Rust 1.81.0

Language

• Abort on uncaught panics in extern "C" functions.
• Fix ambiguous cases of multiple & in elided self lifetimes.
• Stabilize #[expect] for lints (RFC 2383), like #[allow] with a warning if the lint is not fulfilled.
• Change method resolution to constrain hidden types instead of rejecting method candidates.
• Bump elided_lifetimes_in_associated_constant to deny.
• offset_from: always allow pointers to point to the same address.
• Allow constraining opaque types during subtyping in the trait system.
• Allow constraining opaque types during various unsizing casts.
• Deny keyword lifetimes pre-expansion.

Compiler

• Make casts of pointers to trait objects stricter.
• Check alias args for well-formedness even if they have escaping bound vars.
• Deprecate no-op codegen option -Cinline-threshold=....
• Re-implement a type-size based limit.
• Properly account for alignment in transmute size checks.
• Remove the box_pointers lint.
• Ensure the interpreter checks bool/char for validity when they are used in a cast.
• Improve coverage instrumentation for functions containing nested items.
• Target changes:
  • Add Tier 3 no_std Xtensa targets: xtensa-esp32-none-elf, xtensa-esp32s2-none-elf, xtensa-esp32s3-none-elf
  • Add Tier 3 std Xtensa targets: xtensa-esp32-espidf, xtensa-esp32s2-espidf, xtensa-esp32s3-espidf
  • Add Tier 3 i686 Redox OS target: i686-unknown-redox
  • Promote arm64ec-pc-windows-msvc to Tier 2.
  • Promote loongarch64-unknown-linux-musl to Tier 2 with host tools.
  • Enable full tools and profiler for LoongArch Linux targets.
  • Unconditionally warn on usage of wasm32-wasi. (see compatibility note below)
  • Refer to Rust's platform support page for more information on Rust's tiered platform support.

Libraries

• Split core's PanicInfo and std's PanicInfo. (see compatibility note below)
• Generalize {Rc,Arc}::make_mut() to unsized types.
• Replace sort implementations with stable driftsort and unstable ipnsort. All slice::sort* and slice::select_nth* methods are expected to see significant performance improvements. See the research project for more details.
• Document behavior of create_dir_all with respect to empty paths.
• Fix interleaved output in the default panic hook when multiple threads panic simultaneously.

Stabilized APIs

• core::error
• hint::assert_unchecked
• fs::exists
• AtomicBool::fetch_not
• Duration::abs_diff
• IoSlice::advance
• IoSlice::advance_slices
• IoSliceMut::advance
• IoSliceMut::advance_slices
• PanicHookInfo
• PanicInfo::message
• PanicMessage

These APIs are now stable in const contexts:

• char::from_u32_unchecked (function)
• char::from_u32_unchecked (method)
• CStr::count_bytes
• CStr::from_ptr

Cargo

• Generated .cargo_vcs_info.json is always included, even when --allow-dirty is passed.
• Disallow package.license-file and package.readme pointing to non-existent files during packaging.
• Disallow passing --release/--debug flag along with the --profile flag.
• Remove lib.plugin key support in Cargo.toml. Rust plugin support has been deprecated for four years and was removed in 1.75.0.

Compatibility Notes

• Usage of the wasm32-wasi target will now issue a compiler warning and request users switch to the wasm32-wasip1 target instead. Both targets are the same, wasm32-wasi is only being renamed, and this change to the WASI target is being done to enable removing wasm32-wasi in January 2025.

• We have renamed std::panic::PanicInfo to std::panic::PanicHookInfo. The old name will continue to work as an alias, but will result in a deprecation warning starting in Rust 1.82.0.

  core::panic::PanicInfo will remain unchanged, however, as this is now a different type.

  The reason is that these types have different roles: std::panic::PanicHookInfo is the argument to the panic hook in std context (where panics can have an arbitrary payload), while core::panic::PanicInfo is the argument to the #[panic_handler] in no_std context (where panics always carry a formatted message). Separating these types allows us to add more useful methods to these types, such as std::panic::PanicHookInfo::payload_as_str() and core::panic::PanicInfo::message().

• The new sort implementations may panic if a type's implementation of Ord (or the given comparison function) does not implement a total order as the trait requires. Ord's supertraits (PartialOrd, Eq, and PartialEq) must also be consistent. The previous implementations would not "notice" any problem, but the new implementations have a good chance of detecting inconsistencies, throwing a panic rather than returning knowingly unsorted data.

• In very rare cases, a change in the internal evaluation order of the trait solver may result in new fatal overflow errors.

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.

• Add a Rust-for Linux auto CI job to check kernel builds.

