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Refactor weak symbols in std::sys::unix #90846

Merged
merged 1 commit into from
Nov 27, 2021
Merged

Refactor weak symbols in std::sys::unix #90846

merged 1 commit into from
Nov 27, 2021

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cuviper
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@cuviper cuviper commented Nov 12, 2021

This makes a few changes to the weak symbol macros in sys::unix:

  • dlsym! is added to keep the functionality for runtime dlsym
    lookups, like for __pthread_get_minstack@GLIBC_PRIVATE that we don't
    want to show up in ELF symbol tables.
  • weak! now uses #[linkage = "extern_weak"] symbols, so its runtime
    behavior is just a simple null check. This is also used by syscall!.
    • On non-ELF targets (macos/ios) where that linkage is not known to
      behave, weak! is just an alias to dlsym! for the old behavior.
  • raw_syscall! is added to always call libc::syscall on linux and
    android, for cases like clone3 that have no known libc wrapper.

The new weak! linkage does mean that you'll get versioned symbols if
you build with a newer glibc, like WEAK DEFAULT UND statx@GLIBC_2.28.
This might seem problematic, but old non-weak symbols can tie the build
to new versions too, like dlsym@GLIBC_2.34 from their recent library
unification. If you build with an old glibc like dist-x86_64-linux
does, you'll still get unversioned WEAK DEFAULT UND statx, which may
be resolved based on the runtime glibc.

I also found a few functions that don't need to be weak anymore:

  • Android can directly use ftruncate64, pread64, and pwrite64, as
    these were added in API 12, and our baseline is API 14.
  • Linux can directly use splice, added way back in glibc 2.5 and
    similarly old musl. Android only added it in API 21 though.

This makes a few changes to the weak symbol macros in `sys::unix`:

- `dlsym!` is added to keep the functionality for runtime `dlsym`
  lookups, like for `__pthread_get_minstack@GLIBC_PRIVATE` that we don't
  want to show up in ELF symbol tables.
- `weak!` now uses `#[linkage = "extern_weak"]` symbols, so its runtime
  behavior is just a simple null check. This is also used by `syscall!`.
  - On non-ELF targets (macos/ios) where that linkage is not known to
    behave, `weak!` is just an alias to `dlsym!` for the old behavior.
- `raw_syscall!` is added to always call `libc::syscall` on linux and
  android, for cases like `clone3` that have no known libc wrapper.

The new `weak!` linkage does mean that you'll get versioned symbols if
you build with a newer glibc, like `WEAK DEFAULT UND statx@GLIBC_2.28`.
This might seem problematic, but old non-weak symbols can tie the build
to new versions too, like `dlsym@GLIBC_2.34` from their recent library
unification. If you build with an old glibc like `dist-x86_64-linux`
does, you'll still get unversioned `WEAK DEFAULT UND statx`, which may
be resolved based on the runtime glibc.

I also found a few functions that don't need to be weak anymore:

- Android can directly use `ftruncate64`, `pread64`, and `pwrite64`, as
  these were added in API 12, and our baseline is API 14.
- Linux can directly use `splice`, added way back in glibc 2.5 and
  similarly old musl. Android only added it in API 21 though.
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r? @dtolnay

(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 Nov 12, 2021
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@bors try

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bors commented Nov 15, 2021

⌛ Trying commit 5ff6ac4 with merge 74a1f0e96f2bed047969c1c6fb3f898632bdc774...

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bors commented Nov 16, 2021

☀️ Try build successful - checks-actions
Build commit: 74a1f0e96f2bed047969c1c6fb3f898632bdc774 (74a1f0e96f2bed047969c1c6fb3f898632bdc774)

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cuviper commented Nov 16, 2021

Note that try only builds dist-x86_64-linux, but you can take a look at those symbols after running:

rustup-toolchain-install-master 74a1f0e96f2bed047969c1c6fb3f898632bdc774

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This seems like a reasonable change to me.

cc @glandium for additional exposure. Does this seem likely to create issues?

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I don't think there's much more risk with this change that a build environment change for the rust compiler would bump the glibc requirements for the prebuilt libstd.

@apiraino apiraino added the T-libs Relevant to the library team, which will review and decide on the PR/issue. label Nov 18, 2021
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Nice!

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dtolnay commented Nov 26, 2021

@bors r+ rollup=iffy

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bors commented Nov 26, 2021

📌 Commit 5ff6ac4 has been approved by dtolnay

@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 Nov 26, 2021
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bors commented Nov 27, 2021

⌛ Testing commit 5ff6ac4 with merge 0881b3a...

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bors commented Nov 27, 2021

☀️ Test successful - checks-actions
Approved by: dtolnay
Pushing 0881b3a to master...

@bors bors added the merged-by-bors This PR was explicitly merged by bors. label Nov 27, 2021
@bors bors merged commit 0881b3a into rust-lang:master Nov 27, 2021
@rustbot rustbot added this to the 1.59.0 milestone Nov 27, 2021
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📣 Toolstate changed by #90846!

Tested on commit 0881b3a.
Direct link to PR: #90846

💔 miri on linux: test-pass → test-fail (cc @eddyb @oli-obk @RalfJung).

rust-highfive added a commit to rust-lang-nursery/rust-toolstate that referenced this pull request Nov 27, 2021
Tested on commit rust-lang/rust@0881b3a.
Direct link to PR: <rust-lang/rust#90846>

💔 miri on linux: test-pass → test-fail (cc @eddyb @oli-obk @RalfJung).
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Finished benchmarking commit (0881b3a): comparison url.

Summary: This benchmark run did not return any relevant changes.

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

@rustbot label: -perf-regression

matthiaskrgr added a commit to matthiaskrgr/rust that referenced this pull request Dec 3, 2021
Android: -ldl must appear after -lgcc when linking

rust-lang#90846 accidentally broke Android builds because it causes the standard library to no longer use `dlsym` on Android. This results in `libdl` being ignored by the linker since no symbols are needed from it. However, we later import `libgcc` for unwinding which *does* depend on `libdl` for `dl_iterate_phdr`. Since linkers don't revisit previous libraries when resolving symbols, this causes a linker error due to an undefined reference to `dl_iterate_phdr`.

This is resolved by adding a second `-ldl` after `-lgcc` in the linker command-line.
matthiaskrgr added a commit to matthiaskrgr/rust that referenced this pull request Dec 3, 2021
Android: -ldl must appear after -lgcc when linking

rust-lang#90846 accidentally broke Android builds because it causes the standard library to no longer use `dlsym` on Android. This results in `libdl` being ignored by the linker since no symbols are needed from it. However, we later import `libgcc` for unwinding which *does* depend on `libdl` for `dl_iterate_phdr`. Since linkers don't revisit previous libraries when resolving symbols, this causes a linker error due to an undefined reference to `dl_iterate_phdr`.

