Stacked Borrows: make scalar field retagging the default #2636
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RalfJung
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Manishearth
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update Miri Notable PRs: - rust-lang/miri#2636 - rust-lang/miri#2641 - rust-lang/miri#2638
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update Miri Notable PRs: - rust-lang#2636 - rust-lang#2641 - rust-lang#2638
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update Miri Notable PRs: - rust-lang/miri#2636 - rust-lang/miri#2641 - rust-lang/miri#2638
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I think it is time to finally close this soundness gap. Any objections? :)
Unfortunately the latest released versions of hashbrown and scopeguard can fail under full field retagging. The fixes have landed in the git repos but have not been released yet. I don't know if scalar field retagging as enabled by this PR is sufficient to cause problems with these crates, but it seems likely that this would be the case -- e.g. if both
valueanddropfnare scalars, the entire scopeguard struct will be aScalarPairand thus get field retagging.However, given that we actually generate LLVM
noaliasfor these cases, it seems prudent to inform users of this risk. They can easily set-Zmiri-field-retag=noneto opt-out of this change.Cc #2528