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Allow (unsafe) access to the UnsafeCell inside RefCell #18131

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kmcallister opened this issue Oct 17, 2014 · 4 comments · Fixed by #18212
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Allow (unsafe) access to the UnsafeCell inside RefCell #18131

kmcallister opened this issue Oct 17, 2014 · 4 comments · Fixed by #18212
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E-easy Call for participation: Easy difficulty. Experience needed to fix: Not much. Good first issue.

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@kmcallister
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This would be useful in cases where we mostly want to enforce RefCell guarantees but need to break the rules in one place. (e.g. the Servo interface to html5ever which needs to GC-trace a mutably-borrowed parser)
@kmcallister kmcallister added A-libs E-easy Call for participation: Easy difficulty. Experience needed to fix: Not much. Good first issue. labels Oct 17, 2014
@jdm
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jdm commented Oct 18, 2014

Similarly, this would be useful for RAII classes that need to be fail-proof in the face of task failure while there are outstanding RefCell borrows.

@sfackler
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@jdm I don't think that case should be an issue; the Ref/RefMut destructors have to run before their RefCell's. They don't right now in some cases due to some unsoundness problems but that will be fixed: #8861.

@Ms2ger
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Ms2ger commented Oct 21, 2014

Same for Cell, please, for https://github.com/servo/servo/blob/1690a40bf4de9183d4e840f0654785a4d4a4e240/components/script/dom/bindings/utils.rs#L454-461.

@kmcallister
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Does the accessor itself need to be unsafe? I don't think so, because the relevant UnsafeCell ops are unsafe and we're only handing out shared references to it.

kmcallister added a commit to kmcallister/servo that referenced this issue Oct 24, 2014
@kmcallister
Customize RefCell instead of wrapping it
bb0ffb3 
This gets rid of a dubious transmute:

    let val = mem::transmute::<&RefCell<T>, &T>(&self.base);

The code duplication will be reduced once rust-lang/rust#18131 is fixed.
kmcallister added a commit to kmcallister/rust that referenced this issue Oct 24, 2014
@kmcallister
Add as_unsafe_cell() for Cell and RefCell
7317ef5 
Fixes rust-lang#18131.
kmcallister added a commit to kmcallister/servo that referenced this issue Oct 24, 2014
@kmcallister
Customize RefCell instead of wrapping it
96e180a 
This gets rid of a dubious transmute:

    let val = mem::transmute::<&RefCell<T>, &T>(&self.base);

The code duplication will be reduced once rust-lang/rust#18131 is fixed.
bors added a commit that referenced this issue Oct 26, 2014
@bors
auto merge of #18212 : kmcallister/rust/unsafecell, r=thestinger
cb943b7 
Fixes #18131.
RonakNisher pushed a commit to RonakNisher/servo that referenced this issue Nov 19, 2014
@kmcallister @RonakNisher
Customize RefCell instead of wrapping it
223f103 
This gets rid of a dubious transmute:

    let val = mem::transmute::<&RefCell<T>, &T>(&self.base);

The code duplication will be reduced once rust-lang/rust#18131 is fixed.
lnicola pushed a commit to lnicola/rust that referenced this issue Sep 25, 2024
@bors
Auto merge of rust-lang#18131 - ChayimFriedman2:macro-expand-dollar-c…
4ed7f4b 
…rate, r=Veykril

fix: Get rid of `$crate` in expansions shown to the user

Be it "Expand Macro Recursively", "Inline macro" or few other things.

We replace it with the crate name, as should've always been.

Probably fixes some issues, but I don't know what they are.
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Add as_unsafe_cell() for Cell and RefCell kmcallister/rust
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@jdm @Ms2ger @kmcallister @sfackler