Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Enforce Copy bounds for repeat elements while considering lifetimes #95819

Merged
merged 5 commits into from
Apr 29, 2022

Conversation

oli-obk
Copy link
Contributor

@oli-obk oli-obk commented Apr 8, 2022

fixes #95477

this is a breaking change in order to fix a soundness bug.

Before this PR we only checked whether the repeat element type had an impl Copy, but not whether that impl also had the appropriate lifetimes. E.g. if the impl was for YourType<'static> and not a general 'a, then copying any type other than a 'static one should have been rejected, but wasn't.

r? @lcnr

@oli-obk oli-obk added relnotes Marks issues that should be documented in the release notes of the next release. I-lang-nominated Nominated for discussion during a lang team meeting. labels Apr 8, 2022
@rustbot rustbot added the T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. label Apr 8, 2022
@rust-highfive rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Apr 8, 2022
@compiler-errors
Copy link
Member

Crater perhaps?

@oli-obk
Copy link
Contributor Author

oli-obk commented Apr 8, 2022

@bors try

Oh yea, I knew I had forgotten some step here, thanks!

@bors
Copy link
Contributor

bors commented Apr 8, 2022

⌛ Trying commit 26a448bb57ca0923995c6b71ff0f1a28e03fb750 with merge 378b6a8a384b3bd0818af5f1745e5747a98bff7b...

@bors
Copy link
Contributor

bors commented Apr 8, 2022

☀️ Try build successful - checks-actions
Build commit: 378b6a8a384b3bd0818af5f1745e5747a98bff7b (378b6a8a384b3bd0818af5f1745e5747a98bff7b)

@oli-obk
Copy link
Contributor Author

oli-obk commented Apr 8, 2022

@craterbot check

@craterbot
Copy link
Collaborator

👌 Experiment pr-95819 created and queued.
🤖 Automatically detected try build 378b6a8a384b3bd0818af5f1745e5747a98bff7b
🔍 You can check out the queue and this experiment's details.

ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

@craterbot craterbot added S-waiting-on-crater Status: Waiting on a crater run to be completed. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Apr 8, 2022
@scottmcm
Copy link
Member

scottmcm commented Apr 9, 2022

I think we're good to do this under the usual "it was a bug" exception.

Hopefully crater says we can just do this, without a future compat dance.

@craterbot
Copy link
Collaborator

🚧 Experiment pr-95819 is now running

ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

@lcnr
Copy link
Contributor

lcnr commented Apr 10, 2022

I there something blocking you from using self.cx.prove_trait_ref here?

@oli-obk
Copy link
Contributor Author

oli-obk commented Apr 10, 2022

Yes, that function will ICE if the bound doesn't hold. Hmm.. I don't remember whether I tried it or not. I think I did, but i'll try again. Maybe I discarded it as a possibility just by looking at the code and misinterpreting the fact that it'll only ICE if there's no copy impl at all, which typeck should've already prevented

@oli-obk
Copy link
Contributor Author

oli-obk commented Apr 11, 2022

Ah yes, I remember these ICEs, I did try this before, but get lots of failures like

--- stderr -------------------------------
error: internal compiler error: no errors encountered even though `delay_span_bug` issued

error: internal compiler error: broken MIR in DefId(0:7 ~ repeat_to_run_dtor_twice[6a18]::main) (NoSolution): could not prove Binder(TraitPredicate(<Foo as std::marker::Copy>, polarity:Positive), [])
  --> /home/ubuntu/rust5/src/test/ui/repeat-to-run-dtor-twice.rs:17:13
   |
LL |     let _ = [ a; 5 ];
   |             ^^^^^^^^
   |
   = note: delayed at compiler/rustc_borrowck/src/type_check/canonical.rs:149:13

Which is happening because we are trying to borrowck a function that tries to copy a value that is never copy, irrespective of the lifetimes. So... I guess we can use prove_trait_ref if we patch typeck to at least do a minimal check.

This is going to get into MCP territory, but what if we just stopped trying to prove things in HIR typeck? Basically we do the bare minimum needed for building MIR. During MIR typeck/borrowck to do the real checks and can avoid any of the modulo-lifetimes checks.

