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