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Comments (3)

lukas-code avatar lukas-code commented on August 23, 2024 1

This is incidentally fixed by #122493 by making unions always sized.

from rust.

matthiaskrgr avatar matthiaskrgr commented on August 23, 2024

#121208 cc @nnethercote

from rust.

lukas-code avatar lukas-code commented on August 23, 2024

smaller:

union Union {
    val: [u8],
}

fn cast(ptr: *const ()) -> *const Union {
    ptr as _
}

The union is currently in fact not sized, but this code assumes that non-struct ADTs must be sized:

rust/compiler/rustc_hir_typeck/src/cast.rs

Lines 101 to 144 in 7aa1de7

Ok(match *t.kind() {
ty::Slice(_) | ty::Str => Some(PointerKind::Length),
ty::Dynamic(tty, _, ty::Dyn) => Some(PointerKind::VTable(tty.principal_def_id())),
ty::Adt(def, args) if def.is_struct() => match def.non_enum_variant().tail_opt() {
None => Some(PointerKind::Thin),
Some(f) => {
let field_ty = self.field_ty(span, f, args);
self.pointer_kind(field_ty, span)?
}
},
ty::Tuple(fields) => match fields.last() {
None => Some(PointerKind::Thin),
Some(&f) => self.pointer_kind(f, span)?,
},
// Pointers to foreign types are thin, despite being unsized
ty::Foreign(..) => Some(PointerKind::Thin),
// We should really try to normalize here.
ty::Alias(_, pi) => Some(PointerKind::OfAlias(pi)),
ty::Param(p) => Some(PointerKind::OfParam(p)),
// Insufficient type information.
ty::Placeholder(..) | ty::Bound(..) | ty::Infer(_) => None,
ty::Bool
| ty::Char
| ty::Int(..)
| ty::Uint(..)
| ty::Float(_)
| ty::Array(..)
| ty::CoroutineWitness(..)
| ty::RawPtr(_)
| ty::Ref(..)
| ty::FnDef(..)
| ty::FnPtr(..)
| ty::Closure(..)
| ty::CoroutineClosure(..)
| ty::Coroutine(..)
| ty::Adt(..)
| ty::Never
| ty::Dynamic(_, _, ty::DynStar)
| ty::Error(_) => {
self.dcx().span_bug(span, format!("`{t:?}` should be sized but is not?"));
}
})

from rust.

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