Updatify / Rust | Release notes

Language

• Allow passing expr metavariable to cfg
• Always coerce never types in tuple expressions
• Avoid incorrect inference guidance of function arguments in rare cases
• Support s390x vector registers in inline assembly
• Allow using constants of type ManuallyDrop as patterns (fixing a regression introduced in 1.94.0)

Compiler

• Enable link relaxation feature for LoongArch Linux targets
• Update riscv64gc-unknown-fuchsia baseline to RVA22 + vector

Libraries

• Support iterating over ranges of NonZero integers
• refactor ‘valid for read/write’ definition: exclude null; add that as an exception on individual methods instead
• Fix SGX delayed host lookup via ToSocketAddr

Stabilized APIs

• assert_matches!
• debug_assert_matches!
• From<T> for AssertUnwindSafe<T>
• From<T> for LazyCell<T, F>
• From<T> for LazyLock<T, F>
• core::range::RangeToInclusive
• core::range::RangeToInclusiveIter
• core::range::RangeFrom
• core::range::RangeFromIter
• core::range::Range
• core::range::RangeIter

Cargo

• Allow a dependency to specify both a git repository and an alternate registry. Just like with crates.io, the git repository will be used locally, but the registry version will be used when published.
• Added target.'cfg(..)'.rustdocflags support in configuration.
• Fixed CVE-2026-5222 and CVE-2026-5223.

Rustdoc

• Deprecation notes are now rendered like any other documentation. Previously they used the css white-space: pre-wrap; property and stripped any <p> elements from the rendered html, however this caused issues and unintuitive behavior. The new behavior should be more predictable, however some multi-line deprecation notes will now be rendered as as single lines. If this is undesirable, you can use the standard markdown method of forcing a linebreak, which is two spaces followed by a newline ("\n").
• Don’t emit rustdoc missing_doc_code_examples lint on impl items
• Separate methods and associated functions in sidebar

Compatibility Notes

• Fix layout of #[repr(Int)] enums in some edge cases involving fields of uninhabited zero-sized types
• Prevent unsize-coercing into Pin<Foo> where Foo doesn’t implement Deref. Some such coercions were previously allowed, but produce a type with no useful public API.
• rustc: Stop passing --allow-undefined on wasm targets
• Gate the accidentally stabilized #![reexport_test_harness_main] attribute
• Error on return-position-impl-trait-in-traits whose types are too private
• Report the uninhabited_static lint in dependencies and make it deny-by-default
• Distributed builds now contain non-split debuginfo for windows-gnu This appears to improve the quality of backtraces. This change has no effect on the defaults for the output of rustc/cargo on these targets.
• Check const generic arguments are correctly typed in more positions
• Remove -Csoft-float
• Importing structs with ::{self [as name]}, e.g., struct S {}; use S::{self as Other};, is now no longer permitted because {self} imports require a module parent.
• For export_name, link_name, and link_section attributes, if multiple of the same attribute is present, the first one now takes precedence.
• Update the minimum external LLVM to 21
• On avr targets, C’s double type is 32-bit by default, so change c_double to f32 on avr targets to match. This is a breaking change, but necessary to make c_double match C’s double.
• BTreeMap::append() was optimized, which may now cause panics for types with incorrect Ord impls

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.

• JSON targets: aarch64 softfloat targets now have to have rustc_abi set to "softfloat"
• target specs: stricter checks for LLVM ABI values, and correlate that with cfg(target_abi)

Language

• Stabilize if let guards on match arms
• irrefutable_let_patterns lint no longer lints on let chains
• Support importing path-segment keywords with renaming
• Stabilize inline assembly for PowerPC and PowerPC64
• const-eval: be more consistent in the behavior of padding during typed copies
• Const blocks are no longer evaluated to determine if expressions involving fallible operations can implicitly be constant-promoted.. Expressions whose ability to implicitly be promoted would depend on the result of a const block are no longer implicitly promoted.
• Make operational semantics of pattern matching independent of crate and module

Compiler

• Stabilize --remap-path-scope for controlling the scoping of how paths get remapped in the resulting binary
• Apply patches for CVE-2026-6042 and CVE-2026-40200 to vendored musl

Platform Support

• Promote powerpc64-unknown-linux-musl to Tier 2 with host tools
• Promote aarch64-apple-tvos to Tier 2
• Promote aarch64-apple-tvos-sim to Tier 2
• Promote aarch64-apple-watchos to Tier 2
• Promote aarch64-apple-watchos-sim to Tier 2
• Promote aarch64-apple-visionos to Tier 2
• Promote aarch64-apple-visionos-sim to Tier 2

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

Libraries

• thread::scope: document how join interacts with TLS destructors
• Speed up str::contains on aarch64 targets with neon target feature enabled by default

Stabilized APIs

• MaybeUninit<[T; N]>: From<[MaybeUninit<T>; N]>
• MaybeUninit<[T; N]>: AsRef<[MaybeUninit<T>; N]>
• MaybeUninit<[T; N]>: AsRef<[MaybeUninit<T>]>
• MaybeUninit<[T; N]>: AsMut<[MaybeUninit<T>; N]>
• MaybeUninit<[T; N]>: AsMut<[MaybeUninit<T>]>
• [MaybeUninit<T>; N]: From<MaybeUninit<[T; N]>>
• Cell<[T; N]>: AsRef<[Cell<T>; N]>
• Cell<[T; N]>: AsRef<[Cell<T>]>
• Cell<[T]>: AsRef<[Cell<T>]>
• bool: TryFrom<{integer}>
• AtomicPtr::update
• AtomicPtr::try_update
• AtomicBool::update
• AtomicBool::try_update
• AtomicIn::update
• AtomicIn::try_update
• AtomicUn::update
• AtomicUn::try_update
• cfg_select!
• mod core::range
• core::range::RangeInclusive
• core::range::RangeInclusiveIter
• core::hint::cold_path
• <*const T>::as_ref_unchecked
• <*mut T>::as_ref_unchecked
• <*mut T>::as_mut_unchecked
• Vec::push_mut
• Vec::insert_mut
• VecDeque::push_front_mut
• VecDeque::push_back_mut
• VecDeque::insert_mut
• LinkedList::push_front_mut
• LinkedList::push_back_mut
• Layout::dangling_ptr
• Layout::repeat
• Layout::repeat_packed
• Layout::extend_packed

These previously stable APIs are now stable in const contexts:

• fmt::from_fn
• ControlFlow::is_break
• ControlFlow::is_continue

Rustdoc

• In search results, rank unstable items lower
• Add new “hide deprecated items” setting in rustdoc

Compatibility Notes

• Array coercions may now result in less inference constraints than before
• Importing $crate without renaming, i.e. use $crate::{self};, is now no longer permitted due to stricter error checking for self imports.
• const-eval: be more consistent in the behavior of padding during typed copies. In very rare cases, this may cause compilation errors due to bytes from parts of a pointer ending up in the padding bytes of a const or static.
• A future-incompatibility warning lint ambiguous_glob_imported_traits is now reported when using an ambiguously glob imported trait
• Check lifetime bounds of types mentioning only type parameters
• Report more visibility-related ambiguous import errors
• Deprecate Eq::assert_receiver_is_total_eq and emit future compatibility warnings on manual impls
• powerpc64: Use the ELF ABI version set in target spec instead of guessing (fixes the ELF ABI used by the OpenBSD target)
• Matching on a #[non_exhaustive] enum now reads the discriminant, even if the enum has only one variant. This can cause closures to capture values that they previously wouldn’t.
• mut ref and mut ref mut patterns, part of the unstable Match Ergonomics 2024 RFC, were accidentally allowed on stable within struct pattern field shorthand. These patterns are now correctly feature-gated as unstable in this position.
• Add future-compatibility warning for derive helper attributes which conflict with built-in attributes
• JSON target specs have been destabilized and now require -Z unstable-options to use. Previously, they could not be used without the standard library, which has no stable build mechanism. In preparation for the build-std project adding that support, JSON target specs are being proactively gated to ensure they remain unstable even if build-std is stabilized. Cargo now includes the -Z json-target-spec CLI flag to automatically pass -Z unstable-options to the compiler when needed. See #150151, #151534, and rust-lang/cargo#16557.
• The arguments of #[feature] attributes on invalid targets are now checked

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 22

• Fix std::thread::spawn on wasm32-wasip1-threads
• Remove new methods added to std::os::windows::fs::OpenOptionsExt The new methods were unstable, but the trait itself is not sealed and so cannot be extended with non-default methods.
• Clippy: fix ICE in match_same_arms
• Cargo: update tar to 0.4.45 This resolves CVE-2026-33055 and CVE-2026-33056. Users of crates.io are not affected. See blog for more details.

Language

• Impls and impl items inherit dead_code lint level of the corresponding traits and trait items
• Stabilize additional 29 RISC-V target features including large portions of the RVA22U64 / RVA23U64 profiles
• Add warn-by-default unused_visibilities lint for visibility on const _ declarations
• Update to Unicode 17
• Avoid incorrect lifetime errors for closures

Platform Support

• Add riscv64im-unknown-none-elf as a tier 3 target

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

Libraries

• Relax T: Ord bound for some BinaryHeap<T> methods.

