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Guarantee 8 bytes of alignment in Thread::into_raw #143859

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Merged
merged 2 commits into from
Jul 26, 2025
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Guarantee 8 bytes of alignment in Thread::into_raw #143859

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Guarantee 8 bytes of alignment in Thread::into_raw
orlp Jul 12, 2025
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orlp Jul 12, 2025
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8 changes: 7 additions & 1 deletion library/std/src/thread/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1380,6 +1380,11 @@ where
}

/// The internal representation of a `Thread` handle
///
/// We explicitly set the alignment for our guarantee in Thread::into_raw. This
/// allows applications to stuff extra metadata bits into the alignment, which
/// can be rather useful when working with atomics.
#[repr(align(8))]
struct Inner {
name: Option<ThreadNameString>,
id: ThreadId,
Expand Down Expand Up @@ -1563,7 +1568,8 @@ impl Thread {
/// Consumes the `Thread`, returning a raw pointer.
///
/// To avoid a memory leak the pointer must be converted
/// back into a `Thread` using [`Thread::from_raw`].
/// back into a `Thread` using [`Thread::from_raw`]. The pointer is
/// guaranteed to be aligned to at least 8 bytes.
///
/// # Examples
///
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