Rust 1.80.1

• Fix miscompilation in the jump threading MIR optimization when comparing floats
• Revert changes to the dead_code lint from 1.80.0

Rust 1.80.0

Language

• Document maximum allocation size
• Allow zero-byte offsets and ZST read/writes on arbitrary pointers
• Support C23's variadics without a named parameter
• Stabilize exclusive_range_pattern feature
• Guarantee layout and ABI of Result in some scenarios

Compiler

• Update cc crate to v1.0.97 allowing additional spectre mitigations on MSVC targets
• Allow field reordering on types marked repr(packed(1))
• Add a lint against never type fallback affecting unsafe code
• Disallow cast with trailing braced macro in let-else
• Expand for_loops_over_fallibles lint to lint on fallibles behind references.
• self-contained linker: retry linking without -fuse-ld=lld on CCs that don't support it
• Do not parse CVarArgs (...) as a type in trait bounds
• Improvements to LLDB formatting #124458 #124500
• For the wasm32-wasip2 target default to PIC and do not use -fuse-ld=lld
• Add x86_64-unknown-linux-none as a tier 3 target
• Lint on foo.into_iter() resolving to &Box<[T]>: IntoIterator

Libraries

• Add size_of and size_of_val and align_of and align_of_val to the prelude
• Abort a process when FD ownership is violated
• io::Write::write_fmt: panic if the formatter fails when the stream does not fail
• Panic if PathBuf::set_extension would add a path separator
• Add assert_unsafe_precondition to unchecked_{add,sub,neg,mul,shl,shr} methods
• Update c_char on AIX to use the correct type
• offset_of! no longer returns a temporary
• Handle sigma in str.to_lowercase correctly
• Raise DEFAULT_MIN_STACK_SIZE to at least 64KiB

Stabilized APIs

• impl Default for Rc<CStr>
• impl Default for Rc<str>
• impl Default for Rc<[T]>
• impl Default for Arc<str>
• impl Default for Arc<CStr>
• impl Default for Arc<[T]>
• impl IntoIterator for Box<[T]>
• impl FromIterator<String> for Box<str>
• impl FromIterator<char> for Box<str>
• LazyCell
• LazyLock
• Duration::div_duration_f32
• Duration::div_duration_f64
• Option::take_if
• Seek::seek_relative
• BinaryHeap::as_slice
• NonNull::offset
• NonNull::byte_offset
• NonNull::add
• NonNull::byte_add
• NonNull::sub
• NonNull::byte_sub
• NonNull::offset_from
• NonNull::byte_offset_from
• NonNull::read
• NonNull::read_volatile
• NonNull::read_unaligned
• NonNull::write
• NonNull::write_volatile
• NonNull::write_unaligned
• NonNull::write_bytes
• NonNull::copy_to
• NonNull::copy_to_nonoverlapping
• NonNull::copy_from
• NonNull::copy_from_nonoverlapping
• NonNull::replace
• NonNull::swap
• NonNull::drop_in_place
• NonNull::align_offset
• <[T]>::split_at_checked
• <[T]>::split_at_mut_checked
• str::split_at_checked
• str::split_at_mut_checked
• str::trim_ascii
• str::trim_ascii_start
• str::trim_ascii_end
• <[u8]>::trim_ascii
• <[u8]>::trim_ascii_start
• <[u8]>::trim_ascii_end
• Ipv4Addr::BITS
• Ipv4Addr::to_bits
• Ipv4Addr::from_bits
• Ipv6Addr::BITS
• Ipv6Addr::to_bits
• Ipv6Addr::from_bits
• Vec::<[T; N]>::into_flattened
• <[[T; N]]>::as_flattened
• <[[T; N]]>::as_flattened_mut

These APIs are now stable in const contexts:

• <[T]>::last_chunk
• BinaryHeap::new

Cargo

• Stabilize -Zcheck-cfg as always enabled
• Warn, rather than fail publish, if a target is excluded
• Add special check-cfg lint config for the unexpected_cfgs lint
• [Stabilize `cargo update --pr...

Rust 1.79.0

Language

• Stabilize inline const {} expressions.
• Prevent opaque types being instantiated twice with different regions within the same function.
• Stabilize WebAssembly target features that are in phase 4 and 5.
• Add the redundant_lifetimes lint to detect lifetimes which are semantically redundant.
• Stabilize the unnameable_types lint for public types that can't be named.
• Enable debuginfo in macros, and stabilize -C collapse-macro-debuginfo and #[collapse_debuginfo].
• Propagate temporary lifetime extension into if and match expressions.
• Restrict promotion of const fn calls.
• Warn against refining impls of crate-private traits with refining_impl_trait lint.
• Stabilize associated type bounds (RFC 2289).
• Stabilize importing main from other modules or crates.
• Check return types of function types for well-formedness
• Rework impl Trait lifetime inference
• Change inductive trait solver cycles to be ambiguous

Compiler

• Define -C strip to only affect binaries, not artifacts like .pdb.
• Stabilize -Crelro-level for controlling runtime link hardening.
• Stabilize checking of cfg names and values at compile-time with --check-cfg. Note that this only stabilizes the compiler part, the Cargo part is still unstable in this release.
• Add aarch64-apple-visionos and aarch64-apple-visionos-sim tier 3 targets.
• Add riscv32ima-unknown-none-elf tier 3 target.
• Promote several Windows targets to tier 2: aarch64-pc-windows-gnullvm, i686-pc-windows-gnullvm, and x86_64-pc-windows-gnullvm.