This is resolved by adding a second `-ldl` after `-lgcc` in the linker command-line.
@cuviper cuviper deleted the weak branch December 8, 2021 07:29
wip-sync pushed a commit to NetBSD/pkgsrc-wip that referenced this pull request Jan 22, 2022
Pkgsrc changes:
 * Bump available bootstraps to 1.57.0.
 * For some reason, the vendor/libc checksums don't need fixing.
 * Bump required external LLVM to 12.0, according to upstream change log.
 * Adapt the Darwin linker patch.

(For some reason I've not figured out yet, cargo is a lot more
verbose while building, echoes the rustc invocation.)

Upstream changes:

Version 1.58.1 (2022-01-19)
===========================

* Fix race condition in `std::fs::remove_dir_all` ([CVE-2022-21658])
* [Handle captured arguments in the `useless_format` Clippy lint][clippy/8295]
* [Move `non_send_fields_in_send_ty` Clippy lint to nursery][clippy/8075]
* [Fix wrong error message displayed when some imports are missing][91254]
* [Fix rustfmt not formatting generated files from stdin][92912]

[CVE-2022-21658]: https://www.cve.org/CVERecord?id=CVE-2022-21658]
[91254]: rust-lang/rust#91254
[92912]: rust-lang/rust#92912
[clippy/8075]: rust-lang/rust-clippy#8075
[clippy/8295]: rust-lang/rust-clippy#8295

Version 1.58.0 (2022-01-13)
==========================

Language
--------

- [Format strings can now capture arguments simply by writing
  `{ident}` in the string.][90473] This works in all macros accepting
  format strings. Support for this in `panic!` (`panic!("{ident}")`)
  requires the 2021 edition; panic invocations in previous editions
  that appear to be trying to use this will result in a warning lint
  about not having the intended effect.
- [`*const T` pointers can now be dereferenced in const contexts.][89551]
- [The rules for when a generic struct implements `Unsize` have
  been relaxed.][90417]

Compiler
--------

- [Add LLVM CFI support to the Rust compiler][89652]
- [Stabilize -Z strip as -C strip][90058]. Note that while release
  builds already don't add debug symbols for the code you compile,
  the compiled standard library that ships with Rust includes debug
  symbols, so you may want to use the `strip` option to remove these
  symbols to produce smaller release binaries. Note that this release
  only includes support in rustc, not directly in cargo.
- [Add support for LLVM coverage mapping format versions 5 and 6][91207]
- [Emit LLVM optimization remarks when enabled with `-Cremark`][90833]
- [Update the minimum external LLVM to 12][90175]
- [Add `x86_64-unknown-none` at Tier 3*][89062]
- [Build musl dist artifacts with debuginfo enabled][90733]. When
  building release binaries using musl, you may want to use the newly
  stabilized strip option to remove these debug symbols, reducing
  the size of your binaries.
- [Don't abort compilation after giving a lint error][87337]
- [Error messages point at the source of trait bound obligations
  in more places][89580]

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

Libraries
---------

- [All remaining functions in the standard library have `#[must_use]`
  annotations where appropriate][89692], producing a warning when
  ignoring their return value. This helps catch mistakes such as
  expecting a function to mutate a value in place rather than return
  a new value.
- [Paths are automatically canonicalized on Windows for operations
  that support it][89174]
- [Re-enable debug checks for `copy` and `copy_nonoverlapping`][90041]
- [Implement `RefUnwindSafe` for `Rc<T>`][87467]
- [Make RSplit<T, P>: Clone not require T: Clone][90117]
- [Implement `Termination` for `Result<Infallible, E>`][88601].
  This allows writing `fn main() -> Result<Infallible, ErrorType>`,
  for a program whose successful exits never involve returning from
  `main` (for instance, a program that calls `exit`, or that uses
  `exec` to run another program).

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

- [`Metadata::is_symlink`]
- [`Path::is_symlink`]
- [`{integer}::saturating_div`]
- [`Option::unwrap_unchecked`]
- [`Result::unwrap_unchecked`]
- [`Result::unwrap_err_unchecked`]
- [`NonZero{unsigned}::is_power_of_two`]
- [`File::options`]

These APIs are now usable in const contexts:

- [`Duration::new`]
- [`Duration::checked_add`]
- [`Duration::saturating_add`]
- [`Duration::checked_sub`]
- [`Duration::saturating_sub`]
- [`Duration::checked_mul`]
- [`Duration::saturating_mul`]
- [`Duration::checked_div`]
- [`MaybeUninit::as_ptr`]
- [`MaybeUninit::as_mut_ptr`]
- [`MaybeUninit::assume_init`]
- [`MaybeUninit::assume_init_ref`]

Cargo
-----

- [Add --message-format for install command][cargo/10107]
- [Warn when alias shadows external subcommand][cargo/10082]

Rustdoc
-------

- [Show all Deref implementations recursively in rustdoc][90183]
- [Use computed visibility in rustdoc][88447]

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

- [Try all stable method candidates first before trying unstable
  ones][90329]. This change ensures that adding new nightly-only
  methods to the Rust standard library will not break code invoking
  methods of the same name from traits outside the standard library.
- Windows: [`std::process::Command` will no longer search the
  current directory for executables.][87704]
- [All proc-macro backward-compatibility lints are now deny-by-default.][88041]
- [proc_macro: Append .0 to unsuffixed float if it would otherwise
  become int token][90297]
- [Refactor weak symbols in std::sys::unix][90846]. This optimizes
  accesses to glibc functions, by avoiding the use of dlopen. This
  does not increase the [minimum expected version of
  glibc](https://doc.rust-lang.org/nightly/rustc/platform-support.html).
  However, software distributions that use symbol versions to detect
  library dependencies, and which take weak symbols into account in
  that analysis, may detect rust binaries as requiring newer versions
  of glibc.
- [rustdoc now rejects some unexpected semicolons in doctests][91026]

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.

