self(i)),
            Err(_) => None,
        }
    }
}

impl Add<Duration> for Instant { type Output = Instant; fn add(self, other: Duration) -> Instant { self.checked_add(other).unwrap() } }
impl Sub<Duration> for Instant { type Output = Instant; fn sub(self, other: Duration) -> Instant { self.checked_sub(other).unwrap() } }
impl Sub<Instant>  for Instant { type Output = Duration; fn sub(self, other: Instant) -> Duration { self.duration_since(other) } }
impl AddAssign<Duration> for Instant { fn add_assign(&mut self, other: Duration) { *self = *self + other; } }
impl SubAssign<Duration> for Instant { fn sub_assign(&mut self, other: Duration) { *self = *self - other; } }

cheako · 2020-06-12T21:09:08Z

So it compiles, but for sure doesn't run... and I stress again Rust compiles it.

Edit: This is a misunderstanding on my part, compiled rust code is not garnered to be bug free. You have to deal with panics, throw renamed, and there are a few good ways to achieve this.

Tails · 2020-07-11T19:42:56Z

I just spent days debugging coming to this. What is the workaround? Is it not possible to get the current timestamp in WASM?

cheako · 2020-07-14T15:14:20Z

@Tails You have to use the code from #48564 (comment) though I wonder why it's not a crate...

I can see where getting the time differs from wasm runtime to runtime, but I also see the target being used is wasm32-unknown-unknown, where something like wasm32-unknown-html5, wasm32-unknown-node could be used to enable getting the time on those 'systems'.

crawlingChaos · 2020-09-19T03:57:06Z

Why does std::time::SystemTime::now() not fail when the target is wasm32-unknown-emscripten, but it does fail when the target is wasm32-unknown-unknown ?

cheako · 2020-09-19T15:31:57Z

@crawlingChaos I think it's because the system type is emscripten and as such the API is known... emscripten has a libc/POSIX API, right? Where as with an unknown system designation the API is literally unknown.

kupiakos · 2020-09-25T04:27:11Z

The code in #48564 (comment) is great, but missing an important detail. Date.now() breaks the requirement that std::time::Instant be monotonic. Right now, it's more like std::time::SystemTime. A better replacement can use performance.now().

#48564 (comment) rewritten to use performance.now:

#![allow(dead_code, unused_imports)]

use wasm_bindgen::prelude::*;
use std::convert::{TryInto};
use std::ops::{Add, Sub, AddAssign, SubAssign};

pub use std::time::*;

#[cfg(not(target_arch = "wasm32"))]
#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct Instant(std::time::Instant);

#[cfg(not(target_arch = "wasm32"))]
impl Instant {
    pub fn now() -> Self { Self(std::time::Instant::now()) }
    pub fn duration_since(&self, earlier: Instant) -> Duration { self.0.duration_since(earlier.0) }
    pub fn elapsed(&self) -> Duration { self.0.elapsed() }
    pub fn checked_add(&self, duration: Duration) -> Option<Self> { self.0.checked_add(duration).map(|i| Self(i)) }
    pub fn checked_sub(&self, duration: Duration) -> Option<Self> { self.0.checked_sub(duration).map(|i| Self(i)) }
}

#[cfg(target_arch = "wasm32")]
#[wasm_bindgen(inline_js = r#"
export function performance_now() {
  return performance.now();
}"#)]
extern "C" {
    fn performance_now() -> f64;
}

#[cfg(target_arch = "wasm32")]
#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct Instant(u64);

