weak-into-raw: Clarify some details in Safety #66710
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| /// is or *was* managed by an [`Rc`] and the weak count of that [`Rc`] must not have reached | ||
| /// 0. It is allowed for the strong count to be 0. | ||
| /// The pointer must have originated from the [`from_raw`] (or [`as_raw`], provided there was | ||
| /// corresponding [`forget`] on the `Weak<T>`) and must still own its potential weak reference |
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This isn't perfectly accurate, as you don't have to forget the original weak in the past, you can forget this weak if the pointer is from as_raw.
I'm not sure how to reword this note, though. Probably something along the lines of "only as many Weak are dropped as are created by non-raw methods".
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Technically yes, but only as long as some other Weak<T> or Strong<T> pointing to the same thing exists. If you created it after the weak count dropped to 0 and then forgot it, it would be UB, because it would play with the weak count field that no longer exists.
But if you hold a Weak<T> somewhere, then you probably don't really need to create and forget it. So I believe this might be good enough ‒ especially because this safety section errs on the safe side ‒ it's more restrictive than needs to be.
Anyway, I don't see how to make it more accurate, still readable and not ramble about it over two pages :-(.
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I've added a fixup. That one should be squashed before merging ‒ I'll do so once it gets completely reviewed. |
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r? @RalfJung perhaps |
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The job Click to expand the log.I'm a bot! I can only do what humans tell me to, so if this was not helpful or you have suggestions for improvements, please ping or otherwise contact |
CAD97
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Nov 24, 2019
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I can add this to my queue but given that my next free week-end is sometime in January, don't expect a quick review -- sorry. |
There's no code changed, it's just documentation changes to avoid people getting confused by it. I believe quite anyone should be able to review this, following the discussion in the linked ticket. It's not really about some deep unsafe magic. |
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It's less about being able to and more about finding the time. I only have 1-2 hours of time for Rust per day (taking up almost my entire free time) and there are quite a few things that are already waiting in my queue for more than a week. |
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My point was that I don't think it has to be you, @RalfJung, that anyone else could take it instead. |
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The job Click to expand the log.I'm a bot! I can only do what humans tell me to, so if this was not helpful or you have suggestions for improvements, please ping or otherwise contact |
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What about r? @SimonSapin |
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Sorry, I’m in a similar situation as Ralf. I’ve removed myself (a while ago) from the review auto-assignment because of limited bandwidth. I don’t really have a suggestion for more precise wording here. r? @Centril |
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Nov 30, 2019
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Also, can you squash the commits? |
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Thank you. I've included the suggestions and squashed. |
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Ups, I've force-pushed an older version ☹. I'll fix it once I get to the other computer where the right version still lives. |
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Looks good to me also, but r? @dtolnay |
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I've just squashed and force-pushed the correct version including all the link fixes. 🤞 |
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Thanks! @bors r+ rollup |
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📌 Commit 196cbfb4a6d75b5f6a01d2d33b2e41e02a1ba5f5 has been approved by |
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Let's fix those typos before landing. @bors r- |
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Clarify it is OK to pass a pointer that never owned a weak count (one from Weak::new) back into it as it was created from it. Relates to discussion in rust-lang#60728.
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Thanks! @bors r=dtolnay |
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📌 Commit 4731510 has been approved by |
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…tolnay weak-into-raw: Clarify some details in Safety Clarify it is OK to pass a pointer that never owned a weak count (one from Weak::new) back into it as it was created from it. Relates to discussion in rust-lang#60728. @CAD97 Do you want to have a look at the new docs?
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Rollup of 9 pull requests Successful merges: - #66710 (weak-into-raw: Clarify some details in Safety) - #66863 (Check break target availability when checking breaks with values) - #67002 (Fix documentation of pattern for str::matches()) - #67005 (capitalize Rust) - #67010 (Accurately portray raw identifiers in error messages) - #67011 (Include a span in more `expected...found` notes) - #67044 (E0023: handle expected != tuple pattern type) - #67045 (rustc_parser: cleanup imports) - #67055 (Make const-qualification look at more `const fn`s) Failed merges: r? @ghost
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Clarify it is OK to pass a pointer that never owned a weak count (one
from Weak::new) back into it as it was created from it. Relates to
discussion in #60728.
@CAD97 Do you want to have a look at the new docs?