Rust (programming language): Difference between revisions

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'''Rust''' is a [[General-purpose programming language|general-purpose]] [[programming language]]. It is noted emphasizingfor its emphasis on [[Computer performance|performance]], [[type safety]], and [[Concurrency (computer science)|concurrency]]. It enforces [[memory safety]], meaning that alland [[Reference (computer science)|references]] point to valid memory. It does so without a conventional [[Garbage collection (computer science)|garbage collector]]; instead, memory safety errors and [[data race]]s are prevented by the "borrow checker", which tracks the [[object lifetime]] of references [[Compiler|at compile time]].

Rust supports multiple [[programming paradigm]]s. It was influenced by ideas from [[functional programming]], including [[Immutable object|immutability]], [[higher-order function]]s, [[algebraic data type]]s, and [[pattern matching]]. It also supports [[object-oriented programming]] via structs, [[Union type|enums]], traits, and methods. Rust is noted for enforcing memory safety (i.e., that all [[Reference (computer science)|references]] point to valid memory) without a conventional [[Garbage collection (computer science)|garbage collector]]; instead, memory safety errors and [[data race]]s are prevented by the "borrow checker", which tracks the [[object lifetime]] of references [[Compiler|at compile time]].

Software developer Graydon Hoare created Rust asin a personal project2006 while working at [[Mozilla]] Research, in 2006. Mozillawhich officially sponsored the project in 2009. The first stable release of Rust, Rust 1.0, was published in May 2015. Following a large layoff of Mozilla employees in August 2020, multiplefour other companies joined Mozilla in sponsoring Rust through the creation of the [[#Rust Foundation|Rust Foundation]] in February 2021. In December 2022, Rust became the first language other than [[C (programming language)|C]] and [[Assembly language|assembly]] to be supported in the development of the [[Linux kernel]].

Rust has been noted for its adoption in many software projects, especially [[web services]] and [[system software]], and is the first language other than [[C (programming language)|C]] and [[Assembly language|assembly]] to be supported in the development of the [[Linux kernel]]. It has been studied academically and has a growing community of developers.

==Etymology==

Rust was named for the [[Rust (fungus)|group of fungi]] that are "over-engineered for survival".<ref name="MITTechReview"/>

The Rust logo was developed in 2011 based on a bicycle [[Crankset#Chainring|chainring]].<ref>{{cite web |title=Rust logo |url=https://bugzilla.mozilla.org/show_bug.cgi?id=680521 |website=[[Bugzilla]] |access-date=2 February 2024 |archive-date=2024-02-02 |archive-url=https://web.archive.org/web/20240202045212/https://bugzilla.mozilla.org/show_bug.cgi?id=680521 |url-status=live }}</ref>

== History ==

=== 2006–2009: Early years ===

[[File:MozillaCaliforniaHeadquarters.JPG|thumb|right|Mozilla Foundation headquarters, 650 Castro Street in [[Mountain View, California]], June 2009]]

Rust began as a personal project by [[Mozilla]] employee Graydon Hoare in 2006.<ref name="MITTechReview">{{cite web |url=https://www.technologyreview.com/2023/02/14/1067869/rust-worlds-fastest-growing-programming-language/ |title=How Rust went from a side project to the world's most-loved programming language |last=Thompson |first=Clive |date=2023-02-14 |website=MIT Technology Review |language=en |access-date=2023-02-23 |archive-date=2024-09-19 |archive-url=https://web.archive.org/web/20240919102849/https://www.technologyreview.com/2023/02/14/1067869/rust-worlds-fastest-growing-programming-language/ |url-status=live }}</ref> Hoare started the project due to his frustration with a broken elevator in his apartment building.<ref name="MITTechReview"/> Hoare has stated that Rust was named for the [[Rust (fungus)|group of fungi]] that are "over-engineered for survival".<ref name="MITTechReview"/> During the time period between 2006 and 2009, Rust was not publicized to others at Mozilla and was written in Hoare's free time;<ref name=Klabnik2016ACMHistory>{{Cite book |last=Klabnik |first=Steve |chapter=The History of Rust |date=2016-06-02 |title=Applicative 2016 |chapter-url=https://dl.acm.org/doi/10.1145/2959689.2960081 |page=80 |___location=New York, NY, USA |publisher=Association for Computing Machinery |doi=10.1145/2959689.2960081 |isbn=978-1-4503-4464-7}}</ref>{{rp|at=7:50}} Hoare began speaking about the language around 2009 after a small group at Mozilla became interested in the project.<ref name=Hoare2010>{{Cite conference |url=http://venge.net/graydon/talks/intro-talk-2.pdf |archive-url=https://archive.today/20211226213836/http://venge.net/graydon/talks/intro-talk-2.pdf |archive-date=2021-12-26 |last=Hoare |first=Graydon |title=Project Servo: Technology from the past come to save the future from itself |publisher=Mozilla Annual Summit |date=July 2010 |access-date=2024-10-29 }}</ref> Hoare emphasized prioritizing good ideas from old languages over new development, citing languages including [[CLU (programming language)|CLU]] (1974), [[BETA (programming language)|BETA]] (1975), [[Mesa (programming language)|Mesa]] (1977), [[NIL (programming language)|NIL]] (1981), [[Erlang (programming language)|Erlang]] (1987), [[Newsqueak]] (1988), [[Napier88|Napier]] (1988), [[Hermes (programming language)|Hermes]] (1990), [[Sather]] (1990), [[Alef (programming language)|Alef]] (1992), and [[Limbo (programming language)|Limbo]] (1996) as influences, stating "many older languages [are] better than new ones", and describing the language as "technology from the past come to save the future from itself."<ref name=Klabnik2016ACMHistory/>{{rp|at=8:17}}<ref name=Hoare2010/> Early Rust developer Manish Goregaokar similarly described Rust as being based on "mostly decades-old research."<ref name="MITTechReview"/>

During the early years, the Rust [[compiler]] was written in about 38,000 lines of [[OCaml]].<ref name=Klabnik2016ACMHistory/>{{rp|at=15:34}}<ref name=OCamlCompiler>{{Cite web |last=Hoare |first=Graydon |title=Rust Prehistory (Archive of the original Rust OCaml compiler source code) |website=[[GitHub]] |date=November 2016 |url=https://github.com/graydon/rust-prehistory/tree/master |access-date=2024-10-29 }}</ref> Early Rust contained features such as explicit [[object-oriented programming]] via an {{code|obj}} keyword (later removed),<ref name=Klabnik2016ACMHistory/>{{rp|at=10:08}} and a [[typestate analysis|typestates]] system that would allow variables of a type to be tracked along with state changes (such as going from uninitialized to initialized, also removed).<ref name=Klabnik2016ACMHistory/>{{rp|at=13:12}}

=== 2009–2012: Mozilla sponsorship ===

Mozilla officially sponsored the Rust project in 2009.<ref name="MITTechReview"/> [[Brendan Eich]] and other executives, intrigued by the possibility of using Rust for a safe [[web browser]] [[browser engine|engine]], placed engineers on the project including Patrick Walton, Niko Matsakis, Felix Klock, and Manish Goregaokar.<ref name="MITTechReview"/> A conference room taken by the project developers was dubbed "the nerd cave," with a sign placed outside the door.<ref name="MITTechReview"/>

During this time period, work had shifted from the initial OCaml compiler to a [[Self-hosting (compilers)|self-hosting compiler]], ''i.e.'', written in Rust, based on [[LLVM]].<ref name=Rust0.1>{{Cite web |title=0.1 first supported public release Milestone · rust-lang/rust |url=https://github.com/rust-lang/rust/milestone/3?closed=1 |access-date=2024-10-29 |website=[[GitHub]] |language=en}}</ref>{{refn|group=note|The list of Rust compiler versions (referred to as a bootstrapping chain) has history going back to 2012.<ref name=Nelson2022RustConf>{{Cite AV media |url=https://www.youtube.com/watch?v=oUIjG-y4zaA |last=Nelson |first=Jynn |title=RustConf 2022 - Bootstrapping: The once and future compiler |publisher=Rust Team |date=2022-08-05 |access-date=2024-10-29 |___location=Portland, Oregon |via=YouTube}}</ref>}} The Rust ownership system was also in place by 2010.<ref name="MITTechReview"/> The Rust logo was developed in 2011 based on a bicycle [[Crankset#Chainring|chainring]].<ref>{{cite web |title=Rust logo |url=https://bugzilla.mozilla.org/show_bug.cgi?id=680521 |website=[[Bugzilla]] |access-date=2 February 2024 |archive-date=2024-02-02 |archive-url=https://web.archive.org/web/20240202045212/https://bugzilla.mozilla.org/show_bug.cgi?id=680521 |url-status=live }}</ref>