Stabilized APIs

• <[T]>::array_windows
• <[T]>::element_offset
• LazyCell::get
• LazyCell::get_mut
• LazyCell::force_mut
• LazyLock::get
• LazyLock::get_mut
• LazyLock::force_mut
• impl TryFrom<char> for usize
• std::iter::Peekable::next_if_map
• std::iter::Peekable::next_if_map_mut
• x86 avx512fp16 intrinsics (excluding those that depend directly on the unstable f16 type)
• AArch64 NEON fp16 intrinsics (excluding those that depend directly on the unstable f16 type)
• f32::consts::EULER_GAMMA
• f64::consts::EULER_GAMMA
• f32::consts::GOLDEN_RATIO
• f64::consts::GOLDEN_RATIO

These previously stable APIs are now stable in const contexts:

• f32::mul_add
• f64::mul_add

Cargo

• Stabilize the config include key. The top-level include config key allows loading additional config files, enabling better organization, sharing, and management of Cargo configurations across projects and environments. docs #16284
• Stabilize the pubtime field in registry index. This records when a crate version was published and enables time-based dependency resolution in the future. Note that crates.io will gradually backfill existing packages when a new version is published. Not all crates have pubtime yet. #16369 #16372
• Cargo now parses TOML v1.1 for manifests and configuration files. Note that using these features in Cargo.toml will raise your development MSRV, but the published manifest remains compatible with older parsers. #16415
• Make CARGO_BIN_EXE_<crate> available at runtime

Compatibility Notes

• Forbid freely casting lifetime bounds of dyn-types
• Make closure capturing have consistent and correct behaviour around patterns Some finer details of how precise closure captures get affected by pattern matching have been changed. In some cases, this can cause a non-move closure that was previously capturing an entire variable by move, to now capture only part of that variable by move, and other parts by borrow. This can cause the borrow checker to complain where it previously didn’t, or cause Drop to run at a different point in time.
• Standard library macros are now imported via prelude, not via injected #[macro_use] This will raise an error if macros of the same name are glob imported. For example if a crate defines their own matches macro and then glob imports that, it’s now ambiguous whether the custom or standard library matches is meant and an explicit import of the name is required to resolve the ambiguity. One exception is core::panic and std::panic, if their import is ambiguous a new warning (ambiguous_panic_imports) is raised. This may raise a new warning (ambiguous_panic_imports) on #![no_std] code glob importing the std crate. Both core::panic! and std::panic! are then in scope and which is used is ambiguous.
• Don’t strip shebang in expression-context include!(…)s This can cause previously working includes to no longer compile if they included files which started with a shebang.
• Ambiguous glob reexports are now also visible cross-crate This unifies behavior between local and cross-crate errors on these exports, which may introduce new ambiguity errors.
• Don’t normalize where-clauses before checking well-formedness
• Introduce a future compatibility warning on codegen attributes on body-free trait methods These attributes currently have no effect in this position.
• On Windows std::time::SystemTime::checked_sub_duration will return None for times before the Windows epoch (1/1/1601)
• Lifetime identifiers such as 'a are now NFC normalized.
• Overhaul filename handling for cross-compiler consistency Any paths emitted by compiler now always respect the relative-ness of the paths and --remap-path-prefix given originally. One side-effect of this change is that paths emitted for local crates in Cargo (path dependencies and workspace members) are no longer absolute but relative when emitted as part of a diagnostic in a downstream crate.

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.

• Switch to annotate-snippets for error emission This should preserve mostly the same outputs in rustc error messages.

• Don’t try to recover keyword as non-keyword identifier, fixing an ICE that especially affected rustfmt.
• Fix clippy::panicking_unwrap false-positive on field access with implicit deref.
• Revert “Update wasm-related dependencies in CI”, fixing file descriptor leaks on the wasm32-wasip2 target.

Language

• Stabilize several s390x vector-related target features and the is_s390x_feature_detected! macro
• Stabilize declaration of C-style variadic functions for the system ABI
• Emit error when using some keyword as a cfg predicate
• Stabilize asm_cfg
• During const-evaluation, support copying pointers byte-by-byte
• LUB coercions now correctly handle function item types, and functions with differing safeties
• Allow const items that contain mutable references to static (which is very unsafe, but not always UB)
• Add warn-by-default const_item_interior_mutations lint to warn against calls which mutate interior mutable const items
• Add warn-by-default function_casts_as_integer lint

Compiler

• Stabilize -Cjump-tables=bool. The flag was previously called -Zno-jump-tables.

Platform Support

• Promote riscv64a23-unknown-linux-gnu to Tier 2 (without host tools)

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

Libraries

• Stop internally using specialization on the Copy trait as it is unsound in the presence of lifetime dependent Copy implementations. This may result in some performance regressions as some standard library APIs may now call Clone::clone instead of performing bitwise copies
• Allow the global allocator to use thread-local storage and std::thread::current()
• Make BTree::append not update existing keys when appending an entry which already exists
• Don’t require T: RefUnwindSafe for vec::IntoIter<T>: UnwindSafe

Stabilized APIs

• <[MaybeUninit<T>]>::assume_init_drop
• <[MaybeUninit<T>]>::assume_init_ref
• <[MaybeUninit<T>]>::assume_init_mut
• <[MaybeUninit<T>]>::write_copy_of_slice
• <[MaybeUninit<T>]>::write_clone_of_slice
• String::into_raw_parts
• Vec::into_raw_parts
• <iN>::unchecked_neg
• <iN>::unchecked_shl
• <iN>::unchecked_shr
• <uN>::unchecked_shl
• <uN>::unchecked_shr
• <[T]>::as_array
• <[T]>::as_mut_array
• <*const [T]>::as_array
• <*mut [T]>::as_mut_array
• VecDeque::pop_front_if
• VecDeque::pop_back_if
• Duration::from_nanos_u128
• char::MAX_LEN_UTF8
• char::MAX_LEN_UTF16
• std::fmt::from_fn
• std::fmt::FromFn

Cargo

• Enable CARGO_CFG_DEBUG_ASSERTIONS in build scripts based on profile
• In cargo tree, support long forms for --format variables
• Add --workspace to cargo clean

Rustdoc

• Remove #![doc(document_private_items)]
• Include attribute and derive macros in search filters for “macros”
• Include extern crates in search filters for import
• Validate usage of crate-level doc attributes. This means if any of html_favicon_url, html_logo_url, html_playground_url, issue_tracker_base_url, or html_no_source either has a missing value, an unexpected value, or a value of the wrong type, rustdoc will emit the deny-by-default lint rustdoc::invalid_doc_attributes.

Compatibility Notes

• Introduce pin_v2 into the builtin attributes namespace
• Update bundled musl to 1.2.5
• On Emscripten, the unwinding ABI used when compiling with panic=unwind was changed from the JS exception handling ABI to the wasm exception handling ABI. If linking C/C++ object files with Rust objects, -fwasm-exceptions must be passed to the linker now. On nightly Rust, it is possible to get the old behavior with -Zwasm-emscripten-eh=false -Zbuild-std, but it will be removed in a future release.
• The #[test] attribute, used to define tests, was previously ignored in various places where it had no meaning (e.g on trait methods or types). Putting the #[test] attribute in these places is no longer ignored, and will now result in an error; this may also result in errors when generating rustdoc. Error when test attribute is applied to structs
• Cargo now sets the CARGO_CFG_DEBUG_ASSERTIONS environment variable in more situations. This will cause crates depending on static-init versions 1.0.1 to 1.0.3 to fail compilation with “failed to resolve: use of unresolved module or unlinked crate parking_lot“. See the linked issue for details.
• User written types in the offset_of! macro are now checked to be well formed.
• cargo publish no longer emits .crate files as a final artifact for user access when the build.build-dir config is unset
• Upgrade the deref_nullptr lint from warn-by-default to deny-by-default
• Add future-incompatibility warning for ... function parameters without a pattern outside of extern blocks
• Introduce future-compatibility warning for repr(C) enums whose discriminant values do not fit into a c_int or c_uint
• Introduce future-compatibility warning against ignoring repr(C) types as part of repr(transparent)

Language

• Document MaybeUninit representation and validity

• Allow &raw [mut | const] for union field in safe code

• Prefer item bounds of associated types over where-bounds for auto-traits and Sized
• Do not materialize X in [X; 0] when X is unsizing a const
• Support combining #[track_caller] and #[no_mangle] (requires every declaration specifying #[track_caller] as well)
• Make never type lints never_type_fallback_flowing_into_unsafe and dependency_on_unit_never_type_fallback deny-by-default
• Allow specifying multiple bounds for same associated item, except in trait objects
• Slightly strengthen higher-ranked region handling in coherence
• The unused_must_use lint no longer warns on Result<(), Uninhabited> (for instance, Result<(), !>), or ControlFlow<Uninhabited, ()>. This avoids having to check for an error that can never happen.

Compiler

• Make mips64el-unknown-linux-muslabi64 link dynamically
• Remove current code for embedding command-line args in PDB Command-line information is typically not needed by debugging tools, and the removed code was causing problems for incremental builds even on targets that don’t use PDB debuginfo.

Libraries

• Specialize Iterator::eq{_by} for TrustedLen iterators
• Simplify Extend for tuples
• Added details to Debug for EncodeWide.
• iter::Repeat::last and count will now panic, rather than looping infinitely.

Stabilized APIs

• NonZero<u{N}>::div_ceil
• Location::file_as_c_str
• RwLockWriteGuard::downgrade
• Box::new_zeroed
• Box::new_zeroed_slice
• Rc::new_zeroed
• Rc::new_zeroed_slice
• Arc::new_zeroed
• Arc::new_zeroed_slice
• btree_map::Entry::insert_entry
• btree_map::VacantEntry::insert_entry
• impl Extend<proc_macro::Group> for proc_macro::TokenStream
• impl Extend<proc_macro::Literal> for proc_macro::TokenStream
• impl Extend<proc_macro::Punct> for proc_macro::TokenStream
• impl Extend<proc_macro::Ident> for proc_macro::TokenStream

These previously stable APIs are now stable in const contexts:

• <[_]>::rotate_left
• <[_]>::rotate_right

Cargo

• Added a new chapter to the Cargo book, “Optimizing Build Performance”.

Rustdoc

• If a trait item appears in rustdoc search, hide the corresponding impl items. Previously a search for “last” would show both Iterator::last as well as impl methods like std::vec::IntoIter::last. Now these impl methods will be hidden, freeing up space for inherent methods like BTreeSet::last.
• Relax rules for identifiers in search. Previously you could only search for identifiers that were valid in rust code, now searches only need to be valid as part of an identifier. For example, you can now perform a search that starts with a digit.

Compatibility Notes

• Fix backtraces with -C panic=abort on Linux by generating unwind tables by default. Build with -C force-unwind-tables=no to keep omitting unwind tables.

• As part of the larger effort refactoring compiler built-in attributes and their diagnostics, the future-compatibility lint invalid_macro_export_arguments is upgraded to deny-by-default and will be reported in dependencies too.
• Update the minimum external LLVM to 20
• Prevent downstream impl DerefMut for Pin<LocalType>
• Don’t apply temporary lifetime extension rules to the arguments of non-extended pin! and formatting macros

• Enable file locking support in illumos. This fixes Cargo not locking the build directory on illumos.
• Fix wasm_import_module attribute cross-crate. This fixes linker errors on WASM targets.

Language

• Lower pattern bindings in the order they’re written and base drop order on primary bindings’ order
• Stabilize declaration of C-style variadic functions for sysv64, win64, efiapi, and aapcs ABIs. This brings these ABIs in line with the C ABI: variadic functions can be declared in extern blocks but not defined.
• Add dangling_pointers_from_locals lint to warn against dangling pointers from local variables
• Upgrade semicolon_in_expressions_from_macros from warn to deny
• Stabilize LoongArch32 inline assembly
• Add warn-by-default integer_to_ptr_transmutes lint against integer-to-pointer transmutes
• Stabilize sse4a and tbm target features
• Add target_env = "macabi" and target_env = "sim" cfgs as replacements for the target_abi cfgs with the same values.