- [Implement coherence checks for negative trait impls][90104]
- [Add rustc lint, warning when iterating over hashmaps][89558]
- [Optimize live point computation][90491]
- [Enable verification for 1/32nd of queries loaded from disk][90361]
- [Implement version of normalize_erasing_regions that allows for
  normalization failure][91255]

[87337]: rust-lang/rust#87337
[87467]: rust-lang/rust#87467
[87704]: rust-lang/rust#87704
[88041]: rust-lang/rust#88041
[88300]: rust-lang/rust#88300
[88447]: rust-lang/rust#88447
[88601]: rust-lang/rust#88601
[88624]: rust-lang/rust#88624
[89062]: rust-lang/rust#89062
[89174]: rust-lang/rust#89174
[89542]: rust-lang/rust#89542
[89551]: rust-lang/rust#89551
[89558]: rust-lang/rust#89558
[89580]: rust-lang/rust#89580
[89652]: rust-lang/rust#89652
[89677]: rust-lang/rust#89677
[89951]: rust-lang/rust#89951
[90041]: rust-lang/rust#90041
[90058]: rust-lang/rust#90058
[90104]: rust-lang/rust#90104
[90117]: rust-lang/rust#90117
[90175]: rust-lang/rust#90175
[90183]: rust-lang/rust#90183
[90297]: rust-lang/rust#90297
[90329]: rust-lang/rust#90329
[90361]: rust-lang/rust#90361
[90417]: rust-lang/rust#90417
[90473]: rust-lang/rust#90473
[90491]: rust-lang/rust#90491
[90733]: rust-lang/rust#90733
[90833]: rust-lang/rust#90833
[90846]: rust-lang/rust#90846
[90896]: rust-lang/rust#90896
[91026]: rust-lang/rust#91026
[91207]: rust-lang/rust#91207
[91255]: rust-lang/rust#91255
[91301]: rust-lang/rust#91301
[cargo/10082]: rust-lang/cargo#10082
[cargo/10107]: rust-lang/cargo#10107
[`Metadata::is_symlink`]: https://doc.rust-lang.org/stable/std/fs/struct.Metadata.html#method.is_symlink
[`Path::is_symlink`]: https://doc.rust-lang.org/stable/std/path/struct.Path.html#method.is_symlink
[`{integer}::saturating_div`]: https://doc.rust-lang.org/stable/std/primitive.i8.html#method.saturating_div
[`Option::unwrap_unchecked`]: https://doc.rust-lang.org/stable/std/option/enum.Option.html#method.unwrap_unchecked
[`Result::unwrap_unchecked`]: https://doc.rust-lang.org/stable/std/result/enum.Result.html#method.unwrap_unchecked
[`Result::unwrap_err_unchecked`]: https://doc.rust-lang.org/stable/std/result/enum.Result.html#method.unwrap_err_unchecked
[`NonZero{unsigned}::is_power_of_two`]: https://doc.rust-lang.org/stable/std/num/struct.NonZeroU8.html#method.is_power_of_two
[`File::options`]: https://doc.rust-lang.org/stable/std/fs/struct.File.html#method.options
[`unix::process::ExitStatusExt::core_dumped`]: https://doc.rust-lang.org/stable/std/os/unix/process/trait.ExitStatusExt.html#tymethod.core_dumped
[`unix::process::ExitStatusExt::stopped_signal`]: https://doc.rust-lang.org/stable/std/os/unix/process/trait.ExitStatusExt.html#tymethod.stopped_signal
[`unix::process::ExitStatusExt::continued`]: https://doc.rust-lang.org/stable/std/os/unix/process/trait.ExitStatusExt.html#tymethod.continued
[`unix::process::ExitStatusExt::into_raw`]: https://doc.rust-lang.org/stable/std/os/unix/process/trait.ExitStatusExt.html#tymethod.into_raw
[`Duration::new`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.new
[`Duration::checked_add`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.checked_add
[`Duration::saturating_add`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.saturating_add
[`Duration::checked_sub`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.checked_sub
[`Duration::saturating_sub`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.saturating_sub
[`Duration::checked_mul`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.checked_mul
[`Duration::saturating_mul`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.saturating_mul
[`Duration::checked_div`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.checked_div
[`Duration::as_secs_f64`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.as_secs_f64
[`Duration::as_secs_f32`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.as_secs_f32
[`Duration::from_secs_f64`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.from_secs_f64
[`Duration::from_secs_f32`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.from_secs_f32
[`Duration::mul_f64`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.mul_f64
[`Duration::mul_f32`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.mul_f32
[`Duration::div_f64`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.div_f64
[`Duration::div_f32`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.div_f32
[`Duration::div_duration_f64`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.div_duration_f64
[`Duration::div_duration_f32`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.div_duration_f32
[`MaybeUninit::as_ptr`]: https://doc.rust-lang.org/stable/std/mem/union.MaybeUninit.html#method.as_ptr
[`MaybeUninit::as_mut_ptr`]: https://doc.rust-lang.org/stable/std/mem/union.MaybeUninit.html#method.as_mut_ptr
[`MaybeUninit::assume_init`]: https://doc.rust-lang.org/stable/std/mem/union.MaybeUninit.html#method.assume_init
[`MaybeUninit::assume_init_ref`]: https://doc.rust-lang.org/stable/std/mem/union.MaybeUninit.html#method.assume_init_ref
netbsd-srcmastr pushed a commit to NetBSD/pkgsrc that referenced this pull request Mar 1, 2022
Pkgsrc changes:
 * Bump bootstrap kit version to 1.57.0.
 * Bump require external LLVM to 12.0, according to upstream change log.
 * Adjust patches as needed, adjust line numbers.
 * Update checksum adjustments.  For some reason the vendor/libc checksum
   doesn't need fixing, apparently, it remains as commented out.
 * Add makefile to do all the NetBSD boostrap/cross builds (do-cross.mk).
   Allow passing in additions to CONFIGURE_ARGS via ADD_CONFIGURE_ARGS.

Upstream changes:

Version 1.58.1 (2022-01-19)
===========================

* Fix race condition in `std::fs::remove_dir_all` ([CVE-2022-21658])
* [Handle captured arguments in the `useless_format` Clippy lint][clippy/8295]
* [Move `non_send_fields_in_send_ty` Clippy lint to nursery][clippy/8075]
* [Fix wrong error message displayed when some imports are missing][91254]
* [Fix rustfmt not formatting generated files from stdin][92912]

[CVE-2022-21658]: https://www.cve.org/CVERecord?id=CVE-2022-21658]
[91254]: rust-lang/rust#91254
[92912]: rust-lang/rust#92912
[clippy/8075]: rust-lang/rust-clippy#8075
[clippy/8295]: rust-lang/rust-clippy#8295

Version 1.58.0 (2022-01-13)
==========================

Language
--------

- [Format strings can now capture arguments simply by writing
  `{ident}` in the string.][90473] This works in all macros accepting
  format strings. Support for this in `panic!` (`panic!("{ident}")`)
  requires the 2021 edition; panic invocations in previous editions
  that appear to be trying to use this will result in a warning lint
  about not having the intended effect.
- [`*const T` pointers can now be dereferenced in const contexts.][89551]
- [The rules for when a generic struct implements `Unsize` have
  been relaxed.][90417]