The first public release, Rust 0.1 was released on January 20, 2012<ref name=Rust0.1a>{{Cite mailing list |last=Anderson |first=Brian |date=2012-01-24 |title=[rust-dev] The Rust compiler 0.1 is unleashed |url=https://mail.mozilla.org/pipermail/rust-dev/2012-January/001256.html |mailing-list=rust-dev |access-date=2025-01-07 |archive-url=https://web.archive.org/web/20120124160628/https://mail.mozilla.org/pipermail/rust-dev/2012-January/001256.html |archive-date=January 24, 2012 }}</ref> for Windows, Linux, and MacOS.<ref name=ExtremeTechRust0.1>{{Cite web |last=Anthony |first=Sebastian |date=2012-01-24 |title=Mozilla releases Rust 0.1, the language that will eventually usurp Firefox's C++ |url=https://www.extremetech.com/internet/115207-mozilla-releases-rust-0-1-the-language-that-will-eventually-usurp-firefoxs-c |access-date=2025-01-07 |website=ExtremeTech |language=en}}</ref> The early 2010s saw increasing involvement from open source volunteers outside of Mozilla and outside of the United States. At Mozilla, executives would eventually employ over a dozen engineers to work on Rust full time over the next decade.<ref name="MITTechReview"/>

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The years from 2012 to 2015 were marked by substantial changes to the Rust [[type system]], especially, removal of the typestate system, consolidation of other language features, and the removal of the [[Garbage collection (computer science)|garbage collector]].<ref name=Klabnik2016ACMHistory/>{{rp|at=18:36}}<ref name="MITTechReview"/> Memory management through the ownership system was gradually consolidated and expanded to prevent memory-related bugs. By 2013, the garbage collector feature was rarely used, and was removed by the team in favor of the ownership system.<ref name="MITTechReview"/> Other changes during this time included the removal of [[pure function]]s, which were declared by an explicit {{code|pure}} annotation, in March 2013.<ref>{{Cite web |title=Purity by pcwalton · Pull Request #5412 · rust-lang/rust |url=https://github.com/rust-lang/rust/pull/5412 |access-date=2024-10-29 |website=[[GitHub]] |language=en}}</ref> Specialized syntax support for [[channel (programming)|channels]] and various pointer types were removed to simplify the language.<ref name=Klabnik2016ACMHistory/>{{rp|at=22:32}}

According to Rust's expansiondeveloper andSteve consolidationKlabnik, Rust was influenced during this period by developers coming from [[C++]] (e.g., low-level performance of features), [[scripting language]]s (e.g., Cargo and package management), and [[functional programming]] (e.g., type systems development).<ref name=Klabnik2016ACMHistory/>{{rp|at=30:50}}

Graydon Hoare stepped down from Rust in 2013.<ref name="MITTechReview"/> ThisAfter allowedHoare's departure, it to evolveevolved organically under a more federated governance structure, with a "core team" of initially six people,<ref name=Klabnik2016ACMHistory/>{{rp|at=21:45}} around 30-40 developers total across various other teams,<ref name=Klabnik2016ACMHistory/>{{rp|at=22:22}} and a Request for Comments (RFC) process for new language features added in March 2014.<ref name=Klabnik2016ACMHistory/>{{rp|at=33:47}} The core team would grow to nine people by 2016<ref name=Klabnik2016ACMHistory/>{{rp|at=21:45}} with over 1600 proposed RFCs.<ref name=Klabnik2016ACMHistory/>{{rp|at=34:08}}

According to Andrew Binstock writing for ''[[Dr. Dobb's Journal]]'' in January 2014, while Rust was "widely viewed as a remarkably elegant language", adoption slowed because it radically changed from version to version.<ref>{{cite news |last=Binstock |first=Andrew |date=January 7, 2014 |title=The Rise And Fall of Languages in 2013 |website=[[Dr. Dobb's Journal]] |url=https://www.drdobbs.com/jvm/the-rise-and-fall-of-languages-in-2013/240165192 |url-status=dead |archive-url=https://web.archive.org/web/20160807075745/http://www.drdobbs.com/jvm/the-rise-and-fall-of-languages-in-2013/240165192 |archive-date=2016-08-07 |access-date=2022-11-20}}</ref> Rust development at this time was focused on finalizing the language features and moving towards 1.0 so it could begin promising [[backward compatibility]].<ref name=Klabnik2016ACMHistory/>{{rp|at=41:26}}

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The development of the [[Servo (software)|Servo browser engine]] continued in parallel with Rust, jointly funded by Mozilla and [[Samsung]].<ref>{{cite news|last=Lardinois|first=Frederic|date=2015-04-03|title=Mozilla And Samsung Team Up To Develop Servo, Mozilla's Next-Gen Browser Engine For Multicore Processors|work=[[TechCrunch]]|url=https://techcrunch.com/2013/04/03/mozilla-and-samsung-collaborate-on-servo-mozillas-next-gen-browser-engine-for-tomorrows-multicore-processors/|access-date=2017-06-25|archive-date=2016-09-10|archive-url=https://web.archive.org/web/20160910211537/https://techcrunch.com/2013/04/03/mozilla-and-samsung-collaborate-on-servo-mozillas-next-gen-browser-engine-for-tomorrows-multicore-processors/|url-status=live}}</ref> The teams behind the two projects worked in close collaboration; new features in Rust were tested out by the Servo team, and new features in Servo were used to give feedback back to the Rust team.<ref name=Klabnik2016ACMHistory/>{{rp|at=5:41}} The first version of Servo was released in 2016.<ref name="MITTechReview"/> The [[Firefox]] web browser shipped with Rust code as of 2016 (version 45),<ref name=Klabnik2016ACMHistory/>{{rp|at=53:30}}<ref>{{Cite web |title=Firefox 45.0, See All New Features, Updates and Fixes |url=https://www.mozilla.org/en-US/firefox/45.0/releasenotes/ |access-date=2024-10-31 |website=Mozilla |language=en |archive-date=2016-03-17 |archive-url=https://web.archive.org/web/20160317215950/https://www.mozilla.org/en-US/firefox/45.0/releasenotes/ |url-status=live }}</ref> but components of Servo did not appear in Firefox until September 2017 (version 57) as part of the [[Gecko (software)|Gecko]] and [[Gecko (software)#Quantum|Quantum]] projects.<ref>{{Cite web |last=Lardinois |first=Frederic |date=2017-09-29 |title=It's time to give Firefox another chance |url=https://techcrunch.com/2017/09/29/its-time-to-give-firefox-another-chance/ |access-date=2023-08-15 |website=[[TechCrunch]] |language=en-US |archive-date=2023-08-15 |archive-url=https://web.archive.org/web/20230815025149/https://techcrunch.com/2017/09/29/its-time-to-give-firefox-another-chance/ |url-status=live }}</ref>

Improvements were made to the Rust toolchain ecosystem during the years following 1.0 including [[#Rustfmt|Rustfmt]], [[integrated development environment]] integration,<ref name=Klabnik2016ACMHistory/>{{rp|at=44:56}} and a regular compiler testing and release cycle,.<ref name=Klabnik2016ACMHistory/>{{rp|at=46:48}} Rust also gained a community [[code of conduct]], and community discussion organized through an [[IRC]] chat for community discussion.<ref name=Klabnik2016ACMHistory/>{{rp|at=50:36}}