Compiler

• Don’t warn on never-to-any as casts as unreachable

Platform Support

• Promote aarch64-pc-windows-gnullvm and x86_64-pc-windows-gnullvm to Tier 2 with host tools. Note: llvm-tools and MSI installers are missing but will be added in future releases.
• Promote aarch64-pc-windows-msvc to Tier 1

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

Libraries

• Print thread ID in panic message
• Fix overly restrictive lifetime in core::panic::Location::file return type
• Guarantee parameter order for _by() variants of min / max/ minmax in std::cmp
• Document assumptions about Clone and Eq traits
• std::thread: Return error if setting thread stack size fails This used to panic within the standard library.

Stabilized APIs

• Path::file_prefix
• AtomicPtr::fetch_ptr_add
• AtomicPtr::fetch_ptr_sub
• AtomicPtr::fetch_byte_add
• AtomicPtr::fetch_byte_sub
• AtomicPtr::fetch_or
• AtomicPtr::fetch_and
• AtomicPtr::fetch_xor
• {integer}::strict_add
• {integer}::strict_sub
• {integer}::strict_mul
• {integer}::strict_div
• {integer}::strict_div_euclid
• {integer}::strict_rem
• {integer}::strict_rem_euclid
• {integer}::strict_neg
• {integer}::strict_shl
• {integer}::strict_shr
• {integer}::strict_pow
• i{N}::strict_add_unsigned
• i{N}::strict_sub_unsigned
• i{N}::strict_abs
• u{N}::strict_add_signed
• u{N}::strict_sub_signed
• PanicHookInfo::payload_as_str
• core::iter::chain
• u{N}::checked_signed_diff
• core::array::repeat
• PathBuf::add_extension
• PathBuf::with_added_extension
• Duration::from_mins
• Duration::from_hours
• impl PartialEq<str> for PathBuf
• impl PartialEq<String> for PathBuf
• impl PartialEq<str> for Path
• impl PartialEq<String> for Path
• impl PartialEq<PathBuf> for String
• impl PartialEq<Path> for String
• impl PartialEq<PathBuf> for str
• impl PartialEq<Path> for str
• Ipv4Addr::from_octets
• Ipv6Addr::from_octets
• Ipv6Addr::from_segments
• impl<T> Default for Pin<Box<T>> where Box<T>: Default, T: ?Sized
• impl<T> Default for Pin<Rc<T>> where Rc<T>: Default, T: ?Sized
• impl<T> Default for Pin<Arc<T>> where Arc<T>: Default, T: ?Sized
• Cell::as_array_of_cells
• u{N}::carrying_add
• u{N}::borrowing_sub
• u{N}::carrying_mul
• u{N}::carrying_mul_add
• BTreeMap::extract_if
• BTreeSet::extract_if
• impl Debug for windows::ffi::EncodeWide<'_>
• str::ceil_char_boundary
• str::floor_char_boundary
• impl Sum for Saturating<u{N}>
• impl Sum<&Self> for Saturating<u{N}>
• impl Product for Saturating<u{N}>
• impl Product<&Self> for Saturating<u{N}>

These previously stable APIs are now stable in const contexts:

• <[T; N]>::each_ref
• <[T; N]>::each_mut
• OsString::new
• PathBuf::new
• TypeId::of
• ptr::with_exposed_provenance
• ptr::with_exposed_provenance_mut

Cargo

• 🎉 Stabilize build.build-dir. This config sets the directory where intermediate build artifacts are stored. These artifacts are produced by Cargo and rustc during the build process. End users usually won’t need to interact with them, and the layout inside build-dir is an implementation detail that may change without notice. (config doc) (build cache doc) #15833 #15840
• The --target flag and the build.target configuration can now take literal "host-tuple" string, which will internally be substituted by the host machine’s target triple. #15838 #16003 #16032

Rustdoc

• In search results, rank doc aliases lower than non-alias items with the same name
• Raw pointers now work in type-based search like references. This means you can now search for things like *const u8 ->, and additionally functions that take or return raw pointers will now display their signature properly in search results.

Compatibility Notes

• Always require coroutine captures to be drop-live
• Apple: Always pass SDK root when linking with cc, and pass it via SDKROOT env var. This should fix linking issues with rustc running inside Xcode. Libraries in /usr/local/lib may no longer be linked automatically, if you develop or use a crate that relies on this, you should explicitly set cargo::rustc-link-search=/usr/local/lib in a build.rs script.
• Relaxed bounds in associated type bound position like in TraitRef<AssocTy: ?Sized> are now correctly forbidden
• Add unstable #[sanitize(xyz = "on|off")] built-in attribute that shadows procedural macros with the same name
• Fix the drop checker being more permissive for bindings declared with let-else
• Be more strict when parsing attributes, erroring on many invalid attributes
  • Error on invalid #[should_panic] attributes
  • Error on invalid #[link] attributes
• Mark all deprecation lints in name resolution as deny-by-default and also report in dependencies
• The lint semicolon_in_expressions_from_macros, for macro_rules! macros in expression position that expand to end in a semicolon (;), is now deny-by-default. It was already warn-by-default, and a future compatibility warning (FCW) that warned even in dependencies. This lint will become a hard error in the future.
• Trait impl modifiers (e.g., unsafe, !, default) in inherent impls are no longer syntactically valid
• Start reporting future breakage for ill_formed_attribute_input in dependencies
• Restrict the scope of temporaries created by the macros pin!, format_args!, write!, and writeln! in if let scrutinees in Rust Edition 2024. This applies Rust Edition 2024’s if let temporary scope rules to these temporaries, which previously could live past the if expression regardless of Edition.
• Invalid numeric literal suffixes in tuple indexing, tuple struct indexing, and struct field name positions are now correctly rejected
• Closures marked with the keyword static are now syntactically invalid
• Shebangs inside --cfg and --check-cfg arguments are no longer allowed
• Add future incompatibility lint for temporary lifetime shortening in Rust 1.92

Cargo compatibility notes:

• cargo publish no longer keeps .crate tarballs as final build artifacts when build.build-dir is set. These tarballs were previously included due to an oversight and are now treated as intermediate artifacts. To get .crate tarballs as final artifacts, use cargo package. In a future version, this change will apply regardless of build.build-dir. #15910
• Adjust Cargo messages to match rustc diagnostic style. This changes some of the terminal colors used by Cargo messages. #15928
• Tools and projects relying on the internal details of Cargo’s build-dir may not work for users changing their build-dir layout. For those doing so, we’d recommend proactively testing these cases particularly as we are considering changing the default location of the build-dir in the future (cargo#16147). If you can’t migrate off of Cargo’s internal details, we’d like to learn more about your use case as we prepare to change the layout of the build-dir (cargo#15010).

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 21

Language

• Split up the unknown_or_malformed_diagnostic_attributes lint. This lint has been split up into four finer-grained lints, with unknown_or_malformed_diagnostic_attributes now being the lint group that contains these lints:
  1. unknown_diagnostic_attributes: unknown to the current compiler
  2. misplaced_diagnostic_attributes: placed on the wrong item
  3. malformed_diagnostic_attributes: malformed attribute syntax or options
  4. malformed_diagnostic_format_literals: malformed format string literal
• Allow constants whose final value has references to mutable/external memory, but reject such constants as patterns
• Allow volatile access to non-Rust memory, including address 0

Compiler

• Use lld by default on x86_64-unknown-linux-gnu.
• Tier 3 musl targets now link dynamically by default. Affected targets:
  • mips64-unknown-linux-muslabi64
  • powerpc64-unknown-linux-musl
  • powerpc-unknown-linux-musl
  • powerpc-unknown-linux-muslspe
  • riscv32gc-unknown-linux-musl
  • s390x-unknown-linux-musl
  • thumbv7neon-unknown-linux-musleabihf

Platform Support

• Demote x86_64-apple-darwin to Tier 2 with host tools

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

Libraries

• Stabilize u*::{checked,overflowing,saturating,wrapping}_sub_signed
• Allow comparisons between CStr, CString, and Cow<CStr>
• Remove some unsized tuple impls since unsized tuples can’t be constructed
• Set MSG_NOSIGNAL for UnixStream
• proc_macro::Ident::new now supports $crate.
• Guarantee the pointer returned from Thread::into_raw has at least 8 bytes of alignment

Stabilized APIs

• u{n}::checked_sub_signed
• u{n}::overflowing_sub_signed
• u{n}::saturating_sub_signed
• u{n}::wrapping_sub_signed
• impl Copy for IntErrorKind
• impl Hash for IntErrorKind
• impl PartialEq<&CStr> for CStr
• impl PartialEq<CString> for CStr
• impl PartialEq<Cow<CStr>> for CStr
• impl PartialEq<&CStr> for CString
• impl PartialEq<CStr> for CString
• impl PartialEq<Cow<CStr>> for CString
• impl PartialEq<&CStr> for Cow<CStr>
• impl PartialEq<CStr> for Cow<CStr>
• impl PartialEq<CString> for Cow<CStr>

These previously stable APIs are now stable in const contexts:

• <[T]>::reverse
• f32::floor
• f32::ceil
• f32::trunc
• f32::fract
• f32::round
• f32::round_ties_even
• f64::floor
• f64::ceil
• f64::trunc
• f64::fract
• f64::round
• f64::round_ties_even

Cargo

• Add http.proxy-cainfo config for proxy certs
• Use gix for cargo package
• feat(publish): Stabilize multi-package publishing

Rustdoc

• Add ways to collapse all impl blocks. Previously the “Summary” button and “-“ keyboard shortcut would never collapse impl blocks, now they do when shift is held
• Display unsafe attributes with unsafe() wrappers

