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//@ run-pass
//@ revisions: normal randomize-layout
//@ [randomize-layout]compile-flags: -Zrandomize-layout -Zlayout-seed=2
#![feature(offset_of_enum)]
use std::ptr;
// these types only have their field offsets taken, they're never constructed
#[allow(dead_code)]
pub struct Foo<T>(u32, T, u8);
#[allow(dead_code)]
pub struct Wrapper<T>(T);
#[repr(transparent)]
#[allow(dead_code)]
pub struct TransparentWrapper(u16);
const _: () = {
// Behavior of the current non-randomized implementation, not guaranteed
#[cfg(not(randomize_layout))]
assert!(std::mem::offset_of!(Foo::<u16>, 1) == std::mem::offset_of!(Foo::<Wrapper<u16>>, 1));
// under randomization Foo<T> != Foo<U>
#[cfg(randomize_layout)]
assert!(std::mem::offset_of!(Foo::<u16>, 1) != std::mem::offset_of!(Foo::<Wrapper<u16>>, 1));
// Even transparent wrapper inner types get a different layout since associated type
// specialization could result in the outer type behaving differently depending on the exact
// inner type.
#[cfg(randomize_layout)]
assert!(
std::mem::offset_of!(Foo::<u16>, 1) != std::mem::offset_of!(Foo::<TransparentWrapper>, 1)
);
// Currently all fn pointers are treated interchangably even with randomization. Not guaranteed.
// Associated type specialization could also break this.
assert!(
std::mem::offset_of!(Foo::<fn(u32)>, 1) == std::mem::offset_of!(Foo::<fn() -> usize>, 1)
);
// But subtype coercions must always result in the same layout.
assert!(
std::mem::offset_of!(Foo::<fn(&u32)>, 1) == std::mem::offset_of!(Foo::<fn(&'static u32)>, 1)
);
// Randomization must uphold NPO guarantees
assert!(std::mem::offset_of!(Option::<&usize>, Some.0) == 0);
assert!(std::mem::offset_of!(Result::<&usize, ()>, Ok.0) == 0);
};
#[allow(dead_code)]
struct Unsizable<T: ?Sized>(usize, T);
fn main() {
// offset_of doesn't let us probe the unsized field, check at runtime.
let x = &Unsizable::<[u32; 4]>(0, [0; 4]);
let y: &Unsizable::<[u32]> = x;
// type coercion must not change the layout.
assert_eq!(ptr::from_ref(&x.1).addr(), ptr::from_ref(&y.1).addr());
}
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