The earliest known adoption outside of Mozilla was by individual projects at Samsung, [[Facebook]] (now [[Meta Platforms]]), [[Dropbox]], and others including Tilde, Inc. (the company behind [[ember.js]]).<ref name=Klabnik2016ACMHistory/>{{rp|at=55:44}}<ref name="MITTechReview"/> [[Amazon Web Services]] followed in 2020.<ref name="MITTechReview"/> Engineers acknowledged the risks of adopting a new technology; they cited performance, lack of a garbage collector, safety, and pleasantness of working in the language as reasons for the adoption, while acknowledging that it was a risky bet as Rust was new technology. Amazon developers cited a finding by Portuguese researchers that Rust code used [[Energy efficiency in computing|uses less energy]] compared to similar code written in [[Java (programming language)|Java]] and [[C++]], (behind only [[C (programming language)|C]]).<ref name="MITTechReview"/><ref name=2017PortugalEnergyStudy>{{Cite book |last1=Pereira |first1=Rui |last2=Couto |first2=Marco |last3=Ribeiro |first3=Francisco |last4=Rua |first4=Rui |last5=Cunha |first5=Jácome |last6=Fernandes |first6=João Paulo |last7=Saraiva |first7=João |chapter=Energy efficiency across programming languages: How do energy, time, and memory relate? |date=2017-10-23 |title=Proceedings of the 10th ACM SIGPLAN International Conference on Software Language Engineering |chapter-url=https://dl.acm.org/doi/10.1145/3136014.3136031 |series=SLE 2017 |___location=New York, NY, USA |publisher=Association for Computing Machinery |pages=256–267 |doi=10.1145/3136014.3136031 |hdl=1822/65359 |isbn=978-1-4503-5525-4}}</ref>{{refn|group=note|Energy compared to C was 3% more for Rust and 34% more for C++; time was 4% more and 56% more, respectively.}}

=== 2020–present: Mozilla layoffs and Rust Foundation ===

In August 2020, Mozilla laid off 250 of its 1,000 employees worldwide, as part of a corporate restructuring caused by the [[COVID-19 pandemic]].<ref>{{cite web |url=https://www.zdnet.com/article/mozilla-lays-off-250-employees-while-it-refocuses-on-commercial-products/ |title=Mozilla lays off 250 employees while it refocuses on commercial products |last=Cimpanu |first=Catalin |website=[[ZDNET]] |access-date=2020-12-02 |date=2020-08-11 |archive-date=March 18, 2022 |archive-url=https://web.archive.org/web/20220318025804/https://www.zdnet.com/article/mozilla-lays-off-250-employees-while-it-refocuses-on-commercial-products/ |url-status=live}}</ref><ref>{{cite web |url=https://www.engadget.com/mozilla-firefox-250-employees-layoffs-151324924.html |title=Mozilla lays off 250 employees due to the pandemic |website=[[Engadget]] |last=Cooper |first=Daniel |access-date=2020-12-02 |date=2020-08-11 |archive-date=2020-12-13 |archive-url=https://web.archive.org/web/20201213020220/https://www.engadget.com/mozilla-firefox-250-employees-layoffs-151324924.html |url-status=live}}</ref> The team behind Servo was disbanded. The event raised concerns about the future of Rust, due to the overlap between the two projects.<ref>{{Cite web |last=Tung |first=Liam |date=2020-08-21 |title=Programming language Rust: Mozilla job cuts have hit us badly but here's how we'll survive |url=https://www.zdnet.com/article/programming-language-rust-mozilla-job-cuts-have-hit-us-badly-but-heres-how-well-survive/ |access-date=2022-04-21 |website=[[ZDNET]] |language=en |archive-date=April 21, 2022 |archive-url=https://web.archive.org/web/20220421083509/https://www.zdnet.com/article/programming-language-rust-mozilla-job-cuts-have-hit-us-badly-but-heres-how-well-survive/ |url-status=live}}</ref> In the following week, the Rust Core Team acknowledged the severe impact of the layoffs and announced that plans for a Rust foundation were underway. The first goal of the foundation would be to take ownership of all [[trademark]]s and [[___domain name]]s, and to take financial responsibility for their costs.<ref>{{cite web |url=https://blog.rust-lang.org/2020/08/18/laying-the-foundation-for-rusts-future.html |title=Laying the foundation for Rust's future |website=Rust Blog |access-date=2020-12-02 |date=2020-08-18 |archive-date=2020-12-02 |archive-url=https://web.archive.org/web/20201202022933/https://blog.rust-lang.org/2020/08/18/laying-the-foundation-for-rusts-future.html |url-status=live}}</ref>

On February 8, 2021, the formation of the [[#Rust Foundation|Rust Foundation]] was announced by five founding companies: [[Amazon Web Services]], [[Google]], [[Huawei]], [[Microsoft]], and [[Mozilla]].<ref>{{Cite web |date=2020-02-08 |title=Hello World! |url=https://foundation.rust-lang.org/news/2021-02-08-hello-world/ |access-date=2022-06-04 |website=Rust Foundation |language=en |archive-date=April 19, 2022 |archive-url=https://web.archive.org/web/20220419124635/https://foundation.rust-lang.org/news/2021-02-08-hello-world/ |url-status=live}}</ref><ref>{{Cite web|date=2021-02-09|title=Mozilla Welcomes the Rust Foundation |website=Mozilla Blog |url=https://blog.mozilla.org/blog/2021/02/08/mozilla-welcomes-the-rust-foundation |archive-url=https://web.archive.org/web/20210208212031/https://blog.mozilla.org/blog/2021/02/08/mozilla-welcomes-the-rust-foundation/|archive-date=2021-02-08|access-date=2021-02-09|url-status=live}}</ref> The foundation, led by Shane Miller for its first two years, offered $20,000 grants and other support for programmers working on major Rust features.<ref name="MITTechReview"/> In a [[blog]] post published on April 6, 2021, Google announced support for Rust within the [[Android Open Source Project]] as an alternative to C/C++.<ref>{{Cite web|last=Amadeo|first=Ron|date=2021-04-07 |title=Google is now writing low-level Android code in Rust |url=https://arstechnica.com/gadgets/2021/04/google-is-now-writing-low-level-android-code-in-rust/ |access-date=2021-04-08|website=Ars Technica|language=en-us|archive-date=2021-04-08|archive-url=https://web.archive.org/web/20210408001446/https://arstechnica.com/gadgets/2021/04/google-is-now-writing-low-level-android-code-in-rust/|url-status=live}}</ref>

On November 22, 2021, the Moderation Team, which was responsible for enforcing the community code of conduct, announced their resignation "in protest of the Core Team placing themselves unaccountable to anyone but themselves".<ref name="moderation">{{Cite news |first=Tim |last=Anderson |title=Entire Rust moderation team resigns |url=https://www.theregister.com/2021/11/23/rust_moderation_team_quits/ |date=2021-11-23 |access-date=2022-08-04 |website=[[The Register]] |language=en |archive-date=2022-07-14 |archive-url=https://web.archive.org/web/20220714093245/https://www.theregister.com/2021/11/23/rust_moderation_team_quits/ |url-status=live }}</ref> In May 2022, the Rust Core Team, other lead programmers, and certain members of the Rust Foundation board implemented governance reforms in response to the incident.<ref>{{Cite web |title=Governance Update |first1=Ryan |last1=Levick |first2=Mara |last2=Bos |url=https://blog.rust-lang.org/inside-rust/2022/05/19/governance-update.html |access-date=2022-10-27 |website=Inside Rust Blog |language=en |archive-date=2022-10-27 |archive-url=https://web.archive.org/web/20221027030926/https://blog.rust-lang.org/inside-rust/2022/05/19/governance-update.html |url-status=live }}</ref>

The Rust Foundation posted a draft for a new trademark policy on April 6, 2023, including rules for how the Rust logo and name can be used, which resulted in widespread negative reactions from Rust users and contributors.<ref name=ApologizesTrademarkPolicy>{{Cite news |last=Claburn |first=Thomas |title=Rust Foundation apologizes for trademark policy confusion |date=2023-04-17 |url=https://www.theregister.com/2023/04/17/rust_foundation_apologizes_trademark_policy/ |access-date=2023-05-07 |website=[[The Register]] |language=en |archive-date=2023-05-07 |archive-url=https://web.archive.org/web/20230507053637/https://www.theregister.com/2023/04/17/rust_foundation_apologizes_trademark_policy/ |url-status=live }}</ref> The trademark policy included rules for how the Rust logo and name could be used.<ref name=ApologizesTrademarkPolicy/>