I mean... we were already doing this right here, we just didn't check lifetimes

@lcnr
Copy link
Contributor

lcnr commented Apr 11, 2022

So... I guess we can use prove_trait_ref if we patch typeck to at least do a minimal check.

would really prefer that 👍 I assume that checking whether something is copy can influence type inference? 🤔 I am kind of wary of completely moving any checks to mir typeck

@lcnr
Copy link
Contributor

lcnr commented Apr 11, 2022

https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=9d20dd6e1989c761a16255a4f73ca78b

#[derive(Clone, Default)]
struct MaybeCopy<T>(T);

impl Copy for MaybeCopy<u8> {}

fn is_copy<T: Copy>(x: T) {
    println!("{}", std::any::type_name::<T>());
} 

fn main() {
    is_copy(MaybeCopy::default())
    // [MaybeCopy::default(); 13]
    // ^ doesn't work cause `Copy` is only checked in the mir here
}

@oli-obk oli-obk force-pushed the mir_can't_hold_all_these_lifetimes branch from 26a448b to be25ae3 Compare April 11, 2022 16:39
if !self.infcx.type_is_copy_modulo_regions(self.param_env, ty, span) {
let ccx = ConstCx::new_with_param_env(tcx, body, self.param_env);
let is_const_fn =
is_const_fn_in_array_repeat_expression(&ccx, &place, &body);
Copy link
Contributor

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

that function is now unused, so you can remove it

let res = self.typeck_results.borrow().qpath_res(qpath, element.hir_id);
matches!(
res,
Res::Def(DefKind::Const | DefKind::AssocConst | DefKind::AnonConst, _)
Copy link
Contributor

@lcnr lcnr Apr 12, 2022

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

you may want to add Res::Err here as well, to avoid Copy bounds if the repeat length uses an invalid path

Copy link
Contributor

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

+1

Copy link
Contributor

@lcnr lcnr left a comment

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

impl r=me

I personally think this is strictly a bugfix and doesn't need t-lang or t-compiler signoff? 🤔

@oli-obk
Copy link
Contributor Author

oli-obk commented Apr 12, 2022

Yea, once crater is clean i'll assign to a lang team member for language level review

@craterbot
Copy link
Collaborator

🎉 Experiment pr-95819 is completed!
📊 8 regressed and 5 fixed (225074 total)
📰 Open the full report.

⚠️ If you notice any spurious failure please add them to the blacklist!
ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

@craterbot craterbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-crater Status: Waiting on a crater run to be completed. labels Apr 13, 2022
@oli-obk
Copy link
Contributor Author

oli-obk commented Apr 13, 2022

All regressions are definitely spurious

r? @nikomatsakis as you commented on the issue

This only breaks user code that is already unsound, and crater found no cases of people relying on this. We were only checking if a type has a Copy impl, not if it actually applies for the given lifetimes. So if the Copy impl was only for 'static, but we had a non-static lifetime, the code was accepted.

|
= note: the `Copy` trait is required because the repeated element will be copied
= note: the `Copy` trait is required because this value will be copied for each element of the array
Copy link
Contributor

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

The only nitpick I'd have with the output would be to point at the whole array, But I think that'd be useful only in uncommon code, so it's not worth it to change it in this PR, particularly with the verbosity tradeoff:

let headers = [
    Header { value: &[] };
    128
];

Copy link
Contributor Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

We had this before. I could revert the spans to point at the entire array again, but I thought it was actually neat that we were just pointing to the repeat element now.

Copy link
Contributor

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Nono, what we have now it's good.

}

fn main() {
is_copy(MaybeCopy::default());
Copy link
Contributor

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Wait, I'm confused as to why this works. Is Default: Copy?

Copy link
Contributor

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Oh, wait. This is because MabeCopy::default(): ~const, right?

Copy link
Contributor Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

This worked because there was only one type T for which MaybeCopy<T> could be Copy. If we also had impl Copy for MaybeCopy<i8> {} then this would stop working: https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=a4fa25d4154048a62eca08aedcceb090

Copy link
Contributor

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Ah! Wow! Hadn't realized that that's how it works.

let code = traits::ObligationCauseCode::RepeatElementCopy { is_const_fn };
self.require_type_meets(element_ty, element.span, code, lang_item);
}
}
Copy link
Contributor

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Should we move that entire block to its own maybe_require_copy_value (or something) function? That might make skimming easier.