Compiler
--------

- [Add LLVM CFI support to the Rust compiler][89652]
- [Stabilize -Z strip as -C strip][90058]. Note that while release
  builds already don't add debug symbols for the code you compile,
  the compiled standard library that ships with Rust includes debug
  symbols, so you may want to use the `strip` option to remove these
  symbols to produce smaller release binaries. Note that this release
  only includes support in rustc, not directly in cargo.
- [Add support for LLVM coverage mapping format versions 5 and 6][91207]
- [Emit LLVM optimization remarks when enabled with `-Cremark`][90833]
- [Update the minimum external LLVM to 12][90175]
- [Add `x86_64-unknown-none` at Tier 3*][89062]
- [Build musl dist artifacts with debuginfo enabled][90733]. When
  building release binaries using musl, you may want to use the newly
  stabilized strip option to remove these debug symbols, reducing
  the size of your binaries.
- [Don't abort compilation after giving a lint error][87337]
- [Error messages point at the source of trait bound obligations
  in more places][89580]

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

Libraries
---------

- [All remaining functions in the standard library have `#[must_use]`
  annotations where appropriate][89692], producing a warning when
  ignoring their return value. This helps catch mistakes such as
  expecting a function to mutate a value in place rather than return
  a new value.
- [Paths are automatically canonicalized on Windows for operations
  that support it][89174]
- [Re-enable debug checks for `copy` and `copy_nonoverlapping`][90041]
- [Implement `RefUnwindSafe` for `Rc<T>`][87467]
- [Make RSplit<T, P>: Clone not require T: Clone][90117]
- [Implement `Termination` for `Result<Infallible, E>`][88601].
  This allows writing `fn main() -> Result<Infallible, ErrorType>`,
  for a program whose successful exits never involve returning from
  `main` (for instance, a program that calls `exit`, or that uses
  `exec` to run another program).

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

- [`Metadata::is_symlink`]
- [`Path::is_symlink`]
- [`{integer}::saturating_div`]
- [`Option::unwrap_unchecked`]
- [`Result::unwrap_unchecked`]
- [`Result::unwrap_err_unchecked`]
- [`NonZero{unsigned}::is_power_of_two`]
- [`File::options`]

These APIs are now usable in const contexts:

- [`Duration::new`]
- [`Duration::checked_add`]
- [`Duration::saturating_add`]
- [`Duration::checked_sub`]
- [`Duration::saturating_sub`]
- [`Duration::checked_mul`]
- [`Duration::saturating_mul`]
- [`Duration::checked_div`]
- [`MaybeUninit::as_ptr`]
- [`MaybeUninit::as_mut_ptr`]
- [`MaybeUninit::assume_init`]
- [`MaybeUninit::assume_init_ref`]

Cargo
-----

- [Add --message-format for install command][cargo/10107]
- [Warn when alias shadows external subcommand][cargo/10082]

Rustdoc
-------

- [Show all Deref implementations recursively in rustdoc][90183]
- [Use computed visibility in rustdoc][88447]

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

- [Try all stable method candidates first before trying unstable
  ones][90329]. This change ensures that adding new nightly-only
  methods to the Rust standard library will not break code invoking
  methods of the same name from traits outside the standard library.
- Windows: [`std::process::Command` will no longer search the
  current directory for executables.][87704]
- [All proc-macro backward-compatibility lints are now deny-by-default.][88041]
- [proc_macro: Append .0 to unsuffixed float if it would otherwise
  become int token][90297]
- [Refactor weak symbols in std::sys::unix][90846]. This optimizes
  accesses to glibc functions, by avoiding the use of dlopen. This
  does not increase the [minimum expected version of
  glibc](https://doc.rust-lang.org/nightly/rustc/platform-support.html).
  However, software distributions that use symbol versions to detect
  library dependencies, and which take weak symbols into account in
  that analysis, may detect rust binaries as requiring newer versions
  of glibc.
- [rustdoc now rejects some unexpected semicolons in doctests][91026]

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.

- [Implement coherence checks for negative trait impls][90104]
- [Add rustc lint, warning when iterating over hashmaps][89558]
- [Optimize live point computation][90491]
- [Enable verification for 1/32nd of queries loaded from disk][90361]
- [Implement version of normalize_erasing_regions that allows for
  normalization failure][91255]

[87337]: rust-lang/rust#87337
[87467]: rust-lang/rust#87467
[87704]: rust-lang/rust#87704
[88041]: rust-lang/rust#88041
[88300]: rust-lang/rust#88300
[88447]: rust-lang/rust#88447
[88601]: rust-lang/rust#88601
[88624]: rust-lang/rust#88624
[89062]: rust-lang/rust#89062
[89174]: rust-lang/rust#89174
[89542]: rust-lang/rust#89542
[89551]: rust-lang/rust#89551
[89558]: rust-lang/rust#89558
[89580]: rust-lang/rust#89580
[89652]: rust-lang/rust#89652
[89677]: rust-lang/rust#89677
[89951]: rust-lang/rust#89951
[90041]: rust-lang/rust#90041
[90058]: rust-lang/rust#90058
[90104]: rust-lang/rust#90104
[90117]: rust-lang/rust#90117
[90175]: rust-lang/rust#90175
[90183]: rust-lang/rust#90183
[90297]: rust-lang/rust#90297
[90329]: rust-lang/rust#90329
[90361]: rust-lang/rust#90361
[90417]: rust-lang/rust#90417
[90473]: rust-lang/rust#90473
[90491]: rust-lang/rust#90491
[90733]: rust-lang/rust#90733
[90833]: rust-lang/rust#90833
[90846]: rust-lang/rust#90846
[90896]: rust-lang/rust#90896
[91026]: rust-lang/rust#91026
[91207]: rust-lang/rust#91207
[91255]: rust-lang/rust#91255
[91301]: rust-lang/rust#91301
[cargo/10082]: rust-lang/cargo#10082
[cargo/10107]: rust-lang/cargo#10107
[`Metadata::is_symlink`]: https://doc.rust-lang.org/stable/std/fs/struct.Metadata.html#method.is_symlink
[`Path::is_symlink`]: https://doc.rust-lang.org/stable/std/path/struct.Path.html#method.is_symlink
[`{integer}::saturating_div`]: https://doc.rust-lang.org/stable/std/primitive.i8.html#method.saturating_div
[`Option::unwrap_unchecked`]: https://doc.rust-lang.org/stable/std/option/enum.Option.html#method.unwrap_unchecked
[`Result::unwrap_unchecked`]: https://doc.rust-lang.org/stable/std/result/enum.Result.html#method.unwrap_unchecked
[`Result::unwrap_err_unchecked`]: https://doc.rust-lang.org/stable/std/result/enum.Result.html#method.unwrap_err_unchecked
[`NonZero{unsigned}::is_power_of_two`]: https://doc.rust-lang.org/stable/std/num/struct.NonZeroU8.html#method.is_power_of_two
[`File::options`]: https://doc.rust-lang.org/stable/std/fs/struct.File.html#method.options
[`unix::process::ExitStatusExt::core_dumped`]: https://doc.rust-lang.org/stable/std/os/unix/process/trait.ExitStatusExt.html#tymethod.core_dumped
[`unix::process::ExitStatusExt::stopped_signal`]: https://doc.rust-lang.org/stable/std/os/unix/process/trait.ExitStatusExt.html#tymethod.stopped_signal
[`unix::process::ExitStatusExt::continued`]: https://doc.rust-lang.org/stable/std/os/unix/process/trait.ExitStatusExt.html#tymethod.continued
[`unix::process::ExitStatusExt::into_raw`]: https://doc.rust-lang.org/stable/std/os/unix/process/trait.ExitStatusExt.html#tymethod.into_raw
[`Duration::new`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.new
[`Duration::checked_add`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.checked_add
[`Duration::saturating_add`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.saturating_add
[`Duration::checked_sub`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.checked_sub
[`Duration::saturating_sub`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.saturating_sub
[`Duration::checked_mul`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.checked_mul
[`Duration::saturating_mul`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.saturating_mul
[`Duration::checked_div`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.checked_div
[`Duration::as_secs_f64`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.as_secs_f64
[`Duration::as_secs_f32`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.as_secs_f32
[`Duration::from_secs_f64`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.from_secs_f64
[`Duration::from_secs_f32`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.from_secs_f32
[`Duration::mul_f64`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.mul_f64
[`Duration::mul_f32`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.mul_f32
[`Duration::div_f64`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.div_f64
[`Duration::div_f32`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.div_f32
[`Duration::div_duration_f64`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.div_duration_f64
[`Duration::div_duration_f32`]: https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.div_duration_f32
[`MaybeUninit::as_ptr`]: https://doc.rust-lang.org/stable/std/mem/union.MaybeUninit.html#method.as_ptr
[`MaybeUninit::as_mut_ptr`]: https://doc.rust-lang.org/stable/std/mem/union.MaybeUninit.html#method.as_mut_ptr
[`MaybeUninit::assume_init`]: https://doc.rust-lang.org/stable/std/mem/union.MaybeUninit.html#method.assume_init
[`MaybeUninit::assume_init_ref`]: https://doc.rust-lang.org/stable/std/mem/union.MaybeUninit.html#method.assume_init_ref
wip-sync pushed a commit to NetBSD/pkgsrc-wip that referenced this pull request Mar 2, 2022
Pkgsrc changes:
 * Bump available bootstraps to 1.58.1.
 * Adjust one patch (and checksum) so that it still applies.