On February 26, 2024, the U.S. [[White House]] through the [[Office of the National Cyber Director]] released a 19-page press report urging software development to move away from C and C++ and encouraging the use ofto memory-safe languages like C#, Go, Java, Ruby, Swift, and Rust.<ref name=WhiteHouse1>{{Cite web |last=Gross |first=Grant |title=White House urges developers to dump C and C++ |url=https://www.infoworld.com/article/2336216/white-house-urges-developers-to-dump-c-and-c.html |date=2024-02-27 |access-date=2025-01-26 |website=[[InfoWorld]] |language=en}}</ref><ref name=WhiteHouse2>{{Cite web |last=Warminsky |first=Joe |date=2024-02-27 |title=After decades of memory-related software bugs, White House calls on industry to act |url=https://therecord.media/memory-related-software-bugs-white-house-code-report-oncd |access-date=2025-01-26 |website=The Record |language=en}}</ref><ref name=WhiteHouseFullReport>{{Cite web |date=2024-02-26 |title=Press Release: Future Software Should Be Memory Safe |url=https://www.whitehouse.gov/oncd/briefing-room/2024/02/26/press-release-technical-report/ |archive-url=https://web.archive.org/web/20250118013136/https://www.whitehouse.gov/oncd/briefing-room/2024/02/26/press-release-technical-report/ |publisher=[[White House|The White House]] |url-status=dead |archive-date=2025-01-18 |access-date=2025-01-26 }}</ref> TheNews reportcoverage hasof beenRust interpretedincreased asin increasinglight interestof inthe Rustreport.<ref name=WhiteHouse3>{{Cite web |last=Jack |first=Bobby |date=2024-02-29 |title=The White House Wants Memory-Safe Programming, but What Is That? |url=https://www.makeuseof.com/memory-safe-programming-white-house-wants/ |access-date=2025-01-26 |website=MakeUseOf |language=en}}</ref><ref name=WhiteHouse4>{{Cite web |last=Donovan |first=Ryan |date=2024-12-30 |title=In Rust we trust? White House Office urges memory safety |url=https://stackoverflow.blog/2024/12/30/in-rust-we-trust-white-house-office-urges-memory-safety/ |access-date=2025-01-26 |website=[[Stack Overflow|The Stack Overflow Blog]] |language=en}}</ref>

== Syntax and features ==

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=== Variables ===

[[Variable (computer science)|Variables]] in Rust are defined through the {{rust|let}} keyword.{{sfn|Klabnik|Nichols|2023|p=32}} The example below assigns a value to the variable with name {{coderust|foo}} of type {{rust|i32}} and outputs its value.

<syntaxhighlight lang="rust">

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</syntaxhighlight>

Variables are [[Immutable object|immutable]] by default, but adding the {{rust|mut}} keyword allows the variable to be mutated.{{sfn|Klabnik|Nichols|2023|pp=32-33}} The following example uses {{coderust|//}}, which denotes the start of a [[Comment (computer programming)|comment]].{{sfn|Klabnik|Nichols|2023|pp=49-50}}

<syntaxhighlight lang="rust">

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</syntaxhighlight>

Multiple {{coderust|let}} expressions can define multiple variables with the same name, known as [[variable shadowing]]. Variable shadowing allows transforming variables without having to name the variables differently.{{sfn|Klabnik|Nichols|2023|pp=34-36}} The example below declares a new variable with the same name that is double the original value:

<syntaxhighlight lang="rust">

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</syntaxhighlight>

==== {{coderust|if}} expressions ====

An {{rust|if}} [[conditional expression]] executes code based on whether the given value is {{coderust|true}}. {{rust|else}} can be used for when the value evaluates to {{coderust|false}}, and {{rust|else if}} can be used for combining multiple expressions.{{sfn|Klabnik|Nichols|2023|pp=50-53}}

<syntaxhighlight lang="rust">

Line 233 ⟶ 236:

</syntaxhighlight>

==== {{coderust|while}} loops ====

<code>[[While loop|while]]</code> can be used to repeat a block of code while a condition is met.{{sfn|Klabnik|Nichols|2023|p=56}}

Line 247 ⟶ 250:

</syntaxhighlight>

==== {{coderust|for}} loops and iterators ====

[[For loop]]s in Rust loop over elements of a collection.{{sfn|Klabnik|Nichols|2023|pp=57-58}}

Line 267 ⟶ 270:

<syntaxhighlight lang="rust">

(1..=100).filter(|&x: i8| -> bool { x % 3 == 0 }).sum()

</syntaxhighlight>

==== {{coderust|loop}} and {{coderust|break}} statements ====

More generally, the {{rust|loop}} keyword allows repeating a portion of code until a {{rust|break}} occurs. {{rust|break}} may optionally exit the loop with a value. In the case of nested loops, labels denoted by {{rust|'label_name}} can be used to break an outer loop rather than the innermost loop.{{sfn|Klabnik|Nichols|2023|pp=54-56}}

Line 333 ⟶ 336:

=== Types ===

Rust is [[strongly typed]] and [[statically typed]], meaning that the types of all variables must be known at compilation time. Assigning a value of a particular type to a differently typed variable causes a [[compilation error]]. [[Type inference]] is used to determine the type of variables if unspecified.{{sfn|Klabnik|Nichols|2019|pp=24}}

The type <code>()</code>, called the "unit type" in Rust, is a concrete type that has exactly one value. It occupies no memory (as it represents the absence of value). All functions that do not have an indicated return type implicitly return <code>()</code>. It is similar to {{cpp|void}} in other C-style languages, however {{cpp|void}} denotes the absence of a type and cannot have any value.

The default integer type is {{rust|i32}}, and the default [[floating point]] type is {{rust|f64}}. If the type of a [[Literal (computer programming)|literal]] number is not explicitly provided, it is either inferred from the context or the default type is used.{{sfn|Klabnik|Nichols|2019|pp=36–38}}

==== Primitive types ====

[[Integer type]]s in Rust are named based on the [[signedness]] and the number of bits the type takes. For example, {{rust|i32}} is a signed integer that takes 32 bits of storage, whereas {{coderust|u8}} is unsigned and only takes 8 bits of storage. {{rust|isize}} and {{rust|usize}} take storage depending on the architecture of the computer that runs the code, for example, on computers with [[32-bit architecture]]s, both types will take up 32 bits of space.{{cn|date=August 2025}}

By default, integer literals are in base-10, but different [[radix|radices]] are supported with prefixes, for example, {{rust|0b11}} for [[binary number]]s, {{rust|0o567}} for [[octal]]s, and {{rust|0xDB}} for [[hexadecimal]]s. By default, integer literals default to {{rust|i32}} as its type. Suffixes such as {{rust|4u32}} can be used to explicitly set the type of a literal.{{sfn|Klabnik|Nichols|2023|pp=36-38}} Byte literals such as {{rust|b'X'}} are available to represent the [[ASCII]] value (as a {{rust|u8}}) of a specific character.{{sfn|Klabnik|Nichols|2023|p=502}}

Line 348 ⟶ 353:

<syntaxhighlight lang="rust">

let tuple: (u32, i64bool) = (3, -3true);

let array: [i8; 5] = [1, 2, 3, 4, 5];

let tuple:value (bool,= bool)tuple.1; =// (true, true);

let value = tuple.1; // -3

let value = array[2]; // 3

</syntaxhighlight>

Line 362 ⟶ 366:

<!-- todo str, and ! -->

=== Ownership and references ===

Line 379 ⟶ 384:

</syntaxhighlight>

The function {{coderust|print_string}} takes ownership over the {{rust|String}} value passed in; Alternatively, {{coderust|&}} can be used to indicate a [[Reference (computer science)|reference]] type (in {{coderust|&String}}) and to create a reference (in {{coderust|&s}}):{{sfn|Klabnik|Nichols|2023|pp=71–72}}

<syntaxhighlight lang="rust">

Line 396 ⟶ 401:

