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// should find the bug even without, but gets masked by optimizations
//@compile-flags: -Zmiri-disable-stacked-borrows -Cdebug-assertions=no
//@normalize-stderr-test: "but found [0-9]+" -> "but found $$ALIGN"
#[repr(align(256))]
#[derive(Debug)]
struct MuchAlign;
fn main() {
// Try many times as this might work by chance.
for _ in 0..20 {
let buf = [0u32; 256];
// `buf` is sufficiently aligned for `layout.align` on a `dyn Debug`, but not
// for the actual alignment required by `MuchAlign`.
// We craft a wide reference `&dyn Debug` with the vtable for `MuchAlign`. That should be UB,
// as the reference is not aligned to its dynamic alignment requirements.
let mut ptr = &MuchAlign as &dyn std::fmt::Debug;
// Overwrite the data part of `ptr` so it points to `buf`.
unsafe {
(&mut ptr as *mut _ as *mut *const u8).write(&buf as *const _ as *const u8);
}
// Re-borrow that. This should be UB.
let _ptr = &*ptr; //~ERROR: required 256 byte alignment
}
}
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