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Rollup merge of #61969 - MikailBag:master, r=Centril

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Add #[repr(transparent)] for several types

In some functions, types mentioned in this PR are transmuted into their inner value.
Example for `PathBuf`: https://github.com/rust-lang/rust/blob/master/src/libstd/path.rs#L1132.
This PR adds `#[repr(transparent)]` to those types, so their correct behavior doesn't depend on compiler details. (As far as I understand, currently that line, converting `PathBuf` to `Vec<u8>`, is UB).
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Mark Rousskov 2019-08-11 15:18:38 -04:00 • committed by GitHub
commit 88629778e6
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12
src/libstd/path.rs
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@ -1123,6 +1123,12 @@ impl FusedIterator for Ancestors<'_> {}
/// Which method works best depends on what kind of situation you're in.
#[derive(Clone)]
#[stable(feature = "rust1", since = "1.0.0")]
// FIXME:
// `PathBuf::as_mut_vec` current implementation relies
// on `PathBuf` being layout-compatible with `Vec<u8>`.
// When attribute privacy is implemented, `PathBuf` should be annotated as `#[repr(transparent)]`.
// Anyway, `PathBuf` representation and layout are considered implementation detail, are
// not documented and must not be relied upon.
pub struct PathBuf {
inner: OsString,
}
@ -1745,6 +1751,12 @@ impl AsRef<OsStr> for PathBuf {
/// assert_eq!(extension, Some(OsStr::new("txt")));
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
// FIXME:
// `Path::new` current implementation relies
// on `Path` being layout-compatible with `OsStr`.
// When attribute privacy is implemented, `Path` should be annotated as `#[repr(transparent)]`.
// Anyway, `Path` representation and layout are considered implementation detail, are
// not documented and must not be relied upon.
pub struct Path {
inner: OsStr,
}