1.71.0 #

• Released on: 13 July, 2023
• Branched from master on: 26 May, 2023

Language #

• Stabilize raw-dylib, link_ordinal, import_name_type and -Cdlltool.
• Uplift clippy::{drop,forget}_{ref,copy} lints.
• Type inference is more conservative around constrained vars.
• Use fulfillment to check Drop impl compatibility

Compiler #

• Evaluate place expression in PlaceMention, making let _ = patterns more consistent with respect to the borrow checker.
• Add --print deployment-target flag for Apple targets.
• Stabilize extern "C-unwind" and friends. The existing extern "C" etc. may change behavior for cross-language unwinding in a future release.
• Update the version of musl used on *-linux-musl targets to 1.2.3, enabling time64 on 32-bit systems.
• Stabilize debugger_visualizer for embedding metadata like Microsoft’s Natvis.
• Enable flatten-format-args by default.
• Make Self respect tuple constructor privacy.
• Improve niche placement by trying two strategies and picking the better result.
• Use apple-m1 as the target CPU for aarch64-apple-darwin.
• Add Tier 3 support for the x86_64h-apple-darwin target.
• Promote loongarch64-unknown-linux-gnu to Tier 2 with host tools.

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

Libraries #

• Rework handling of recursive panics. Additional panics are allowed while unwinding, as long as they are caught before escaping a Drop implementation, but panicking within a panic hook is now an immediate abort.
• Loosen From<&[T]> for Box<[T]> bound to T: Clone.
• Remove unnecessary T: Send bound in Error for mpsc::SendError<T> and TrySendError<T>.
• Fix docs for alloc::realloc to match Layout requirements that the size must not exceed isize::MAX.
• Document const {} syntax for std::thread_local. This syntax was stabilized in Rust 1.59, but not previously mentioned in release notes.

Stabilized APIs #

• CStr::is_empty
• BuildHasher::hash_one
• NonZeroI*::is_positive
• NonZeroI*::is_negative
• NonZeroI*::checked_neg
• NonZeroI*::overflowing_neg
• NonZeroI*::saturating_neg
• NonZeroI*::wrapping_neg
• Neg for NonZeroI*
• Neg for &NonZeroI*
• From<[T; N]> for (T...) (array to N-tuple for N in 1..=12)
• From<(T...)> for [T; N] (N-tuple to array for N in 1..=12)
• windows::io::AsHandle for Box<T>
• windows::io::AsHandle for Rc<T>
• windows::io::AsHandle for Arc<T>
• windows::io::AsSocket for Box<T>
• windows::io::AsSocket for Rc<T>
• windows::io::AsSocket for Arc<T>

These APIs are now stable in const contexts:

• <*const T>::read
• <*const T>::read_unaligned
• <*mut T>::read
• <*mut T>::read_unaligned
• ptr::read
• ptr::read_unaligned
• <[T]>::split_at

Cargo #

• Allow named debuginfo options in Cargo.toml.
• Add workspace_default_members to the output of cargo metadata.
• Automatically inherit workspace fields when running cargo new/cargo init.

Rustdoc #

• Add a new rustdoc::unescaped_backticks lint for broken inline code.
• Support strikethrough with single tildes. (~~old~~ vs. ~new~)

Misc #

Compatibility Notes #

• Remove structural match from TypeId. Code that uses a constant TypeId in a pattern will potentially be broken. Known cases have already been fixed – in particular, users of the log crate’s kv_unstable feature should update to log v0.4.18 or later.
• Add a sysroot crate to represent the standard library crates. This does not affect stable users, but may require adjustment in tools that build their own standard library.
• Cargo optimizes its usage under rustup. When Cargo detects it will run rustc pointing to a rustup proxy, it’ll try bypassing the proxy and use the underlying binary directly. There are assumptions around the interaction with rustup and RUSTUP_TOOLCHAIN. However, it’s not expected to affect normal users.
• When querying a package, Cargo tries only the original name, all hyphens, and all underscores to handle misspellings. Previously, Cargo tried each combination of hyphens and underscores, causing excessive requests to crates.io.
• Cargo now disallows RUSTUP_HOME and RUSTUP_TOOLCHAIN in the [env] configuration table. This is considered to be not a use case Cargo would like to support, since it will likely cause problems or lead to confusion.

Internal Changes #

These changes do not affect any public interfaces of Rust, but they represent significant improvements to the performance or internals of rustc and related tools.