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