Rust 1.76.0

Language

• Document Rust ABI compatibility between various types
• Also: guarantee that char and u32 are ABI-compatible
• Add lint ambiguous_wide_pointer_comparisons that supersedes clippy::vtable_address_comparisons

Compiler

• Lint pinned #[must_use] pointers (in particular, Box<T> where T is #[must_use]) in unused_must_use.
• Soundness fix: fix computing the offset of an unsized field in a packed struct
• Soundness fix: fix dynamic size/align computation logic for packed types with dyn Trait tail
• Add $message_type field to distinguish json diagnostic outputs
• Enable Rust to use the EHCont security feature of Windows
• Add tier 3 {x86_64,i686}-win7-windows-msvc targets
• Add tier 3 aarch64-apple-watchos target
• Add tier 3 arm64e-apple-ios & arm64e-apple-darwin targets

Refer to Rust's platform support page for more information on Rust's tiered platform support.

Libraries

• Add a column number to dbg!()
• Add std::hash::{DefaultHasher, RandomState} exports
• Fix rounding issue with exponents in fmt
• Add T: ?Sized to RwLockReadGuard and RwLockWriteGuard's Debug impls.
• Windows: Allow File::create to work on hidden files

Stabilized APIs

• Arc::unwrap_or_clone
• Rc::unwrap_or_clone
• Result::inspect
• Result::inspect_err
• Option::inspect
• type_name_of_val
• std::hash::{DefaultHasher, RandomState} These were previously available only through std::collections::hash_map.
• ptr::{from_ref, from_mut}
• ptr::addr_eq

Cargo

See Cargo release notes.

Rustdoc

• Don't merge cfg and doc(cfg) attributes for re-exports
• rustdoc: allow resizing the sidebar / hiding the top bar
• rustdoc-search: add support for traits and associated types
• rustdoc: Add highlighting for comments in items declaration

Compatibility Notes

• Add allow-by-default lint for unit bindings This is expected to be upgraded to a warning by default in a future Rust release. Some macros emit bindings with type () with user-provided spans, which means that this lint will warn for user code.
• Remove x86_64-sun-solaris target.
• Remove asmjs-unknown-emscripten target
• Report errors in jobserver inherited through environment variables This may warn on benign problems too.
• Update the minimum external LLVM to 16.
• Improve print_tts This change can break some naive manual parsing of token trees in proc macro code which expect a particular structure after .to_string(), rather than just arbitrary Rust code.
• Make IMPLIED_BOUNDS_ENTAILMENT into a hard error from a lint
• Vec's allocation behavior was changed when collecting some iterators Allocation behavior is currently not specified, nevertheless changes can be surprising. See impl FromIterator for Vec for more details.
• Properly reject default on free const items

Rust 1.75.0

Language

• Stabilize async fn and return-position impl Trait in traits.
• Allow function pointer signatures containing &mut T in const contexts.
• Match usize/isize exhaustively with half-open ranges.
• Guarantee that char has the same size and alignment as u32.
• Document that the null pointer has the 0 address.
• Allow partially moved values in match.
• Add notes about non-compliant FP behavior on 32bit x86 targets.
• Stabilize ratified RISC-V target features.

Compiler

• Rework negative coherence to properly consider impls that only partly overlap.
• Bump COINDUCTIVE_OVERLAP_IN_COHERENCE to deny, and warn in dependencies.
• Consider alias bounds when computing liveness in NLL.
• Add the V (vector) extension to the riscv64-linux-android target spec.
• Automatically enable cross-crate inlining for small functions
• Add several new tier 3 targets:
  • csky-unknown-linux-gnuabiv2hf
  • i586-unknown-netbsd
  • mipsel-unknown-netbsd

Refer to Rust's platform support page for more information on Rust's tiered platform support.

Libraries

• Override Waker::clone_from to avoid cloning Wakers unnecessarily.
• Implement BufRead for VecDeque<u8>.
• Implement FusedIterator for DecodeUtf16 when the inner iterator does.
• Implement Not, Bit{And,Or}{,Assign} for IP addresses.
• Implement Default for ExitCode.
• Guarantee representation of None in NPO
• Document when atomic loads are guaranteed read-only.
• Broaden the consequences of recursive TLS initialization.
• Windows: Support sub-millisecond sleep.
• Fix generic bound of str::SplitInclusive's DoubleEndedIterator impl
• Fix exit status / wait status on non-Unix cfg(unix) platforms.

