3aa14e3b2e
In its first step of computing transmutability, `rustc_transmutability` constructs a byte-level representation of type layout (`Tree`). Previously, this representation was computed for ADTs by inspecting the ADT definition and performing our own layout computations. This process was error-prone, verbose, and limited our ability to analyze many types (particularly default-repr types). In this PR, we instead construct `Tree`s from `rustc_target::abi::Layout`s. This helps ensure that layout optimizations are reflected our analyses, and increases the kinds of types we can now analyze, including: - default repr ADTs - transparent unions - `UnsafeCell`-containing types Overall, this PR expands the expressvity of `rustc_transmutability` to be much closer to the transmutability analysis performed by miri. Future PRs will work to close the remaining gaps (e.g., support for `Box`, raw pointers, `NonZero*`, coroutines, etc.).
47 lines
1.3 KiB
Rust
47 lines
1.3 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, BikeshedIntrinsicFrom};
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pub fn is_maybe_transmutable<Src, Dst>()
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where
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Dst: BikeshedIntrinsicFrom<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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