Language

• Stabilize &mut, *mut, &Cell, and *const Cell in const.
• Allow creating references to statics in const initializers.
• Implement raw lifetimes and labels ('r#ident).
• Define behavior when atomic and non-atomic reads race.
• Non-exhaustive structs may now be empty.
• Disallow implicit coercions from places of type !
• const extern functions can now be defined for other calling conventions.
• Stabilize expr_2021 macro fragment specifier in all editions.
• The non_local_definitions lint now fires on less code and warns by default.

Compiler

• Deprecate unsound -Csoft-float flag.
• Add many new tier 3 targets:
  • aarch64_unknown_nto_qnx700
  • arm64e-apple-tvos
  • armv7-rtems-eabihf
  • loongarch64-unknown-linux-ohos
  • riscv32-wrs-vxworks and riscv64-wrs-vxworks
  • riscv32{e|em|emc}-unknown-none-elf
  • x86_64-unknown-hurd-gnu
  • x86_64-unknown-trusty

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

Libraries

• Implement PartialEq for ExitCode.
• Document that catch_unwind can deal with foreign exceptions without UB, although the exact behavior is unspecified.
• Implement Default for HashMap/HashSet iterators that don't already have it.
• Bump Unicode to version 16.0.0.
• Change documentation of ptr::add/sub to not claim equivalence with offset..

Stabilized APIs

• BufRead::skip_until
• ControlFlow::break_value
• ControlFlow::continue_value
• ControlFlow::map_break
• ControlFlow::map_continue
• DebugList::finish_non_exhaustive
• DebugMap::finish_non_exhaustive
• DebugSet::finish_non_exhaustive
• DebugTuple::finish_non_exhaustive
• ErrorKind::ArgumentListTooLong
• ErrorKind::Deadlock
• ErrorKind::DirectoryNotEmpty
• ErrorKind::ExecutableFileBusy
• ErrorKind::FileTooLarge
• ErrorKind::HostUnreachable
• ErrorKind::IsADirectory
• ErrorKind::NetworkDown
• ErrorKind::NetworkUnreachable
• ErrorKind::NotADirectory
• ErrorKind::NotSeekable
• ErrorKind::ReadOnlyFilesystem
• ErrorKind::ResourceBusy
• ErrorKind::StaleNetworkFileHandle
• ErrorKind::StorageFull
• ErrorKind::TooManyLinks
• Option::get_or_insert_default
• Waker::data
• Waker::new
• Waker::vtable
• char::MIN
• hash_map::Entry::insert_entry
• hash_map::VacantEntry::insert_entry

These APIs are now stable in const contexts:

• Cell::into_inner
• Duration::as_secs_f32
• Duration::as_secs_f64
• Duration::div_duration_f32
• Duration::div_duration_f64
• MaybeUninit::as_mut_ptr
• NonNull::as_mut
• NonNull::copy_from
• NonNull::copy_from_nonoverlapping
• NonNull::copy_to
• NonNull::copy_to_nonoverlapping
• NonNull::slice_from_raw_parts
• NonNull::write
• NonNull::write_bytes
• NonNull::write_unaligned
• OnceCell::into_inner
• Option::as_mut
• Option::expect
• Option::replace
• Option::take
• Option::unwrap
• Option::unwrap_unchecked
• Option::<&_>::copied
• Option::<&mut _>::copied
• Option::<Option<_>>::flatten
• Option::<Result<_, _>>::transpose
• RefCell::into_inner
• Result::as_mut
• Result::<&_, _>::copied
• Result::<&mut _, _>::copied
• Result::<Option<_>, _>::transpose
• UnsafeCell::get_mut
• UnsafeCell::into_inner
• array::from_mut
• char::encode_utf8
• {float}::classify
• {float}::is_finite
• {float}::is_infinite
• {float}::is_nan
• {float}::is_normal
• {float}::is_sign_negative
• {float}::is_sign_positive
• {float}::is_subnormal
• {float}::from_bits
• {float}::from_be_bytes
• {float}::from_le_bytes
• {float}::from_ne_bytes
• {float}::to_bits
• {float}::to_be_bytes
• {float}::to_le_bytes
• {float}::to_ne_bytes
• mem::replace
• ptr::replace
• ptr::slice_from_raw_parts_mut
• ptr::write
• ptr::write_unaligned
• <*const _>::copy_to
• <*const _>::copy_to_nonoverlapping
• <*mut _>::copy_from
• <*mut _>::copy_from_nonoverlapping
• <*mut _>::copy_to
• <*mut _>::copy_to_nonoverlapping
• <*mut _>::write
• <*mut _>::write_bytes
• <*mut _>::write_unaligned
• slice::from_mut
• slice::from_raw_parts_mut
• <[_]>::first_mut
• <[_]>::last_mut
• <[_]>::first_chunk_mut
• <[_]>::last_chunk_mut
• <[_]>::split_at_mut
• <[_]>::split_at_mut_checked
• <[_]>::split_at_mut_unchecked
• <[_]>::split_first_mut
• <[_]>::split_last_mut
• <[_]>::split_first_chunk_mut
• <[_]>::split_last_chunk_mut
• str::as_bytes_mut
• str::as_mut_ptr
• str::from_utf8_unchecked_mut