Copy link
Contributor Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Damn I love rust analyzer. Just selected the code and clicked "extract into fn". Add some lifetimes to types and remove the generated tcx argument done

Copy link
Contributor

@estebank estebank left a comment

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

r=me with the nitpicks addressed

@rfcbot rfcbot added finished-final-comment-period The final comment period is finished for this PR / Issue. 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 Apr 29, 2022
@rfcbot
Copy link

rfcbot commented Apr 29, 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.

@oli-obk
Copy link
Contributor Author

oli-obk commented Apr 29, 2022

/me pets the rfcbot, you have :chefkissfingers: timing

@oli-obk
Copy link
Contributor Author

oli-obk commented Apr 29, 2022

@bors r=estebank

@bors
Copy link
Contributor

bors commented Apr 29, 2022

📌 Commit 67ce547 has been approved by estebank

@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 Apr 29, 2022
@bors
Copy link
Contributor

bors commented Apr 29, 2022

⌛ Testing commit 67ce547 with merge a707f40...

@bors
Copy link
Contributor

bors commented Apr 29, 2022

☀️ Test successful - checks-actions
Approved by: estebank
Pushing a707f40 to master...

@bors bors added the merged-by-bors This PR was explicitly merged by bors. label Apr 29, 2022
@bors bors merged commit a707f40 into rust-lang:master Apr 29, 2022
@rustbot rustbot added this to the 1.62.0 milestone Apr 29, 2022
@rust-timer
Copy link
Collaborator

Finished benchmarking commit (a707f40): comparison url.

Summary:

  • Primary benchmarks: 😿 relevant regressions found
  • Secondary benchmarks: no relevant changes found
Regressions 😿
(primary)
Regressions 😿
(secondary)
Improvements 🎉
(primary)
Improvements 🎉
(secondary)
All 😿 🎉
(primary)
count1 2 0 0 0 2
mean2 0.8% N/A N/A N/A 0.8%
max 1.0% N/A N/A N/A 1.0%

If you disagree with this performance assessment, please file an issue in rust-lang/rustc-perf.

Next Steps: If you can justify the regressions found in this perf run, please indicate this with @rustbot label: +perf-regression-triaged along with sufficient written justification. If you cannot justify the regressions please open an issue or create a new PR that fixes the regressions, add a comment linking to the newly created issue or PR, and then add the perf-regression-triaged label to this PR.

@rustbot label: +perf-regression

Footnotes

  1. number of relevant changes

  2. the arithmetic mean of the percent change

@rustbot rustbot added the perf-regression Performance regression. label Apr 29, 2022
@oli-obk oli-obk deleted the mir_can't_hold_all_these_lifetimes branch April 30, 2022 05:00
@oli-obk
Copy link
Contributor Author

oli-obk commented Apr 30, 2022

This does add new dependency edges from typeck to other queries, so I'm not surprised there's more being marked dirty in incremental. I'll Loki at the benchmark itself to see what it is, but likely simply the fact that we now evaluate an array length in typeck.

@Mark-Simulacrum Mark-Simulacrum added the perf-regression-triaged The performance regression has been triaged. label May 3, 2022
@apiraino apiraino removed the to-announce Announce this issue on triage meeting label May 6, 2022
wip-sync pushed a commit to NetBSD/pkgsrc-wip that referenced this pull request Jul 12, 2022
Pkgsrc changes:
 * adapt patches (libc crate version bump)
 * no longer pass -I/usr/pkg/include through via gcc-wrap script.
   Attempt at fixing version skew with curl package vs. internal
   version of curl.
 * new checksums

Upstream changes:

Version 1.62.0 (2022-06-30)
==========================

Language
--------

- [Stabilize `#[derive(Default)]` on enums with a `#[default]` variant][94457]
- [Stop validating some checks in dead code after functions with
  uninhabited return types][93313]
- [Fix constants not getting dropped if part of a diverging expression][94775]
- [Support unit struct/enum variant in destructuring assignment][95380]
- [Remove mutable_borrow_reservation_conflict lint and allow the
  code pattern][96268]

Compiler
--------

- [linker: Stop using whole-archive on dependencies of dylibs][96436]
- [Make `unaligned_references` lint deny-by-default][95372]
  This lint is also a future compatibility lint, and is expected to eventually
  become a hard error.
- [Only add codegen backend to dep info if -Zbinary-dep-depinfo is used][93969]
- [Reject `#[thread_local]` attribute on non-static items][95006]
- [Add tier 3 `aarch64-pc-windows-gnullvm` and `x86_64-pc-windows-gnullvm`
  targets\*][94872]
- [Implement a lint to warn about unused macro rules][96150]
- [Promote `x86_64-unknown-none` target to Tier 2\*][95705]

\* Refer to Rust's [platform support page][platform-support-doc] for more
   information on Rust's tiered platform support.