Stabilized APIs

• Atomic*::from_ptr
• FileTimes
• FileTimesExt
• File::set_modified
• File::set_times
• IpAddr::to_canonical
• Ipv6Addr::to_canonical
• Option::as_slice
• Option::as_mut_slice
• pointer::byte_add
• pointer::byte_offset
• pointer::byte_offset_from
• pointer::byte_sub
• pointer::wrapping_byte_add
• pointer::wrapping_byte_offset
• pointer::wrapping_byte_sub

These APIs are now stable in const contexts:

• Ipv6Addr::to_ipv4_mapped
• MaybeUninit::assume_init_read
• MaybeUninit::zeroed
• mem::discriminant
• mem::zeroed

Cargo

• Add new packages to [workspace.members] automatically.
• Allow version-less Cargo.toml manifests.
• Make browser links out of HTML file paths.

Rustdoc

• Accept less invalid Rust in rustdoc.
• Document lack of object safety on affected traits.
• Hide #[repr(transparent)] if it isn't part of the public ABI.
• Show enum discriminant if it is a C-like variant.

Compatibility Notes

• FreeBSD targets now require at least version 12.
• Formally demote tier 2 MIPS targets to tier 3.
• Make misalignment a hard error in const contexts.
• Fix detecting references to packed unsized fields.
• Remove support for compiler plugins.

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.

• Optimize librustc_driver.so with BOLT.
• Enable parallel rustc front end in dev and nightly builds.
• Distribute rustc-codegen-cranelift as rustup component on the nightly channel.

Rust 1.74.1

• Resolved spurious STATUS_ACCESS_VIOLATIONs in LLVM
• Clarify guarantees for std::mem::discriminant
• Fix some subtyping-related regressions

Rust 1.74.0

Language

• Codify that std::mem::Discriminant<T> does not depend on any lifetimes in T
• Replace private_in_public lint with private_interfaces and private_bounds per RFC 2145. Read more in RFC 2145.
• Allow explicit #[repr(Rust)]
• closure field capturing: don't depend on alignment of packed fields
• Enable MIR-based drop-tracking for async blocks
• Stabilize impl_trait_projections

Compiler

• stabilize combining +bundle and +whole-archive link modifiers
• Stabilize PATH option for --print KIND=PATH
• Enable ASAN/LSAN/TSAN for *-apple-ios-macabi
• Promote loongarch64-unknown-none* to Tier 2
• Add i686-pc-windows-gnullvm as a tier 3 target

Libraries

• Implement From<OwnedFd/Handle> for ChildStdin/out/err
• Implement From<{&,&mut} [T; N]> for Vec<T> where T: Clone
• impl Step for IP addresses
• Implement From<[T; N]> for Rc<[T]> and Arc<[T]>
• impl TryFrom<char> for u16
• Stabilize io_error_other feature
• Stabilize the Saturating type
• Stabilize const_transmute_copy

Stabilized APIs

• core::num::Saturating
• impl From<io::Stdout> for std::process::Stdio
• impl From<io::Stderr> for std::process::Stdio
• impl From<OwnedHandle> for std::process::Child{Stdin, Stdout, Stderr}
• impl From<OwnedFd> for std::process::Child{Stdin, Stdout, Stderr}
• std::ffi::OsString::from_encoded_bytes_unchecked
• std::ffi::OsString::into_encoded_bytes
• std::ffi::OsStr::from_encoded_bytes_unchecked
• std::ffi::OsStr::as_encoded_bytes
• std::io::Error::other
• impl TryFrom<char> for u16
• impl<T: Clone, const N: usize> From<&[T; N]> for Vec<T>
• impl<T: Clone, const N: usize> From<&mut [T; N]> for Vec<T>
• impl<T, const N: usize> From<[T; N]> for Arc<[T]>
• impl<T, const N: usize> From<[T; N]> for Rc<[T]>