#[cfg(target_arch = "wasm32")]
impl Instant {
    pub fn now() -> Self { Self((performance_now() * 1000.0) as u64) }
    pub fn duration_since(&self, earlier: Instant) -> Duration { Duration::from_micros(self.0 - earlier.0) }
    pub fn elapsed(&self) -> Duration { Self::now().duration_since(*self) }
    pub fn checked_add(&self, duration: Duration) -> Option<Self> {
        match duration.as_micros().try_into() {
            Ok(duration) => self.0.checked_add(duration).map(|i| Self(i)),
            Err(_) => None,
        }
    }
    pub fn checked_sub(&self, duration: Duration) -> Option<Self> {
        match duration.as_micros().try_into() {
            Ok(duration) => self.0.checked_sub(duration).map(|i| Self(i)),
            Err(_) => None,
        }
    }
}

impl Add<Duration> for Instant { type Output = Instant; fn add(self, other: Duration) -> Instant { self.checked_add(other).unwrap() } }
impl Sub<Duration> for Instant { type Output = Instant; fn sub(self, other: Duration) -> Instant { self.checked_sub(other).unwrap() } }
impl Sub<Instant>  for Instant { type Output = Duration; fn sub(self, other: Instant) -> Duration { self.duration_since(other) } }
impl AddAssign<Duration> for Instant { fn add_assign(&mut self, other: Duration) { *self = *self + other; } }
impl SubAssign<Duration> for Instant { fn sub_assign(&mut self, other: Duration) { *self = *self - other; } }

Note: If you're targeting Node, it needs to be at least v8.5.0.

Fixed the WASM crashes by reverting to wgpu = 0.14. This surfaced two more bugs in the repo for which I included fixes. A big issue is wasm32-unknown-unknown does not support std::time::Instant, so I implemented a polyfill based on rust-lang/rust#48564 (comment). The animated examples, SVG loader, and the frame statistics monitor won't work in WASM without this. Once there is progress on the wgpu end, I'll turn that into a proper PR.

Fixed the WASM crashes by reverting to wgpu = 0.14. This surfaced two more bugs in the repo for which I included fixes. A big issue is wasm32-unknown-unknown does not support std::time::Instant, so I implemented a polyfill based on rust-lang/rust#48564 (comment). The animated examples, SVG loader, and the frame statistics monitor won't work in WASM without this. Once there is progress on the wgpu end, I'll turn that into a proper PR. Other issues: * The WGSL won't compile on native since this version of wgpu/naga doesn't support `const`. Chrome Canary in WASM works though. * There are serious visual artifacts in the examples when run in the browser.

Fixed the WASM crashes by reverting to wgpu = 0.14. This surfaced two more bugs in the repo for which I included fixes. A big issue is wasm32-unknown-unknown does not support std::time::Instant, so I implemented a polyfill based on rust-lang/rust#48564 (comment). The animated examples, SVG loader, and the frame statistics monitor won't work in WASM without this. Once there is progress on the wgpu end, I'll turn that into a proper PR. Also currently need to run the example with `cargo run_wasm --package with_winit --bin with_winit_bin` Other issues: * The WGSL won't compile on native since this version of wgpu/naga doesn't support `const`. Chrome Canary in WASM works though. * There are serious visual artifacts in the examples when run in the browser.

See rust-lang/rust#48564 for more information.

vivekvpandya · 2024-01-15T10:48:52Z

So it compiles, but for sure doesn't run... and I stress again Rust compiles it.

@cheako I am also facing same issue, adding the code above compiles fine but at runtime I am still getting "time not implemented" assert failed. how to fix it?

cheako · 2024-01-23T20:50:02Z

@vivekvpandya This is a misunderstanding on my part, compiled rust code is not garnered to be bug free. You have to deal with panics, throw renamed, and there are a few good ways to achieve this.

woelper · 2024-03-10T20:06:44Z

I've found https://crates.io/crates/web-time to be a good solution - it is a drop-in replacement for Instant and SystemTime - from their readme:

use web_time::{Instant, SystemTime};

let now = Instant::now();
let time = SystemTime::now();

gilescope · 2024-07-28T17:18:43Z

Is it time we had a wasm32-browser-browser triple so that we can assume a better minimum level of host support... the www foundation has standardised a lot over the last 30 years.
This feels unresolved.

