Rust 1.25.0

Language

• The #[repr(align(x))] attribute is now stable. RFC 1358
• You can now use nested groups of imports. e.g. use std::{fs::File, io::Read, path::{Path, PathBuf}};
• You can now have | at the start of a match arm. e.g.

enum Foo { A, B, C }

fn main() {
    let x = Foo::A;
    match x {
        | Foo::A
        | Foo::B => println!("AB"),
        | Foo::C => println!("C"),
    }
}

Compiler

• Upgraded to LLVM 6.
• Added -C lto=val option.
• Added i586-unknown-linux-musl target

Libraries

• Impl Send for process::Command on Unix.
• Impl PartialEq and Eq for ParseCharError.
• UnsafeCell::into_inner is now safe.
• Implement libstd for CloudABI.
• Float::{from_bits, to_bits} is now available in libcore.
• Implement AsRef<Path> for Component
• Implemented Write for Cursor<&mut Vec<u8>>
• Moved Duration to libcore.

Stabilized APIs

• Location::column
• ptr::NonNull

The following functions can now be used in a constant expression. eg. static MINUTE: Duration = Duration::from_secs(60);

• Duration::new
• Duration::from_secs
• Duration::from_millis

Cargo

• cargo new no longer removes rust or rs prefixes/suffixes.
• cargo new now defaults to creating a binary crate, instead of a library crate.

Misc

• Rust by example is now shipped with new releases

Compatibility Notes

• Deprecated net::lookup_host.
• rustdoc has switched to pulldown as the default markdown renderer.
• The borrow checker was sometimes incorrectly permitting overlapping borrows around indexing operations (see #47349). This has been fixed (which also enabled some correct code that used to cause errors (e.g. #33903 and #46095).
• Removed deprecated unstable attribute #[simd].

Rust 1.24.1

• Do not abort when unwinding through FFI
• Emit UTF-16 files for linker arguments on Windows
• Make the error index generator work again
• Cargo will warn on Windows 7 if an update is needed.

Rust 1.24.0

Language

• External sysv64 ffi is now available. eg. extern "sysv64" fn foo () {}

Compiler

• rustc now uses 16 codegen units by default for release builds. For the fastest builds, utilize codegen-units=1.
• Added armv4t-unknown-linux-gnueabi target.
• Add aarch64-unknown-openbsd support

Libraries

• str::find::<char> now uses memchr. This should lead to a 10x improvement in performance in the majority of cases.
• OsStr's Debug implementation is now lossless and consistent with Windows.
• time::{SystemTime, Instant} now implement Hash.
• impl From<bool> for AtomicBool
• impl From<{CString, &CStr}> for {Arc<CStr>, Rc<CStr>}
• impl From<{OsString, &OsStr}> for {Arc<OsStr>, Rc<OsStr>}
• impl From<{PathBuf, &Path}> for {Arc<Path>, Rc<Path>}
• float::from_bits now just uses transmute. This provides some optimisations from LLVM.
• Copied AsciiExt methods onto char
• Remove T: Sized requirement on ptr::is_null()
• impl From<RecvError> for {TryRecvError, RecvTimeoutError}
• Optimised f32::{min, max} to generate more efficient x86 assembly
• [u8]::contains now uses memchr which provides a 3x speed improvement

Stabilized APIs

• RefCell::replace
• RefCell::swap
• atomic::spin_loop_hint

The following functions can now be used in a constant expression. eg. let buffer: [u8; size_of::<usize>()];, static COUNTER: AtomicUsize = AtomicUsize::new(1);

• AtomicBool::new
• AtomicUsize::new
• AtomicIsize::new
• AtomicPtr::new
• Cell::new
• {integer}::min_value
• {integer}::max_value
• mem::size_of
• mem::align_of
• ptr::null
• ptr::null_mut
• RefCell::new
• UnsafeCell::new

Cargo

• Added a workspace.default-members config that overrides implied --all in virtual workspaces.
• Enable incremental by default on development builds. Also added configuration keys to Cargo.toml and .cargo/config to disable on a per-project or global basis respectively.

