Rust release · May 26, 2016

Rust 1.9: what's new, what was stabilized

Short answerRust 1.9 was released on May 26, 2016: 86 newly stable APIs (std::panic, std::panic::catch_unwind, std::panic::resume_unwind, std::panic::AssertUnwindSafe, ...); 4 compatibility notes that can affect existing code.

May 26, 2016release date

0language stabilizations

86APIs stabilized

-new edition

← Rust 1.8 All versions Rust 1.10 →

86 APIs stabilized

std::panic, std::panic::catch_unwind, std::panic::resume_unwind, std::panic::AssertUnwindSafe, std::panic::UnwindSafe, str::is_char_boundary, <*const T>::as_ref, <*mut T>::as_ref, <*mut T>::as_mut, AsciiExt::make_ascii_uppercase, AsciiExt::make_ascii_lowercase, char::decode_utf16, char::DecodeUtf16, char::DecodeUtf16Error, char::DecodeUtf16Error::unpaired_surrogate, BTreeSet::take, BTreeSet::replace, BTreeSet::get, HashSet::take, HashSet::replace, HashSet::get, OsString::with_capacity, OsString::clear, OsString::capacity, OsString::reserve, OsString::reserve_exact, OsStr::is_empty, OsStr::len, std::os::unix::thread, RawPthread, JoinHandleExt, JoinHandleExt::as_pthread_t, JoinHandleExt::into_pthread_t, HashSet::hasher, HashMap::hasher, CommandExt::exec, File::try_clone, 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, slice::copy_from_slice, ptr::read_volatile, ptr::write_volatile, OpenOptions::create_new, TcpStream::set_nodelay, TcpStream::nodelay, TcpStream::set_ttl, TcpStream::ttl, TcpStream::set_only_v6, TcpStream::only_v6, TcpStream::take_error, TcpStream::set_nonblocking, TcpListener::set_ttl, TcpListener::ttl, TcpListener::set_only_v6, TcpListener::only_v6, TcpListener::take_error, TcpListener::set_nonblocking, UdpSocket::set_broadcast, UdpSocket::broadcast, UdpSocket::set_multicast_loop_v4, UdpSocket::multicast_loop_v4, UdpSocket::set_multicast_ttl_v4, UdpSocket::multicast_ttl_v4, UdpSocket::set_multicast_loop_v6, UdpSocket::multicast_loop_v6, UdpSocket::set_multicast_ttl_v6, UdpSocket::multicast_ttl_v6, UdpSocket::set_ttl, UdpSocket::ttl, UdpSocket::set_only_v6, UdpSocket::only_v6, UdpSocket::join_multicast_v4, UdpSocket::join_multicast_v6, UdpSocket::leave_multicast_v4, UdpSocket::leave_multicast_v6, UdpSocket::take_error, UdpSocket::connect, UdpSocket::send, UdpSocket::recv, UdpSocket::set_nonblocking

Can it break my build?

The release lists these compatibility notes. Most only affect rare code, but read them before you raise your toolchain in CI:

[std::sync::Once is poisoned if its initialization function
[It is illegal to define methods with the same name in overlapping
[fn item types are zero sized, and each fn names a unique
[Improvements to const evaluation may trigger new errors when integer

Use it

rustup update stable        # get the newest release
rustup install 1.9          # or exactly this one
rustup override set 1.9     # pin a project to it

To require at least this version from users of your crate, set rust-version = "1.9" under [package] in Cargo.toml. Cargo then refuses to build it on older compilers with a clear message, and with resolver 3 (the default on the 2024 edition, Rust 1.85+) it also prefers dependency versions that support it.

Full release notes

Language

The #[deprecated] attribute when applied to an API will generate warnings when used. The warnings may be suppressed with #[allow(deprecated)]. [RFC 1270].
[fn item types are zero sized, and each fn names a unique type][1.9fn]. This will break code that transmutes fns, so calling transmute on a fn type will generate a warning for a few cycles, then will be converted to an error.
[Field and method resolution understand visibility, so private fields and methods cannot prevent the proper use of public fields and methods][1.9fv].
[The parser considers unicode codepoints in the PATTERN_WHITE_SPACE category to be whitespace][1.9ws].

