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Rust 1.61.0

Released on May 19, 2022

What's Changed

  • [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]

  • [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]

  • [ManuallyDrop 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.
  • [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 APIs now makes it possible for programs to return errors from main with custom exit codes.
  • [std::thread::JoinHandle::is_finished]
  • [<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]

  • 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]

  • [debuginfo: Refactor debuginfo generation for types][94261]
  • [Remove the everybody loops pass][93913]
Full Changelog

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 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 APIs 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]: https://github.com/rust-lang/rust/pull/88375/

[89887]: https://github.com/rust-lang/rust/pull/89887/

[90621]: https://github.com/rust-lang/rust/pull/90621/

[92285]: https://github.com/rust-lang/rust/pull/92285/

[92472]: https://github.com/rust-lang/rust/pull/92472/

[92697]: https://github.com/rust-lang/rust/pull/92697/

[92714]: https://github.com/rust-lang/rust/pull/92714/

[92911]: https://github.com/rust-lang/rust/pull/92911/

[93263]: https://github.com/rust-lang/rust/pull/93263/

[93745]: https://github.com/rust-lang/rust/pull/93745/

[93827]: https://github.com/rust-lang/rust/pull/93827/

[93901]: https://github.com/rust-lang/rust/pull/93901/

[93913]: https://github.com/rust-lang/rust/pull/93913/

[93965]: https://github.com/rust-lang/rust/pull/93965/

[94081]: https://github.com/rust-lang/rust/pull/94081/

[94261]: https://github.com/rust-lang/rust/pull/94261/

[94295]: https://github.com/rust-lang/rust/pull/94295/

[94832]: https://github.com/rust-lang/rust/pull/94832/

[95016]: https://github.com/rust-lang/rust/pull/95016/

[95251]: https://github.com/rust-lang/rust/pull/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]: https://github.com/rust-lang/cargo/pull/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