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Unrolled build for rust-lang#127447
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Rollup merge of rust-lang#127447 - RalfJung:once_lock_miri, r=joboet

once_lock: make test not take as long in Miri

Allocating 1000 list elements takes a while (`@zachs18` reported >5min), so let's reduce the iteration count when running in Miri. Unfortunately due to this clever `while let i @ 0..LEN =` thing, the count needs to be a constants, and constants cannot be shadowed, so we need to use another trick to hide the `cfg!(miri)` from the docs. (I think this loop condition may be a bit too clever, it took me a bit to decipher. Ideally this would be `while let i = ... && i < LEN`, but that is not stable yet.)
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rust-timer authored Jul 7, 2024
2 parents 959a2eb + bee9120 commit 4f0d7c6
Showing 1 changed file with 13 additions and 6 deletions.
19 changes: 13 additions & 6 deletions library/std/src/sync/once_lock.rs
Original file line number Diff line number Diff line change
Expand Up @@ -80,14 +80,21 @@ use crate::sync::Once;
/// static LIST: OnceList<u32> = OnceList::new();
/// static COUNTER: AtomicU32 = AtomicU32::new(0);
///
/// let vec = (0..thread::available_parallelism().unwrap().get()).map(|_| thread::spawn(|| {
/// while let i @ 0..=1000 = COUNTER.fetch_add(1, Ordering::Relaxed) {
/// LIST.push(i);
/// # const LEN: u32 = if cfg!(miri) { 50 } else { 1000 };
/// # /*
/// const LEN: u32 = 1000;
/// # */
/// thread::scope(|s| {
/// for _ in 0..thread::available_parallelism().unwrap().get() {
/// s.spawn(|| {
/// while let i @ 0..LEN = COUNTER.fetch_add(1, Ordering::Relaxed) {
/// LIST.push(i);
/// }
/// });
/// }
/// })).collect::<Vec<thread::JoinHandle<_>>>();
/// vec.into_iter().for_each(|handle| handle.join().unwrap());
/// });
///
/// for i in 0..=1000 {
/// for i in 0..LEN {
/// assert!(LIST.contains(&i));
/// }
///
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