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Update unsafe trait example to zerocopy version 0.8 (#2434)

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Zerocopy crate version 0.8 introduced changes to its API, which caused
the example code to break.
https://github.com/google/zerocopy/discussions/1680
> AsBytes ->
[IntoBytes](https://docs.rs/zerocopy/0.8.*/zerocopy/trait.IntoBytes.html)

---------

Co-authored-by: Martin Geisler <martin@geisler.net>
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Semih Buyukgungor 2024-11-04 14:01:45 +03:00 committed by GitHub
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1 changed files with 7 additions and 12 deletions
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19
src/unsafe-rust/unsafe-traits.md
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@ -8,28 +8,23 @@ Like with functions, you can mark a trait as `unsafe` if the implementation must
guarantee particular conditions to avoid undefined behaviour.
For example, the `zerocopy` crate has an unsafe trait that looks
[something like this](https://docs.rs/zerocopy/latest/zerocopy/trait.AsBytes.html):
[something like this](https://docs.rs/zerocopy/latest/zerocopy/trait.IntoBytes.html):
```rust,editable
use std::mem::size_of_val;
use std::slice;
use std::{mem, slice};
/// ...
/// # Safety
/// The type must have a defined representation and no padding.
pub unsafe trait AsBytes {
pub unsafe trait IntoBytes {
fn as_bytes(&self) -> &[u8] {
unsafe {
slice::from_raw_parts(
self as *const Self as *const u8,
size_of_val(self),
)
}
let len = mem::size_of_val(self);
unsafe { slice::from_raw_parts((&raw const self).cast::<u8>(), len) }
}
}
// SAFETY: `u32` has a defined representation and no padding.
unsafe impl AsBytes for u32 {}
unsafe impl IntoBytes for u32 {}
```
<details>
@ -37,7 +32,7 @@ unsafe impl AsBytes for u32 {}
There should be a `# Safety` section on the Rustdoc for the trait explaining the
requirements for the trait to be safely implemented.
The actual safety section for `AsBytes` is rather longer and more complicated.
The actual safety section for `IntoBytes` is rather longer and more complicated.
The built-in `Send` and `Sync` traits are unsafe.