Stabilized APIs

[std::panic]
[std::panic::catch_unwind] (renamed from recover)
[std::panic::resume_unwind] (renamed from propagate)
[std::panic::AssertUnwindSafe] (renamed from AssertRecoverSafe)
[std::panic::UnwindSafe] (renamed from RecoverSafe)
[str::is_char_boundary]
[<*const T>::as_ref]
[<*mut T>::as_ref]
[<*mut T>::as_mut]
[AsciiExt::make_ascii_uppercase]
[AsciiExt::make_ascii_lowercase]
[char::decode_utf16]
[char::DecodeUtf16]
[char::DecodeUtf16Error]
[char::DecodeUtf16Error::unpaired_surrogate]
[BTreeSet::take]
[BTreeSet::replace]
[BTreeSet::get]
[HashSet::take]
[HashSet::replace]
[HashSet::get]
[OsString::with_capacity]
[OsString::clear]
[OsString::capacity]
[OsString::reserve]
[OsString::reserve_exact]
[OsStr::is_empty]
[OsStr::len]
[std::os::unix::thread]
[RawPthread]
[JoinHandleExt]
[JoinHandleExt::as_pthread_t]
[JoinHandleExt::into_pthread_t]
[HashSet::hasher]
[HashMap::hasher]
[CommandExt::exec]
[File::try_clone]
[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]
[slice::copy_from_slice]
[ptr::read_volatile]
[ptr::write_volatile]
[OpenOptions::create_new]
[TcpStream::set_nodelay]
[TcpStream::nodelay]
[TcpStream::set_ttl]
[TcpStream::ttl]
[TcpStream::set_only_v6]
[TcpStream::only_v6]
[TcpStream::take_error]
[TcpStream::set_nonblocking]
[TcpListener::set_ttl]
[TcpListener::ttl]
[TcpListener::set_only_v6]
[TcpListener::only_v6]
[TcpListener::take_error]
[TcpListener::set_nonblocking]
[UdpSocket::set_broadcast]
[UdpSocket::broadcast]
[UdpSocket::set_multicast_loop_v4]
[UdpSocket::multicast_loop_v4]
[UdpSocket::set_multicast_ttl_v4]
[UdpSocket::multicast_ttl_v4]
[UdpSocket::set_multicast_loop_v6]
[UdpSocket::multicast_loop_v6]
[UdpSocket::set_multicast_ttl_v6]
[UdpSocket::multicast_ttl_v6]
[UdpSocket::set_ttl]
[UdpSocket::ttl]
[UdpSocket::set_only_v6]
[UdpSocket::only_v6]
[UdpSocket::join_multicast_v4]
[UdpSocket::join_multicast_v6]
[UdpSocket::leave_multicast_v4]
[UdpSocket::leave_multicast_v6]
[UdpSocket::take_error]
[UdpSocket::connect]
[UdpSocket::send]
[UdpSocket::recv]
[UdpSocket::set_nonblocking]

Libraries

[std::sync::Once is poisoned if its initialization function fails][1.9o].
[cell::Ref and cell::RefMut can contain unsized types][1.9cu].
[Most types implement fmt::Debug][1.9db].
[The default buffer size used by BufReader and BufWriter was reduced to 8K, from 64K][1.9bf]. This is in line with the buffer size used by other languages.
[Instant, SystemTime and Duration implement += and -=. Duration additionally implements *= and /=][1.9ta].
[Skip is a DoubleEndedIterator][1.9sk].
[From<[u8; 4]> is implemented for Ipv4Addr][1.9fi].
[Chain implements BufRead][1.9ch].
[HashMap, HashSet and iterators are covariant][1.9hc].

Cargo

[Cargo can now run concurrently][1.9cc].
[Top-level overrides allow specific revisions of crates to be overridden through the entire crate graph][1.9ct]. This is intended to make upgrades easier for large projects, by allowing crates to be forked temporarily until they've been upgraded and republished.
[Cargo exports a CARGO_PKG_AUTHORS environment variable][1.9cp].
[Cargo will pass the contents of the RUSTFLAGS variable to rustc on the commandline][1.9cf]. rustc arguments can also be specified in the build.rustflags configuration key.

Performance

[The time complexity of comparing variables for equivalence during type unification is reduced from _O_(_n_!) to _O_(_n_)][1.9tu]. This leads to major compilation time improvement in some scenarios.
[ToString is specialized for str, giving it the same performance as to_owned][1.9ts].
[Spawning processes with Command::output no longer creates extra threads][1.9sp].
[#[derive(PartialEq)] and #[derive(PartialOrd)] emit less code for C-like enums][1.9cl].

Misc

[Passing the --quiet flag to a test runner will produce much-abbreviated output][1.9q].
The Rust Project now publishes std binaries for the mips-unknown-linux-musl, mipsel-unknown-linux-musl, and i586-pc-windows-msvc targets.

Compatibility Notes

std::sync::Once is poisoned if its initialization function fails.
It is illegal to define methods with the same name in overlapping inherent impl blocks.
fn item types are zero sized, and each fn names a unique type. This will break code that transmutes fns, so calling transmute on a fn type will generate a warning for a few cycles, then will be converted to an error.
Improvements to const evaluation may trigger new errors when integer literals are out of range.

Release notes from the Rust project's RELEASES.md (MIT or Apache-2.0); summaries above are ours.