From<&[T]> for Rc creates underaligned reference · Issue #54908 · rust-lang/rust (original) (raw)
The function allocate_for_ptr is passed a *const [T], which it turns into a &RcBox<[T]>. Unfortunately, the latter has an alignment of 8 even if T has smaller alignment. This leads to UB because we have a not-sufficiently-aligned reference.
This got introduced in #42565.
Found by miri (in my branch that verified the validity invariants).