Cargo

• Introduced a new CARGO_MANIFEST_PATH environment variable, similar to CARGO_MANIFEST_DIR but pointing directly to the manifest file.
• Added package.autolib to the manifest, allowing [lib] auto-discovery to be disabled.
• Declare support level for each crate in Cargo's Charter / crate docs.
• Declare new Intentional Artifacts as 'small' changes.

Rustdoc

• The sidebar / hamburger menu table of contents now includes the # headers from the main item's doc comment. This is similar to a third-party feature provided by the rustdoc-search-enhancements browser extension.

Compatibility Notes

• Warn against function pointers using unsupported ABI strings.

• Check well-formedness of the source type's signature in fn pointer casts. This partly closes a soundness hole that comes when casting a function item to function pointer

• Use equality instead of subtyping when resolving type dependent paths.

• Linking on macOS now correctly includes Rust's default deployment target. Due to a linker bug, you might have to pass MACOSX_DEPLOYMENT_TARGET or fix your #[link] attributes to point to the correct frameworks. See https://github.com/rust-lang/rust/pull/129369.

• Rust will now correctly raise an error for repr(Rust) written on non-struct/enum/union items, since it previous did not have any effect.

• The future incompatibility lint deprecated_cfg_attr_crate_type_name has been made into a hard error. It was used to deny usage of #![crate_type] and #![crate_name] attributes in #![cfg_attr], which required a hack in the compiler to be able to change the used crate type and crate name after cfg expansion. Users can use --crate-type instead of #![cfg_attr(..., crate_type = "...")] and --crate-name instead of #![cfg_attr(..., crate_name = "...")] when running rustc/cargo rustc on the command line. Use of those two attributes outside of #![cfg_attr] continue to be fully supported.

• Until now, paths into the sysroot were always prefixed with /rustc/$hash in diagnostics, codegen, backtrace, e.g.

  thread 'main' panicked at 'hello world', map-panic.rs:2:50
  stack backtrace:
     0: std::panicking::begin_panic
               at /rustc/a55dd71d5fb0ec5a6a3a9e8c27b2127ba491ce52/library/std/src/panicking.rs:616:12
     1: map_panic::main::{{closure}}
               at ./map-panic.rs:2:50
     2: core::option::Option<T>::map
               at /rustc/a55dd71d5fb0ec5a6a3a9e8c27b2127ba491ce52/library/core/src/option.rs:929:29
     3: map_panic::main
               at ./map-panic.rs:2:30
     4: core::ops::function::FnOnce::call_once
               at /rustc/a55dd71d5fb0ec5a6a3a9e8c27b2127ba491ce52/library/core/src/ops/function.rs:248:5
  note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
  

  RFC 3127 said

  We want to change this behaviour such that, when rust-src source files can be discovered, the virtual path is discarded and therefore the local path will be embedded, unless there is a --remap-path-prefix that causes this local path to be remapped in the usual way.

  #129687 implements this behaviour, when rust-src is present at compile time, rustc replaces /rustc/$hash with a real path into the local rust-src component with best effort. To sanitize this, users must explicitly supply --remap-path-prefix=<path to rust-src>=foo or not have the rust-src component installed.

• The allow-by-default missing_docs lint used to disable itself when invoked through rustc --test/cargo test, resulting in #[expect(missing_docs)] emitting false positives due to the expectation being wrongly unfulfilled. This behavior has now been removed, which allows #[expect(missing_docs)] to be fulfilled in all scenarios, but will also report new missing_docs diagnostics for publicly reachable #[cfg(test)] items, integration test crate-level documentation, and publicly reachable items in integration tests.

• The armv8r-none-eabihf target now uses the Armv8-R required set of floating-point features.

• Fix a soundness bug where rustc wouldn't detect unconstrained higher-ranked lifetimes in a dyn Trait's associated types that occur due to supertraits.

• Update the minimum external LLVM version to 18.

• Remove aarch64-fuchsia and x86_64-fuchsia target aliases in favor of aarch64-unknown-fuchsia and x86_64-unknown-fuchsia respectively.

• The ABI-level exception class of a Rust panic is now encoded with native-endian bytes, so it is legible in hex dumps.

• Visual Studio 2013 is no longer supported for MSVC targets.

• The sysroot no longer contains the std dynamic library in its top-level lib/ dir.