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

Libraries

• Implement FromIterator for (impl Default + Extend, impl Default + Extend).
• Implement {Div,Rem}Assign<NonZero<X>> on X.
• Document overrides of clone_from() in core/std.
• Link MSVC default lib in core.
• Caution against using transmute between pointers and integers.
• Enable frame pointers for the standard library.

Stabilized APIs

• {integer}::unchecked_add
• {integer}::unchecked_mul
• {integer}::unchecked_sub
• <[T]>::split_at_unchecked
• <[T]>::split_at_mut_unchecked
• <[u8]>::utf8_chunks
• str::Utf8Chunks
• str::Utf8Chunk
• <*const T>::is_aligned
• <*mut T>::is_aligned
• NonNull::is_aligned
• <*const [T]>::len
• <*mut [T]>::len
• <*const [T]>::is_empty
• <*mut [T]>::is_empty
• NonNull::<[T]>::is_empty
• CStr::count_bytes
• io::Error::downcast
• num::NonZero<T>
• path::absolute
• proc_macro::Literal::byte_character
• proc_macro::Literal::c_string

These APIs are now stable in const contexts:

• Atomic*::into_inner
• io::Cursor::new
• io::Cursor::get_ref
• io::Cursor::position
• io::empty
• io::repeat
• io::sink
• panic::Location::caller
• panic::Location::file
• panic::Location::line
• panic::Location::column

Cargo

• Prevent dashes in lib.name, always normalizing to _.
• Stabilize MSRV-aware version requirement selection in cargo add.
• Switch to using gitoxide by default for listing files.

Rustdoc

• Always display stability version even if it's the same as the containing item.
• Show a single search result for items with multiple paths.
• Support typing / in docs to begin a search.

Misc

Compatibility Notes

• Update the minimum external LLVM to 17.
• RustcEncodable and RustcDecodable are soft-destabilized, to be removed from the prelude in next edition.
• The wasm_c_abi future-incompatibility lint will warn about use of the non-spec-compliant C ABI. Use wasm-bindgen v0.2.88 to generate forward-compatible bindings.
• Check return types of function types for well-formedness

Rust 1.78.0

Language

• Stabilize #[cfg(target_abi = ...)]
• Stabilize the #[diagnostic] namespace and #[diagnostic::on_unimplemented] attribute
• Make async-fn-in-trait implementable with concrete signatures
• Make matching on NaN a hard error, and remove the rest of illegal_floating_point_literal_pattern
• static mut: allow mutable reference to arbitrary types, not just slices and arrays
• Extend invalid_reference_casting to include references casting to bigger memory layout
• Add non_contiguous_range_endpoints lint for singleton gaps after exclusive ranges
• Add wasm_c_abi lint for use of older wasm-bindgen versions This lint currently only works when using Cargo.
• Update indirect_structural_match and pointer_structural_match lints to match RFC
• Make non-PartialEq-typed consts as patterns a hard error
• Split refining_impl_trait lint into _reachable, _internal variants
• Remove unnecessary type inference when using associated types inside of higher ranked where-bounds
• Weaken eager detection of cyclic types during type inference
• trait Trait: Auto {}: allow upcasting from dyn Trait to dyn Trait + Auto

Compiler

• Made INVALID_DOC_ATTRIBUTES lint deny by default
• Increase accuracy of redundant use checking
• Suggest moving definition if non-found macro_rules! is defined later
• Lower transmutes from int to pointer type as gep on null

Target changes:

• Windows tier 1 targets now require at least Windows 10
  • Enable CMPXCHG16B, SSE3, SAHF/LAHF and 128-bit Atomics in tier 1 Windows
• Add wasm32-wasip1 tier 2 (without host tools) target
• Add wasm32-wasip2 tier 3 target
• Rename wasm32-wasi-preview1-threads to wasm32-wasip1-threads
• Add arm64ec-pc-windows-msvc tier 3 target
• Add armv8r-none-eabihf tier 3 target for the Cortex-R52
• Add loongarch64-unknown-linux-musl tier 3 target

