MathiasKoch[m]: > <@mathias_koch:matrix.org> > maybe make sure you aren't using an older compiler version with the outlining miscompilation if you use opt-level=z)
> 
> What does this cover? 
> 
> > It could also be unrelated undefined behavior, sometimes totally unrelated changes will impact whether UB will be misoptimized or not.
> 
> Yeah, this would be my suspicion.. But how to hunt for UB?

https://github.com/rust-lang/rust/pull/119861, I think it landed in 1.76, maybe 1.77? 1.73-1.75 should definitely be considered sus: https://github.com/rust-embedded/cortex-m/discussions/503