These APIs are now stable in const contexts:

• core::mem::transmute_copy
• str::is_ascii
• [u8]::is_ascii

Cargo

• In Cargo.toml, stabilize [lints]
• Stabilize credential-process and registry-auth
• Stabilize --keep-going build flag
• Add styling to --help output
• For cargo clean, add --dry-run flag and summary line at the end
• For cargo update, make --package more convenient by being positional
• For cargo update, clarify meaning of --aggressive as --recursive
• Add '-n' as an alias for --dry-run
• Allow version-prefixes in pkgid's (e.g. --package flags) to resolve ambiguities
• In .cargo/config.toml, merge lists in precedence order
• Add support for target.'cfg(..)'.linker

Rustdoc

• Add warning block support in rustdoc
• rustdoc-search: add support for type parameters
• rustdoc: show inner enum and struct in type definition for concrete type

Compatibility Notes

• Raise minimum supported Apple OS versions
• make Cell::swap panic if the Cells partially overlap
• Reject invalid crate names in --extern
• Don't resolve generic impls that may be shadowed by dyn built-in impls
• The new impl From<{&,&mut} [T; N]> for Vec<T> is known to cause some inference failures with overly-generic code. In those examples using the tui crate, the combination of AsRef<_> and Into<Vec> leaves the middle type ambiguous, and the new impl adds another possibility, so it now requires an explicit type annotation.

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.

None this cycle.

Rust 1.73.0

Language

• Uplift clippy::fn_null_check lint as useless_ptr_null_checks.
• Make noop_method_call warn by default.
• Support interpolated block for try and async in macros.
• Make unconditional_recursion lint detect recursive drops.
• Future compatibility warning for some impls being incorrectly considered not overlapping.
• The invalid_reference_casting lint is now deny-by-default (instead of allow-by-default)

Compiler

• Write version information in a .comment section like GCC/Clang.
• Add documentation on v0 symbol mangling.
• Stabilize extern "thiscall" and "thiscall-unwind" ABIs.
• Only check outlives goals on impl compared to trait.
• Infer type in irrefutable slice patterns with fixed length as array.
• Discard default auto trait impls if explicit ones exist.
• Add several new tier 3 targets:
  • aarch64-unknown-teeos
  • csky-unknown-linux-gnuabiv2
  • riscv64-linux-android
  • riscv64gc-unknown-hermit
  • x86_64-unikraft-linux-musl
  • x86_64-unknown-linux-ohos
• Add wasm32-wasi-preview1-threads as a tier 2 target.

Refer to Rust's platform support page for more information on Rust's tiered platform support.

Libraries

• Add Read, Write and Seek impls for Arc<File>.
• Merge functionality of io::Sink into io::Empty.
• Implement RefUnwindSafe for Backtrace
• Make ExitStatus implement Default
• impl SliceIndex<str> for (Bound<usize>, Bound<usize>)
• Change default panic handler message format.
• Cleaner assert_eq! & assert_ne! panic messages.
• Correct the (deprecated) Android stat struct definitions.

Stabilized APIs

• Unsigned {integer}::div_ceil
• Unsigned {integer}::next_multiple_of
• Unsigned {integer}::checked_next_multiple_of
• std::ffi::FromBytesUntilNulError
• std::os::unix::fs::chown
• std::os::unix::fs::fchown
• std::os::unix::fs::lchown
• LocalKey::<Cell<T>>::get
• LocalKey::<Cell<T>>::set
• LocalKey::<Cell<T>>::take
• LocalKey::<Cell<T>>::replace
• LocalKey::<RefCell<T>>::with_borrow
• LocalKey::<RefCell<T>>::with_borrow_mut
• LocalKey::<RefCell<T>>::set
• LocalKey::<RefCell<T>>::take
• LocalKey::<RefCell<T>>::replace

These APIs are now stable in const contexts:

• rc::Weak::new
• sync::Weak::new
• NonNull::as_ref

Cargo

• Bail out an error when using cargo:: in custom build script.

Misc

Compatibility Notes

• Update the minimum external LLVM to 15.
• Check for non-defining uses of return position impl Trait.

