Source code
Revision control
Copy as Markdown
Other Tools
// Copyright 2019 The Fuchsia Authors
//
// Licensed under a BSD-style license <LICENSE-BSD>, Apache License, Version 2.0
// This file may not be copied, modified, or distributed except according to
// those terms.
#![allow(warnings)]
use std::{marker::PhantomData, option::IntoIter};
use {static_assertions::assert_impl_all, zerocopy::Unaligned};
// A union is `Unaligned` if:
// - `repr(align)` is no more than 1 and either
// - `repr(C)` or `repr(transparent)` and
// - all fields `Unaligned`
// - `repr(packed)`
#[derive(Unaligned)]
#[repr(C)]
union Foo {
a: u8,
}
assert_impl_all!(Foo: Unaligned);
// Transparent unions are unstable; see issue #60405
// #[derive(Unaligned)]
// #[repr(transparent)]
// union Bar {
// a: u8,
// }
// is_unaligned!(Bar);
#[derive(Unaligned)]
#[repr(packed)]
union Baz {
// NOTE: The `u16` type is not guaranteed to have alignment 2, although it
// does on many platforms. However, to fix this would require a custom type
// with a `#[repr(align(2))]` attribute, and `#[repr(packed)]` types are not
// allowed to transitively contain `#[repr(align(...))]` types. Thus, we
// have no choice but to use `u16` here. Luckily, these tests run in CI on
// platforms on which `u16` has alignment 2, so this isn't that big of a
// deal.
a: u16,
}
assert_impl_all!(Baz: Unaligned);
#[derive(Unaligned)]
#[repr(C, align(1))]
union FooAlign {
a: u8,
}
assert_impl_all!(FooAlign: Unaligned);
#[derive(Unaligned)]
#[repr(C)]
union TypeParams<'a, T: Copy, I: Iterator>
where
I::Item: Copy,
{
a: T,
c: I::Item,
d: u8,
e: PhantomData<&'a [u8]>,
f: PhantomData<&'static str>,
g: PhantomData<String>,
}
assert_impl_all!(TypeParams<'static, (), IntoIter<()>>: Unaligned);