Libraries
---------

- [Move `CStr` to libcore, and `CString` to liballoc][94079]
- [Windows: Use a pipe relay for chaining pipes][95841]
- [Replace Linux Mutex and Condvar with futex based ones.][95035]
- [Replace RwLock by a futex based one on Linux][95801]
- [std: directly use pthread in UNIX parker implementation][96393]

Stabilized APIs
---------------

- [`bool::then_some`]
- [`f32::total_cmp`]
- [`f64::total_cmp`]
- [`Stdin::lines`]
- [`windows::CommandExt::raw_arg`]
- [`impl<T: Default> Default for AssertUnwindSafe<T>`]
- [`From<Rc<str>> for Rc<[u8]>`][rc-u8-from-str]
- [`From<Arc<str>> for Arc<[u8]>`][arc-u8-from-str]
- [`FusedIterator for EncodeWide`]
- [RDM intrinsics on aarch64][stdarch/1285]

Clippy
------

- [Create clippy lint against unexpectedly late drop for temporaries
  in match scrutinee expressions][94206]

Cargo
-----

- Added the `cargo add` command for adding dependencies to `Cargo.toml` from
  the command-line.
  [docs](https://doc.rust-lang.org/nightly/cargo/commands/cargo-add.html)
- Package ID specs now support `name@version` syntax in addition to the
  previous `name:version` to align with the behavior in `cargo add` and other
  tools. `cargo install` and `cargo yank` also now support this syntax so the
  version does not need to passed as a separate flag.
- The `git` and `registry` directories in Cargo's home directory (usually
  `~/.cargo`) are now marked as cache directories so that they are not
  included in backups or content indexing (on Windows).
- Added automatic `@` argfile support, which will use "response files" if the
  command-line to `rustc` exceeds the operating system's limit.

Compatibility Notes
-------------------

- `cargo test` now passes `--target` to `rustdoc` if the specified target is
  the same as the host target.
  [#10594](rust-lang/cargo#10594)
- [rustdoc: Remove .woff font files][96279]
- [Enforce Copy bounds for repeat elements while considering lifetimes][95819]

Internal Changes
----------------

- [Unify ReentrantMutex implementations across all platforms][96042]

These changes provide no direct user facing benefits, but represent
significant improvements to the internals and overall performance
of rustc and related tools.

[93313]: rust-lang/rust#93313
[93969]: rust-lang/rust#93969
[94079]: rust-lang/rust#94079
[94206]: rust-lang/rust#94206
[94457]: rust-lang/rust#94457
[94775]: rust-lang/rust#94775
[94872]: rust-lang/rust#94872
[95006]: rust-lang/rust#95006
[95035]: rust-lang/rust#95035
[95372]: rust-lang/rust#95372
[95380]: rust-lang/rust#95380
[95431]: rust-lang/rust#95431
[95705]: rust-lang/rust#95705
[95801]: rust-lang/rust#95801
[95819]: rust-lang/rust#95819
[95841]: rust-lang/rust#95841
[96042]: rust-lang/rust#96042
[96150]: rust-lang/rust#96150
[96268]: rust-lang/rust#96268
[96279]: rust-lang/rust#96279
[96393]: rust-lang/rust#96393
[96436]: rust-lang/rust#96436
[96557]: rust-lang/rust#96557

[`bool::then_some`]: https://doc.rust-lang.org/stable/std/primitive.bool.html#method.then_some
[`f32::total_cmp`]: https://doc.rust-lang.org/stable/std/primitive.f32.html#method.total_cmp
[`f64::total_cmp`]: https://doc.rust-lang.org/stable/std/primitive.f64.html#method.total_cmp
[`Stdin::lines`]: https://doc.rust-lang.org/stable/std/io/struct.Stdin.html#method.lines
[`impl<T: Default> Default for AssertUnwindSafe<T>`]: https://doc.rust-lang.org/stable/std/panic/struct.AssertUnwindSafe.html#impl-Default
[rc-u8-from-str]: https://doc.rust-lang.org/stable/std/rc/struct.Rc.html#impl-From%3CRc%3Cstr%3E%3E
[arc-u8-from-str]: https://doc.rust-lang.org/stable/std/sync/struct.Arc.html#impl-From%3CArc%3Cstr%3E%3E
[stdarch/1285]: rust-lang/stdarch#1285
[`windows::CommandExt::raw_arg`]: https://doc.rust-lang.org/stable/std/os/windows/process/trait.CommandExt.html#tymethod.raw_arg
[`FusedIterator for EncodeWide`]: https://doc.rust-lang.org/stable/std/os/windows/ffi/struct.EncodeWide.html#impl-FusedIterator
netbsd-srcmastr pushed a commit to NetBSD/pkgsrc that referenced this pull request Aug 31, 2022
Pkgsrc changes:

