bdb72edb5c
To handle packed structs with destructors (which you'll think are a rare case, but the `#[repr(packed)] struct Packed<T>(T);` pattern is ever-popular, which requires handling packed structs with destructors to avoid monomorphization-time errors), drops of subfields of packed structs should drop a local move of the field instead of the original one. cc #27060 - this should deal with that issue after codegen of drop glue is updated. The new errors need to be changed to future-compatibility warnings, but I'll rather do a crater run first with them as errors to assess the impact.
30 lines
1.1 KiB
Rust
30 lines
1.1 KiB
Rust
// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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#[repr(packed)]
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struct Packed<T: Copy>(T);
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impl<T: Copy> Copy for Packed<T> {}
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impl<T: Copy> Clone for Packed<T> {
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fn clone(&self) -> Self { *self }
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}
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fn main() {
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let one = (Some(Packed((&(), 0))), true);
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let two = [one, one];
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let stride = (&two[1] as *const _ as usize) - (&two[0] as *const _ as usize);
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// This can fail if rustc and LLVM disagree on the size of a type.
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// In this case, `Option<Packed<(&(), u32)>>` was erronously not
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// marked as packed despite needing alignment `1` and containing
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// its `&()` discriminant, which has alignment larger than `1`.
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assert_eq!(stride, std::mem::size_of_val(&one));
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}
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