Because of these ownership rules, Rust types are known as ''[[linear types|linear]]'' or ''affine'' types, meaning each value can be used exactly once. This enforces a form of [[software fault isolation]] as the owner of a value is solely responsible for its correctness and deallocation.<ref name="BeyondSafety">{{Cite book |last1=Balasubramanian |first1=Abhiram |last2=Baranowski |first2=Marek S. |last3=Burtsev |first3=Anton |last4=Panda |first4=Aurojit |last5=Rakamarić |first5=Zvonimir |last6=Ryzhyk |first6=Leonid |title=Proceedings of the 16th Workshop on Hot Topics in Operating Systems |chapter=System Programming in Rust |date=2017-05-07 |chapter-url=https://doi.org/10.1145/3102980.3103006 |series=HotOS '17 |___location=New York, NY, US |publisher=Association for Computing Machinery |pages=156–161 |doi=10.1145/3102980.3103006 |isbn=978-1-4503-5068-6 |s2cid=24100599 |access-date=June 1, 2022 |archive-date=June 11, 2022 |archive-url=https://web.archive.org/web/20220611034046/https://dl.acm.org/doi/10.1145/3102980.3103006 |url-status=live}}</ref>

When a value goes out of scope, it is ''dropped'' by running its [[Destructor (computer programming)|destructor]]. The destructor may be programmatically defined through implementing the {{coderust|Drop}} [[#Traits|trait]]. This helps manage resources such as file handles, network sockets, and [[Lock (computer science)|locks]], since when objects are dropped, the resources associated with them are closed or released automatically.{{sfn|Klabnik|Nichols|2023|pp=327-30}}

==== Lifetimes ====

[[Object lifetime]] refers to the period of time during which a reference is valid; that is, the time between the object creation and destruction.<ref>{{Cite web |title=Lifetimes |url=https://doc.rust-lang.org/rust-by-example/scope/lifetime.html |access-date=2024-10-29 |website=Rust by Example |archive-date=2024-11-16 |archive-url=https://web.archive.org/web/20241116192422/https://doc.rust-lang.org/rust-by-example/scope/lifetime.html |url-status=live }}</ref> These ''lifetimes'' are implicitly associated with all Rust reference types. While often inferred, they can also be indicated explicitly with named lifetime parameters (often denoted {{coderust|'a}}, {{coderust|'b}}, and so on).<ref>{{Cite web |title=Explicit annotation |url=https://doc.rust-lang.org/rust-by-example/scope/lifetime/explicit.html |access-date=2024-10-29 |website=Rust by Example}}</ref>

Lifetimes in Rust can be thought of as [[Scope (computer science)|lexically scoped]], meaning that the duration of an object lifetime is inferred from the set of locations in the source code (i.e., function, line, and column numbers) for which a variable is valid.{{sfn|Klabnik|Nichols|2019|p=194}} For example, a reference to a local variable has a lifetime corresponding to the block it is defined in:{{sfn|Klabnik|Nichols|2019|p=194}}

Line 416 ⟶ 421:

</syntaxhighlight>

The borrow checker in the Rust compiler then enforces that references are only used in the locations of the source code where the associated lifetime is valid.{{sfn|Klabnik|Nichols|2019|pp=75,134}}<ref>{{Cite web |last=Shamrell-Harrington |first=Nell |date=2022-04-15 |title=The Rust Borrow Checker – a Deep Dive |url=https://www.infoq.com/presentations/rust-borrow-checker/ |access-date=2022-06-25 |website=InfoQ |language=en |archive-date=2022-06-25 |archive-url=https://web.archive.org/web/20220625140128/https://www.infoq.com/presentations/rust-borrow-checker/ |url-status=live }}</ref> In the example above, storing a reference to variable {{coderust|x}} in {{coderust|r}} is valid, as variable {{coderust|x}} has a longer lifetime ({{coderust|'a}}) than variable {{coderust|r}} ({{coderust|'b}}). However, when {{coderust|x}} has a shorter lifetime, the borrow checker would reject the program:

<syntaxhighlight lang="rust">

Line 431 ⟶ 436:

</syntaxhighlight>

Since the lifetime of the referenced variable ({{coderust|'b}}) is shorter than the lifetime of the variable holding the reference ({{coderust|'a}}), the borrow checker errors, preventing {{coderust|x}} from being used from outside its scope.{{sfn|Klabnik|Nichols|2019|pp=194-195}}

Lifetimes can be indicated using explicit ''lifetime parameters'' on function arguments. For example, the following code specifies that the reference returned by the function has the same lifetime as {{coderust|original}} (and ''not'' necessarily the same lifetime as {{coderust|prefix}}):{{sfn|Klabnik|Nichols|2023|pp=208–12}}

<syntaxhighlight lang="rust">

Line 452 ⟶ 457:

==== Standard library ====

[[File:Rust standard libraries.svg|thumb|A diagram of the dependencies between the standard library modules of Rust.]]

The Rust [[standard library]] defines and implements many widely used custom data types, including core data structures such as {{coderust|Vec}}, {{coderust|Option}}, and {{coderust|HashMap}}, as well as [[smart pointer]] types. Rust also provides a way to exclude most of the standard library using the attribute {{rust|#![no_std]}};, this enablesfor applications, such as embedded devices, which want to remove dependency code or provide their own core data structures. Internally, the standard library is divided into three parts, {{coderust|core}}, {{coderust|alloc}}, and {{coderust|std}}, where {{coderust|std}} and {{Coderust|alloc}} are excluded by {{rust|#![no_std]}}.{{sfn|Gjengset|2021|pp=213-215}}

Rust uses [[Option type|<code>Option</code>]] to define optional values, which can be matched using <code>if let</code> or <code>match</code> to access the inner value:{{sfn|Klabnik|Nichols|2023|pp=108-110,113-114,116-117}}

Line 482 ⟶ 487:

=== Polymorphism ===

Rust supports [[bounded parametric polymorphism]] through [[Trait (computer programming)|traits]] and [[generic function]]s.{{sfn|Klabnik|Nichols|2023|p=378}} Common behavior between types may be declared using traits and {{rust|impl}}s:{{sfn|Klabnik|Nichols|2023|pp=192-198}}

==== Generics ====

Rust's more advanced features include the use of [[generic function]]s. A generic function is given [[Generic programming|generic]] [[Parameter (computer programming)|parameters]], which allow the same function to be applied to different variable types. This capability reduces [[duplicate code]]{{sfn|Klabnik|Nichols|2019|pp=171–172}} and is known as [[parametric polymorphism]].

The following program calculates the sum of two things, for which addition is implemented using a generic function:

<syntaxhighlight lang="rust">

trait Zero: Sized {

use std::ops::Add;

fn zero() -> Self;

fn is_zero(&self) -> bool

where

Self: PartialEq,

{

self == &Zero::zero()

}

}

impl Zero for u32 {

// sum is a generic function with one type parameter, T

fn zero() -> u32 { 0 }

fn sum<T>(num1: T, num2: T) -> T

where

T: Add<Output = T>, // T must implement the Add trait where addition returns another T

{

num1 + num2 // num1 + num2 is syntactic sugar for num1.add(num2) provided by the Add trait

}

impl Zero for f32 {

fn main() {

letfn result1zero() =-> sum(10,Self 20);{ 0.0 }

println!("Sum is: {}", result1); // Sum is: 30

let result2 = sum(10.23, 20.45);

println!("Sum is: {}", result2); // Sum is: 30.68

}

</syntaxhighlight>

The example above also includes a method {{rust|is_zero}} which provides a default implementation that is not required when implementing the trait.{{sfn|Klabnik|Nichols|2023|pp=192-198}}

At compile time, polymorphic functions like <code>sum</code> are [[Instance (computer science)|instantiated]] with the specific types the code requires; in this case, sum of integers and sum of floats.

A function can then be made generic by adding type parameters inside angle brackets ({{rust|<Num>}}), which only allow types that implement the trait:

Generics can be used in functions to allow implementing a behavior for different types without repeating the same code. Generic functions can be written in relation to other generics, without knowing the actual type.{{sfn|Klabnik|Nichols|2019|pp=171–172,205}}

<syntaxhighlight lang="rust">

==== Traits ====

// sumzero is a generic function with one type parameter, TNum

[[File:UML class diagram Rust stdio.svg|thumb|Excerpt from {{Mono|std::io}}]]

fn zero<Num: Zero>() -> Num {

Rust's type system supports a mechanism called traits, inspired by [[type class]]es in the [[Haskell]] language,<ref name="influences"/> to define shared behavior between different types. For example, the <code>Add</code> trait can be implemented for floats and integers, which can be added; and the <code>Display</code> or <code>Debug</code> traits can be implemented for any type that can be converted to a string. Traits can be used to provide a set of common behavior for different types without knowing the actual type. This facility is known as [[ad hoc polymorphism]].