 * Bump required GCC to 7 (same as LLVM) to avoid ABI issues
   Fixes native i386 and powerpc 8.x build w/pkgsrc LLVM 14
 * Bump available bootstraps to 1.61.0.
 * Also unlimit stacksize
 * Sync patches over from wip/rust
 * Adjust line number in patches which had non-zero offsets.
 * no longer pass -I/usr/pkg/include through via gcc-wrap script
   when building natively.  Attempt at fixing version skew with curl
   package vs. internal version of curl (may not work...)
 * The NetBSD bootstraps now use .xz compression.
 * Use mk/atomic64.mk.  Still have conditional for libatomic-links.
 * Default to using the internal LLVM when cross-building.


Upstream changes:

Version 1.62.1 (2022-07-19)
==========================

Rust 1.62.1 addresses a few recent regressions in the compiler and standard
library, and also mitigates a CPU vulnerability on Intel SGX.

* [The compiler fixed unsound function coercions involving `impl
  Trait` return types.][98608]
* [The compiler fixed an incremental compilation bug with `async
  fn` lifetimes.][98890]
* [Windows added a fallback for overlapped I/O in synchronous reads
  and writes.][98950]
* [The `x86_64-fortanix-unknown-sgx` target added a mitigation for the
  MMIO stale data vulnerability][98126], advisory [INTEL-SA-00615].

[98608]: rust-lang/rust#98608
[98890]: rust-lang/rust#98890
[98950]: rust-lang/rust#98950
[98126]: rust-lang/rust#98126
[INTEL-SA-00615]: https://www.intel.com/content/www/us/en/security-center/advisory/intel-sa-00615.html


Version 1.62.0 (2022-06-30)
==========================

Language
--------

- [Stabilize `#[derive(Default)]` on enums with a `#[default]` variant][94457]
- [Stop validating some checks in dead code after functions with
  uninhabited return types][93313]
- [Fix constants not getting dropped if part of a diverging expression][94775]
- [Support unit struct/enum variant in destructuring assignment][95380]
- [Remove mutable_borrow_reservation_conflict lint and allow the
  code pattern][96268]

Compiler
--------

- [linker: Stop using whole-archive on dependencies of dylibs][96436]
- [Make `unaligned_references` lint deny-by-default][95372]
  This lint is also a future compatibility lint, and is expected to eventually
  become a hard error.
- [Only add codegen backend to dep info if -Zbinary-dep-depinfo is used][93969]
- [Reject `#[thread_local]` attribute on non-static items][95006]
- [Add tier 3 `aarch64-pc-windows-gnullvm` and `x86_64-pc-windows-gnullvm`
  targets\*][94872]
- [Implement a lint to warn about unused macro rules][96150]
- [Promote `x86_64-unknown-none` target to Tier 2\*][95705]

\* Refer to Rust's [platform support page][platform-support-doc] for more
   information on Rust's tiered platform support.

Libraries
---------

- [Move `CStr` to libcore, and `CString` to liballoc][94079]
- [Windows: Use a pipe relay for chaining pipes][95841]
- [Replace Linux Mutex and Condvar with futex based ones.][95035]
- [Replace RwLock by a futex based one on Linux][95801]
- [std: directly use pthread in UNIX parker implementation][96393]

Stabilized APIs
---------------

- [`bool::then_some`]
- [`f32::total_cmp`]
- [`f64::total_cmp`]
- [`Stdin::lines`]
- [`windows::CommandExt::raw_arg`]
- [`impl<T: Default> Default for AssertUnwindSafe<T>`]
- [`From<Rc<str>> for Rc<[u8]>`][rc-u8-from-str]
- [`From<Arc<str>> for Arc<[u8]>`][arc-u8-from-str]
- [`FusedIterator for EncodeWide`]
- [RDM intrinsics on aarch64][stdarch/1285]

