1ad218f3af
As our implementation of MCP411 nears completion and we begin to solicit testing, it's no longer reasonable to expect testers to type or remember `BikeshedIntrinsicFrom`. The name degrades the ease-of-reading of documentation, and the overall experience of using compiler safe transmute. Tentatively, we'll instead adopt `TransmuteFrom`. This name seems to be the one most likely to be stabilized, after discussion on Zulip [1]. We may want to revisit the ordering of `Src` and `Dst` before stabilization, at which point we'd likely consider `TransmuteInto` or `Transmute`. [1] https://rust-lang.zulipchat.com/#narrow/stream/216762-project-safe-transmute/topic/What.20should.20.60BikeshedIntrinsicFrom.60.20be.20named.3F
47 lines
1.2 KiB
Rust
47 lines
1.2 KiB
Rust
//@ check-pass
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//! The presence of an `align(X)` annotation must be accounted for.
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#![crate_type = "lib"]
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#![feature(transmutability)]
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#![allow(dead_code, incomplete_features, non_camel_case_types)]
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mod assert {
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use std::mem::{Assume, TransmuteFrom};
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pub fn is_maybe_transmutable<Src, Dst>()
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where
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Dst: TransmuteFrom<Src, {
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Assume {
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alignment: true,
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lifetimes: true,
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safety: true,
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validity: true,
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}
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}>
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{}
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}
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fn should_pad_explicitly_aligned_field() {
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#[derive(Clone, Copy)] #[repr(u8)] enum V0u8 { V = 0 }
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#[derive(Clone, Copy)] #[repr(u8)] enum V1u8 { V = 1 }
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#[repr(align(1))]
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pub union Uninit {
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a: (),
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b: V1u8,
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}
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#[repr(align(2))]
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pub union align_2 {
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a: V0u8,
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}
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#[repr(C)] struct ImplicitlyPadded(align_2, V0u8);
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#[repr(C)] struct ExplicitlyPadded(V0u8, Uninit, V0u8);
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// An implementation that (incorrectly) does not place a padding byte after
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// `align_2` will, incorrectly, reject the following transmutations.
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assert::is_maybe_transmutable::<ImplicitlyPadded, ExplicitlyPadded>();
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assert::is_maybe_transmutable::<ExplicitlyPadded, ImplicitlyPadded>();
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}
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