Upstream changes:

Version 1.59.0 (2022-02-24)
==========================

Language
--------

- [Stabilize default arguments for const generics][90207]
- [Stabilize destructuring assignment][90521]
- [Relax private in public lint on generic bounds and where clauses
  of trait impls][90586]
- [Stabilize asm! and global_asm! for x86, x86_64, ARM, Aarch64,
  and RISC-V][91728]

Compiler
--------

- [Stabilize new symbol mangling format, leaving it opt-in
  (-Csymbol-mangling-version=v0)][90128]
- [Emit LLVM optimization remarks when enabled with `-Cremark`][90833]
- [Fix sparc64 ABI for aggregates with floating point members][91003]
- [Warn when a `#[test]`-like built-in attribute macro is present
  multiple times.][91172]
- [Add support for riscv64gc-unknown-freebsd][91284]
- [Stabilize `-Z emit-future-incompat` as `--json future-incompat`][91535]
- [Soft disable incremental compilation][94124]

This release disables incremental compilation, unless the user has explicitly
opted in via the newly added RUSTC_FORCE_INCREMENTAL=1 environment variable.
This is due to a known and relatively frequently occurring bug in incremental
compilation, which causes builds to issue internal compiler errors. This
particular bug is already fixed on nightly, but that fix has not yet rolled out
to stable and is deemed too risky for a direct stable backport.

As always, we encourage users to test with nightly and report bugs so that we
can track failures and fix issues earlier.

See [94124] for more details.

[94124]: rust-lang/rust#94124

Libraries
---------

- [Remove unnecessary bounds for some Hash{Map,Set} methods][91593]

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

- [`std::thread::available_parallelism`][available_parallelism]
- [`Result::copied`][result-copied]
- [`Result::cloned`][result-cloned]
- [`arch::asm!`][asm]
- [`arch::global_asm!`][global_asm]
- [`ops::ControlFlow::is_break`][is_break]
- [`ops::ControlFlow::is_continue`][is_continue]
- [`TryFrom<char> for u8`][try_from_char_u8]
- [`char::TryFromCharError`][try_from_char_err]
  implementing `Clone`, `Debug`, `Display`, `PartialEq`, `Copy`, `Eq`, `Error`
- [`iter::zip`][zip]
- [`NonZeroU8::is_power_of_two`][is_power_of_two8]
- [`NonZeroU16::is_power_of_two`][is_power_of_two16]
- [`NonZeroU32::is_power_of_two`][is_power_of_two32]
- [`NonZeroU64::is_power_of_two`][is_power_of_two64]
- [`NonZeroU128::is_power_of_two`][is_power_of_two128]
- [`DoubleEndedIterator for ToLowercase`][lowercase]
- [`DoubleEndedIterator for ToUppercase`][uppercase]
- [`TryFrom<&mut [T]> for [T; N]`][tryfrom_ref_arr]
- [`UnwindSafe for Once`][unwindsafe_once]
- [`RefUnwindSafe for Once`][refunwindsafe_once]
- [armv8 neon intrinsics for aarch64][stdarch/1266]

Const-stable:

- [`mem::MaybeUninit::as_ptr`][muninit_ptr]
- [`mem::MaybeUninit::assume_init`][muninit_init]
- [`mem::MaybeUninit::assume_init_ref`][muninit_init_ref]
- [`ffi::CStr::from_bytes_with_nul_unchecked`][cstr_from_bytes]

Cargo
-----

- [Stabilize the `strip` profile option][cargo/10088]
- [Stabilize future-incompat-report][cargo/10165]
- [Support abbreviating `--release` as `-r`][cargo/10133]
- [Support `term.quiet` configuration][cargo/10152]
- [Remove `--host` from cargo {publish,search,login}][cargo/10145]

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

- [Refactor weak symbols in std::sys::unix][90846]
  This may add new, versioned, symbols when building with a newer glibc, as the
  standard library uses weak linkage rather than dynamically attempting to load
  certain symbols at runtime.
- [Deprecate crate_type and crate_name nested inside `#![cfg_attr]`][83744]
  This adds a future compatibility lint to supporting the use of cfg_attr
  wrapping either crate_type or crate_name specification within Rust files;
  it is recommended that users migrate to setting the equivalent command line
  flags.
- [Remove effect of `#[no_link]` attribute on name resolution][92034]
  This may expose new names, leading to conflicts with preexisting names in a
  given namespace and a compilation failure.
- [Cargo will document libraries before binaries.][cargo/10172]
- [Respect doc=false in dependencies, not just the root crate][cargo/10201]
- [Weaken guarantee around advancing underlying iterators in zip][83791]
- [Make split_inclusive() on an empty slice yield an empty output][89825]
- [Update std::env::temp_dir to use GetTempPath2 on Windows when
  available.][89999]
- [unreachable! was updated to match other formatting macro behavior
  on Rust 2021][92137]

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.

