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