Compatibility Notes

• Use lld by default on x86_64-unknown-linux-gnu. See also https://blog.rust-lang.org/2025/09/01/rust-lld-on-1.90.0-stable/.
• Make core::iter::Fuse‘s Default impl construct I::default() internally as promised in the docs instead of always being empty
• Set MSG_NOSIGNAL for UnixStream This may change program behavior but results in the same behavior as other primitives (e.g., stdout, network sockets). Programs relying on signals to terminate them should update handling of sockets to handle errors on write by exiting.
• On Unix std::env::home_dir will use the fallback if the HOME environment variable is empty
• We now reject unsupported extern "{abi}"s consistently in all positions. This primarily affects the use of implementing traits on an extern "{abi}" function pointer, like extern "stdcall" fn(), on a platform that doesn’t support that, like aarch64-unknown-linux-gnu. Direct usage of these unsupported ABI strings by declaring or defining functions was already rejected, so this is only a change for consistency.
• const-eval: error when initializing a static writes to that static
• Check that the proc_macro_derive macro has correct arguments when applied to the crate root

Language

• Stabilize explicitly inferred const arguments (feature(generic_arg_infer))
• Add a warn-by-default mismatched_lifetime_syntaxes lint. This lint detects when the same lifetime is referred to by different syntax categories between function arguments and return values, which can be confusing to read, especially in unsafe code. This lint supersedes the warn-by-default elided_named_lifetimes lint.
• Expand unpredictable_function_pointer_comparisons to also lint on function pointer comparisons in external macros
• Make the dangerous_implicit_autorefs lint deny-by-default
• Stabilize the avx512 target features
• Stabilize kl and widekl target features for x86
• Stabilize sha512, sm3 and sm4 target features for x86
• Stabilize LoongArch target features f, d, frecipe, lasx, lbt, lsx, and lvz
• Remove i128 and u128 from improper_ctypes_definitions
• Stabilize repr128 (#[repr(u128)], #[repr(i128)])
• Allow #![doc(test(attr(..)))] everywhere
• Extend temporary lifetime extension to also go through tuple struct and tuple variant constructors
• extern "C" functions on the wasm32-unknown-unknown target now have a standards compliant ABI

Compiler

• Default to non-leaf frame pointers on aarch64-linux
• Enable non-leaf frame pointers for Arm64EC Windows
• Set Apple frame pointers by architecture

Platform Support

• Add new Tier-3 targets loongarch32-unknown-none and loongarch32-unknown-none-softfloat
• x86_64-apple-darwin is in the process of being demoted to Tier 2 with host tools

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

Libraries

• Specify the base path for file!
• Allow storing format_args!() in a variable
• Add #[must_use] to [T; N]::map
• Implement DerefMut for Lazy{Cell,Lock}
• Implement Default for array::IntoIter
• Implement Clone for slice::ChunkBy
• Implement io::Seek for io::Take

Stabilized APIs

• NonZero<char>
• Many intrinsics for x86, not enumerated here
  • AVX512 intrinsics
  • SHA512, SM3 and SM4 intrinsics
• File::lock
• File::lock_shared
• File::try_lock
• File::try_lock_shared
• File::unlock
• NonNull::from_ref
• NonNull::from_mut
• NonNull::without_provenance
• NonNull::with_exposed_provenance
• NonNull::expose_provenance
• OsString::leak
• PathBuf::leak
• Result::flatten
• std::os::linux::net::TcpStreamExt::quickack
• std::os::linux::net::TcpStreamExt::set_quickack

These previously stable APIs are now stable in const contexts:

• <[T; N]>::as_mut_slice
• <[u8]>::eq_ignore_ascii_case
• str::eq_ignore_ascii_case

Cargo

• cargo fix and cargo clippy --fix now default to the same Cargo target selection as other build commands. Previously it would apply to all targets (like binaries, examples, tests, etc.). The --edition flag still applies to all targets.
• Stabilize doctest-xcompile. Doctests are now tested when cross-compiling. Just like other tests, it will use the runner setting to run the tests. If you need to disable tests for a target, you can use the ignore doctest attribute to specify the targets to ignore.

Rustdoc

• On mobile, make the sidebar full width and linewrap. This makes long section and item names much easier to deal with on mobile.

Compatibility Notes

• Make missing_fragment_specifier an unconditional error
• Enabling the neon target feature on aarch64-unknown-none-softfloat causes a warning because mixing code with and without that target feature is not properly supported by LLVM
• Sized Hierarchy: Part I
  • Introduces a small breaking change affecting ?Sized bounds on impls on recursive types which contain associated type projections. It is not expected to affect any existing published crates. Can be fixed by refactoring the involved types or opting into the sized_hierarchy unstable feature. See the FCP report for a code example.
• The warn-by-default elided_named_lifetimes lint is superseded by the warn-by-default mismatched_lifetime_syntaxes lint.
• Error on recursive opaque types earlier in the type checker
• Type inference side effects from requiring element types of array repeat expressions are Copy are now only available at the end of type checking
• The deprecated accidentally-stable std::intrinsics::{copy,copy_nonoverlapping,write_bytes} are now proper intrinsics. There are no debug assertions guarding against UB, and they cannot be coerced to function pointers.
• Remove long-deprecated std::intrinsics::drop_in_place
• Make well-formedness predicates no longer coinductive
• Remove hack when checking impl method compatibility
• Remove unnecessary type inference due to built-in trait object impls
• Lint against “stdcall”, “fastcall”, and “cdecl” on non-x86-32 targets
• Future incompatibility warnings relating to the never type (!) are now reported in dependencies
• Ensure std::ptr::copy_* intrinsics also perform the static self-init checks
• extern "C" functions on the wasm32-unknown-unknown target now have a standards compliant ABI

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.

• Correctly un-remap compiler sources paths with the rustc-dev component

Language

• Stabilize #![feature(let_chains)] in the 2024 edition. This feature allows &&-chaining let statements inside if and while, allowing intermixture with boolean expressions. The patterns inside the let sub-expressions can be irrefutable or refutable.
• Stabilize #![feature(naked_functions)]. Naked functions allow writing functions with no compiler-generated epilogue and prologue, allowing full control over the generated assembly for a particular function.
• Stabilize #![feature(cfg_boolean_literals)]. This allows using boolean literals as cfg predicates, e.g. #[cfg(true)] and #[cfg(false)].
• Fully de-stabilize the #[bench] attribute. Usage of #[bench] without #![feature(custom_test_frameworks)] already triggered a deny-by-default future-incompatibility lint since Rust 1.77, but will now become a hard error.
• Add warn-by-default dangerous_implicit_autorefs lint against implicit autoref of raw pointer dereference. The lint will be bumped to deny-by-default in the next version of Rust.
• Add invalid_null_arguments lint to prevent invalid usage of null pointers. This lint is uplifted from clippy::invalid_null_ptr_usage.
• Change trait impl candidate preference for builtin impls and trivial where-clauses.
• Check types of generic const parameter defaults

Compiler

• Stabilize -Cdwarf-version for selecting the version of DWARF debug information to generate.

Platform Support

• Demote i686-pc-windows-gnu to Tier 2.

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

Libraries

• Remove backticks from #[should_panic] test failure message.
• Guarantee that [T; N]::from_fn is generated in order of increasing indices., for those passing it a stateful closure.
• The libtest flag --nocapture is deprecated in favor of the more consistent --no-capture flag.
• Guarantee that {float}::NAN is a quiet NaN.

Stabilized APIs

• Cell::update
• impl Default for *const T
• impl Default for *mut T
• HashMap::extract_if
• HashSet::extract_if
• hint::select_unpredictable
• proc_macro::Span::line
• proc_macro::Span::column
• proc_macro::Span::start
• proc_macro::Span::end
• proc_macro::Span::file
• proc_macro::Span::local_file
• <[T]>::as_chunks
• <[T]>::as_chunks_mut
• <[T]>::as_chunks_unchecked
• <[T]>::as_chunks_unchecked_mut
• <[T]>::as_rchunks
• <[T]>::as_rchunks_mut
• mod ffi::c_str

These previously stable APIs are now stable in const contexts:

• NonNull<T>::replace
• <*mut T>::replace
• std::ptr::swap_nonoverlapping
• Cell::replace
• Cell::get
• Cell::get_mut
• Cell::from_mut
• Cell::as_slice_of_cells

Cargo

• Stabilize automatic garbage collection.
• use zlib-rs for gzip compression in rust code

Rustdoc

• Doctests can be ignored based on target names using ignore-* attributes.
• Stabilize the --test-runtool and --test-runtool-arg CLI options to specify a program (like qemu) and its arguments to run a doctest.

Compatibility Notes

• Finish changing the internal representation of pasted tokens. Certain invalid declarative macros that were previously accepted in obscure circumstances are now correctly rejected by the compiler. Use of a tt fragment specifier can often fix these macros.
• Fully de-stabilize the #[bench] attribute. Usage of #[bench] without #![feature(custom_test_frameworks)] already triggered a deny-by-default future-incompatibility lint since Rust 1.77, but will now become a hard error.
• Fix borrow checking some always-true patterns. The borrow checker was overly permissive in some cases, allowing programs that shouldn’t have compiled.
• Update the minimum external LLVM to 19.
• Make it a hard error to use a vector type with a non-Rust ABI without enabling the required target feature.

Language

• Stabilize asm_goto feature
• Allow parsing open beginning ranges (..EXPR) after unary operators !, -, and *.
• Don’t require method impls for methods with Self: Sized bounds in impls for unsized types
• Stabilize feature(precise_capturing_in_traits) allowing use<...> bounds on return position impl Trait in traits

Compiler

• x86: make SSE2 required for i686 targets and use it to pass SIMD types

Platform Support

• Remove i586-pc-windows-msvc target

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

Libraries

• Stabilize the anonymous pipe API
• Add support for unbounded left/right shift operations
• Print pointer metadata in Debug impl of raw pointers
• Vec::with_capacity guarantees it allocates with the amount requested, even if Vec::capacity returns a different number.
• Most std::arch intrinsics which don’t take pointer arguments can now be called from safe code if the caller has the appropriate target features already enabled (https://github.com/rust-lang/stdarch/pull/1714, https://github.com/rust-lang/stdarch/pull/1716, https://github.com/rust-lang/stdarch/pull/1717)
• Undeprecate env::home_dir
• Denote ControlFlow as #[must_use]
• Macros such as assert_eq! and vec! now support const {...} expressions

