Struct rfc::core::convert::transmute::options::NeglectAlignment

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pub struct NeglectAlignment;

[−] Expand description

Neglect the static alignment check.

By default, TransmuteFrom and TransmuteInto are only implemented for references when the minimum alignment of the destination's referent type is no greater than the minimum alignment of the source's referent type. The NeglectAlignment option disables this requirement.

By using the NeglectAlignment option, you are committing to ensure that the transmuted reference satisfies the alignment requirements of the destination's referent type. For instance:

/// Try to convert a `&T` into `&U`.
///
/// This produces `None` if the referent isn't appropriately
/// aligned, as required by the destination type.
pub fn try_cast_ref<'t, 'u, T, U>(src: &'t T) -> Option<&'u U>
where
    &'t T: TransmuteInto<&'u U, NeglectAlignment>,
{
    if (src as *const T as usize) % align_of::<U>() != 0 {
        None
    } else {
        // Safe because we dynamically enforce the alignment
        // requirement, whose static check we chose to neglect.
        Some(unsafe { src.unsafe_transmute_into() })
    }
}

Trait Implementations

impl TransmuteOptions for NeglectAlignment