- [Fix many cases of normalization-related ICEs][91255]
- [Replace dominators algorithm with simple Lengauer-Tarjan][85013]
- [Store liveness in interval sets for region inference][90637]

- [Remove `in_band_lifetimes` from the compiler and standard library,
  in preparation for removing this unstable feature.][91867]

[91867]: rust-lang/rust#91867
[83744]: rust-lang/rust#83744
[83791]: rust-lang/rust#83791
[85013]: rust-lang/rust#85013
[89825]: rust-lang/rust#89825
[89999]: rust-lang/rust#89999
[90128]: rust-lang/rust#90128
[90207]: rust-lang/rust#90207
[90521]: rust-lang/rust#90521
[90586]: rust-lang/rust#90586
[90637]: rust-lang/rust#90637
[90833]: rust-lang/rust#90833
[90846]: rust-lang/rust#90846
[91003]: rust-lang/rust#91003
[91172]: rust-lang/rust#91172
[91255]: rust-lang/rust#91255
[91284]: rust-lang/rust#91284
[91535]: rust-lang/rust#91535
[91593]: rust-lang/rust#91593
[91728]: rust-lang/rust#91728
[91878]: rust-lang/rust#91878
[91896]: rust-lang/rust#91896
[91926]: rust-lang/rust#91926
[91984]: rust-lang/rust#91984
[92020]: rust-lang/rust#92020
[92034]: rust-lang/rust#92034
[92483]: rust-lang/rust#92483
[cargo/10088]: rust-lang/cargo#10088
[cargo/10133]: rust-lang/cargo#10133
[cargo/10145]: rust-lang/cargo#10145
[cargo/10152]: rust-lang/cargo#10152
[cargo/10165]: rust-lang/cargo#10165
[cargo/10172]: rust-lang/cargo#10172
[cargo/10201]: rust-lang/cargo#10201
[cargo/10269]: rust-lang/cargo#10269

[cstr_from_bytes]: https://doc.rust-lang.org/stable/std/ffi/struct.CStr.html#method.from_bytes_with_nul_unchecked
[muninit_ptr]: https://doc.rust-lang.org/stable/std/mem/union.MaybeUninit.html#method.as_ptr
[muninit_init]: https://doc.rust-lang.org/stable/std/mem/union.MaybeUninit.html#method.assume_init
[muninit_init_ref]: https://doc.rust-lang.org/stable/std/mem/union.MaybeUninit.html#method.assume_init_ref
[unwindsafe_once]: https://doc.rust-lang.org/stable/std/sync/struct.Once.html#impl-UnwindSafe
[refunwindsafe_once]: https://doc.rust-lang.org/stable/std/sync/struct.Once.html#impl-RefUnwindSafe
[tryfrom_ref_arr]: https://doc.rust-lang.org/stable/std/convert/trait.TryFrom.html#impl-TryFrom%3C%26%27_%20mut%20%5BT%5D%3E
[lowercase]: https://doc.rust-lang.org/stable/std/char/struct.ToLowercase.html#impl-DoubleEndedIterator
[uppercase]: https://doc.rust-lang.org/stable/std/char/struct.ToUppercase.html#impl-DoubleEndedIterator
[try_from_char_err]: https://doc.rust-lang.org/stable/std/char/struct.TryFromCharError.html
[available_parallelism]: https://doc.rust-lang.org/stable/std/thread/fn.available_parallelism.html
[result-copied]: https://doc.rust-lang.org/stable/std/result/enum.Result.html#method.copied
[result-cloned]: https://doc.rust-lang.org/stable/std/result/enum.Result.html#method.cloned
[asm]: https://doc.rust-lang.org/stable/core/arch/macro.asm.html
[global_asm]: https://doc.rust-lang.org/stable/core/arch/macro.global_asm.html
[is_break]: https://doc.rust-lang.org/stable/std/ops/enum.ControlFlow.html#method.is_break
[is_continue]: https://doc.rust-lang.org/stable/std/ops/enum.ControlFlow.html#method.is_continue
[try_from_char_u8]: https://doc.rust-lang.org/stable/std/primitive.char.html#impl-TryFrom%3Cchar%3E
[zip]: https://doc.rust-lang.org/stable/std/iter/fn.zip.html
[is_power_of_two8]: https://doc.rust-lang.org/stable/core/num/struct.NonZeroU8.html#method.is_power_of_two
[is_power_of_two16]: https://doc.rust-lang.org/stable/core/num/struct.NonZeroU16.html#method.is_power_of_two
[is_power_of_two32]: https://doc.rust-lang.org/stable/core/num/struct.NonZeroU32.html#method.is_power_of_two
[is_power_of_two64]: https://doc.rust-lang.org/stable/core/num/struct.NonZeroU64.html#method.is_power_of_two
[is_power_of_two128]: https://doc.rust-lang.org/stable/core/num/struct.NonZeroU128.html#method.is_power_of_two
[stdarch/1266]: rust-lang/stdarch#1266
@peterwaller-arm
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peterwaller-arm commented Mar 24, 2022

cc @cuviper

Just a heads up, I suspect this broke the musl build with undefined reference to 'gnu_get_libc_version', which is not a symbol I'd expect musl to have. Here's the error:

  = note: /nix/store/3dvmvdf1a4p2ra4myhzdw3i2gr6xhy9b-aarch64-unknown-linux-musl-binutils-2.35.2/bin/aarch64-unknown-linux-musl-ld: /home/petwal01/.rustup/toolchains/nightly-2021-11-29-aarch64-unknown-linux-gnu/lib/rustlib/aarch64-unknown-linux-gnu/lib/libstd-f57035255a9d9f2c.rlib(std-f57035255a9d9f2c.std.c43b9eb8-cgu.0.rcgu.o): in function `std::sys::unix::os::glibc_version':
          /rustc/db9d361a4731ca0bb48533fab6297a8fea75696f//library/std/src/sys/unix/os.rs:644: undefined reference to `gnu_get_libc_version'
          collect2: error: ld returned 1 exit status

I've tested cargo build --target=aarch64-unknown-linux-musl with nightly-2021-11-26-aarch64-unknown-linux-gnu and it works, but with nightly-2021-11-28-aarch64-unknown-linux-gnu, after the commit landed, I get the above error. It remains broken in the current nightly.