Stabilized APIs

• Vec::extract_if
• vec::ExtractIf
• LinkedList::extract_if
• linked_list::ExtractIf
• <[T]>::split_off
• <[T]>::split_off_mut
• <[T]>::split_off_first
• <[T]>::split_off_first_mut
• <[T]>::split_off_last
• <[T]>::split_off_last_mut
• String::extend_from_within
• os_str::Display
• OsString::display
• OsStr::display
• io::pipe
• io::PipeReader
• io::PipeWriter
• impl From<PipeReader> for OwnedHandle
• impl From<PipeWriter> for OwnedHandle
• impl From<PipeReader> for Stdio
• impl From<PipeWriter> for Stdio
• impl From<PipeReader> for OwnedFd
• impl From<PipeWriter> for OwnedFd
• Box<MaybeUninit<T>>::write
• impl TryFrom<Vec<u8>> for String
• <*const T>::offset_from_unsigned
• <*const T>::byte_offset_from_unsigned
• <*mut T>::offset_from_unsigned
• <*mut T>::byte_offset_from_unsigned
• NonNull::offset_from_unsigned
• NonNull::byte_offset_from_unsigned
• <uN>::cast_signed
• NonZero::<uN>::cast_signed.
• <iN>::cast_unsigned.
• NonZero::<iN>::cast_unsigned.
• <uN>::is_multiple_of
• <uN>::unbounded_shl
• <uN>::unbounded_shr
• <iN>::unbounded_shl
• <iN>::unbounded_shr
• <iN>::midpoint
• <str>::from_utf8
• <str>::from_utf8_mut
• <str>::from_utf8_unchecked
• <str>::from_utf8_unchecked_mut

These previously stable APIs are now stable in const contexts:

• core::str::from_utf8_mut
• <[T]>::copy_from_slice
• SocketAddr::set_ip
• SocketAddr::set_port,
• SocketAddrV4::set_ip
• SocketAddrV4::set_port,
• SocketAddrV6::set_ip
• SocketAddrV6::set_port
• SocketAddrV6::set_flowinfo
• SocketAddrV6::set_scope_id
• char::is_digit
• char::is_whitespace
• <[[T; N]]>::as_flattened
• <[[T; N]]>::as_flattened_mut
• String::into_bytes
• String::as_str
• String::capacity
• String::as_bytes
• String::len
• String::is_empty
• String::as_mut_str
• String::as_mut_vec
• Vec::as_ptr
• Vec::as_slice
• Vec::capacity
• Vec::len
• Vec::is_empty
• Vec::as_mut_slice
• Vec::as_mut_ptr

Cargo

• Add terminal integration via ANSI OSC 9;4 sequences
• chore: bump openssl to v3
• feat(package): add –exclude-lockfile flag

Compatibility Notes

• Rust now raises an error for macro invocations inside the #![crate_name] attribute
• Unstable fields are now always considered to be inhabited
• Macro arguments of unary operators followed by open beginning ranges may now be matched differently
• Make Debug impl of raw pointers print metadata if present
• Warn against function pointers using unsupported ABI strings in dependencies
• Associated types on dyn types are no longer deduplicated
• Forbid attributes on .. inside of struct patterns (let Struct { #[attribute] .. }) =
• Make ptr_cast_add_auto_to_object lint into hard error
• Many std::arch intrinsics are now safe to call in some contexts, there may now be new unused_unsafe warnings in existing codebases.
• Limit width and precision formatting options to 16 bits on all targets
• Turn order dependent trait objects future incompat warning into a hard error
• Denote ControlFlow as #[must_use]
• Windows: The standard library no longer links advapi32, except on win7. Code such as C libraries that were relying on this assumption may need to explicitly link advapi32.
• Proc macros can no longer observe expanded cfg(true) attributes.
• Start changing the internal representation of pasted tokens. Certain invalid declarative macros that were previously accepted in obscure circumstances are now correctly rejected by the compiler. Use of a tt fragment specifier can often fix these macros.
• Don’t allow flattened format_args in const.

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 20

Language

• Stabilize upcasting trait objects to supertraits.
• Allow safe functions to be marked with the #[target_feature] attribute.
• The missing_abi lint now warns-by-default.
• Rust now lints about double negations, to catch cases that might have intended to be a prefix decrement operator (--x) as written in other languages. This was previously a clippy lint, clippy::double_neg, and is now available directly in Rust as double_negations.
• More pointers are now detected as definitely not-null based on their alignment in const eval.
• Empty repr() attribute applied to invalid items are now correctly rejected.
• Inner attributes #![test] and #![rustfmt::skip] are no longer accepted in more places than intended.

Compiler

• Debug-assert that raw pointers are non-null on access.
• Change -O to mean -C opt-level=3 instead of -C opt-level=2 to match Cargo’s defaults.
• Fix emission of overflowing_literals under certain macro environments.

Platform Support

• Replace i686-unknown-redox target with i586-unknown-redox.
• Increase baseline CPU of i686-unknown-hurd-gnu to Pentium 4.
• New tier 3 targets:
  • {aarch64-unknown,x86_64-pc}-nto-qnx710_iosock. For supporting Neutrino QNX 7.1 with io-socket network stack.
  • {aarch64-unknown,x86_64-pc}-nto-qnx800. For supporting Neutrino QNX 8.0 (no_std-only).
  • {x86_64,i686}-win7-windows-gnu. Intended for backwards compatibility with Windows 7. {x86_64,i686}-win7-windows-msvc are the Windows MSVC counterparts that already exist as Tier 3 targets.
  • amdgcn-amd-amdhsa.
  • x86_64-pc-cygwin.
  • {mips,mipsel}-mti-none-elf. Initial bare-metal support.
  • m68k-unknown-none-elf.
  • armv7a-nuttx-{eabi,eabihf}, aarch64-unknown-nuttx, and thumbv7a-nuttx-{eabi,eabihf}.

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

Libraries

• The type of FromBytesWithNulError in CStr::from_bytes_with_nul(bytes: &[u8]) -> Result<&Self, FromBytesWithNulError> was changed from an opaque struct to an enum, allowing users to examine why the conversion failed.
• Remove RustcDecodable and RustcEncodable.
• Deprecate libtest’s --logfile option.
• On recent versions of Windows, std::fs::remove_file will now remove read-only files.

Stabilized APIs

• {float}::next_down
• {float}::next_up
• <[_]>::get_disjoint_mut
• <[_]>::get_disjoint_unchecked_mut
• slice::GetDisjointMutError
• HashMap::get_disjoint_mut
• HashMap::get_disjoint_unchecked_mut
• NonZero::count_ones
• Vec::pop_if
• sync::Once::wait
• sync::Once::wait_force
• sync::OnceLock::wait

These APIs are now stable in const contexts:

• hint::black_box
• io::Cursor::get_mut
• io::Cursor::set_position
• str::is_char_boundary
• str::split_at
• str::split_at_checked
• str::split_at_mut
• str::split_at_mut_checked

Cargo

• When merging, replace rather than combine configuration keys that refer to a program path and its arguments.
• Error if both --package and --workspace are passed but the requested package is missing. This was previously silently ignored, which was considered a bug since missing packages should be reported.
• Deprecate the token argument in cargo login to avoid shell history leaks.
• Simplify the implementation of SourceID comparisons. This may potentially change behavior if the canonicalized URL compares differently in alternative registries.

Rustdoc

• Add a sans-serif font setting.

Compatibility Notes

• The wasm_c_abi future compatibility warning is now a hard error. Users of wasm-bindgen should upgrade to at least version 0.2.89, otherwise compilation will fail.
• Remove long-deprecated no-op attributes #![no_start] and #![crate_id].
• The future incompatibility lint cenum_impl_drop_cast has been made into a hard error. This means it is now an error to cast a field-less enum to an integer if the enum implements Drop.
• SSE2 is now required for “i686” 32-bit x86 hard-float targets; disabling it causes a warning that will become a hard error eventually. To compile for pre-SSE2 32-bit x86, use a “i586” target instead.

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.

• Build the rustc on AArch64 Linux with ThinLTO + PGO. The ARM 64-bit compiler (AArch64) on Linux is now optimized with ThinLTO and PGO, similar to the optimizations we have already performed for the x86-64 compiler on Linux. This should make it up to 30% faster.

• Fix the doctest-merging feature of the 2024 Edition.
• Relax some target_feature checks when generating docs.
• Fix errors in std::fs::rename on Windows 10, version 1607.
• Downgrade bootstrap cc to fix custom targets.
• Skip submodule updates when building Rust from a source tarball.

Language

• The 2024 Edition is now stable. See the edition guide for more details.
• Stabilize async closures See RFC 3668 for more details.
• Stabilize #[diagnostic::do_not_recommend]
• Add unpredictable_function_pointer_comparisons lint to warn against function pointer comparisons
• Lint on combining #[no_mangle] and #[export_name] attributes.

Compiler

• The unstable flag -Zpolymorphize has been removed, see https://github.com/rust-lang/compiler-team/issues/810 for some background.

Platform Support

• Promote powerpc64le-unknown-linux-musl to tier 2 with host tools

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

Libraries

• Panics in the standard library now have a leading library/ in their path

• std::env::home_dir() on Windows now ignores the non-standard $HOME environment variable

  It will be un-deprecated in a subsequent release.

• Add AsyncFn* to the prelude in all editions.

Stabilized APIs

• BuildHasherDefault::new
• ptr::fn_addr_eq
• io::ErrorKind::QuotaExceeded
• io::ErrorKind::CrossesDevices
• {float}::midpoint
• Unsigned {integer}::midpoint
• NonZeroU*::midpoint
• impl std::iter::Extend for tuples with arity 1 through 12,))
• FromIterator<(A, ...)> for tuples with arity 1 through 12,))
• std::task::Waker::noop

These APIs are now stable in const contexts:

• mem::size_of_val
• mem::align_of_val
• Layout::for_value
• Layout::align_to
• Layout::pad_to_align
• Layout::extend
• Layout::array
• std::mem::swap
• std::ptr::swap
• NonNull::new
• HashMap::with_hasher
• HashSet::with_hasher
• BuildHasherDefault::new
• <float>::recip
• <float>::to_degrees
• <float>::to_radians
• <float>::max
• <float>::min
• <float>::clamp
• <float>::abs
• <float>::signum
• <float>::copysign
• MaybeUninit::write

Cargo

• Add future-incompatibility warning against keywords in cfgs and add raw-idents
• Stabilize higher precedence trailing flags
• Pass CARGO_CFG_FEATURE to build scripts

Rustdoc

• Doc comment on impl blocks shows the first line, even when the impl block is collapsed

Compatibility Notes

• rustc no longer treats the test cfg as a well known check-cfg, instead it is up to the build systems and users of --check-cfg[^check-cfg] to set it as a well known cfg using --check-cfg=cfg(test).