Clippy
------

- [Create clippy lint against unexpectedly late drop for temporaries
  in match scrutinee expressions][94206]

Cargo
-----

- Added the `cargo add` command for adding dependencies to `Cargo.toml` from
  the command-line.
  [docs](https://doc.rust-lang.org/nightly/cargo/commands/cargo-add.html)
- Package ID specs now support `name@version` syntax in addition to the
  previous `name:version` to align with the behavior in `cargo add` and other
  tools. `cargo install` and `cargo yank` also now support this syntax so the
  version does not need to passed as a separate flag.
- The `git` and `registry` directories in Cargo's home directory (usually
  `~/.cargo`) are now marked as cache directories so that they are not
  included in backups or content indexing (on Windows).
- Added automatic `@` argfile support, which will use "response files" if the
  command-line to `rustc` exceeds the operating system's limit.

Compatibility Notes
-------------------

- `cargo test` now passes `--target` to `rustdoc` if the specified target is
  the same as the host target.
  [#10594](rust-lang/cargo#10594)
- [rustdoc: Remove .woff font files][96279]
- [Enforce Copy bounds for repeat elements while considering lifetimes][95819]

Internal Changes
----------------

- [Unify ReentrantMutex implementations across all platforms][96042]

These changes provide no direct user facing benefits, but represent
significant improvements to the internals and overall performance
of rustc and related tools.

[93313]: rust-lang/rust#93313
[93969]: rust-lang/rust#93969
[94079]: rust-lang/rust#94079
[94206]: rust-lang/rust#94206
[94457]: rust-lang/rust#94457
[94775]: rust-lang/rust#94775
[94872]: rust-lang/rust#94872
[95006]: rust-lang/rust#95006
[95035]: rust-lang/rust#95035
[95372]: rust-lang/rust#95372
[95380]: rust-lang/rust#95380
[95431]: rust-lang/rust#95431
[95705]: rust-lang/rust#95705
[95801]: rust-lang/rust#95801
[95819]: rust-lang/rust#95819
[95841]: rust-lang/rust#95841
[96042]: rust-lang/rust#96042
[96150]: rust-lang/rust#96150
[96268]: rust-lang/rust#96268
[96279]: rust-lang/rust#96279
[96393]: rust-lang/rust#96393
[96436]: rust-lang/rust#96436
[96557]: rust-lang/rust#96557

[`bool::then_some`]: https://doc.rust-lang.org/stable/std/primitive.bool.html#method.then_some
[`f32::total_cmp`]: https://doc.rust-lang.org/stable/std/primitive.f32.html#method.total_cmp
[`f64::total_cmp`]: https://doc.rust-lang.org/stable/std/primitive.f64.html#method.total_cmp
[`Stdin::lines`]: https://doc.rust-lang.org/stable/std/io/struct.Stdin.html#method.lines
[`impl<T: Default> Default for AssertUnwindSafe<T>`]: https://doc.rust-lang.org/stable/std/panic/struct.AssertUnwindSafe.html#impl-Default
[rc-u8-from-str]: https://doc.rust-lang.org/stable/std/rc/struct.Rc.html#impl-From%3CRc%3Cstr%3E%3E
[arc-u8-from-str]: https://doc.rust-lang.org/stable/std/sync/struct.Arc.html#impl-From%3CArc%3Cstr%3E%3E
[stdarch/1285]: rust-lang/stdarch#1285
[`windows::CommandExt::raw_arg`]: https://doc.rust-lang.org/stable/std/os/windows/process/trait.CommandExt.html#tymethod.raw_arg
[`FusedIterator for EncodeWide`]: https://doc.rust-lang.org/stable/std/os/windows/ffi/struct.EncodeWide.html#impl-FusedIterator


Version 1.61.0 (2022-05-19)
==========================

Language
--------

- [`const fn` signatures can now include generic trait bounds][93827]
- [`const fn` signatures can now use `impl Trait` in argument and return
  position][93827]
- [Function pointers can now be created, cast, and passed around in a
  `const fn`][93827]
- [Recursive calls can now set the value of a function's opaque
  `impl Trait` return type][94081]

