mirror of https://github.com/rust-lang/rust
84 lines
2.9 KiB
Rust
84 lines
2.9 KiB
Rust
// For rust-lang/rust#68303: the contents of `UnsafeCell<T>` cannot
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// participate in the niche-optimization for enum discriminants. This
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// test checks that an `Option<UnsafeCell<NonZero<u32>>>` has the same
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// size in memory as an `Option<UnsafeCell<u32>>` (namely, 8 bytes).
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//
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//@ check-pass
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//@ compile-flags: --crate-type=lib
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//@ only-x86
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#![feature(repr_simd)]
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use std::cell::{UnsafeCell, RefCell, Cell};
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use std::mem::size_of;
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use std::num::NonZero;
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use std::sync::{Mutex, RwLock};
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struct Wrapper<T>(#[allow(dead_code)] T);
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#[repr(transparent)]
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struct Transparent<T>(T);
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struct NoNiche<T>(UnsafeCell<T>);
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struct Size<const S: usize>;
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macro_rules! check_sizes {
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(check_one_specific_size: $ty:ty, $size:expr) => {
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const _: Size::<{$size}> = Size::<{size_of::<$ty>()}>;
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};
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// Any tests run on `UnsafeCell` must be the same for `Cell`
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(UnsafeCell<$ty:ty>: $size:expr => $optioned_size:expr) => {
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check_sizes!(Cell<$ty>: $size => $optioned_size);
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check_sizes!(@actual_check: UnsafeCell<$ty>: $size => $optioned_size);
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};
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($ty:ty: $size:expr => $optioned_size:expr) => {
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check_sizes!(@actual_check: $ty: $size => $optioned_size);
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};
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// This branch does the actual checking logic, the `@actual_check` prefix is here to distinguish
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// it from other branches and not accidentally match any.
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(@actual_check: $ty:ty: $size:expr => $optioned_size:expr) => {
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check_sizes!(check_one_specific_size: $ty, $size);
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check_sizes!(check_one_specific_size: Option<$ty>, $optioned_size);
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check_sizes!(check_no_niche_opt: $size != $optioned_size, $ty);
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};
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// only check that there is no niche (size goes up when wrapped in an option),
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// don't check actual sizes
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($ty:ty) => {
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check_sizes!(check_no_niche_opt: true, $ty);
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};
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(check_no_niche_opt: $no_niche_opt:expr, $ty:ty) => {
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const _: () = if $no_niche_opt { assert!(size_of::<$ty>() < size_of::<Option<$ty>>()); };
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};
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}
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const PTR_SIZE: usize = std::mem::size_of::<*const ()>();
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check_sizes!(Wrapper<u32>: 4 => 8);
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check_sizes!(Wrapper<NonZero<u32>>: 4 => 4); // (✓ niche opt)
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check_sizes!(Transparent<u32>: 4 => 8);
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check_sizes!(Transparent<NonZero<u32>>: 4 => 4); // (✓ niche opt)
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check_sizes!(NoNiche<u32>: 4 => 8);
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check_sizes!(NoNiche<NonZero<u32>>: 4 => 8);
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check_sizes!(UnsafeCell<u32>: 4 => 8);
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check_sizes!(UnsafeCell<NonZero<u32>>: 4 => 8);
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check_sizes!(UnsafeCell<&()>: PTR_SIZE => PTR_SIZE * 2);
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check_sizes!( RefCell<&()>: PTR_SIZE * 2 => PTR_SIZE * 3);
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check_sizes!(RwLock<&()>);
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check_sizes!(Mutex<&()>);
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check_sizes!(UnsafeCell<&[i32]>: PTR_SIZE * 2 => PTR_SIZE * 3);
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check_sizes!(UnsafeCell<(&(), &())>: PTR_SIZE * 2 => PTR_SIZE * 3);
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trait Trait {}
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check_sizes!(UnsafeCell<&dyn Trait>: PTR_SIZE * 2 => PTR_SIZE * 3);
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#[repr(simd)]
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pub struct Vec4<T>([T; 4]);
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check_sizes!(UnsafeCell<Vec4<NonZero<u32>>>: 16 => 32);
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