Misc

Compatibility Notes

• Floating point types Debug impl now always prints a decimal point.
• Ipv6Addr now rejects superfluous ::'s in IPv6 addresses This is in accordance with IETF RFC 4291 §2.2.
• Unwinding will no longer go past FFI boundaries, and will instead abort.
• Formatter::flags method is now deprecated. The sign_plus, sign_minus, alternate, and sign_aware_zero_pad should be used instead.
• Leading zeros in tuple struct members is now an error
• column!() macro is one-based instead of zero-based
• fmt::Arguments can no longer be shared across threads
• Access to #[repr(packed)] struct fields is now unsafe
• Cargo sets a different working directory for the compiler

Rust 1.23.0

Language

• Arbitrary auto traits are now permitted in trait objects.
• rustc now uses subtyping on the left hand side of binary operations. Which should fix some confusing errors in some operations.

Compiler

• Enabled TrapUnreachable in LLVM which should mitigate the impact of undefined behavior.
• rustc now suggests renaming import if names clash.
• Display errors/warnings correctly when there are zero-width or wide characters.
• rustc now avoids unnecessary copies of arguments that are simple bindings This should improve memory usage on average by 5-10%.
• Updated musl used to build musl rustc to 1.1.17

Libraries

• Allow a trailing comma in assert_eq/ne macro
• Implement Hash for raw pointers to unsized types
• impl From<*mut T> for AtomicPtr<T>
• impl From<usize/isize> for AtomicUsize/AtomicIsize.
• Removed the T: Sync requirement for RwLock<T>: Send
• Removed T: Sized requirement for {<*const T>, <*mut T>}::as_ref and <*mut T>::as_mut
• Optimized Thread::{park, unpark} implementation
• Improved SliceExt::binary_search performance.
• impl FromIterator<()> for ()
• Copied AsciiExt trait methods to primitive types. Use of AsciiExt is now deprecated.

Stabilized APIs

Cargo

• Cargo now supports uninstallation of multiple packages eg. cargo uninstall foo bar uninstalls foo and bar.
• Added unit test checking to cargo check
• Cargo now lets you install a specific version using cargo install --version

Misc

• Releases now ship with the Cargo book documentation.
• rustdoc now prints rendering warnings on every run.

Compatibility Notes

• Changes have been made to type equality to make it more correct, in rare cases this could break some code. Tracking issue for further information
• char::escape_debug now uses Unicode 10 over 9.
• Upgraded Android SDK to 27, and NDK to r15c. This drops support for Android 9, the minimum supported version is Android 14.
• Bumped the minimum LLVM to 3.9

Rust 1.22.1

• Update Cargo to fix an issue with macOS 10.13 "High Sierra"

Rust 1.22.0

Language

• non_snake_case lint now allows extern no-mangle functions
• Now accepts underscores in unicode escapes
• T op= &T now works for numeric types. eg. let mut x = 2; x += &8;
• types that impl Drop are now allowed in const and static types

Compiler

• rustc now defaults to having 16 codegen units at debug on supported platforms.
• rustc will no longer inline in codegen units when compiling for debug This should decrease compile times for debug builds.
• strict memory alignment now enabled on ARMv6
• Remove support for the PNaCl target le32-unknown-nacl

Libraries

• Allow atomic operations up to 32 bits on armv5te_unknown_linux_gnueabi
• Box<Error> now impls From<Cow<str>>
• std::mem::Discriminant is now guaranteed to be Send + Sync
• fs::copy now returns the length of the main stream on NTFS.
• Properly detect overflow in Instant += Duration.
• impl Hasher for {&mut Hasher, Box<Hasher>}
• impl fmt::Debug for SplitWhitespace.
• Option<T> now impls Try This allows for using ? with Option types.

Stabilized APIs

Cargo

• Cargo will now build multi file examples in subdirectories of the examples folder that have a main.rs file.
• Changed [root] to [package] in Cargo.lock Packages with the old format will continue to work and can be updated with cargo update.
• Now supports vendoring git repositories

Misc

• libbacktrace is now available on Apple platforms.
• Stabilised the compile_fail attribute for code fences in doc-comments. This now lets you specify that a given code example will fail to compile.

Compatibility Notes

• The minimum Android version that rustc can build for has been bumped to 4.0 from 2.3
• Allowing T op= &T for numeric types has broken some type inference cases

Rust 1.21.0

Language

• You can now use static references for literals. Example:

  fn main() {
      let x: &'static u32 = &0;
  }

• Relaxed path syntax. Optional :: before < is now allowed in all contexts. Example:

  my_macro!(Vec<i32>::new); // Always worked
  my_macro!(Vec::<i32>::new); // Now works

Compiler

• Upgraded jemalloc to 4.5.0
• Enabled unwinding panics on Redox
• Now runs LLVM in parallel during translation phase. This should reduce peak memory usage.