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.

• Remove LLVM pointee types, supporting only opaque pointers.
• Port PGO/LTO/BOLT optimized build pipeline to Rust.
• Replace in-tree rustc_apfloat with the new version of the crate.
• Update to LLVM 17.
• Add internal_features lint for internal unstable features.
• Mention style for new syntax in tracking issue template.

Rust 1.72.1

• Adjust codegen change to improve LLVM codegen
• rustdoc: Fix self ty params in objects with lifetimes
• Fix regression in compile times
• Resolve some ICE regressions in the compiler:
  • #115215
  • #115559

Rust 1.72.0

Language

• Replace const eval limit by a lint and add an exponential backoff warning
• expand: Change how #![cfg(FALSE)] behaves on crate root
• Stabilize inline asm for LoongArch64
• Uplift clippy::undropped_manually_drops lint
• Uplift clippy::invalid_utf8_in_unchecked lint as invalid_from_utf8_unchecked and invalid_from_utf8
• Uplift clippy::cast_ref_to_mut lint as invalid_reference_casting
• Uplift clippy::cmp_nan lint as invalid_nan_comparisons
• resolve: Remove artificial import ambiguity errors
• Don't require associated types with Self: Sized bounds in dyn Trait objects

Compiler

• Remember names of cfg-ed out items to mention them in diagnostics
• Support for native WASM exceptions
• Add support for NetBSD/aarch64-be (big-endian arm64).
• Write to stdout if - is given as output file
• Force all native libraries to be statically linked when linking a static binary
• Add Tier 3 support for loongarch64-unknown-none*
• Prevent .eh_frame from being emitted for -C panic=abort
• Support 128-bit enum variant in debuginfo codegen
• compiler: update solaris/illumos to enable tsan support.

Refer to Rust's platform support page for more information on Rust's tiered platform support.

Libraries

• Document memory orderings of thread::{park, unpark}
• io: soften ‘at most one write attempt’ requirement in io::Write::write
• Specify behavior of HashSet::insert
• Relax implicit T: Sized bounds on BufReader<T>, BufWriter<T> and LineWriter<T>
• Update runtime guarantee for select_nth_unstable
• Return Ok on kill if process has already exited
• Implement PartialOrd for Vecs over different allocators
• Use 128 bits for TypeId hash
• Don't drain-on-drop in DrainFilter impls of various collections.
• Make {Arc,Rc,Weak}::ptr_eq ignore pointer metadata

Rustdoc

• Allow whitespace as path separator like double colon
• Add search result item types after their name
• Search for slices and arrays by type with []
• Clean up type unification and "unboxing"

Stabilized APIs

• impl<T: Send> Sync for mpsc::Sender<T>
• impl TryFrom<&OsStr> for &str
• String::leak

These APIs are now stable in const contexts:

• CStr::from_bytes_with_nul
• CStr::to_bytes
• CStr::to_bytes_with_nul
• CStr::to_str

Cargo

• Enable -Zdoctest-in-workspace by default. When running each documentation test, the working directory is set to the root directory of the package the test belongs to. docs #12221 #12288
• Add support of the "default" keyword to reset previously set build.jobs parallelism back to the default. #12222

Compatibility Notes

• Alter Display for Ipv6Addr for IPv4-compatible addresses
• Cargo changed feature name validation check to a hard error. The warning was added in Rust 1.49. These extended characters aren't allowed on crates.io, so this should only impact users of other registries, or people who don't publish to a registry. #12291
• Demoted mips*-unknown-linux-gnu* targets from host tier 2 to target tier 3 support.

Rust 1.71.1

• Fix CVE-2023-38497: Cargo did not respect the umask when extracting dependencies
• Fix bash completion for users of Rustup
• Do not show suspicious_double_ref_op lint when calling borrow()
• Fix ICE: substitute types before checking inlining compatibility
• Fix ICE: don't use can_eq in derive(..) suggestion for missing method
• Fix building Rust 1.71.0 from the source tarball

Rust 1.71.0

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 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.

