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Fix non-associativity of Instant math on aarch64-apple-darwin targets

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This commit is contained in:
Joy 2022-10-26 11:43:18 -07:00 committed by Cameron
parent e4d6307c63
commit 5008a317ce
2 changed files with 23 additions and 3 deletions
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18
library/std/src/sys/unix/time.rs
View File

@ -149,7 +149,11 @@ impl From<libc::timespec> for Timespec {
}
}
#[cfg(any(target_os = "macos", target_os = "ios", target_os = "watchos"))]
#[cfg(any(
all(target_os = "macos", not(target_arch = "aarch64")),
target_os = "ios",
target_os = "watchos"
))]
mod inner {
use crate::sync::atomic::{AtomicU64, Ordering};
use crate::sys::cvt;
@ -265,7 +269,11 @@ mod inner {
}
}
#[cfg(not(any(target_os = "macos", target_os = "ios", target_os = "watchos")))]
#[cfg(not(any(
all(target_os = "macos", not(target_arch = "aarch64")),
target_os = "ios",
target_os = "watchos"
)))]
mod inner {
use crate::fmt;
use crate::mem::MaybeUninit;
@ -281,7 +289,11 @@ mod inner {
impl Instant {
pub fn now() -> Instant {
Instant { t: Timespec::now(libc::CLOCK_MONOTONIC) }
#[cfg(target_os = "macos")]
const clock_id: clock_t = libc::CLOCK_UPTIME_RAW;
#[cfg(not(target_os = "macos"))]
const clock_id: clock_t = libc::CLOCK_MONOTONIC;
Instant { t: Timespec::now(clock_id) }
}
pub fn checked_sub_instant(&self, other: &Instant) -> Option<Duration> {

8
library/std/src/time/tests.rs
View File

@ -88,6 +88,14 @@ fn instant_math_is_associative() {
// Changing the order of instant math shouldn't change the results,
// especially when the expression reduces to X + identity.
assert_eq!((now + offset) - now, (now - now) + offset);
// On any platform, `Instant` should have the same resolution as `Duration` (e.g. 1 nanosecond)
// or better. Otherwise, math will be non-associative (see #91417).
let now = Instant::now();
let provided_offset = Duration::from_nanos(1);
let later = now + provided_offset;
let measured_offset = later - now;
assert_eq!(measured_offset, provided_offset);
}
#[test]