Compiler
--------

- [Linking modifier syntax in `#[link]` attributes and on the command
  line, as well as the `whole-archive` modifier specifically, are now
  supported][93901]
- [The `char` type is now described as UTF-32 in debuginfo][89887]
- The [`#[target_feature]`][target_feature] attribute
  [can now be used with aarch64 features][90621]
- X86 [`#[target_feature = "adx"]` is now stable][93745]

Libraries
---------

- [`ManuallyDrop<T>` is now documented to have the same layout as `T`][88375]
- [`#[ignore = "#"]` messages are printed when running tests][92714]
- [Consistently show absent stdio handles on Windows as NULL handles][93263]
- [Make `std::io::stdio::lock()` return `'static` handles.][93965]
  Previously, the creation of locked handles to stdin/stdout/stderr would
  borrow the handles being locked, which prevented writing
  `let out = std::io::stdout().lock();` because `out` would outlive
  the return value of `stdout()`.
  Such code now works, eliminating a common pitfall that affected many
  Rust users.
- [`Vec::from_raw_parts` is now less restrictive about its inputs][95016]
- [`std::thread::available_parallelism` now takes cgroup quotas into
  account.][92697] Since `available_parallelism` is often used to create a
  thread pool for parallel computation, which may be CPU-bound for
  performance, `available_parallelism` will return a value consistent with
  the ability to use that many threads continuously, if possible.
  For instance, in a container with 8 virtual CPUs but quotas only allowing
  for 50% usage, `available_parallelism` will return 4.

Stabilized APIs
---------------

- [`Pin::static_mut`]
- [`Pin::static_ref`]
- [`Vec::retain_mut`]
- [`VecDeque::retain_mut`]
- [`Write` for `Cursor<[u8; N]>`][cursor-write-array]
- [`std::os::unix::net::SocketAddr::from_pathname`]
- [`std::process::ExitCode`] and [`std::process::Termination`].
  The stabilization of these two API s now makes it possible for
  programs to return errors from `main` with custom exit codes.
- [`std::thread::JoinHandle::is_finished`]

These APIs are now usable in const contexts:

- [`<*const T>::offset` and `<*mut T>::offset`][ptr-offset]
- [`<*const T>::wrapping_offset` and `<*mut T>::wrapping_offset`]
  [ptr-wrapping_offset]
- [`<*const T>::add` and `<*mut T>::add`][ptr-add]
- [`<*const T>::sub` and `<*mut T>::sub`][ptr-sub]
- [`<*const T>::wrapping_add` and `<*mut T>::wrapping_add`][ptr-wrapping_add]
- [`<*const T>::wrapping_sub` and `<*mut T>::wrapping_sub`][ptr-wrapping_sub]
- [`<[T]>::as_mut_ptr`][slice-as_mut_ptr]
- [`<[T]>::as_ptr_range`][slice-as_ptr_range]
- [`<[T]>::as_mut_ptr_range`][slice-as_mut_ptr_range]

Cargo
-----

No feature changes, but see compatibility notes.

Compatibility Notes
-------------------

- Previously native static libraries were linked as `whole-archive` in
  some cases, but now rustc tries not to use `whole-archive` unless
  explicitly requested. This [change][93901] may result in linking errors
  in some cases. To fix such errors, native libraries linked from the
  command line, build scripts, or [`#[link]` attributes][link-attr] need to
  - (more common) either be reordered to respect dependencies between them
    (if `a` depends on `b` then `a` should go first and `b` second)
  - (less common) or be updated to use the [`+whole-archive`] modifier.
- [Catching a second unwind from FFI code while cleaning up from a Rust
  panic now causes the process to abort][92911]
- [Proc macros no longer see `ident` matchers wrapped in groups][92472]
- [The number of `#` in `r#` raw string literals is now required to be
  less than 256][95251]
- [When checking that a dyn type satisfies a trait bound, supertrait
  bounds are now enforced][92285]
- [`cargo vendor` now only accepts one value for each `--sync` flag]
  [cargo/10448]
- [`cfg` predicates in `all()` and `any()` are always evaluated to detect
  errors, instead of short-circuiting.][94295] The compatibility
  considerations here arise in nightly-only code that used the
  short-circuiting behavior of `all` to write something like
  `cfg(all(feature = "nightly", syntax-requiring-nightly))`, which
  will now fail to compile. Instead, use either `cfg_attr(feature
  = "nightly", ...)` or nested uses of `cfg`.
- [bootstrap: static-libstdcpp is now enabled by default, and can
  now be disabled when llvm-tools is enabled][94832]

Internal Changes
----------------

These changes provide no direct user facing benefits, but represent
significant improvements to the internals and overall performance
of rustc and related tools.