Rust 1.70.0

Language

• Relax ordering rules for asm! operands
• Properly allow macro expanded format_args invocations to uses captures
• Lint ambiguous glob re-exports
• Perform const and unsafe checking for expressions in let _ = expr position.

Compiler

• Extend -Cdebuginfo with new options and named aliases This provides a smaller version of debuginfo for cases that only need line number information (-Cdebuginfo=line-tables-only), which may eventually become the default for -Cdebuginfo=1.
• Make unused_allocation lint against Box::new too
• Detect uninhabited types early in const eval
• Switch to LLD as default linker for {arm,thumb}v4t-none-eabi
• Add tier 3 target loongarch64-unknown-linux-gnu
• Add tier 3 target for i586-pc-nto-qnx700 (QNX Neutrino RTOS, version 7.0),
• Insert alignment checks for pointer dereferences as debug assertions This catches undefined behavior at runtime, and may cause existing code to fail.

Refer to Rust's platform support page for more information on Rust's tiered platform support.

Libraries

• Document NonZeroXxx layout guarantees
• Windows: make Command prefer non-verbatim paths
• Implement Default for some alloc/core iterators
• Fix handling of trailing bare CR in str::lines
• allow negative numeric literals in concat!
• Add documentation about the memory layout of Cell
• Use partial_cmp to implement tuple lt/le/ge/gt
• Stabilize atomic_as_ptr
• Stabilize nonnull_slice_from_raw_parts
• Partial stabilization of once_cell
• Stabilize nonzero_min_max
• Flatten/inline format_args!() and (string and int) literal arguments into format_args!()
• Stabilize movbe target feature
• don't splice from files into pipes in io::copy
• Add a builtin unstable FnPtr trait that is implemented for all function pointers This extends Debug, Pointer, Hash, PartialEq, Eq, PartialOrd, and Ord implementations for function pointers with all ABIs.

Stabilized APIs

• NonZero*::MIN/MAX
• BinaryHeap::retain
• Default for std::collections::binary_heap::IntoIter
• Default for std::collections::btree_map::{IntoIter, Iter, IterMut}
• Default for std::collections::btree_map::{IntoKeys, Keys}
• Default for std::collections::btree_map::{IntoValues, Values}
• Default for std::collections::btree_map::Range
• Default for std::collections::btree_set::{IntoIter, Iter}
• Default for std::collections::btree_set::Range
• Default for std::collections::linked_list::{IntoIter, Iter, IterMut}
• Default for std::vec::IntoIter
• Default for std::iter::Chain
• Default for std::iter::Cloned
• Default for std::iter::Copied
• Default for std::iter::Enumerate
• Default for std::iter::Flatten
• Default for std::iter::Fuse
• Default for std::iter::Rev
• Default for std::slice::Iter
• Default for std::slice::IterMut
• Rc::into_inner
• Arc::into_inner
• std::cell::OnceCell
• Option::is_some_and
• NonNull::slice_from_raw_parts
• Result::is_ok_and
• Result::is_err_and
• std::sync::atomic::Atomic*::as_ptr
• std::io::IsTerminal
• std::os::linux::net::SocketAddrExt
• std::os::unix::net::UnixDatagram::bind_addr
• std::os::unix::net::UnixDatagram::connect_addr
• std::os::unix::net::UnixDatagram::send_to_addr
• std::os::unix::net::UnixListener::bind_addr
• std::path::Path::as_mut_os_str
• std::sync::OnceLock

Cargo

• Add CARGO_PKG_README
• Make sparse the default protocol for crates.io
• Accurately show status when downgrading dependencies
• Use registry.default for login/logout
• Stabilize cargo logout

Misc

• Stabilize rustdoc --test-run-directory

Compatibility Notes

• Prevent stable libtest from supporting -Zunstable-options
• Perform const and unsafe checking for expressions in let _ = expr position.
• WebAssembly targets enable sign-ext and mutable-globals features in codegen This may cause incompatibility with older execution environments.
• Insert alignment checks for pointer dereferences as debug assertions This catches undefined behavior at runtime, and may cause existing code to fail.

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.

• Upgrade to LLVM 16
• Use SipHash-1-3 instead of SipHash-2-4 for StableHasher