  This is done to enable build systems like Cargo to set it conditionally, as not all source files are suitable for unit tests. Cargo (for now) unconditionally sets the test cfg as a well known cfg. [^check-cfg]: https://doc.rust-lang.org/nightly/rustc/check-cfg.html

• Disable potentially incorrect type inference if there are trivial and non-trivial where-clauses

• std::env::home_dir() has been deprecated for years, because it can give surprising results in some Windows configurations if the HOME environment variable is set (which is not the normal configuration on Windows). We had previously avoided changing its behavior, out of concern for compatibility with code depending on this non-standard configuration. Given how long this function has been deprecated, we’re now fixing its behavior as a bugfix. A subsequent release will remove the deprecation for this function.

• Make core::ffi::c_char signedness more closely match that of the platform-default char

  This changed c_char from an i8 to u8 or vice versa on many Tier 2 and 3 targets (mostly Arm and RISC-V embedded targets). The new definition may result in compilation failures but fixes compatibility issues with C.

  The libc crate matches this change as of its 0.2.169 release.

• When compiling a nested macro_rules macro from an external crate, the content of the inner macro_rules is now built with the edition of the external crate, not the local crate.

• Increase sparcv9-sun-solaris and x86_64-pc-solaris Solaris baseline to 11.4.

• Show abi_unsupported_vector_types lint in future breakage reports

• Error if multiple super-trait instantiations of dyn Trait need associated types to be specified but only one is provided

• Change powerpc64-ibm-aix default codemodel to large

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.

• Build x86_64-unknown-linux-gnu with LTO for C/C++ code (e.g., jemalloc)

• Fix ICE 132920 in duplicate-crate diagnostics.
• Fix errors for overlapping impls in incremental rebuilds.
• Fix slow compilation related to the next-generation trait solver.
• Fix debuginfo when LLVM’s location discriminator value limit is exceeded.
• Fixes for building Rust from source:
  • Only try to distribute llvm-objcopy if llvm tools are enabled.
  • Add Profile Override for Non-Git Sources.
  • Resolve symlinks of LLVM tool binaries before copying them.
  • Make it possible to use ci-rustc on tarball sources.

Language

• Allow #[deny] inside #[forbid] as a no-op
• Show a warning when -Ctarget-feature is used to toggle features that can lead to unsoundness due to ABI mismatches
• Use the next-generation trait solver in coherence
• Allow coercions to drop the principal of trait objects
• Support / as the path separator for include!() in all cases on Windows
• Taking a raw ref (raw (const|mut)) of a deref of a pointer (*ptr) is now safe
• Stabilize s390x inline assembly
• Stabilize Arm64EC inline assembly
• Lint against creating pointers to immediately dropped temporaries
• Execute drop glue when unwinding in an extern "C" function

Compiler

• Add --print host-tuple flag to print the host target tuple and affirm the “target tuple” terminology over “target triple”
• Declaring functions with a calling convention not supported on the current target now triggers a hard error
• Set up indirect access to external data for loongarch64-unknown-linux-{musl,ohos}
• Enable XRay instrumentation for LoongArch Linux targets
• Extend the unexpected_cfgs lint to also warn in external macros
• Stabilize WebAssembly multivalue, reference-types, and tail-call target features
• Added Tier 2 support for the wasm32v1-none target

Libraries

• Implement From<&mut {slice}> for Box/Rc/Arc<{slice}>
• Move <float>::copysign, <float>::abs, <float>::signum to core
• Add LowerExp and UpperExp implementations to NonZero
• Implement FromStr for CString and TryFrom<CString> for String
• std::os::darwin has been made public

Stabilized APIs

• Ipv6Addr::is_unique_local
• Ipv6Addr::is_unicast_link_local
• core::ptr::with_exposed_provenance
• core::ptr::with_exposed_provenance_mut
• <ptr>::addr
• <ptr>::expose_provenance
• <ptr>::with_addr
• <ptr>::map_addr
• <int>::isqrt
• <int>::checked_isqrt
• <uint>::isqrt
• NonZero::isqrt
• core::ptr::without_provenance
• core::ptr::without_provenance_mut
• core::ptr::dangling
• core::ptr::dangling_mut
• Pin::as_deref_mut

These APIs are now stable in const contexts

• AtomicBool::from_ptr
• AtomicPtr::from_ptr
• AtomicU8::from_ptr
• AtomicU16::from_ptr
• AtomicU32::from_ptr
• AtomicU64::from_ptr
• AtomicUsize::from_ptr
• AtomicI8::from_ptr
• AtomicI16::from_ptr
• AtomicI32::from_ptr
• AtomicI64::from_ptr
• AtomicIsize::from_ptr
• <ptr>::is_null
• <ptr>::as_ref
• <ptr>::as_mut
• Pin::new
• Pin::new_unchecked
• Pin::get_ref
• Pin::into_ref
• Pin::get_mut
• Pin::get_unchecked_mut
• Pin::static_ref
• Pin::static_mut

Cargo

• Stabilize MSRV-aware resolver config
• Stabilize resolver v3

Rustdoc

• rustdoc-search: improve type-driven search

Compatibility Notes

• Enable by default the LSX target feature for LoongArch Linux targets
• The unstable -Zprofile flag (“gcov-style” coverage instrumentation) has been removed. This does not affect the stable flags for coverage instrumentation (-Cinstrument-coverage) and profile-guided optimization (-Cprofile-generate, -Cprofile-use), which are unrelated and remain available.
• Support for the target named wasm32-wasi has been removed as the target is now named wasm32-wasip1. This completes the transition plan for this target following the introduction of wasm32-wasip1 in Rust 1.78. Compiler warnings on use of wasm32-wasi introduced in Rust 1.81 are now gone as well as the target is removed.
• The syntax &pin (mut|const) T is now parsed as a type which in theory could affect macro expansion results in some edge cases
• Legacy syntax for calling std::arch functions is no longer permitted to declare items or bodies (such as closures, inline consts, or async blocks).
• Declaring functions with a calling convention not supported on the current target now triggers a hard error
• The next-generation trait solver is now enabled for coherence, fixing multiple soundness issues

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 previously 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.

Language

• Don’t make statement nonterminals match pattern nonterminals
• Patterns matching empty types can now be omitted in common cases
• Enforce supertrait outlives obligations when using trait impls
• addr_of(_mut)! macros and the newly stabilized &raw (const|mut) are now safe to use with all static items
• size_of_val_raw: for length 0 this is safe to call
• Reorder trait bound modifiers after for<...> binder in trait bounds
• Stabilize + use<'lt> opaque type precise capturing (RFC 3617)
• Stabilize &raw const and &raw mut operators (RFC 2582)
• Stabilize unsafe extern blocks (RFC 3484)
• Stabilize nested field access in offset_of!
• Do not require T to be live when dropping [T; 0]
• Stabilize const operands in inline assembly
• Stabilize floating-point arithmetic in const fn
• Stabilize explicit opt-in to unsafe attributes
• Document NaN bit patterns guarantees

Compiler

• Promote riscv64gc-unknown-linux-musl to tier 2
• Promote Mac Catalyst targets aarch64-apple-ios-macabi and x86_64-apple-ios-macabi to Tier 2, and ship them with rustup
• Add tier 3 NuttX based targets for RISC-V and ARM
• Add tier 3 powerpc-unknown-linux-muslspe target
• Improved diagnostics to explain why a pattern is unreachable
• The compiler now triggers the unreachable code warning properly for async functions that don’t return/are -> !
• Promote aarch64-apple-darwin to Tier 1
• Add Trusty OS target aarch64-unknown-trusty and armv7-unknown-trusty as tier 3 targets
• Promote wasm32-wasip2 to Tier 2.

Libraries

• Generalize {Rc,Arc}::make_mut() to Path, OsStr, and CStr.

Stabilized APIs

• std::thread::Builder::spawn_unchecked
• std::str::CharIndices::offset
• std::option::Option::is_none_or
• [T]::is_sorted
• [T]::is_sorted_by
• [T]::is_sorted_by_key
• Iterator::is_sorted
• Iterator::is_sorted_by
• Iterator::is_sorted_by_key
• std::future::Ready::into_inner
• std::iter::repeat_n
• impl<T: Clone> DoubleEndedIterator for Take<Repeat<T>>
• impl<T: Clone> ExactSizeIterator for Take<Repeat<T>>
• impl<T: Clone> ExactSizeIterator for Take<RepeatWith<T>>
• impl Default for std::collections::binary_heap::Iter
• impl Default for std::collections::btree_map::RangeMut
• impl Default for std::collections::btree_map::ValuesMut
• impl Default for std::collections::vec_deque::Iter
• impl Default for std::collections::vec_deque::IterMut
• Rc<T>::new_uninit
• Rc<MaybeUninit<T>>::assume_init
• Rc<[T]>::new_uninit_slice
• Rc<[MaybeUninit<T>]>::assume_init
• Arc<T>::new_uninit
• Arc<MaybeUninit<T>>::assume_init
• Arc<[T]>::new_uninit_slice
• Arc<[MaybeUninit<T>]>::assume_init
• Box<T>::new_uninit
• Box<MaybeUninit<T>>::assume_init
• Box<[T]>::new_uninit_slice
• Box<[MaybeUninit<T>]>::assume_init
• core::arch::x86_64::_bextri_u64
• core::arch::x86_64::_bextri_u32
• core::arch::x86::_mm_broadcastsi128_si256
• core::arch::x86::_mm256_stream_load_si256
• core::arch::x86::_tzcnt_u16
• core::arch::x86::_mm_extracti_si64
• core::arch::x86::_mm_inserti_si64
• core::arch::x86::_mm_storeu_si16
• core::arch::x86::_mm_storeu_si32
• core::arch::x86::_mm_storeu_si64
• core::arch::x86::_mm_loadu_si16
• core::arch::x86::_mm_loadu_si32
• core::arch::wasm32::u8x16_relaxed_swizzle
• core::arch::wasm32::i8x16_relaxed_swizzle
• core::arch::wasm32::i32x4_relaxed_trunc_f32x4
• core::arch::wasm32::u32x4_relaxed_trunc_f32x4
• core::arch::wasm32::i32x4_relaxed_trunc_f64x2_zero
• core::arch::wasm32::u32x4_relaxed_trunc_f64x2_zero
• core::arch::wasm32::f32x4_relaxed_madd
• core::arch::wasm32::f32x4_relaxed_nmadd
• core::arch::wasm32::f64x2_relaxed_madd
• core::arch::wasm32::f64x2_relaxed_nmadd
• core::arch::wasm32::i8x16_relaxed_laneselect
• core::arch::wasm32::u8x16_relaxed_laneselect
• core::arch::wasm32::i16x8_relaxed_laneselect
• core::arch::wasm32::u16x8_relaxed_laneselect
• core::arch::wasm32::i32x4_relaxed_laneselect
• core::arch::wasm32::u32x4_relaxed_laneselect
• core::arch::wasm32::i64x2_relaxed_laneselect
• core::arch::wasm32::u64x2_relaxed_laneselect
• core::arch::wasm32::f32x4_relaxed_min
• core::arch::wasm32::f32x4_relaxed_max
• core::arch::wasm32::f64x2_relaxed_min
• core::arch::wasm32::f64x2_relaxed_max
• core::arch::wasm32::i16x8_relaxed_q15mulr
• core::arch::wasm32::u16x8_relaxed_q15mulr
• core::arch::wasm32::i16x8_relaxed_dot_i8x16_i7x16
• core::arch::wasm32::u16x8_relaxed_dot_i8x16_i7x16
• core::arch::wasm32::i32x4_relaxed_dot_i8x16_i7x16_add
• core::arch::wasm32::u32x4_relaxed_dot_i8x16_i7x16_add

