69 lines
1.9 KiB
Rust
69 lines
1.9 KiB
Rust
#![feature(maybe_uninit_extra)]
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use std::mem::MaybeUninit;
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use std::cell::{Cell, RefCell, UnsafeCell};
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fn main() {
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aliasing_mut_and_shr();
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aliasing_frz_and_shr();
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into_interior_mutability();
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unsafe_cell_2phase();
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}
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fn aliasing_mut_and_shr() {
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fn inner(rc: &RefCell<i32>, aliasing: &mut i32) {
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*aliasing += 4;
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let _escape_to_raw = rc as *const _;
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*aliasing += 4;
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let _shr = &*rc;
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*aliasing += 4;
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// also turning this into a frozen ref now must work
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let aliasing = &*aliasing;
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let _val = *aliasing;
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let _escape_to_raw = rc as *const _; // this must NOT unfreeze
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let _val = *aliasing;
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let _shr = &*rc; // this must NOT unfreeze
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let _val = *aliasing;
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}
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let rc = RefCell::new(23);
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let mut bmut = rc.borrow_mut();
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inner(&rc, &mut *bmut);
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drop(bmut);
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assert_eq!(*rc.borrow(), 23+12);
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}
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fn aliasing_frz_and_shr() {
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fn inner(rc: &RefCell<i32>, aliasing: &i32) {
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let _val = *aliasing;
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let _escape_to_raw = rc as *const _; // this must NOT unfreeze
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let _val = *aliasing;
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let _shr = &*rc; // this must NOT unfreeze
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let _val = *aliasing;
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}
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let rc = RefCell::new(23);
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let bshr = rc.borrow();
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inner(&rc, &*bshr);
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assert_eq!(*rc.borrow(), 23);
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}
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// Getting a pointer into a union with interior mutability used to be tricky
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// business (https://github.com/rust-lang/miri/issues/615), but it should work
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// now.
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fn into_interior_mutability() {
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let mut x: MaybeUninit<(Cell<u32>, u32)> = MaybeUninit::uninit();
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x.as_ptr();
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x.write((Cell::new(0), 1));
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let ptr = unsafe { x.assume_init_ref() };
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assert_eq!(ptr.1, 1);
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}
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// Two-phase borrows of the pointer returned by UnsafeCell::get() should not
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// invalidate aliases.
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fn unsafe_cell_2phase() { unsafe {
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let x = &UnsafeCell::new(vec![]);
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let x2 = &*x;
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(*x.get()).push(0);
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let _val = (*x2.get()).get(0);
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} }
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