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option is_some() should not require a copyable value #2636

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nikomatsakis opened this issue Jun 16, 2012 · 2 comments
Closed

option is_some() should not require a copyable value #2636

nikomatsakis opened this issue Jun 16, 2012 · 2 comments

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@nikomatsakis
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But it does now. Same with is_none(), iter(), and map() I believe. And possibly others.
@eholk
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eholk commented Jun 18, 2012

Does this go for vectors too? I think I've been having to add copy bounds, but if we're clever we should be able to rewrite them without needing copy.

@nikomatsakis
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It often applies to vectors, yes.

@brson brson closed this as completed in ff536f3 Jun 18, 2012
RalfJung pushed a commit to RalfJung/rust that referenced this issue Nov 6, 2022
@bors
Auto merge of rust-lang#2636 - RalfJung:scalar-field-retag, r=oli-obk
c162fd3 
Stacked Borrows: make scalar field retagging the default

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 `value` and `dropfn` are scalars, the entire scopeguard struct will be a `ScalarPair` and thus get field retagging.

However, given that we actually generate LLVM `noalias` for these cases, it seems prudent to inform users of this risk. They can easily set `-Zmiri-field-retag=none` to opt-out of this change.

Cc rust-lang/miri#2528
Aaron1011 pushed a commit to Aaron1011/rust that referenced this issue Jan 6, 2023
@bors
Auto merge of rust-lang#2636 - RalfJung:scalar-field-retag, r=oli-obk
7138140 
Stacked Borrows: make scalar field retagging the default

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 `value` and `dropfn` are scalars, the entire scopeguard struct will be a `ScalarPair` and thus get field retagging.

However, given that we actually generate LLVM `noalias` for these cases, it seems prudent to inform users of this risk. They can easily set `-Zmiri-field-retag=none` to opt-out of this change.

Cc rust-lang/miri#2528
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@eholk @brson @nikomatsakis