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//@compile-flags: -Zmiri-ignore-leaks
// Tests operations not performable through C++'s atomic API
// but doable in safe (at least sound) Rust.
#![feature(atomic_from_mut)]
use std::sync::atomic::Ordering::*;
use std::sync::atomic::{AtomicU16, AtomicU32};
use std::thread::spawn;
fn static_atomic_mut(val: u32) -> &'static mut AtomicU32 {
let ret = Box::leak(Box::new(AtomicU32::new(val)));
ret
}
fn split_u32(dword: &mut u32) -> &mut [u16; 2] {
unsafe { std::mem::transmute::<&mut u32, &mut [u16; 2]>(dword) }
}
fn mem_replace() {
let mut x = AtomicU32::new(0);
let old_x = std::mem::replace(&mut x, AtomicU32::new(42));
assert_eq!(x.load(Relaxed), 42);
assert_eq!(old_x.load(Relaxed), 0);
}
fn assign_to_mut() {
let x = static_atomic_mut(0);
x.store(1, Relaxed);
*x = AtomicU32::new(2);
assert_eq!(x.load(Relaxed), 2);
}
fn get_mut_write() {
let x = static_atomic_mut(0);
x.store(1, Relaxed);
{
let x_mut = x.get_mut();
*x_mut = 2;
}
let j1 = spawn(move || x.load(Relaxed));
let r1 = j1.join().unwrap();
assert_eq!(r1, 2);
}
// This is technically doable in C++ with atomic_ref
// but little literature exists atm on its involvement
// in mixed size/atomicity accesses
fn from_mut_split() {
let mut x: u32 = 0;
{
let x_atomic = AtomicU32::from_mut(&mut x);
x_atomic.store(u32::from_be(0xabbafafa), Relaxed);
}
// Split the `AtomicU32` into two `AtomicU16`.
// Crucially, there is no non-atomic access to `x`! All accesses are atomic, but of different size.
let (x_hi, x_lo) = split_u32(&mut x).split_at_mut(1);
let x_hi_atomic = AtomicU16::from_mut(&mut x_hi[0]);
let x_lo_atomic = AtomicU16::from_mut(&mut x_lo[0]);
assert_eq!(x_hi_atomic.load(Relaxed), u16::from_be(0xabba));
assert_eq!(x_lo_atomic.load(Relaxed), u16::from_be(0xfafa));
}
pub fn main() {
get_mut_write();
from_mut_split();
assign_to_mut();
mem_replace();
}
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