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ConstProp miscompilation around references #73609
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In fact even level 2 is broken. |
... and level 1, for the union issue (so let's treat the other one separately). |
This doesn't require nightly after all, we have a stable-to-nightly regression when just running this code: fn main() {
#[allow(dead_code)]
union U {
f1: u32,
f2: f32,
}
let mut u = U { f1: 1 };
unsafe {
let b1 = &mut u.f1;
*b1 = 5;
}
assert_eq!(unsafe { u.f1 }, 5);
} gives
|
In fact we don't even need a union, nor an unsafe block: fn main() {
#[allow(dead_code)]
struct U {
f1: u32,
f2: f32,
}
let mut u = U { f1: 1, f2: 1.0 };
let b1 = &mut u.f1;
*b1 = 5;
assert_eq!( { u.f1 }, 5);
} |
Minimized: fn main() {
let mut u = (1,);
*&mut u.0 = 5;
assert_eq!( { u.0 }, 5);
} |
on it |
giving this p-critical based on our discussion |
Why is this |
@RalfJung: Why didn't the assertion failure cause a Miri toolstate change? |
I think this is stable-to-nightly only... @oli-obk why did you change that? @Aaron1011 rustc's CI currently only tests Miri with mir-opt-level=0. |
I tested it in the playground and I thought it also happened on beta? |
Hmm... not sure what happened, must have mis-clicked on the playground |
#71911 introduced a (nightly-to-nightly) regression in mir-opt-level=3: since that landed, this assertion fails when running the test in Miri.
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