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test into_boxed_slice with custom allocator in Miri

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This commit is contained in:
Ralf Jung 2024-03-10 18:04:03 +01:00
parent 81ebaf27cb
commit a7443f5542
1 changed files with 14 additions and 4 deletions
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18
src/tools/miri/tests/pass/box-custom-alloc-aliasing.rs
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@ -92,6 +92,8 @@ fn allocate(&self, layout: Layout) -> Result<NonNull<[u8]>, AllocError> {
} }
unsafe fn deallocate(&self, ptr: NonNull<u8>, _layout: Layout) { unsafe fn deallocate(&self, ptr: NonNull<u8>, _layout: Layout) {
// Make sure accesses via `self` don't disturb anything.
let _val = self.bins[0].top.get();
// Since manually finding the corresponding bin of `ptr` is very expensive, // Since manually finding the corresponding bin of `ptr` is very expensive,
// doing pointer arithmetics is preferred. // doing pointer arithmetics is preferred.
// But this means we access `top` via `ptr` rather than `self`! // But this means we access `top` via `ptr` rather than `self`!
@ -101,22 +103,30 @@ unsafe fn deallocate(&self, ptr: NonNull<u8>, _layout: Layout) {
if self.thread_id == thread_id { if self.thread_id == thread_id {
unsafe { (*their_bin).push(ptr) }; unsafe { (*their_bin).push(ptr) };
} else { } else {
todo!("Deallocating from another thread") todo!("Deallocating from another thread");
} }
// Make sure we can also still access this via `self` after the rest is done.
let _val = self.bins[0].top.get();
} }
} }
// Make sure to involve `Box` in allocating these, // Make sure to involve `Box` in allocating these,
// as that's where `noalias` may come from. // as that's where `noalias` may come from.
fn v<T, A: Allocator>(t: T, a: A) -> Vec<T, A> { fn v1<T, A: Allocator>(t: T, a: A) -> Vec<T, A> {
(Box::new_in([t], a) as Box<[T], A>).into_vec() (Box::new_in([t], a) as Box<[T], A>).into_vec()
} }
fn v2<T, A: Allocator>(t: T, a: A) -> Vec<T, A> {
let v = v1(t, a);
// There was a bug in `into_boxed_slice` that caused aliasing issues,
// so round-trip through that as well.
v.into_boxed_slice().into_vec()
}
fn main() { fn main() {
assert!(mem::size_of::<MyBin>() <= 128); // if it grows bigger, the trick to access the "header" no longer works assert!(mem::size_of::<MyBin>() <= 128); // if it grows bigger, the trick to access the "header" no longer works
let my_alloc = MyAllocator::new(); let my_alloc = MyAllocator::new();
let a = v(1usize, &my_alloc); let a = v1(1usize, &my_alloc);
let b = v(2usize, &my_alloc); let b = v2(2usize, &my_alloc);
assert_eq!(a[0] + 1, b[0]); assert_eq!(a[0] + 1, b[0]);
assert_eq!(addr_of!(a[0]).wrapping_add(1), addr_of!(b[0])); assert_eq!(addr_of!(a[0]).wrapping_add(1), addr_of!(b[0]));
drop((a, b)); drop((a, b));