Announcing Rust 1.7

The Rust team is happy to announce the latest version of Rust, 1.7. Rust is a systems programming language focused on safety, speed, and concurrency.

As always, you can install Rust 1.7 from the appropriate page on our website, and check out the detailed release notes for 1.7 on GitHub. About 1300 patches were landed in this release.

What's in 1.7 stable

This release is primarily about library features. While we have several language features cooking for future releases, the timeframe in which 1.7 was developed included the holidays, which means less time for commenting on GitHub and more time for spending with loved ones.

Library stabilizations

About 40 library functions and methods are now stable in 1.7. One of the largest APIs stabilized was support for custom hash algorithms in the standard library’s HashMap<K, V> type. Previously all hash maps would use SipHash as the hashing algorithm, which provides protection against DOS attacks by default. SipHash, however, is not very fast at hashing small keys. As shown, however, the FNV hash algorithm is much faster for these size of inputs. This means that by switching hash algorithms for types like HashMap<usize, V> there can be a significant speedup so long as the loss of DOS protection is acceptable.

To see this in action, you can check out the fnv crate on crates.io and create a HashMap via:

extern crate fnv;

use std::collections::HashMap;
use std::hash::BuildHasherDefault;
use fnv::FnvHasher;

type MyHasher = BuildHasherDefault<FnvHasher>;

fn main() {
    let mut map: HashMap<_, _, MyHasher> = HashMap::default();
    map.insert(1, "Hello");
    map.insert(2, ", world!");
    println!("{:?}", map);
}

Note that most of the time you don’t even need to specify the hasher as type inference will take care of it, so HashMap::default() should be all you need to get up to 2x faster hashes. It’s also worth pointing out that Hash trait is agnostic to the hashing algorithm used, so no changes are needed to the types being inserted into hash maps to reap the benefits!

Other notable improvements include:

<[T]>::clone_from_slice(), an efficient way to copy the data from one slice and put it into another slice.
Various convenience methods on Ipv4Addr and Ipv6Addr, such as is_loopback(), which returns true or false if the address is a loopback address according to RFC 6890.
Various improvements to CString, used for FFI.
checked, saturated, and overflowing operations for various numeric types. These aren’t counted in that ‘40’ number above, because there are a lot of them, but they all do the same thing.

See the detailed release notes for more.

Cargo features

There were a few small updates to Cargo:

An improvement to build scripts that allows them to precisely inform Cargo about dependencies to ensure that they’re only rerun when those files change. This should help development quite a bit in repositories with build scripts.
A modification to the cargo rustc subcommand, which allows specifying profiles to pull in dev-dependencies during testing and such.

Contributors to 1.7

We had 144 individuals contribute to 1.7. Thank you so much!

Aaron Turon
Adam Perry
Adrian Heine
Aidan Hobson Sayers
Aleksey Kladov
Alexander Lopatin
Alex Burka
Alex Crichton
Ali Clark
Amanieu d’Antras
Andrea Bedini
Andrea Canciani
Andre Bogus
Andrew Barchuk
Andrew Paseltiner
angelsl
Anton Blanchard
arcnmx
Ariel Ben-Yehuda
arthurprs
ashleysommer
Barosl Lee
Benjamin Herr
Björn Steinbrink
bors
Brandon W Maister
Brian Anderson
Brian Campbell
Carlos E. Garcia
Chad Shaffer
Corey Farwell
Daan Sprenkels
Daniel Campbell
Daniel Robertson
Dave Hodder
Dave Huseby
dileepb
Dirk Gadsden
Eduard Burtescu
Erick Tryzelaar
est31
Evan
Fabrice Desré
fbergr
Felix Gruber
Felix S. Klock II
Florian Hahn
Geoff Catlin
Geoffrey Thomas
Georg Brandl
ggomez
Gleb Kozyrev
Gökhan Karabulut
Greg Chapple
Guillaume Bonnet
Guillaume Gomez
Ivan Kozik
Jack O’Connor
Jeffrey Seyfried
Johan Lorenzo
Johannes Oertel
John Hodge
John Kåre Alsaker
Jonas Schievink
Jonathan Reem
Jonathan S
Jorge Aparicio
Josh Stone
Kamal Marhubi
Katze
Keith Yeung
Kenneth Koski
Kevin Stock
Luke Jones
Manish Goregaokar
Marc Bowes
Marvin Löbel
Masood Malekghassemi
Matt Brubeck
Mátyás Mustoha
Michael Huynh
Michael Neumann
Michael Woerister
mitaa
mopp
Nathan Kleyn
Nicholas Mazzuca
Nick Cameron
Nikita Baksalyar
Niko Matsakis
NODA, Kai
nxnfufunezn
Olaf Buddenhagen
Oliver ‘ker’ Schneider
Oliver Middleton
Oliver Schneider
Pascal Hertleif
Paul Dicker
Paul Smith
Peter Atashian
Peter Kolloch
petevine
Pierre Krieger
Piotr Czarnecki
Prayag Verma
qpid
Ravi Shankar
Reeze Xia
Richard Bradfield
Robin Kruppe
rphmeier
Ruud van Asseldonk
Ryan Thomas
Sandeep Datta
Scott Olson
Scott Whittaker
Sean Leffler
Sean McArthur
Sebastian Hahn
Sebastian Wicki
Sébastien Marie
Seo Sanghyeon
Sergey Veselkov
Simonas Kazlauskas
Simon Sapin
Stepan Koltsov
Stephan Hügel
Steve Klabnik
Steven Allen
Steven Fackler
Tamir Duberstein
tgor
Thomas Wickham
Thomas Winwood
Tobias Bucher
Toby Scrace
Tomasz Miąsko
tormol
Tshepang Lekhonkhobe
Ulrik Sverdrup
Vadim Petrochenkov
Vincent Esche
Vlad Ureche
Wangshan Lu
Wesley Wiser