Announcing Rust 1.70.0

posts/2023-06-01-Rust-1.70.0.md

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+---
+layout: post
+title: "Announcing Rust 1.70.0"
+author: The Rust Release Team
+release: true
+---
+
+The Rust team is happy to announce a new version of Rust, 1.70.0. Rust is a programming language empowering everyone to build reliable and efficient software.
+
+If you have a previous version of Rust installed via rustup, you can get 1.70.0 with:
+
+```console
+rustup update stable
+```
+
+If you don't have it already, you can [get `rustup`](https://www.rust-lang.org/install.html) from the appropriate page on our website, and check out the [detailed release notes for 1.70.0](https://github.com/rust-lang/rust/releases/tag/1.70.0) on GitHub.
+
+If you'd like to help us out by testing future releases, you might consider updating locally to use the beta channel (`rustup default beta`) or the nightly channel (`rustup default nightly`). Please [report](https://github.com/rust-lang/rust/issues/new/choose) any bugs you might come across!
+
+## What's in 1.70.0 stable
+
+### Sparse by default for crates.io
+
+Cargo's "sparse" protocol is now enabled by default for reading the index from crates.io. This feature was previously stabilized with [Rust 1.68.0](https://blog.rust-lang.org/2023/03/09/Rust-1.68.0.html#cargos-sparse-protocol), but still required configuration to use that with crates.io. The announced plan was to make that the default in 1.70.0, and here it is!
+
+You should see substantially improved performance when fetching information from the crates.io index. Users behind a restrictive firewall will need to ensure that access to `https://index.crates.io` is available. If for some reason you need to stay with the previous default of using the git index hosted by GitHub, the [`registries.crates-io.protocol`](https://doc.rust-lang.org/cargo/reference/config.html#registriescrates-ioprotocol) config setting can be used to change the default.
+
+### `OnceCell` and `OnceLock`
+
+Two new types have been stabilized for one-time initialization of shared data, `OnceCell` and its thread-safe counterpart `OnceLock`. These can be used anywhere that immediate construction is not wanted, and perhaps not even possible like non-`const` data in global variables.
+
+```rust
+use std::sync::OnceLock;
+
+static WINNER: OnceLock<&str> = OnceLock::new();
+
+fn main() {
+    let winner = std::thread::scope(|s| {
+        s.spawn(|| WINNER.set("thread"));
+
+        std::thread::yield_now(); // give them a chance...
+
+        WINNER.get_or_init(|| "main")
+    });
+
+    println!("{winner} wins!");
+}
+```
+
+Crates such as `lazy_static` and `once_cell` have filled this need in the past, but now these building blocks are part of the standard library, ported from `once_cell`'s `unsync` and `sync` modules. There are still more methods that may be stabilized in the future, as well as companion `LazyCell` and `LazyLock` types that store their initializing function, but this first step in stabilization should already cover many use cases.
+
+### Named levels of debug information
+
+The `-Cdebuginfo` compiler option has previously only supported numbers 0..=2 for increasing amounts of debugging information, where Cargo defaults to 2 in dev and test profiles and 0 in release and bench profiles. These debug levels can now be set by name: "none" (0), "limited" (1), and "full" (2), as well as two new levels, "line-directives-only" and "line-tables-only".
+
+The Cargo and rustc documentation both called level 1 "line tables only" before, but it was more than that with information about all functions, just not types and variables. That level is now called "limited", and the new "line-tables-only" level is further reduced to the minimum needed for backtraces with filenames and line numbers. This may eventually become the level used for `-Cdebuginfo=1`. The other `line-directives-only` level is intended for NVPTX profiling, and is otherwise not recommended.
+
+Note that these named options are not yet available to be used via `Cargo.toml`. Support for that will be available in the next release 1.71.
+
+### Enforced stability in the `test` CLI
+
+When `#[test]` functions are compiled, the executable gets a command-line interface from the `test` crate. This CLI has a number of options, including some that are not yet stabilized and require specifying `-Zunstable-options` as well, like many other commands in the Rust toolchain. However, while that's only intended to be allowed in nightly builds, that restriction wasn't active in `test` -- until now. Starting with 1.70.0, stable and beta builds of Rust will no longer allow unstable `test` options, making them truly nightly-only as documented.
