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Tracking Issue for const_intrinsic_copy #80697

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usbalbin opened this issue Jan 4, 2021 · 11 comments · Fixed by #97276
Open
5 tasks done

Tracking Issue for const_intrinsic_copy #80697

usbalbin opened this issue Jan 4, 2021 · 11 comments · Fixed by #97276
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C-tracking-issue Category: A tracking issue for an RFC or an unstable feature. Libs-Tracked Libs issues that are tracked on the team's project board. T-libs-api Relevant to the library API team, which will review and decide on the PR/issue.

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@usbalbin
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usbalbin commented Jan 4, 2021 •
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Feature gate: #![feature(const_intrinsic_copy)]

This is a tracking issue for making the functions ptr::copy and ptr::copy_nonoverlapping as well as some related functions const fn.

Public API

mod ptr {
    pub const unsafe fn copy_nonoverlapping<T>(src: *const T, dst: *mut T, count: usize);
    pub const unsafe fn copy<T>(src: *const T, dst: *mut T, count: usize);
}

impl *const T {
    pub const unsafe fn copy_to(self, dest: *mut T, count: usize);
    pub const unsafe fn copy_to_nonoverlapping(self, dest: *mut T, count: usize);
}

impl *mut T {
    pub const unsafe fn copy_to(self, dest: *mut T, count: usize);
    pub const unsafe fn copy_to_nonoverlapping(self, dest: *mut T, count: usize);

    pub const unsafe fn copy_from(self, src: *const T, count: usize);
    pub const unsafe fn copy_from_nonoverlapping(self, src: *const T, count: usize);
}

Steps / History

Unresolved Questions

Inorder to make intrinsics::copy and intrinsics::copy_nonoverlapping compile as const fn, some checks were removed.
See comment for some more info

For this PR, I see two options:

  • Leave it as "something we can do once we have a story for const-dependent dispatch".
  • Comment out the debug assertions for now. Their usefulness is anyway limited since the libstd everyone uses is compiled without debug assertions.

I guess the question is one of evaluating the relative usefulness of these new const operations vs the assertions.

(#79684 did the Comment out the debug assertions for now.-thing).

So the question is, how do we bring them back?
@usbalbin usbalbin added C-tracking-issue Category: A tracking issue for an RFC or an unstable feature. T-libs-api Relevant to the library API team, which will review and decide on the PR/issue. labels Jan 4, 2021
This was referenced Jan 4, 2021
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bors added a commit to rust-lang-ci/rust that referenced this issue Jan 5, 2021
@bors
Auto merge of rust-lang#80699 - usbalbin:const_copy_tracking_issue, r…
68ec332 
…=oli-obk

const_intrinsic_copy - Add Reference to tracking issue

Add reference to tracking issue rust-lang#80697 for feature gate added in previous PR rust-lang#79684
@m-ou-se m-ou-se added the Libs-Tracked Libs issues that are tracked on the team's project board. label Jan 6, 2021
@usbalbin
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usbalbin commented Mar 4, 2021

@RalfJung with #81238 merged, is the concern about "bringing back debug assertions" resolved as - we won't bring them back?

@RalfJung
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RalfJung commented Mar 5, 2021

Yeah I guess for now we won't bring them back.

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@jplatte jplatte mentioned this issue Aug 27, 2021
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@joshtriplett
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Seems reasonable, assuming that @rust-lang/wg-const-eval is fine with it.

@rfcbot merge
@rfcbot concern confirm-with-wg-const-eval

@rfcbot
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rfcbot commented Jan 26, 2022 •
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Team member @joshtriplett has proposed to merge this. The next step is review by the rest of the tagged team members:

Concerns:

Once a majority of reviewers approve (and at most 2 approvals are outstanding), 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 Jan 26, 2022
@RalfJung
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Fine from my side -- these are all conceptually simple functions and their implementation has been battle-tested a lot in Miri.

@joshtriplett
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@rfcbot resolve confirm-with-wg-const-eval

@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 Feb 23, 2022
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rfcbot commented Feb 23, 2022

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

@rfcbot rfcbot added the finished-final-comment-period The final comment period is finished for this PR / Issue. label Mar 5, 2022
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rfcbot commented Mar 5, 2022

The final comment period, with a disposition to merge, as per the review above, is now complete.

As the automated representative of the governance process, I would like to thank the author for their work and everyone else who contributed.

This will be merged soon.

@rfcbot rfcbot added to-announce Announce this issue on triage meeting and removed final-comment-period In the final comment period and will be merged soon unless new substantive objections are raised. labels Mar 5, 2022
@apiraino apiraino removed the to-announce Announce this issue on triage meeting label Mar 17, 2022
@JohnTitor JohnTitor mentioned this issue May 22, 2022
Merged
JohnTitor added a commit to JohnTitor/rust that referenced this issue Jun 8, 2022
@JohnTitor
Rollup merge of rust-lang#97276 - JohnTitor:stabilize-const-intrinsic…
6e2b51b 
…-copy, r=dtolnay

Stabilize `const_intrinsic_copy`

FCP has been completed: rust-lang#80697 (comment)
Closes rust-lang#80697
Dylan-DPC added a commit to Dylan-DPC/rust that referenced this issue Jun 8, 2022
@Dylan-DPC
Rollup merge of rust-lang#97276 - JohnTitor:stabilize-const-intrinsic…
16e60cd 
…-copy, r=dtolnay

Stabilize `const_intrinsic_copy`

FCP has been completed: rust-lang#80697 (comment)
Closes rust-lang#80697
@bors bors closed this as completed in f6b04ad Jun 8, 2022
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Opening since stablisation was reverted in #117905

@Dylan-DPC Dylan-DPC reopened this Jun 1, 2024
@Noratrieb Noratrieb removed disposition-merge This issue / PR is in PFCP or FCP with a disposition to merge it. finished-final-comment-period The final comment period is finished for this PR / Issue. labels Jun 1, 2024
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Stabilize const_intrinsic_copy JohnTitor/rust
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@joshtriplett @RalfJung @m-ou-se @apiraino @usbalbin @rfcbot @Noratrieb @Dylan-DPC