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Miscompilation of unsigned division #967
Description
use std::hint::black_box;
use std::mem::transmute;
fn main() {
let pointer = black_box(usize::MAX) as *const ();
let value = unsafe { transmute::<*const (), usize>(pointer) };
assert_eq!(value / black_box(2), usize::MAX / 2);
assert_eq!(value % black_box(2), usize::MAX % 2);
}assertion `left == right` failed
left: 0
right: 9223372036854775807
It seems that a pointer transmuted to usize is somehow being treated as a signed number, which causes signed division to be used instead of unsigned division.
Originally found in rust-lang/rust#157943 and reduced using AI.
Activity
antoyo commentedon Aug 29, 2026
Fixed in #968.
Thanks for reporting this issue.