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Make the size of Option<NonZero*> a documented guarantee. #51396

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merged 1 commit into from
Jun 9, 2018
Merged

Make the size of Option<NonZero*> a documented guarantee. #51396

merged 1 commit into from
Jun 9, 2018

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SimonSapin
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Closes #49137, the tracking issue for NonZero*, as this was the last remaining open question.

Note that ptr::NonNull<T> already documents a similar guarantee.

@SimonSapin SimonSapin added the T-lang Relevant to the language team, which will review and decide on the PR/issue. label Jun 6, 2018
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r? @KodrAus

(rust_highfive has picked a reviewer for you, use r? to override)

@rust-highfive rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Jun 6, 2018
@SimonSapin
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SimonSapin commented Jun 6, 2018 •
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I’d left this out explicitly out of rust-lang/rfcs#2307 in order to have one fewer question to resolve at RFC time, but given the precedent of Option<&T> and Option<NonNull<T>> and others I think it’s reasonable to do this.

Lang team, this is your decision:

@rfcbot fcp merge

Edit: uh, looks like one needs to be part of the team to start FCP.

@SimonSapin
Make the size of Option<NonZero*> a documented guarantee.
5c7ca77 
Closes rust-lang#49137, the tracking issue for `NonZero*`,
as this was the last remaining open question.

Note that `ptr::NonNull<T>` already documents a similar guarantee.
@SimonSapin SimonSapin force-pushed the option-nonzero-layout branch from 65bc71f to 5c7ca77 Compare June 6, 2018 11:58
@SimonSapin SimonSapin changed the title Make the size of Option<NonZero*> a document guarantee. Make the size of Option<NonZero*> a documented guarantee. Jun 6, 2018
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@rfcbot fcp merge

This PR documents the assumption that Option<NonZeroU32> will be the size of a u32. The whole point of the non-zero types is to enable this optimization. We should guarantee it.

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rfcbot commented Jun 6, 2018 •
edited by nrc
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Team member @nikomatsakis has proposed to merge this. The next step is review by the rest of the tagged teams:

No concerns currently listed.

Once a majority of reviewers approve (and none object), this will enter its final comment period. If you spot a major issue that hasn't been raised at any point in this process, please speak up!

See this document for info about what commands tagged team members can give me.

@rfcbot rfcbot added proposed-final-comment-period Proposed to merge/close by relevant subteam, see T-<team> label. Will enter FCP once signed off. disposition-merge This issue / PR is in PFCP or FCP with a disposition to merge it. labels Jun 6, 2018
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rfcbot commented Jun 7, 2018

🔔 This is now entering its final comment period, as per the review above. 🔔

@rfcbot rfcbot added final-comment-period In the final comment period and will be merged soon unless new substantive objections are raised. and removed proposed-final-comment-period Proposed to merge/close by relevant subteam, see T-<team> label. Will enter FCP once signed off. labels Jun 7, 2018
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glandium commented Jun 8, 2018

Should the same guarantee, that applies to e.g. Box, Rc, Arc, Vec, String, ... be documented for those types as well? (There's a mention for Box in the documentation of size_of).

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@glandium Maybe, but I made this PR specifically in the context of closing #49137, the tracking issue for NonZero* types.

@bors r+

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bors commented Jun 8, 2018

📌 Commit 5c7ca77 has been approved by SimonSapin

@bors bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jun 8, 2018
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kennytm commented Jun 8, 2018

@bors rollup

Mark-Simulacrum added a commit to Mark-Simulacrum/rust that referenced this pull request Jun 8, 2018
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Rollup merge of rust-lang#51396 - SimonSapin:option-nonzero-layout, r…
b1a6db2 
…=SimonSapin

Make the size of Option<NonZero*> a documented guarantee.

Closes rust-lang#49137, the tracking issue for `NonZero*`, as this was the last remaining open question.

Note that `ptr::NonNull<T>` already documents a similar guarantee.
@Mark-Simulacrum Mark-Simulacrum mentioned this pull request Jun 8, 2018
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bors added a commit that referenced this pull request Jun 8, 2018
@bors
Auto merge of #51448 - Mark-Simulacrum:rollup, r=Mark-Simulacrum
cf91e9b 
Rollup of 13 pull requests

Successful merges:

 - #50143 (Add deprecation lint for duplicated `macro_export`s)
 - #51099 (Fix Issue 38777)
 - #51276 (Dedup auto traits in trait objects.)
 - #51298 (Stabilize unit tests with non-`()` return type)
 - #51360 (Suggest parentheses when a struct literal needs them)
 - #51391 (Use spans pointing at the inside of a rustdoc attribute)
 - #51394 (Use scope tree depths to speed up `nearest_common_ancestor`.)
 - #51396 (Make the size of Option<NonZero*> a documented guarantee.)
 - #51401 (Warn on `repr` without hints)
 - #51412 (Avoid useless Vec clones in pending_obligations().)
 - #51427 (compiletest: autoremove duplicate .nll.* files (#51204))
 - #51436 (Do not require stage 2 compiler for rustdoc)
 - #51437 (rustbuild: generate full list of dependencies for metadata)

Failed merges:
@bors bors merged commit 5c7ca77 into rust-lang:master Jun 9, 2018
@SimonSapin SimonSapin deleted the option-nonzero-layout branch June 9, 2018 22:02
@rfcbot rfcbot added finished-final-comment-period The final comment period is finished for this PR / Issue. and removed final-comment-period In the final comment period and will be merged soon unless new substantive objections are raised. labels Jun 17, 2018
@scottmcm scottmcm mentioned this pull request Mar 11, 2022
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