Assertion fails in doc example for std::thread::sleep() in 1.32.0 stable

[TheRealOrangus]

The description of std::thread::sleep() says:

Puts the current thread to sleep for at least the specified amount of time.
The thread may sleep longer than the duration specified due to scheduling specifics or platform-dependent functionality. It will never sleep less.

and it gives the example code:

use std::{thread, time};

let ten_millis = time::Duration::from_millis(10);
let now = time::Instant::now();

thread::sleep(ten_millis);

assert!(now.elapsed() >= ten_millis);

But this assertion often fails when I run this code.

If the description is correct and it shouldn't fail, it happens on Windows 7 32 bit, stable-i686-pc-windows-gnu- rustc 1.32.0 (9fda7c223 2019-01-16)

EDIT:

Though, the expected behaviour can be achieved with this wrapper function:

use std::time::{Duration, Instant};
use std::thread::sleep;

fn sleep_noless(wanted_sleep: Duration) {
    let now = Instant::now();
    let mut slept_total = now.elapsed();
    while slept_total < wanted_sleep {
        sleep(wanted_sleep - slept_total);
        slept_total = now.elapsed();
    }
}

[karasjoh000]

I think I noticed this issue also.

[lukaslueg]

Does the underlying implementation on Windows actually uphold the guarantee in the docs? The windows-docs on sleep() say:

If dwMilliseconds is less than the resolution of the system clock, the thread may sleep for less than the specified length of time. [...] Call the timeGetDevCaps function to determine the supported minimum timer resolution and the timeBeginPeriod function to set the timer resolution to its minimum.

.

[ishitatsuyuki]

I think this was recently patched in nightly. Can you try it out?

[TheRealOrangus]

Just installed nightly-i686-pc-windows-gnu- rustc 1.33.0-nightly (0c0c58528 2019-01-19).
Made a new crate, ran rustup override set nightly in it. But the assertion still failed.

[retep998]

Not a regression as this is how this function always behaved on Windows. Also has nothing to do with concurrency nor is it specific to certain architectures nor MinGW specifically.