Libraries

• Generate builtin impls for Clone for all arrays and tuples that are T: Clone
• Stdin, Stdout, and Stderr now implement AsRawFd.
• Rc and Arc now implement From<&[T]> where T: Clone, From<str>, From<String>, From<Box<T>> where T: ?Sized, and From<Vec<T>>.

Stabilized APIs

std::mem::discriminant

Cargo

• You can now call cargo install with multiple package names
• Cargo commands inside a virtual workspace will now implicitly pass --all
• Added a [patch] section to Cargo.toml to handle prepublication dependencies RFC 1969
• include & exclude fields in Cargo.toml now accept gitignore like patterns
• Added the --all-targets option
• Using required dependencies as a feature is now deprecated and emits a warning

Misc

• Cargo docs are moving to doc.rust-lang.org/cargo
• The rustdoc book is now available at doc.rust-lang.org/rustdoc
• Added a preview of RLS has been made available through rustup Install with rustup component add rls-preview
• std::os documentation for Unix, Linux, and Windows now appears on doc.rust-lang.org Previously only showed std::os::unix.

Compatibility Notes

• Changes in method matching against higher-ranked types This may cause breakage in subtyping corner cases. A more in-depth explanation is available.
• rustc's JSON error output's byte position start at top of file. Was previously relative to the rustc's internal CodeMap struct which required the unstable library libsyntax to correctly use.
• unused_results lint no longer ignores booleans

Rust 1.20.0

Language

• Associated constants are now stabilised.
• A lot of macro bugs are now fixed.

Compiler

• Struct fields are now properly coerced to the expected field type.
• Enabled wasm LLVM backend WASM can now be built with the wasm32-experimental-emscripten target.
• Changed some of the error messages to be more helpful.
• Add support for RELRO(RELocation Read-Only) for platforms that support it.
• rustc now reports the total number of errors on compilation failure previously this was only the number of errors in the pass that failed.
• Expansion in rustc has been sped up 29x.
• added msp430-none-elf target.
• rustc will now suggest one-argument enum variant to fix type mismatch when applicable
• Fixes backtraces on Redox
• rustc now identifies different versions of same crate when absolute paths of different types match in an error message.

Libraries

• Relaxed Debug constraints on {HashMap,BTreeMap}::{Keys,Values}.
• Impl PartialEq, Eq, PartialOrd, Ord, Debug, Hash for unsized tuples.
• Impl fmt::{Display, Debug} for Ref, RefMut, MutexGuard, RwLockReadGuard, RwLockWriteGuard
• Impl Clone for DefaultHasher.
• Impl Sync for SyncSender.
• Impl FromStr for char
• Fixed how {f32, f64}::{is_sign_negative, is_sign_positive} handles NaN.
• allow messages in the unimplemented!() macro. ie. unimplemented!("Waiting for 1.21 to be stable")
• pub(restricted) is now supported in the thread_local! macro.
• Upgrade to Unicode 10.0.0
• Reimplemented {f32, f64}::{min, max} in Rust instead of using CMath.
• Skip the main thread's manual stack guard on Linux
• Iterator::nth for ops::{Range, RangeFrom} is now done in O(1) time
• #[repr(align(N))] attribute max number is now 2^31 - 1. This was previously 2^15.
• {OsStr, Path}::Display now avoids allocations where possible

Stabilized APIs

• CStr::into_c_string
• CString::as_c_str
• CString::into_boxed_c_str
• Chain::get_mut
• Chain::get_ref
• Chain::into_inner
• Option::get_or_insert_with
• Option::get_or_insert
• OsStr::into_os_string
• OsString::into_boxed_os_str
• Take::get_mut
• Take::get_ref
• Utf8Error::error_len
• char::EscapeDebug
• char::escape_debug
• compile_error!
• f32::from_bits
• f32::to_bits
• f64::from_bits
• f64::to_bits
• mem::ManuallyDrop
• slice::sort_unstable_by_key
• slice::sort_unstable_by
• slice::sort_unstable
• str::from_boxed_utf8_unchecked
• str::as_bytes_mut
• str::as_bytes_mut
• str::from_utf8_mut
• str::from_utf8_unchecked_mut
• str::get_mut
• str::get_unchecked_mut
• str::get_unchecked
• str::get
• str::into_boxed_bytes

Cargo

• Cargo API token location moved from ~/.cargo/config to ~/.cargo/credentials.
• Cargo will now build main.rs binaries that are in sub-directories of src/bin. ie. Having src/bin/server/main.rs and src/bin/client/main.rs generates target/debug/server and target/debug/client
• You can now specify version of a binary when installed through cargo install using --vers.
• Added --no-fail-fast flag to cargo to run all benchmarks regardless of failure.
• Changed the convention around which file is the crate root.