pietroalbini added T-libs-api Relevant to the library API team, which will review and decide on the PR/issue. O-wasm Target: WASM (WebAssembly), http://webassembly.org/ C-bug Category: This is a bug. labels Feb 27, 2018

alexcrichton closed this as completed Feb 27, 2018

MaksymZavershynskyi mentioned this issue Oct 2, 2019

Support Instant:now() near/near-sdk-rs#4

Closed

pablosichert mentioned this issue Dec 21, 2019

panicked at 'time not implemented on wasm32-unknown-unknown' softdevteam/grmtools#145

Closed

benmkw mentioned this issue Mar 17, 2020

Compile to WASM str4d/rage#46

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Mythra mentioned this issue Jul 17, 2020

Add support for WebAssembly tokio-rs/tracing#642

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jakoschiko mentioned this issue Aug 30, 2020

libtest: Print the total time taken to execute a test suite #75752

Merged

eugineerd mentioned this issue Oct 2, 2020

Support wasm32-unknown-unknown target time-rs/time#282

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huangjj27 mentioned this issue Jan 15, 2021

Add basic wasm32-unknown-unknown support rust-cli/env_logger#148

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justinbowes mentioned this issue Feb 23, 2021

Latest git not building for wasm amethyst/bracket-lib#194

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simlay mentioned this issue May 14, 2021

[Merged by Bors] - feat: generic implementation of tokio_util::codec::Encoder for FluvioEncoder infinyon/fluvio#1081

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dbw9580 mentioned this issue Oct 5, 2021

Fix panic getting timestamp on wasm32-unknown-unknown target tesaguri/oauth1-request-rs#9

Merged

rachitnigam mentioned this issue Apr 21, 2022

Playground deployment broken calyxir/calyx#978

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lastmjs mentioned this issue Jun 10, 2022

Add date capabilities demergent-labs/azle#120

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mgeisler mentioned this issue Jul 3, 2022

Use the system time to seed the default RNG mgeisler/lipsum#92

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WASM crashes linebender/vello#276

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Support for user defined log formatting bevyengine/bevy#8374

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Add client support for the lighthouse/peers route sigp/lighthouse#4937

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FaceFTW added a commit to FaceFTW/rust-pipes that referenced this issue Dec 28, 2023

Add Shim for std::time::Instant on WASM

d722fdb

See rust-lang/rust#48564 for more information.

dotansimha mentioned this issue Jan 23, 2024

feat: add LocalSpans::to_span_records() tikv/minitrace-rust#185

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Weakky mentioned this issue Jul 31, 2024

Add support for UUIDv7 prisma/prisma-engines#4877

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Use web-time for tokio::time::Instant on wasm32-unknown-unknown tokio-rs/tokio#6740

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std::time::SystemTime::now() causes panic on wasm32-unknown-unknown. #48564

std::time::SystemTime::now() causes panic on wasm32-unknown-unknown. #48564

y-ich commented Feb 26, 2018 •

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abonander commented Feb 27, 2018

alexcrichton commented Feb 27, 2018

hodlbank commented Apr 26, 2018

alexcrichton commented Apr 26, 2018

Kwarrtz commented Jul 2, 2018

MaulingMonkey commented Jun 24, 2019

alexcrichton commented Jun 24, 2019

MaulingMonkey commented Jun 24, 2019 •

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cheako commented Jun 12, 2020 •

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Tails commented Jul 11, 2020

cheako commented Jul 14, 2020

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vivekvpandya commented Jan 15, 2024

cheako commented Jan 23, 2024

woelper commented Mar 10, 2024

gilescope commented Jul 28, 2024

std::time::SystemTime::now() causes panic on wasm32-unknown-unknown. #48564

std::time::SystemTime::now() causes panic on wasm32-unknown-unknown. #48564

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y-ich commented Feb 26, 2018 • edited Loading

abonander commented Feb 27, 2018

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hodlbank commented Apr 26, 2018

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