These APIs are now stable in const contexts:

• std::task::Waker::from_raw
• std::task::Context::from_waker
• std::task::Context::waker
• {integer}::from_str_radix
• std::num::ParseIntError::kind

Cargo

• feat: Add info cargo subcommand

Compatibility Notes

• We now disallow setting some built-in cfgs via the command-line with the newly added explicit_builtin_cfgs_in_flags lint in order to prevent incoherent state, eg. windows cfg active but target is Linux based. The appropriate rustc flag should be used instead.
• The standard library has a new implementation of binary_search which significantly improves performance (#128254). However when a sorted slice has multiple values which compare equal, the new implementation may select a different value among the equal ones than the old implementation.
• illumos/Solaris now sets MSG_NOSIGNAL when writing to sockets. This avoids killing the process with SIGPIPE when writing to a closed socket, which matches the existing behavior on other UNIX targets.
• Removes a problematic hack that always passed the –whole-archive linker flag for tests, which may cause linker errors for code accidentally relying on it.
• The WebAssembly target features multivalue and reference-types are now both enabled by default. These two features both have subtle changes implied for generated WebAssembly binaries. For the multivalue feature, WebAssembly target support has changed when upgrading to LLVM 19. Support for generating functions with multiple returns no longer works and -Ctarget-feature=+multivalue has a different meaning than it did in LLVM 18 and prior. There is no longer any supported means to generate a module that has a function with multiple returns in WebAssembly from Rust source code. For the reference-types feature the encoding of immediates in the call_indirect, a commonly used instruction by the WebAssembly backend, has changed. Validators and parsers which don’t understand the reference-types proposal will no longer accept modules produced by LLVM due to this change in encoding of immediates. Additionally these features being enabled are encoded in the target_features custom section and may affect downstream tooling such as wasm-opt consuming the module. Generating a WebAssembly module that disables default features requires -Zbuild-std support from Cargo and more information can be found at rust-lang/rust#128511.
• Rust now raises unsafety errors for union patterns in parameter-position

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 19

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.
• Fix Command‘s batch files argument escaping not working when file name has trailing whitespace or periods (CVE-2024-43402).

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.

• Fix miscompilation in the jump threading MIR optimization when comparing floats
• Revert changes to the dead_code lint from 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 --precise <yanked>
• Don’t change file permissions on Cargo.toml when using cargo add
• Support using cargo fix on IPv6-only networks

Rustdoc

• Allow searching for references
• Stabilize custom_code_classes_in_docs feature
• fix: In cross-crate scenarios show enum variants on type aliases of enums

Compatibility Notes

• rustfmt estimates line lengths differently when using non-ascii characters
• Type aliases are now handled correctly in orphan check
• Allow instructing rustdoc to read from stdin via -
• std::env::{set_var, remove_var} can no longer be converted to safe function pointers and no longer implement the Fn family of traits
• Warn (or error) when Self constructor from outer item is referenced in inner nested item
• Turn indirect_structural_match and pointer_structural_match lints into hard errors
• Make where_clause_object_safety lint a regular object safety violation
• Turn proc_macro_back_compat lint into a hard error.
• Detect unused structs even when implementing private traits
• std::sync::ReentrantLockGuard<T> is no longer Sync if T: !Sync which means std::io::StdoutLock and std::io::StderrLock are no longer Sync
• Type inference will fail in some cases due to new implementations of FromIterator for Box<str>. Notably, this breaks versions of the time crate before 0.3.35, due to no longer inferring the implementation for Box<[_]>.

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.

• Misc improvements to size of generated html by rustdoc e.g. #124738 and #123734
• MSVC targets no longer depend on libc

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

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

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

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

• 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

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 compatibility 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.

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

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.

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

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.

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.

• 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

• 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

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.

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]D) (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.

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

Language

• Deriving built-in traits on packed structs works with Copy fields.
• Stabilize the cmpxchg16b target feature on x86 and x86_64.
• Improve analysis of trait bounds for associated types.
• Allow associated types to be used as union fields.
• Allow Self: Autotrait bounds on dyn-safe trait methods.
• Treat str as containing [u8] for auto trait purposes.

Compiler

• Upgrade *-pc-windows-gnu on CI to mingw-w64 v10 and GCC 12.2.
• Rework min_choice algorithm of member constraints.
• Support true and false as boolean flags in compiler arguments.
• Default repr(C) enums to c_int size.

Libraries

• Implement the unstable DispatchFromDyn for cell types, allowing downstream experimentation with custom method receivers.
• Document that fmt::Arguments::as_str() may return Some(_) in more cases after optimization, subject to change.
• Implement AsFd and AsRawFd for Rc.

Stabilized APIs

• CStr::from_bytes_until_nul
• core::ffi::FromBytesUntilNulError

These APIs are now stable in const contexts:

• SocketAddr::new
• SocketAddr::ip
• SocketAddr::port
• SocketAddr::is_ipv4
• SocketAddr::is_ipv6
• SocketAddrV4::new
• SocketAddrV4::ip
• SocketAddrV4::port
• SocketAddrV6::new
• SocketAddrV6::ip
• SocketAddrV6::port
• SocketAddrV6::flowinfo
• SocketAddrV6::scope_id

Cargo

• Cargo now suggests cargo fix or cargo clippy --fix when compilation warnings are auto-fixable.
• Cargo now suggests cargo add if you try to install a library crate.
• Cargo now sets the CARGO_BIN_NAME environment variable also for binary examples.

Rustdoc

• Vertically compact trait bound formatting.
• Only include stable lints in rustdoc::all group.
• Compute maximum Levenshtein distance based on the query.
• Remove inconsistently-present sidebar tooltips.
• Search by macro when query ends with !.

Compatibility Notes

• The rust-analysis component from rustup now only contains a warning placeholder. This was primarily intended for RLS, and the corresponding -Zsave-analysis flag has been removed from the compiler as well.
• Unaligned references to packed fields are now a hard error. This has been a warning since 1.53, and denied by default with a future-compatibility warning since 1.62.
• Update the minimum external LLVM to 14.
• Cargo now emits errors on invalid characters in a registry token.
• When default-features is set to false of a workspace dependency, and an inherited dependency of a member has default-features = true, Cargo will enable default features of that dependency.
• Cargo denies CARGO_HOME in the [env] configuration table. Cargo itself doesn’t pick up this value, but recursive calls to cargo would, which was not intended.
• Debuginfo for build dependencies is now off if not explicitly set. This is expected to improve the overall build time.
• The Rust distribution no longer always includes rustdoc If tools = [...] is set in bootstrap.toml, we will respect a missing rustdoc in that list. By default rustdoc remains included. To retain the prior behavior explicitly add "rustdoc" to the list.

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.

• Move format_args!() into AST (and expand it during AST lowering)

• Update the GitHub RSA host key bundled within Cargo. The key was rotated by GitHub on 2023-03-24 after the old one leaked.
• Mark the old GitHub RSA host key as revoked. This will prevent Cargo from accepting the leaked key even when trusted by the system.
• Add support for @revoked and a better error message for @cert-authority in Cargo’s SSH host key verification

• Fix miscompilation in produced Windows MSVC artifacts This was introduced by enabling ThinLTO for the distributed rustc which led to miscompilations in the resulting binary. Currently this is believed to be limited to the -Zdylib-lto flag used for rustc compilation, rather than a general bug in ThinLTO, so only rustc artifacts should be affected.
• Fix –enable-local-rust builds
• Treat $prefix-clang as clang in linker detection code
• Fix panic in compiler code

Language

• Stabilize default_alloc_error_handler This allows usage of alloc on stable without requiring the definition of a handler for allocation failure. Defining custom handlers is still unstable.
• Stabilize efiapi calling convention.
• Remove implicit promotion for types with drop glue

Compiler

• Change bindings_with_variant_name to deny-by-default
• Allow .. to be parsed as let initializer
• Add armv7-sony-vita-newlibeabihf as a tier 3 target
• Always check alignment during compile-time const evaluation
• Disable “split dwarf inlining” by default.
• Add vendor to Fuchsia’s target triple
• Enable sanitizers for s390x-linux

Libraries

• Loosen the bound on the Debug implementation of Weak.
• Make std::task::Context !Send and !Sync
• PhantomData layout guarantees
• Don’t derive Debug for OnceWith & RepeatWith
• Implement DerefMut for PathBuf
• Add O(1) Vec -> VecDeque conversion guarantee
• Leak amplification for peek_mut() to ensure BinaryHeap’s invariant is always met

Stabilized APIs

• {core,std}::pin::pin!
• impl From<bool> for {f32,f64}
• std::path::MAIN_SEPARATOR_STR
• impl DerefMut for PathBuf

These APIs are now stable in const contexts:

• VecDeque::new

Cargo

• Stabilize sparse registry support for crates.io
• cargo build --verbose tells you more about why it recompiles.
• Show progress of crates.io index update even net.git-fetch-with-cli option enabled

Misc

Compatibility Notes

• Only support Android NDK 25 or newer
• Add SEMICOLON_IN_EXPRESSIONS_FROM_MACROS to future-incompat report
• Only specify --target by default for -Zgcc-ld=lld on wasm
• Bump IMPLIED_BOUNDS_ENTAILMENT to Deny + ReportNow
• std::task::Context no longer implements Send and Sync

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.