Num::zero()

}

fn main() {

Generic functions can constrain the generic type to implement a particular trait or traits; for example, an <code>add_one</code> function might require the type to implement <code>Add</code>. This means that a generic function can be type-checked as soon as it is defined. The implementation of generics is similar to the typical implementation of C++ templates: a separate copy of the code is generated for each instantiation. This is called [[monomorphization]] and contrasts with the [[type erasure]] scheme typically used in Java and Haskell. Type erasure is also available via the keyword <code>dyn</code> (short for dynamic).{{sfn|Klabnik|Nichols|2019|pp=181,182}} Because monomorphization duplicates the code for each type used, it can result in more optimized code for specific-use cases, but compile time and size of the output binary are also increased.{{sfn|Gjengset|2021|p=25}}

let a: u32 = zero();

let b: f32 = zero();

assert!(a.is_zero() && b.is_zero());

}

</syntaxhighlight>

In the examples above, {{rust|Num: Zero}} as well as {{rust|where Self: PartialEq}} are trait bounds that constrain the type to only allow types that implement {{rust|Zero}} or {{rust|PartialEq}}.{{sfn|Klabnik|Nichols|2023|pp=192-198}} Within a trait or impl, {{rust|Self}} refers to the type that the code is implementing.{{sfn|Klabnik|Nichols|2023|p=98}}

In addition to defining methods for a user-defined type, the <code>impl</code> keyword can be used to implement a trait for a type.{{sfn|Klabnik|Nichols|2019|pp=93}} Traits can provide additional derived methods when implemented.{{sfn|Klabnik|Nichols|2019|pp=182–184}} For example, the trait <code>Iterator</code> requires that the <code>next</code> method be defined for the type. Once the <code>next</code> method is defined, the trait can provide common functional helper methods over the iterator, such as <code>map</code> or <code>filter</code>.{{sfn|Klabnik|Nichols|2019|pp=281–283}}

Generics can be used in functions to allow implementing a behavior for different types without repeating the same code. Generic functions can be written in relation to other generics, without knowing the actual type.{{sfn|Klabnik|Nichols|2019|pp=171–172,205}}

==== Trait objects ====

RustGeneric traitsfunctions are implemented usinguse [[static dispatch]], meaning that the type of all valuesparameters isthat end up being used for the function must be known at compile time;. Generic functions generate separate copies of the code for each combination of generic parameters used in a process called [[monomorphization]].{{sfn|Klabnik|Nichols|2023|pp=191-192}} Because monomorphization duplicates the code for each type used, it is as performant as writing functions using concrete types,{{sfn|Klabnik|Nichols|2023|pp=191-192}} but compile time and size of the output binary could be howeverincreased.{{sfn|Gjengset|2021|p=25}}

However, Rust also uses a feature known as ''trait objects'' to accomplish [[dynamic dispatch]], a type of polymorphism where the implementation of a polymorphic operation is chosen at [[Runtime (program lifecycle phase)|runtime]]. This allows for behavior similar to [[duck typing]], where all data types that implement a given trait can be treated as functionally equivalent.{{sfn|Klabnik|Nichols|2023|loc=[https://doc.rust-lang.org/book/ch18-02-trait-objects.html 18.2. Using Trait Objects That Allow for Values of Different Types]}} Trait objects are declared using the syntax <code>dyn Tr</code> where <code>Tr</code> is a trait. Trait objects are dynamically sized, therefore they must be put behind a pointer, such as <code>Box</code>.{{sfn|Klabnik|Nichols|2019|pp=441–442}} The following example creates a list of objects where each object can be printed out using the <code>Display</code> trait:

<syntaxhighlight lang="Rust">

Line 540 ⟶ 553:

=== Memory safety ===

Rust is designed to be [[memory safe]]. It does not permit null pointers, [[dangling pointer]]s, or [[data race]]s.<ref name="cnet">{{cite web |url=http://reviews.cnet.com/8301-3514_7-57577639/samsung-joins-mozillas-quest-for-rust/ |title=Samsung joins Mozilla's quest for Rust |last=Rosenblatt |first=Seth |date=2013-04-03 |publisher=[[CNET]] |access-date=2013-04-05 |archive-date=2013-04-04 |archive-url=https://web.archive.org/web/20130404142333/http://reviews.cnet.com/8301-3514_7-57577639/samsung-joins-mozillas-quest-for-rust/ |url-status=live}}</ref><ref name="lwn">{{cite web |last=Brown |first=Neil |date=2013-04-17 |title=A taste of Rust |url=https://lwn.net/Articles/547145/ |url-status=live |archive-url=https://web.archive.org/web/20130426010754/http://lwn.net/Articles/547145/ |archive-date=2013-04-26 |access-date=2013-04-25 |website=[[LWN.net]]}}</ref><ref name="The Rustonomicon">{{Cite web|url=https://doc.rust-lang.org/nomicon/races.html|title=Races|website=The Rustonomicon|access-date=2017-07-03|archive-date=2017-07-10|archive-url=https://web.archive.org/web/20170710194643/https://doc.rust-lang.org/nomicon/races.html|url-status=live}}</ref><ref name="Sensors">{{cite journal |last1=Vandervelden |first1=Thibaut |last2=De Smet |first2=Ruben |last3=Deac |first3=Diana |last4=Steenhaut |first4=Kris |last5=Braeken |first5=An |title=Overview of Embedded Rust Operating Systems and Frameworks |journal= Sensors|doi=10.3390/s24175818 |date=7 September 2024 |volume=24 |issue=17 |page=5818 |doi-access=free |pmid=39275729 |pmc=11398098 |bibcode=2024Senso..24.5818V }}</ref> Data values can be initialized only through a fixed set of forms, all of which require their inputs to be already initialized.<ref name="lang-faq">{{cite web |title=The Rust Language FAQ |publisher=The Rust Programming Language |url=http://static.rust-lang.org/doc/master/complement-lang-faq.html |url-status=dead |archive-url=https://web.archive.org/web/20150420104147/http://static.rust-lang.org/doc/master/complement-lang-faq.html |archive-date=2015-04-20 |year=2015 |access-date=2017-04-24}}</ref>

Unsafe code can subvert some of these restrictions, using the <code>unsafe</code> keyword.{{sfn|Klabnik|Nichols|2019|pp=418–427}} Unsafe code may also be used for low-level functionality, such as [[Volatile (computer programming)|volatile memory access]], architecture-specific intrinsics, [[type punning]], and inline assembly.{{sfn|McNamara|2021|p=139, 376–379, 395}}

=== Memory management ===

Line 547 ⟶ 558:

The built-in reference types using the <code>&</code> symbol do not involve run-time reference counting. The safety and validity of the underlying pointers is verified at compile time, preventing [[dangling pointers]] and other forms of [[undefined behavior]].{{sfn|Klabnik|Nichols|2019|pp=70–75}} Rust's type system separates shared, [[Immutable object|immutable]] references of the form <code>&T</code> from unique, mutable references of the form <code>&mut T</code>. A mutable reference can be coerced to an immutable reference, but not vice versa.{{sfn|Klabnik|Nichols|2019|p=323}}

==== GenericsUnsafe ====

UnsafeRust's codememory cansafety subvertchecks may be circumvented through the someuse of these{{rust|unsafe}} restrictionsblocks. This allows programmers to deference arbitrary raw pointers, usingcall theexternal <code>unsafe</code>, or perform other low-level functionality not allowed by safe keywordRust.{{sfn|Klabnik|Nichols|20192023|pp=418–427420-429}} Unsafe code may also be used forSome low-level functionality, suchenabled in this way asincludes [[Volatile (computer programming)|volatile memory access]], architecture-specific intrinsics, [[type punning]], and inline assembly.{{sfn|McNamara|2021|p=139, 376–379, 395}}