- [debuginfo: Refactor debuginfo generation for types][94261]
- [Remove the everybody loops pass][93913]

[88375]: rust-lang/rust#88375
[89887]: rust-lang/rust#89887
[90621]: rust-lang/rust#90621
[92285]: rust-lang/rust#92285
[92472]: rust-lang/rust#92472
[92697]: rust-lang/rust#92697
[92714]: rust-lang/rust#92714
[92911]: rust-lang/rust#92911
[93263]: rust-lang/rust#93263
[93745]: rust-lang/rust#93745
[93827]: rust-lang/rust#93827
[93901]: rust-lang/rust#93901
[93913]: rust-lang/rust#93913
[93965]: rust-lang/rust#93965
[94081]: rust-lang/rust#94081
[94261]: rust-lang/rust#94261
[94295]: rust-lang/rust#94295
[94832]: rust-lang/rust#94832
[95016]: rust-lang/rust#95016
[95251]: rust-lang/rust#95251
[`+whole-archive`]: https://doc.rust-lang.org/stable/rustc/command-line-arguments.html#linking-modifiers-whole-archive
[`Pin::static_mut`]: https://doc.rust-lang.org/stable/std/pin/struct.Pin.html#method.static_mut
[`Pin::static_ref`]: https://doc.rust-lang.org/stable/std/pin/struct.Pin.html#method.static_ref
[`Vec::retain_mut`]: https://doc.rust-lang.org/stable/std/vec/struct.Vec.html#method.retain_mut
[`VecDeque::retain_mut`]: https://doc.rust-lang.org/stable/std/collections/struct.VecDeque.html#method.retain_mut
[`std::os::unix::net::SocketAddr::from_pathname`]: https://doc.rust-lang.org/stable/std/os/unix/net/struct.SocketAddr.html#method.from_pathname
[`std::process::ExitCode`]: https://doc.rust-lang.org/stable/std/process/struct.ExitCode.html
[`std::process::Termination`]: https://doc.rust-lang.org/stable/std/process/trait.Termination.html
[`std::thread::JoinHandle::is_finished`]: https://doc.rust-lang.org/stable/std/thread/struct.JoinHandle.html#method.is_finished
[cargo/10448]: rust-lang/cargo#10448
[cursor-write-array]: https://doc.rust-lang.org/stable/std/io/struct.Cursor.html#impl-Write-4
[link-attr]: https://doc.rust-lang.org/stable/reference/items/external-blocks.html#the-link-attribute
[ptr-add]: https://doc.rust-lang.org/stable/std/primitive.pointer.html#method.add
[ptr-offset]: https://doc.rust-lang.org/stable/std/primitive.pointer.html#method.offset
[ptr-sub]: https://doc.rust-lang.org/stable/std/primitive.pointer.html#method.sub
[ptr-wrapping_add]: https://doc.rust-lang.org/stable/std/primitive.pointer.html#method.wrapping_add
[ptr-wrapping_offset]: https://doc.rust-lang.org/stable/std/primitive.pointer.html#method.wrapping_offset
[ptr-wrapping_sub]: https://doc.rust-lang.org/stable/std/primitive.pointer.html#method.wrapping_sub
[slice-as_mut_ptr]: https://doc.rust-lang.org/stable/std/primitive.slice.html#method.as_mut_ptr
[slice-as_mut_ptr_range]: https://doc.rust-lang.org/stable/std/primitive.slice.html#method.as_mut_ptr_range
[slice-as_ptr_range]: https://doc.rust-lang.org/stable/std/primitive.slice.html#method.as_ptr_range
[target_feature]: https://doc.rust-lang.org/reference/attributes/codegen.html#the-target_feature-attribute
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
Labels
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. merged-by-bors This PR was explicitly merged by bors. perf-regression Performance regression. perf-regression-triaged The performance regression has been triaged. relnotes Marks issues that should be documented in the release notes of the next release. S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. T-lang Relevant to the language team, which will review and decide on the PR/issue.
Projects
None yet
Development

Successfully merging this pull request may close these issues.

repeat expression do not honor lt bounds of copy