Compatibility Notes

• Functions with 'static in their return types will now not be as usable as if they were using lifetime parameters instead.
• The reimplementation of {f32, f64}::is_sign_{negative, positive} now takes the sign of NaN into account where previously didn't.

Rust 1.19.0

Language

• Numeric fields can now be used for creating tuple structs. RFC 1506 For example struct Point(u32, u32); let x = Point { 0: 7, 1: 0 };.
• Macro recursion limit increased to 1024 from 64.
• Added lint for detecting unused macros.
• loop can now return a value with break. RFC 1624 For example: let x = loop { break 7; };
• C compatible unions are now available. RFC 1444 They can only contain Copy types and cannot have a Drop implementation. Example: union Foo { bar: u8, baz: usize }
• Non capturing closures can now be coerced into fns, RFC 1558 Example: let foo: fn(u8) -> u8 = |v: u8| { v };

Compiler

• Add support for bootstrapping the Rust compiler toolchain on Android.
• Change arm-linux-androideabi to correspond to the armeabi official ABI. If you wish to continue targeting the armeabi-v7a ABI you should use --target armv7-linux-androideabi.
• Fixed ICE when removing a source file between compilation sessions.
• Minor optimisation of string operations.
• Compiler error message is now aborting due to previous error(s) instead of aborting due to N previous errors This was previously inaccurate and would only count certain kinds of errors.
• The compiler now supports Visual Studio 2017
• The compiler is now built against LLVM 4.0.1 by default
• Added a lot of new error codes
• Added target-feature=+crt-static option RFC 1721 Which allows libraries with C Run-time Libraries(CRT) to be statically linked.
• Fixed various ARM codegen bugs

Libraries

• String now implements FromIterator<Cow<'a, str>> and Extend<Cow<'a, str>>
• Vec now implements From<&mut [T]>
• Box<[u8]> now implements From<Box<str>>
• SplitWhitespace now implements Clone
• [u8]::reverse is now 5x faster and [u16]::reverse is now 1.5x faster
• eprint! and eprintln! macros added to prelude. Same as the print! macros, but for printing to stderr.

Stabilized APIs

• OsString::shrink_to_fit
• cmp::Reverse
• Command::envs
• thread::ThreadId

Cargo

• Build scripts can now add environment variables to the environment the crate is being compiled in. Example: println!("cargo:rustc-env=FOO=bar");
• Subcommands now replace the current process rather than spawning a new child process
• Workspace members can now accept glob file patterns
• Added --all flag to the cargo bench subcommand to run benchmarks of all the members in a given workspace.
• Updated libssh2-sys to 0.2.6
• Target directory path is now in the cargo metadata
• Cargo no longer checks out a local working directory for the crates.io index This should provide smaller file size for the registry, and improve cloning times, especially on Windows machines.
• Added an --exclude option for excluding certain packages when using the --all option
• Cargo will now automatically retry when receiving a 5xx error from crates.io
• The --features option now accepts multiple comma or space delimited values.
• Added support for custom target specific runners

Misc

• Added rust-windbg.cmd for loading rust .natvis files in the Windows Debugger.
• Rust will now release XZ compressed packages
• rustup will now prefer to download rust packages with XZ compression over GZip packages.
• Added the ability to escape # in rust documentation By adding additional #'s ie. ## is now #