Unsafe code is sometimes needed to implement complex data structures.<ref name="UnsafeRustUse">{{Cite journal |last1=Astrauskas |first1=Vytautas |last2=Matheja |first2=Christoph |last3=Poli |first3=Federico |last4=Müller |first4=Peter |last5=Summers |first5=Alexander J. |date=2020-11-13 |title=How do programmers use unsafe rust? |url=https://dl.acm.org/doi/10.1145/3428204 |journal=Proceedings of the ACM on Programming Languages |language=en |volume=4 |issue=OOPSLA |pages=1–27 |doi=10.1145/3428204 |issn=2475-1421|hdl=20.500.11850/465785 |hdl-access=free}}</ref> A frequently cited example is that it is difficult or impossible to implement [[doubly linked list]]s in safe Rust.<ref>{{Cite journal |last=Lattuada |first=Andrea |last2=Hance |first2=Travis |last3=Cho |first3=Chanhee |last4=Brun |first4=Matthias |last5=Subasinghe |first5=Isitha |last6=Zhou |first6=Yi |last7=Howell |first7=Jon |last8=Parno |first8=Bryan |last9=Hawblitzel |first9=Chris |date=2023-04-06 |title=Verus: Verifying Rust Programs using Linear Ghost Types |url=https://dl.acm.org/doi/10.1145/3586037 |journal=Software Artifact (virtual machine, pre-built distributions) for "Verus: Verifying Rust Programs using Linear Ghost Types" |volume=7 |issue=OOPSLA1 |pages=85:286–85:315 |doi=10.1145/3586037|hdl=20.500.11850/610518 |hdl-access=free }}</ref><ref>{{Cite journal |last=Milano |first=Mae |last2=Turcotti |first2=Julia |last3=Myers |first3=Andrew C. |date=2022-06-09 |title=A flexible type system for fearless concurrency |url=https://dl.acm.org/doi/10.1145/3519939.3523443 |journal=Proceedings of the 43rd ACM SIGPLAN International Conference on Programming Language Design and Implementation |series=PLDI 2022 |___location=New York, NY, USA |publisher=Association for Computing Machinery |pages=458–473 |doi=10.1145/3519939.3523443 |isbn=978-1-4503-9265-5|doi-access=free }}</ref><ref>{{Cite web |title=Introduction - Learning Rust With Entirely Too Many Linked Lists |url=https://rust-unofficial.github.io/too-many-lists/ |access-date=2025-08-06 |website=rust-unofficial.github.io}}</ref><ref>{{Cite journal |last=Noble |first=James |last2=Mackay |first2=Julian |last3=Wrigstad |first3=Tobias |date=2023-10-16 |title=Rusty Links in Local Chains✱ |url=https://doi.org/10.1145/3611096.3611097 |journal=Proceedings of the 24th ACM International Workshop on Formal Techniques for Java-like Programs |series=FTfJP '22 |___location=New York, NY, USA |publisher=Association for Computing Machinery |pages=1–3 |doi=10.1145/3611096.3611097 |isbn=979-8-4007-0784-1|url-access=subscription }}</ref>

Programmers using unsafe Rust are considered responsible for upholding Rust's memory and type safety requirements, for example, that no two mutable references exist pointing to the same ___location.<ref name=IsRustSafely>{{Cite journal |last=Evans |first=Ana Nora |last2=Campbell |first2=Bradford |last3=Soffa |first3=Mary Lou |date=2020-10-01 |title=Is rust used safely by software developers? |url=https://doi.org/10.1145/3377811.3380413 |journal=Proceedings of the ACM/IEEE 42nd International Conference on Software Engineering |series=ICSE '20 |___location=New York, NY, USA |publisher=Association for Computing Machinery |pages=246–257 |doi=10.1145/3377811.3380413 |isbn=978-1-4503-7121-6|arxiv=2007.00752 }}</ref> If programmers write code which violates these requirements, this results in [[undefined behavior]].<ref name=IsRustSafely/> The Rust documentation includes a list of behavior considered undefined, including accessing dangling or misaligned pointers, or breaking the aliasing rules for references.<ref>{{Cite web |title=Behavior considered undefined - The Rust Reference |url=https://doc.rust-lang.org/reference/behavior-considered-undefined.html |access-date=2025-08-06 |website=doc.rust-lang.org}}</ref>

<!--

Line 586 ⟶ 605:

<syntaxhighlight lang="rust">

#[unsafe(no_mangle)]

pub extern "C" fn exported_from_rust(x: i32) -> i32 { x + 1 }

unsafe extern "C" {

Line 593 ⟶ 612:

</syntaxhighlight>

The {{rust|#[repr(C)]}} attribute enables deterministic memory layouts for {{rust|struct}}s and {{rust|enum}}s for use across FFI boundaries.{{sfn|Gjengset|2021|pp=193-209}} External libraries such as {{coderust|bindgen}} and {{coderust|cxx}} can generate Rust bindings for C/C++.{{sfn|Gjengset|2021|pp=193-209}}<ref>{{Cite web|title=Safe Interoperability between Rust and C++ with CXX|url=https://www.infoq.com/news/2020/12/cpp-rust-interop-cxx/|date=2020-12-06|access-date=2021-01-03|website=InfoQ|language=en|archive-date=January 22, 2021|archive-url=https://web.archive.org/web/20210122142035/https://www.infoq.com/news/2020/12/cpp-rust-interop-cxx/|url-status=live}}</ref>

== Ecosystem ==

Line 623 ⟶ 642:

Following Rust 1.0, new features are developed in ''nightly'' versions which are released daily. During each six-week release cycle, changes to nightly versions are released to beta, while changes from the previous beta version are released to a new stable version.<ref name="Rust Book G">{{harvnb|Klabnik|Nichols|2019|loc=Appendix G – How Rust is Made and "Nightly Rust"}}</ref>

Every two or three years, a new "edition" is produced. Editions are released to allow making limited [[breaking changes]], such as promoting {{coderust|await}} to a keyword to support [[async/await]] features. Crates targeting different editions can interoperate with each other, so a crate can upgrade to a new edition even if its callers or its dependencies still target older editions. Migration to a new edition can be assisted with automated tooling.{{sfn|Blandy|Orendorff|Tindall|2021|pp=176–177}}

=== IDE support ===

''rust-analyzer'' is a collectionset of [[Utility software|utilities]] that provides [[Integratedintegrated development environment]]s (IDEs) and [[text editor]]s with information about a Rust project through the [[Language Server Protocol]]. This enables features including [[autocompletionautocomplete]], and the display of [[compilation errorserror]] display, while editing code.{{sfn|Klabnik|Nichols|2023|p=623}}

== Performance ==

Since it performs no garbage collection, Rust is often faster than other memory-safe languages.<ref>{{Cite web |last1=Anderson |first1=Tim |date=2021-11-30 |title=Can Rust save the planet? Why, and why not |url=https://www.theregister.com/2021/11/30/aws_reinvent_rust/ |access-date=2022-07-11 |website=[[The Register]] |language=en |archiveurl-datestatus=2022-07-11live |archive-url=https://web.archive.org/web/20220711001629/https://www.theregister.com/2021/11/30/aws_reinvent_rust/ |urlarchive-statusdate=live2022-07-11}}</ref><ref name="BeyondSafety"/><ref>{{Cite web |last1=Yegulalp |first1=Serdar |date=2021-10-06 |title=What is the Rust language? Safe, fast, and easy software development |url=https://www.infoworld.com/article/3218074/what-is-rust-safe-fast-and-easy-software-development.html |access-date=2022-06-25 |website=[[InfoWorld]] |language=en |archiveurl-datestatus=2022-06-24live |archive-url=https://web.archive.org/web/20220624101013/https://www.infoworld.com/article/3218074/what-is-rust-safe-fast-and-easy-software-development.html |urlarchive-statusdate=live2022-06-24}}</ref> Most of Rust's memory safety guarantees impose no runtime overhead,{{sfn|McNamara|2021|p=11}} with the exception of [[Array (data structure)|array indexing]] which is checked at runtime by default.<ref name=SaferAtAnySpeed>{{Cite journal |last1=Popescu |first1=Natalie |last2=Xu |first2=Ziyang |last3=Apostolakis |first3=Sotiris |last4=August |first4=David I. |last5=Levy |first5=Amit |date=2021-10-15 |title=Safer at any speed: automatic context-aware safety enhancement for Rust |journal=Proceedings of the ACM on Programming Languages |volume=5 |issue=OOPSLA |quote="We observe a large variance in the overheads of checked indexing: 23.6% of benchmarks do report significant performance hits from checked indexing, but 64.5% report little-to-no impact and, surprisingly, 11.8% report improved performance ... Ultimately, while unchecked indexing can improve performance, most of the time it does not." |quote-page=5 |at=Section 2 |doi=10.1145/3485480 |s2cid=238212612|doi-access=free}}</ref> PerformanceThe performance impact of array indexing bounds checks varies, but can be significant in some cases.<ref name=SaferAtAnySpeed/>