+
+### Stabilized APIs
+
+- [`NonZero*::MIN/MAX`](https://doc.rust-lang.org/stable/std/num/struct.NonZeroI8.html#associatedconstant.MIN)
+- [`BinaryHeap::retain`](https://doc.rust-lang.org/stable/std/collections/struct.BinaryHeap.html#method.retain)
+- [`Default for std::collections::binary_heap::IntoIter`](https://doc.rust-lang.org/stable/std/collections/binary_heap/struct.IntoIter.html)
+- [`Default for std::collections::btree_map::{IntoIter, Iter, IterMut}`](https://doc.rust-lang.org/stable/std/collections/btree_map/struct.IntoIter.html)
+- [`Default for std::collections::btree_map::{IntoKeys, Keys}`](https://doc.rust-lang.org/stable/std/collections/btree_map/struct.IntoKeys.html)
+- [`Default for std::collections::btree_map::{IntoValues, Values}`](https://doc.rust-lang.org/stable/std/collections/btree_map/struct.IntoKeys.html)
+- [`Default for std::collections::btree_map::Range`](https://doc.rust-lang.org/stable/std/collections/btree_map/struct.Range.html)
+- [`Default for std::collections::btree_set::{IntoIter, Iter}`](https://doc.rust-lang.org/stable/std/collections/btree_set/struct.IntoIter.html)
+- [`Default for std::collections::btree_set::Range`](https://doc.rust-lang.org/stable/std/collections/btree_set/struct.Range.html)
+- [`Default for std::collections::linked_list::{IntoIter, Iter, IterMut}`](https://doc.rust-lang.org/stable/alloc/collections/linked_list/struct.IntoIter.html)
+- [`Default for std::vec::IntoIter`](https://doc.rust-lang.org/stable/alloc/vec/struct.IntoIter.html#impl-Default-for-IntoIter%3CT,+A%3E)
+- [`Default for std::iter::Chain`](https://doc.rust-lang.org/stable/std/iter/struct.Chain.html)
+- [`Default for std::iter::Cloned`](https://doc.rust-lang.org/stable/std/iter/struct.Cloned.html)
+- [`Default for std::iter::Copied`](https://doc.rust-lang.org/stable/std/iter/struct.Copied.html)
+- [`Default for std::iter::Enumerate`](https://doc.rust-lang.org/stable/std/iter/struct.Enumerate.html)
+- [`Default for std::iter::Flatten`](https://doc.rust-lang.org/stable/std/iter/struct.Flatten.html)
+- [`Default for std::iter::Fuse`](https://doc.rust-lang.org/stable/std/iter/struct.Fuse.html)
+- [`Default for std::iter::Rev`](https://doc.rust-lang.org/stable/std/iter/struct.Rev.html)
+- [`Default for std::slice::Iter`](https://doc.rust-lang.org/stable/std/slice/struct.Iter.html)
+- [`Default for std::slice::IterMut`](https://doc.rust-lang.org/stable/std/slice/struct.IterMut.html)
+- [`Rc::into_inner`](https://doc.rust-lang.org/stable/alloc/rc/struct.Rc.html#method.into_inner)
+- [`Arc::into_inner`](https://doc.rust-lang.org/stable/alloc/sync/struct.Arc.html#method.into_inner)
+- [`std::cell::OnceCell`](https://doc.rust-lang.org/stable/std/cell/struct.OnceCell.html)
+- [`Option::is_some_and`](https://doc.rust-lang.org/stable/std/option/enum.Option.html#method.is_some_and)
+- [`NonNull::slice_from_raw_parts`](https://doc.rust-lang.org/stable/std/ptr/struct.NonNull.html#method.slice_from_raw_parts)
+- [`Result::is_ok_and`](https://doc.rust-lang.org/stable/std/result/enum.Result.html#method.is_ok_and)
+- [`Result::is_err_and`](https://doc.rust-lang.org/stable/std/result/enum.Result.html#method.is_err_and)
+- [`std::sync::atomic::Atomic*::as_ptr`](https://doc.rust-lang.org/stable/std/sync/atomic/struct.AtomicU8.html#method.as_ptr)
+- [`std::io::IsTerminal`](https://doc.rust-lang.org/stable/std/io/trait.IsTerminal.html)
+- [`std::os::linux::net::SocketAddrExt`](https://doc.rust-lang.org/stable/std/os/linux/net/trait.SocketAddrExt.html)
+- [`std::os::unix::net::UnixDatagram::bind_addr`](https://doc.rust-lang.org/stable/std/os/unix/net/struct.UnixDatagram.html#method.bind_addr)
+- [`std::os::unix::net::UnixDatagram::connect_addr`](https://doc.rust-lang.org/stable/std/os/unix/net/struct.UnixDatagram.html#method.connect_addr)
+- [`std::os::unix::net::UnixDatagram::send_to_addr`](https://doc.rust-lang.org/stable/std/os/unix/net/struct.UnixDatagram.html#method.send_to_addr)
+- [`std::os::unix::net::UnixListener::bind_addr`](https://doc.rust-lang.org/stable/std/os/unix/net/struct.UnixListener.html#method.bind_addr)
+- [`std::path::Path::as_mut_os_str`](https://doc.rust-lang.org/stable/std/path/struct.Path.html#method.as_mut_os_str)
+- [`std::sync::OnceLock`](https://doc.rust-lang.org/stable/std/sync/struct.OnceLock.html)
+
+### Other changes
+
+Check out everything that changed in [Rust](https://github.com/rust-lang/rust/releases/tag/1.70.0), [Cargo](https://github.com/rust-lang/cargo/blob/master/CHANGELOG.md#cargo-1700-2023-06-01, and [Clippy](https://github.com/rust-lang/rust-clippy/blob/master/CHANGELOG.md#rust-170).
+
+## Contributors to 1.70.0
+
+Many people came together to create Rust 1.70.0. We couldn't have done it without all of you. [Thanks!](https://thanks.rust-lang.org/rust/1.70.0/)