Compatibility Notes

• MutexGuard<T> may only be Sync if T is Sync.
• -Z flags are now no longer allowed to be used on the stable compiler. This has been a warning for a year previous to this.
• As a result of the -Z flag change, the cargo-check plugin no longer works. Users should migrate to the built-in check command, which has been available since 1.16.
• Ending a float literal with ._ is now a hard error. Example: 42._ .
• Any use of a private extern crate outside of its module is now a hard error. This was previously a warning.
• use ::self::foo; is now a hard error. self paths are always relative while the :: prefix makes a path absolute, but was ignored and the path was relative regardless.
• Floating point constants in match patterns is now a hard error This was previously a warning.
• Struct or enum constants that don't derive PartialEq & Eq used match patterns is now a hard error This was previously a warning.
• Lifetimes named '_ are no longer allowed. This was previously a warning.
• From the pound escape, lines consisting of multiple #s are now visible
• It is an error to re-export private enum variants. This is known to break a number of crates that depend on an older version of mustache.
• On Windows, if VCINSTALLDIR is set incorrectly, rustc will try to use it to find the linker, and the build will fail where it did not previously

Rust 1.18.0

Language

• Stabilize pub(restricted) pub can now accept a module path to make the item visible to just that module tree. Also accepts the keyword crate to make something public to the whole crate but not users of the library. Example: pub(crate) mod utils;. RFC 1422.
• Stabilize #![windows_subsystem] attribute conservative exposure of the /SUBSYSTEM linker flag on Windows platforms. RFC 1665.
• Refactor of trait object type parsing Now ty in macros can accept types like Write + Send, trailing + are now supported in trait objects, and better error reporting for trait objects starting with ?Sized.
• 0e+10 is now a valid floating point literal
• Now warns if you bind a lifetime parameter to 'static
• Tuples, Enum variant fields, and structs with no repr attribute or with #[repr(Rust)] are reordered to minimize padding and produce a smaller representation in some cases.

Compiler

• rustc can now emit mir with --emit mir
• Improved LLVM IR for trivial functions
• Added explanation for E0090(Wrong number of lifetimes are supplied)
• rustc compilation is now 15%-20% faster Thanks to optimisation opportunities found through profiling
• Improved backtrace formatting when panicking

Libraries

• Specialized Vec::from_iter being passed vec::IntoIter if the iterator hasn't been advanced the original Vec is reassembled with no actual iteration or reallocation.
• Simplified HashMap Bucket interface provides performance improvements for iterating and cloning.
• Specialize Vec::from_elem to use calloc
• Fixed Race condition in fs::create_dir_all
• No longer caching stdio on Windows
• Optimized insertion sort in slice insertion sort in some cases 2.50%~ faster and in one case now 12.50% faster.
• Optimized AtomicBool::fetch_nand

Stabilized APIs

• Child::try_wait
• HashMap::retain
• HashSet::retain
• PeekMut::pop
• TcpStream::peek
• UdpSocket::peek
• UdpSocket::peek_from

Cargo

• Added partial Pijul support Pijul is a version control system in Rust. You can now create new cargo projects with Pijul using cargo new --vcs pijul
• Now always emits build script warnings for crates that fail to build
• Added Android build support
• Added --bins and --tests flags now you can build all programs of a certain type, for example cargo build --bins will build all binaries.
• Added support for haiku

Misc

• rustdoc can now use pulldown-cmark with the --enable-commonmark flag
• Rust now uses the official cross compiler for NetBSD
• rustdoc now accepts # at the start of files
• Fixed jemalloc support for musl

Compatibility Notes

• Changes to how the 0 flag works in format! Padding zeroes are now always placed after the sign if it exists and before the digits. With the # flag the zeroes are placed after the prefix and before the digits.

• Due to the struct field optimisation, using transmute on structs that have no repr attribute or #[repr(Rust)] will no longer work. This has always been undefined behavior, but is now more likely to break in practice.

• The refactor of trait object type parsing fixed a bug where + was receiving the wrong priority parsing things like &for<'a> Tr<'a> + Send as &(for<'a> Tr<'a> + Send) instead of (&for<'a> Tr<'a>) + Send

• Overlapping inherent impls are now a hard error

• PartialOrd and Ord must agree on the ordering.

• rustc main.rs -o out --emit=asm,llvm-ir Now will output out.asm and out.ll instead of only one of the filetypes.

• calling a function that returns Self will no longer work when the size of Self cannot be statically determined.

• rustc now builds with a "pthreads" flavour of MinGW for Windows GNU this has caused a few regressions namely:

  • Changed the link order of local static/dynamic libraries (respecting the order on given rather than having the compiler reorder).
  • Changed how MinGW is linked, native code linked to dynamic libraries may require manually linking to the gcc support library (for the native code itself)