@cuviper
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cuviper commented Mar 24, 2022

I don't know how that could happen. That symbol is a plain extern, not weak, and it's also cfg-gated for target_env = "gnu".

@cuviper
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cuviper commented Mar 24, 2022

Somehow you're mixing linux-musl-ld with the linux-gnu libstd? That's probably for a host part of your build (a proc macro or build script), versus your linux-musl target.

@peterwaller-arm
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peterwaller-arm commented Mar 24, 2022

Aha! Great spot, thank you so much for the response and sorry for the noise.

I had put cc as a symlink to my musl compiler in my $PATH for the cargo build without regard for host-built items as you say. So, how do I tell rust to use the correct C compiler for both the host part of the build and the target part of the build? What I'm finding is that when crates get built something is invoking cc, for example for the zstd crate. I presume this is the cc-rs crate in action. I got quite confused about what works and what doesn't work due to the cache. I have a config.toml like the below for example, but I find that the [env] section is having no effect. These environment variables do have an effect if I set them for cargo build, however, confusingly. Must I set CC in my environment, or is there a neat way to rely only on config.toml?

[target.aarch64-unknown-linux-musl]
linker = "/nix/store/dwahbddyz5y2xj1sj43d0yl5qbhammzy-aarch64-unknown-linux-musl-stage-final-gcc-9.3.0/bin/aarch64-unknown-linux-musl-gcc"
[env]
CROSS_COMPILE = "/nix/store/dwahbddyz5y2xj1sj43d0yl5qbhammzy-aarch64-unknown-linux-musl-stage-final-gcc-9.3.0/bin/aarch64-unknown-linux-musl"
CC = "/nix/store/dwahbddyz5y2xj1sj43d0yl5qbhammzy-aarch64-unknown-linux-musl-stage-final-gcc-9.3.0/bin/aarch64-unknown-linux-musl-gcc"

@cuviper
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cuviper commented Mar 24, 2022

The cc crate understands target-specific environment variables too -- try setting CC_aarch64_unknown_linux_musl.

@peterwaller-arm
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Ah yes. I have that part working. The part which I believe is not working is that the build script wants a linker [0], and it's trying to invoke "cc". For the target linker I set CARGO_TARGET_AARCH64_UNKNOWN_LINUX_MUSL=musl-gcc, but I haven't yet figured out what the equivalent is for the build script. I've tried CARGO_TARGET_AARCH64_UNKNOWN_LINUX_GNU, but this appears ignored. There is RUSTC_LINKER but this suggests in the docs it's for the target, not the host.

You can see others are hitting what seem similar issues in #79791 and #94864. If you do a build it is not obvious that the build is failing within a buildscript which is targetting the host, which is confusing.

[0] process didn't exit successfully: rustc --crate-name build_script_build ...

error: linker `cc` not found
  |
  = note: No such file or directory (os error 2)
error: could not compile `zstd-safe` due to previous error

@peterwaller-arm
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I figured it out. I needed to set CARGO_TARGET_AARCH64_UNKNOWN_LINUX_MUSL_LINKER, not CARGO_TARGET_AARCH64_UNKNOWN_LINUX_MUSL.

In the end, I was able to get binaries to build with no compiler in my $PATH, only setting: (note HOSTCC vs MUSLCC)

CARGO_TARGET_AARCH64_UNKNOWN_LINUX_GNU_LINKER=$HOSTCC
CARGO_TARGET_AARCH64_UNKNOWN_LINUX_MUSL_LINKER=$MUSLCC
CC_aarch64_unknown_linux_musl=$MUSLCC

netbsd-srcmastr pushed a commit to NetBSD/pkgsrc that referenced this pull request Apr 15, 2022
Pkgsrc changes:
 * Bump available bootstraps to 1.58.1.
 * Adjust one patch (and checksum) so that it still applies.

Upstream changes:

Version 1.59.0 (2022-02-24)
==========================

Language
--------

- [Stabilize default arguments for const generics][90207]
- [Stabilize destructuring assignment][90521]
- [Relax private in public lint on generic bounds and where clauses
  of trait impls][90586]
- [Stabilize asm! and global_asm! for x86, x86_64, ARM, Aarch64,
  and RISC-V][91728]

Compiler
--------

- [Stabilize new symbol mangling format, leaving it opt-in
  (-Csymbol-mangling-version=v0)][90128]
- [Emit LLVM optimization remarks when enabled with `-Cremark`][90833]
- [Fix sparc64 ABI for aggregates with floating point members][91003]
- [Warn when a `#[test]`-like built-in attribute macro is present
  multiple times.][91172]
- [Add support for riscv64gc-unknown-freebsd][91284]
- [Stabilize `-Z emit-future-incompat` as `--json future-incompat`][91535]
- [Soft disable incremental compilation][94124]

This release disables incremental compilation, unless the user has explicitly
opted in via the newly added RUSTC_FORCE_INCREMENTAL=1 environment variable.
This is due to a known and relatively frequently occurring bug in incremental
compilation, which causes builds to issue internal compiler errors. This
particular bug is already fixed on nightly, but that fix has not yet rolled out
to stable and is deemed too risky for a direct stable backport.

As always, we encourage users to test with nightly and report bugs so that we
can track failures and fix issues earlier.

See [94124] for more details.

[94124]: rust-lang/rust#94124

Libraries
---------

- [Remove unnecessary bounds for some Hash{Map,Set} methods][91593]

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

- [`std::thread::available_parallelism`][available_parallelism]
- [`Result::copied`][result-copied]
- [`Result::cloned`][result-cloned]
- [`arch::asm!`][asm]
- [`arch::global_asm!`][global_asm]
- [`ops::ControlFlow::is_break`][is_break]
- [`ops::ControlFlow::is_continue`][is_continue]
- [`TryFrom<char> for u8`][try_from_char_u8]
- [`char::TryFromCharError`][try_from_char_err]
  implementing `Clone`, `Debug`, `Display`, `PartialEq`, `Copy`, `Eq`, `Error`
- [`iter::zip`][zip]
- [`NonZeroU8::is_power_of_two`][is_power_of_two8]
- [`NonZeroU16::is_power_of_two`][is_power_of_two16]
- [`NonZeroU32::is_power_of_two`][is_power_of_two32]
- [`NonZeroU64::is_power_of_two`][is_power_of_two64]
- [`NonZeroU128::is_power_of_two`][is_power_of_two128]
- [`DoubleEndedIterator for ToLowercase`][lowercase]
- [`DoubleEndedIterator for ToUppercase`][uppercase]
- [`TryFrom<&mut [T]> for [T; N]`][tryfrom_ref_arr]
- [`UnwindSafe for Once`][unwindsafe_once]
- [`RefUnwindSafe for Once`][refunwindsafe_once]
- [armv8 neon intrinsics for aarch64][stdarch/1266]