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

Libraries

• Bump Unicode to version 15.1.0, regenerate tables
• Make align_offset, align_to well-behaved in all cases
• PartialEq, PartialOrd: document expectations for transitive chains
• Optimize away poison guards when std is built with panic=abort
• Replace pthread RwLock with custom implementation
• Implement unwind safety for Condvar on all platforms
• Add ASCII fast-path for char::is_grapheme_extended

Stabilized APIs

• impl Read for &Stdin
• Accept non 'static lifetimes for several std::error::Error related implementations
• Make impl<Fd: AsFd> impl take ?Sized
• impl From<TryReserveError> for io::Error

These APIs are now stable in const contexts:

• Barrier::new()

Cargo

• Stabilize lockfile v4
• Respect rust-version when generating lockfile
• Control --charset via auto-detecting config value
• Support target.<triple>.rustdocflags officially
• Stabilize global cache data tracking

Misc

• rustdoc: add --test-builder-wrapper arg to support wrappers such as RUSTC_WRAPPER when building doctests

Compatibility Notes

• Many unsafe precondition checks now run for user code with debug assertions enabled This change helps users catch undefined behavior in their code, though the details of how much is checked are generally not stable.
• riscv only supports split_debuginfo=off for now
• Consistently check bounds on hidden types of impl Trait
• Change equality of higher ranked types to not rely on subtyping
• When called, additionally check bounds on normalized function return type
• Expand coverage for arithmetic_overflow lint
• Fix detection of potential interior mutability in const initializers This code was accidentally accepted. The fix can break generic code that borrows a value of unknown type, as there is currently no way to declare "this type has no interior mutability". In the future, stabilizing the Freeze trait will allow proper support for such code.

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.

• Update to LLVM 18
• Build rustc with 1CGU on x86_64-pc-windows-msvc
• Build rustc with 1CGU on x86_64-apple-darwin
• Introduce run-make V2 infrastructure, a run_make_support library and port over 2 tests as example
• Windows: Implement condvar, mutex and rwlock using futex

Rust 1.77.2

• CVE-2024-24576: fix escaping of Windows batch file arguments in std::process::Command

Rust 1.77.1

• Revert stripping debuginfo by default for Windows This fixes a regression in 1.77 by reverting to the previous default. Platforms other than Windows are not affected.
• Internal: Fix heading anchor rendering in doc pages

Rust 1.77.0

Language

• Reveal opaque types within the defining body for exhaustiveness checking.
• Stabilize C-string literals.
• Stabilize THIR unsafeck.
• Add lint static_mut_refs to warn on references to mutable statics.
• Support async recursive calls (as long as they have indirection).
• Undeprecate lint unstable_features and make use of it in the compiler.
• Make inductive cycles in coherence ambiguous always.
• Get rid of type-driven traversal in const-eval interning, only as a future compatiblity lint for now.
• Deny braced macro invocations in let-else.

Compiler

• Include lint soft_unstable in future breakage reports.
• Make i128 and u128 16-byte aligned on x86-based targets.
• Use --verbose in diagnostic output.
• Improve spacing between printed tokens.
• Merge the unused_tuple_struct_fields lint into dead_code.
• Error on incorrect implied bounds in well-formedness check, with a temporary exception for Bevy.
• Fix coverage instrumentation/reports for non-ASCII source code.
• Fix fn/const items implied bounds and well-formedness check.
• Promote riscv32{im|imafc}-unknown-none-elf targets to tier 2.
• Add several new tier 3 targets:
  • aarch64-unknown-illumos
  • hexagon-unknown-none-elf
  • riscv32imafc-esp-espidf
  • riscv32im-risc0-zkvm-elf

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

Libraries

• Implement From<&[T; N]> for Cow<[T]>.
• Remove special-case handling of vec.split_off(0).

Stabilized APIs

• array::each_ref
• array::each_mut
• core::net
• f32::round_ties_even
• f64::round_ties_even
• mem::offset_of!
• slice::first_chunk
• slice::first_chunk_mut
• slice::split_first_chunk
• slice::split_first_chunk_mut
• slice::last_chunk
• slice::last_chunk_mut
• slice::split_last_chunk
• slice::split_last_chunk_mut
• slice::chunk_by
• slice::chunk_by_mut
• Bound::map
• File::create_new
• Mutex::clear_poison
• RwLock::clear_poison

Cargo

• Extend the build directive syntax with cargo::.
• Stabilize metadata id format as PackageIDSpec.
• Pull out cargo-util-schemas as a crate.
• Strip all debuginfo when debuginfo is not requested.
• Inherit jobserver from env for all kinds of runners.
• Deprecate rustc plugin support in cargo.

Rustdoc

• Allows links in markdown headings.
• Search for tuples and unit by type with ().
• Clean up the source sidebar's hide button.
• Prevent JS injection from localStorage.

Misc

• Recommend version-sorting for all sorting in style guide.

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.

• Add more weirdness to weird-exprs.rs.

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.