• Encode spans relative to the enclosing item
• Don’t normalize in AstConv
• Find the right lower bound region in the scenario of partial order relations
• Fix impl block in const expr
• Check ADT fields for copy implementations considering regions
• rustdoc: simplify JS search routine by not messing with lev distance
• Enable ThinLTO for rustc on x86_64-pc-windows-msvc
• Enable ThinLTO for rustc on x86_64-apple-darwin

• Fix interoperability with thin archives.
• Fix an internal error in the compiler build process.
• Downgrade clippy::uninlined_format_args to pedantic.

Language

• Make Sized predicates coinductive, allowing cycles.
• #[must_use] annotations on async fn also affect the Future::Output.
• Elaborate supertrait obligations when deducing closure signatures.
• Invalid literals are no longer an error under cfg(FALSE).
• Unreserve braced enum variants in value namespace.

Compiler

• Enable varargs support for calling conventions other than C or cdecl.
• Add new MIR constant propagation based on dataflow analysis.
• Optimize field ordering by grouping m*2^n-sized fields with equivalently aligned ones.
• Stabilize native library modifier verbatim.

Added, updated, and removed targets:

• Add a tier 3 target for PowerPC on AIX, powerpc64-ibm-aix.
• Add a tier 3 target for the Sony PlayStation 1, mipsel-sony-psx.
• Add tier 3 no_std targets for the QNX Neutrino RTOS, aarch64-unknown-nto-qnx710 and x86_64-pc-nto-qnx710.
• Promote UEFI targets to tier 2, aarch64-unknown-uefi, i686-unknown-uefi, and x86_64-unknown-uefi.
• Remove tier 3 linuxkernel targets (not used by the actual kernel).

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

Libraries

• Merge crossbeam-channel into std::sync::mpsc.
• Fix inconsistent rounding of 0.5 when formatted to 0 decimal places.
• Derive Eq and Hash for ControlFlow.
• Don’t build compiler_builtins with -C panic=abort.

Stabilized APIs

• {integer}::checked_ilog
• {integer}::checked_ilog2
• {integer}::checked_ilog10
• {integer}::ilog
• {integer}::ilog2
• {integer}::ilog10
• NonZeroU*::ilog2
• NonZeroU*::ilog10
• NonZero*::BITS

These APIs are now stable in const contexts:

• char::from_u32
• char::from_digit
• char::to_digit
• core::char::from_u32
• core::char::from_digit

Compatibility Notes

• The layout of repr(Rust) types now groups m*2^n-sized fields with equivalently aligned ones. This is intended to be an optimization, but it is also known to increase type sizes in a few cases for the placement of enum tags. As a reminder, the layout of repr(Rust) types is an implementation detail, subject to change.
• 0.5 now rounds to 0 when formatted to 0 decimal places. This makes it consistent with the rest of floating point formatting that rounds ties toward even digits.
• Chains of && and || will now drop temporaries from their sub-expressions in evaluation order, left-to-right. Previously, it was “twisted” such that the first expression dropped its temporaries last, after all of the other expressions dropped in order.
• Underscore suffixes on string literals are now a hard error. This has been a future-compatibility warning since 1.20.0.
• Stop passing -export-dynamic to wasm-ld.
• main is now mangled as __main_void on wasm32-wasi.
• Cargo now emits an error if there are multiple registries in the configuration with the same index URL.

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.

• Rewrite LLVM’s archive writer in Rust.

• Added validation of SSH host keys for git URLs in Cargo (CVE-2022-46176)

Language

• Permit specifying explicit discriminants on all repr(Int) enums

  #[repr(u8)]
  enum Foo {
      A(u8) = 0,
      B(i8) = 1,
      C(bool) = 42,
  }

• Allow transmutes between the same type differing only in lifetimes
• Change constant evaluation errors from a deny-by-default lint to a hard error
• Trigger must_use on impl Trait for supertraits This makes impl ExactSizeIterator respect the existing #[must_use] annotation on Iterator.
• Allow ..=X in patterns
• Uplift clippy::for_loops_over_fallibles lint into rustc
• Stabilize sym operands in inline assembly
• Update to Unicode 15
• Opaque types no longer imply lifetime bounds This is a soundness fix which may break code that was erroneously relying on this behavior.

Compiler

• Add armv5te-none-eabi and thumbv5te-none-eabi tier 3 targets
  • Refer to Rust’s platform support page for more information on Rust’s tiered platform support.
• Add support for linking against macOS universal libraries

Libraries

• Fix #[derive(Default)] on a generic #[default] enum adding unnecessary Default bounds
• Update to Unicode 15

Stabilized APIs

• proc_macro::Span::source_text
• uX::{checked_add_signed, overflowing_add_signed, saturating_add_signed, wrapping_add_signed}
• iX::{checked_add_unsigned, overflowing_add_unsigned, saturating_add_unsigned, wrapping_add_unsigned}
• iX::{checked_sub_unsigned, overflowing_sub_unsigned, saturating_sub_unsigned, wrapping_sub_unsigned}
• BTreeSet::{first, last, pop_first, pop_last}
• BTreeMap::{first_key_value, last_key_value, first_entry, last_entry, pop_first, pop_last}
• Add AsFd implementations for stdio lock types on WASI.
• impl TryFrom<Vec<T>> for Box<[T; N]>
• core::hint::black_box
• Duration::try_from_secs_{f32,f64}
• Option::unzip
• std::os::fd

Rustdoc

• Add Rustdoc warning for invalid HTML tags in the documentation

Cargo

• Added cargo remove to remove dependencies from Cargo.toml
• cargo publish now waits for the new version to be downloadable before exiting

See detailed release notes for more.

Compatibility Notes

• Only apply ProceduralMasquerade hack to older versions of rental
• Don’t export __heap_base and __data_end on wasm32-wasi.
• Don’t export __wasm_init_memory on WebAssembly.
• Only export __tls_* on wasm32-unknown-unknown.
• Don’t link to libresolv in libstd on Darwin
• Update libstd’s libc to 0.2.135 (to make libstd no longer pull in libiconv.dylib on Darwin)
• Opaque types no longer imply lifetime bounds This is a soundness fix which may break code that was erroneously relying on this behavior.
• Make order_dependent_trait_objects show up in future-breakage reports
• Change std::process::Command spawning to default to inheriting the parent’s signal mask

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.

• Enable BOLT for LLVM compilation
• Enable LTO for rustc_driver.so

Language

• Error on as casts of enums with #[non_exhaustive] variants
• Stabilize let else
• Stabilize generic associated types (GATs)
• Add lints let_underscore_drop and let_underscore_lock from Clippy
• Stabilize breaking from arbitrary labeled blocks (“label-break-value”)
• Uninitialized integers, floats, and raw pointers are now considered immediate UB. Usage of MaybeUninit is the correct way to work with uninitialized memory.
• Stabilize raw-dylib for Windows x86_64, aarch64, and thumbv7a
• Do not allow Drop impl on foreign ADTs

Compiler

• Stabilize -Csplit-debuginfo on Linux
• Use niche-filling optimization even when multiple variants have data
• Associated type projections are now verified to be well-formed prior to resolving the underlying type
• Stringify non-shorthand visibility correctly
• Normalize struct field types when unsizing
• Update to LLVM 15
• Fix aarch64 call abi to correctly zeroext when needed
• debuginfo: Generalize C++-like encoding for enums
• Add special_module_name lint
• Add support for generating unique profraw files by default when using -C instrument-coverage
• Allow dynamic linking for iOS/tvOS targets

New targets:

• Add armv4t-none-eabi as a tier 3 target
• Add powerpc64-unknown-openbsd and riscv64-unknown-openbsd as tier 3 targets
  • Refer to Rust’s platform support page for more information on Rust’s tiered platform support.

Libraries

• Don’t generate PartialEq::ne in derive(PartialEq)
• Windows RNG: Use BCRYPT_RNG_ALG_HANDLE by default
• Forbid mixing System with direct system allocator calls
• Document no support for writing to non-blocking stdio/stderr
• std::layout::Layout size must not overflow isize::MAX when rounded up to align This also changes the safety conditions on Layout::from_size_align_unchecked.

Stabilized APIs

• std::backtrace::Backtrace
• Bound::as_ref
• std::io::read_to_string
• <*const T>::cast_mut
• <*mut T>::cast_const

These APIs are now stable in const contexts:

• <*const T>::offset_from
• <*mut T>::offset_from

Cargo

• Apply GitHub fast path even for partial hashes
• Do not add home bin path to PATH if it’s already there
• Take priority into account within the pending queue. This slightly optimizes job scheduling by Cargo, with typically small improvements on larger crate graph builds.

Compatibility Notes

• std::layout::Layout size must not overflow isize::MAX when rounded up to align. This also changes the safety conditions on Layout::from_size_align_unchecked.
• PollFn now only implements Unpin if the closure is Unpin. This is a possible breaking change if users were relying on the blanket unpin implementation. See discussion on the PR for details of why this change was made.
• Drop ExactSizeIterator impl from std::char::EscapeAscii This is a backwards-incompatible change to the standard library’s surface area, but is unlikely to affect real world usage.
• Do not consider a single repeated lifetime eligible for elision in the return type This behavior was unintentionally changed in 1.64.0, and this release reverts that change by making this an error again.
• Reenable disabled early syntax gates as future-incompatibility lints
• Update the minimum external LLVM to 13
• Don’t duplicate file descriptors into stdio fds
• Sunset RLS
• Deny usage of #![cfg_attr(..., crate_type = ...)] to set the crate type This strengthens the forward compatibility lint deprecated_cfg_attr_crate_type_name to deny.
• llvm-has-rust-patches allows setting the build system to treat the LLVM as having Rust-specific patches This option may need to be set for distributions that are building Rust with a patched LLVM via llvm-config, not the built-in LLVM.
• Combining three or more languages (e.g. Objective C, C++ and Rust) into one binary may hit linker limitations when using lld. For more information, see issue 102754.

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 x.sh and x.ps1 shell scripts
• compiletest: use target cfg instead of hard-coded tables
• Use object instead of LLVM for reading bitcode from rlibs
• Enable MIR inlining for optimized compilations This provides a 3-10% improvement in compiletimes for real world crates. See perf results.

Language

• Unions with mutable references or tuples of allowed types are now allowed
• It is now considered valid to deallocate memory pointed to by a shared reference &T if every byte in T is inside an UnsafeCell
• Unused tuple struct fields are now warned against in an allow-by-default lint, unused_tuple_struct_fields, similar to the existing warning for unused struct fields. This lint will become warn-by-default in the future.