Const-stable:

- [`mem::MaybeUninit::as_ptr`][muninit_ptr]
- [`mem::MaybeUninit::assume_init`][muninit_init]
- [`mem::MaybeUninit::assume_init_ref`][muninit_init_ref]
- [`ffi::CStr::from_bytes_with_nul_unchecked`][cstr_from_bytes]

Cargo
-----

- [Stabilize the `strip` profile option][cargo/10088]
- [Stabilize future-incompat-report][cargo/10165]
- [Support abbreviating `--release` as `-r`][cargo/10133]
- [Support `term.quiet` configuration][cargo/10152]
- [Remove `--host` from cargo {publish,search,login}][cargo/10145]

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

- [Refactor weak symbols in std::sys::unix][90846]
  This may add new, versioned, symbols when building with a newer glibc, as the
  standard library uses weak linkage rather than dynamically attempting to load
  certain symbols at runtime.
- [Deprecate crate_type and crate_name nested inside `#![cfg_attr]`][83744]
  This adds a future compatibility lint to supporting the use of cfg_attr
  wrapping either crate_type or crate_name specification within Rust files;
  it is recommended that users migrate to setting the equivalent command line
  flags.
- [Remove effect of `#[no_link]` attribute on name resolution][92034]
  This may expose new names, leading to conflicts with preexisting names in a
  given namespace and a compilation failure.
- [Cargo will document libraries before binaries.][cargo/10172]
- [Respect doc=false in dependencies, not just the root crate][cargo/10201]
- [Weaken guarantee around advancing underlying iterators in zip][83791]
- [Make split_inclusive() on an empty slice yield an empty output][89825]
- [Update std::env::temp_dir to use GetTempPath2 on Windows when
  available.][89999]
- [unreachable! was updated to match other formatting macro behavior
  on Rust 2021][92137]

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.

- [Fix many cases of normalization-related ICEs][91255]
- [Replace dominators algorithm with simple Lengauer-Tarjan][85013]
- [Store liveness in interval sets for region inference][90637]

- [Remove `in_band_lifetimes` from the compiler and standard library,
  in preparation for removing this unstable feature.][91867]

[91867]: rust-lang/rust#91867
[83744]: rust-lang/rust#83744
[83791]: rust-lang/rust#83791
[85013]: rust-lang/rust#85013
[89825]: rust-lang/rust#89825
[89999]: rust-lang/rust#89999
[90128]: rust-lang/rust#90128
[90207]: rust-lang/rust#90207
[90521]: rust-lang/rust#90521
[90586]: rust-lang/rust#90586
[90637]: rust-lang/rust#90637
[90833]: rust-lang/rust#90833
[90846]: rust-lang/rust#90846
[91003]: rust-lang/rust#91003
[91172]: rust-lang/rust#91172
[91255]: rust-lang/rust#91255
[91284]: rust-lang/rust#91284
[91535]: rust-lang/rust#91535
[91593]: rust-lang/rust#91593
[91728]: rust-lang/rust#91728
[91878]: rust-lang/rust#91878
[91896]: rust-lang/rust#91896
[91926]: rust-lang/rust#91926
[91984]: rust-lang/rust#91984
[92020]: rust-lang/rust#92020
[92034]: rust-lang/rust#92034
[92483]: rust-lang/rust#92483
[cargo/10088]: rust-lang/cargo#10088
[cargo/10133]: rust-lang/cargo#10133
[cargo/10145]: rust-lang/cargo#10145
[cargo/10152]: rust-lang/cargo#10152
[cargo/10165]: rust-lang/cargo#10165
[cargo/10172]: rust-lang/cargo#10172
[cargo/10201]: rust-lang/cargo#10201
[cargo/10269]: rust-lang/cargo#10269

[cstr_from_bytes]: https://doc.rust-lang.org/stable/std/ffi/struct.CStr.html#method.from_bytes_with_nul_unchecked
[muninit_ptr]: https://doc.rust-lang.org/stable/std/mem/union.MaybeUninit.html#method.as_ptr
[muninit_init]: https://doc.rust-lang.org/stable/std/mem/union.MaybeUninit.html#method.assume_init
[muninit_init_ref]: https://doc.rust-lang.org/stable/std/mem/union.MaybeUninit.html#method.assume_init_ref
[unwindsafe_once]: https://doc.rust-lang.org/stable/std/sync/struct.Once.html#impl-UnwindSafe
[refunwindsafe_once]: https://doc.rust-lang.org/stable/std/sync/struct.Once.html#impl-RefUnwindSafe
[tryfrom_ref_arr]: https://doc.rust-lang.org/stable/std/convert/trait.TryFrom.html#impl-TryFrom%3C%26%27_%20mut%20%5BT%5D%3E
[lowercase]: https://doc.rust-lang.org/stable/std/char/struct.ToLowercase.html#impl-DoubleEndedIterator
[uppercase]: https://doc.rust-lang.org/stable/std/char/struct.ToUppercase.html#impl-DoubleEndedIterator
[try_from_char_err]: https://doc.rust-lang.org/stable/std/char/struct.TryFromCharError.html
[available_parallelism]: https://doc.rust-lang.org/stable/std/thread/fn.available_parallelism.html
[result-copied]: https://doc.rust-lang.org/stable/std/result/enum.Result.html#method.copied
[result-cloned]: https://doc.rust-lang.org/stable/std/result/enum.Result.html#method.cloned
[asm]: https://doc.rust-lang.org/stable/core/arch/macro.asm.html
[global_asm]: https://doc.rust-lang.org/stable/core/arch/macro.global_asm.html
[is_break]: https://doc.rust-lang.org/stable/std/ops/enum.ControlFlow.html#method.is_break
[is_continue]: https://doc.rust-lang.org/stable/std/ops/enum.ControlFlow.html#method.is_continue
[try_from_char_u8]: https://doc.rust-lang.org/stable/std/primitive.char.html#impl-TryFrom%3Cchar%3E
[zip]: https://doc.rust-lang.org/stable/std/iter/fn.zip.html
[is_power_of_two8]: https://doc.rust-lang.org/stable/core/num/struct.NonZeroU8.html#method.is_power_of_two
[is_power_of_two16]: https://doc.rust-lang.org/stable/core/num/struct.NonZeroU16.html#method.is_power_of_two
[is_power_of_two32]: https://doc.rust-lang.org/stable/core/num/struct.NonZeroU32.html#method.is_power_of_two
[is_power_of_two64]: https://doc.rust-lang.org/stable/core/num/struct.NonZeroU64.html#method.is_power_of_two
[is_power_of_two128]: https://doc.rust-lang.org/stable/core/num/struct.NonZeroU128.html#method.is_power_of_two
[stdarch/1266]: rust-lang/stdarch#1266
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