Many of Rust's features are so-called ''zero-cost abstractions'', meaning they are optimized away at compile time and incur no runtime penalty.{{sfn|McNamara|2021|p=19, 27}} The ownership and borrowing system permits [[zero-copy]] implementations for some performance-sensitive tasks, such as [[parsing]].<ref>{{Cite book |last=Couprie |first=Geoffroy |title=2015 IEEE Security and Privacy Workshops |chapter=Nom, A Byte oriented, streaming, Zero copy, Parser Combinators Library in Rust |date=2015 |chapter-url=https://ieeexplore.ieee.org/document/7163218 |pages=142–148 |doi=10.1109/SPW.2015.31 |isbn=978-1-4799-9933-0 |s2cid=16608844 |archive-date=2022-10-09 |access-date=2022-10-09 |archive-url=https://web.archive.org/web/20221009201729/https://ieeexplore.ieee.org/document/7163218 |url-status=live}}</ref> [[Static dispatch]] is used by default to eliminate [[method call]]s, except for methods called on dynamic trait objects.{{sfn|McNamara|2021|p=20}} The compiler also uses [[inline expansion]] to eliminate [[function call]]s and statically-dispatched method invocations.<ref>{{Cite web |title=Code generation |url=https://doc.rust-lang.org/reference/attributes/codegen.html |access-date=2022-10-09 |website=The Rust Reference |archive-date=2022-10-09 |archive-url=https://web.archive.org/web/20221009202615/https://doc.rust-lang.org/reference/attributes/codegen.html |url-status=live}}</ref>

Rust provides two "modes": safe and unsafe. Safe mode is the "normal" one, in which most Rust is written. In unsafe mode, the developer is responsible for the code's memory safety, which is used by developers for cases where the compiler is too restrictive.<ref name="UnsafeRustUse">{{Cite journal |last1=Astrauskas |first1=Vytautas |last2=Matheja |first2=Christoph |last3=Poli |first3=Federico |last4=Müller |first4=Peter |last5=Summers |first5=Alexander J. |date=2020-11-13 |title=How do programmers use unsafe rust? |url=https://dl.acm.org/doi/10.1145/3428204 |journal=Proceedings of the ACM on Programming Languages |language=en |volume=4 |issue=OOPSLA |pages=1–27 |doi=10.1145/3428204 |issn=2475-1421|hdl=20.500.11850/465785 |hdl-access=free}}</ref>

Since Rust uses [[LLVM]], all performance improvements in LLVM apply to Rust also.<ref name="how-fast-is-rust">{{cite web |url=https://doc.rust-lang.org/1.0.0/complement-lang-faq.html#how-fast-is-rust? |title=How Fast Is Rust? |website=The Rust Programming Language FAQ |access-date=11 April 2019 |archive-date=28 October 2020 |archive-url=https://web.archive.org/web/20201028102013/https://doc.rust-lang.org/1.0.0/complement-lang-faq.html#how-fast-is-rust? |url-status=live}}</ref> Unlike C and C++, Rust allows for reordering struct and enum elements<ref>{{Cite book |url=https://dlnext.acm.org/doi/abs/10.1145/3445814.3446724 |access-date=2022-07-12 |year=2021 |language=en |doi=10.1145/3445814.3446724 |quote=... While some compilers (e.g., Rust) support structure reordering [82], C & C++ compilers are forbidden to reorder data structures (e.g., struct or class) [74] ... |last1=Farshin |first1=Alireza |last2=Barbette |first2=Tom |last3=Roozbeh |first3=Amir |last4=Maguire Jr |first4=Gerald Q. Jr |last5=Kostić |first5=Dejan |year=2021 |url=https://dlnext.acm.org/doi/abs/10.1145/3445814.3446724 |access-date=2022-07-12 |language=en |doi=10.1145/3445814.3446724|title=Proceedings of the 26th ACM International Conference on Architectural Support for Programming Languages and Operating Systems |chapter=PacketMill: Toward per-Core 100-GBPS networking |pages=1–17 |isbn=9781450383172 |s2cid=231949599 |archiveurl-datestatus=2022-07-12live |archive-url=https://web.archive.org/web/20220712060927/https://dlnext.acm.org/doi/abs/10.1145/3445814.3446724 |urlarchive-statusdate=live2022-07-12 |quote=... While some compilers (e.g., Rust) support structure reordering [82], C & C++ compilers are forbidden to reorder data structures (e.g., struct or class) [74] ... }}</ref> to reduce the sizes of structures in memory, for better memory alignment and efficiency.{{sfn|Gjengset|2021|p=22}}

Many of Rust's features are so-called ''zero-cost abstractions'', meaning they are optimized away at compile time and incur no runtime penalty.{{sfn|McNamara|2021|p=19, 27}} The ownership and borrowing system permits [[zero-copy]] implementations for some performance-sensitive tasks, such as [[parsing]].<ref>{{Cite book |last=Couprie |first=Geoffroy |title=2015 IEEE Security and Privacy Workshops |chapter=Nom, A Byte oriented, streaming, Zero copy, Parser Combinators Library in Rust |date=2015 |chapter-url=https://ieeexplore.ieee.org/document/7163218 |pages=142–148 |doi=10.1109/SPW.2015.31 |isbn=978-1-4799-9933-0 |s2cid=16608844 |archive-date=2022-10-09 |access-date=2022-10-09 |archive-url=https://web.archive.org/web/20221009201729/https://ieeexplore.ieee.org/document/7163218 |url-status=live}}</ref> [[Static dispatch]] is used by default to eliminate [[method call]]s, except for methods called on dynamic trait objects.{{sfn|McNamara|2021|p=20}} The compiler also uses [[inline expansion]] to eliminate [[function call]]s and statically-dispatched method invocations.<ref>{{Cite web |title=Code generation |url=https://doc.rust-lang.org/reference/attributes/codegen.html |access-date=2022-10-09 |website=The Rust Reference |archive-date=2022-10-09 |archive-url=https://web.archive.org/web/20221009202615/https://doc.rust-lang.org/reference/attributes/codegen.html |url-status=live}}</ref>

Since Rust uses [[LLVM]], all performance improvements in LLVM apply to Rust also.<ref name="how-fast-is-rust">{{cite web |url=https://doc.rust-lang.org/1.0.0/complement-lang-faq.html#how-fast-is-rust? |title=How Fast Is Rust? |website=The Rust Programming Language FAQ |access-date=11 April 2019 |archive-date=28 October 2020 |archive-url=https://web.archive.org/web/20201028102013/https://doc.rust-lang.org/1.0.0/complement-lang-faq.html#how-fast-is-rust? |url-status=live}}</ref> Unlike C and C++, Rust allows for reordering struct and enum elements<ref>{{Cite book |url=https://dlnext.acm.org/doi/abs/10.1145/3445814.3446724 |access-date=2022-07-12 |year=2021 |language=en |doi=10.1145/3445814.3446724 |quote=... While some compilers (e.g., Rust) support structure reordering [82], C & C++ compilers are forbidden to reorder data structures (e.g., struct or class) [74] ... |last1=Farshin |first1=Alireza |last2=Barbette |first2=Tom |last3=Roozbeh |first3=Amir |last4=Maguire Jr |first4=Gerald Q. |last5=Kostić |first5=Dejan |title=Proceedings of the 26th ACM International Conference on Architectural Support for Programming Languages and Operating Systems |chapter=PacketMill: Toward per-Core 100-GBPS networking |pages=1–17 |isbn=9781450383172 |s2cid=231949599 |archive-date=2022-07-12 |archive-url=https://web.archive.org/web/20220712060927/https://dlnext.acm.org/doi/abs/10.1145/3445814.3446724 |url-status=live}}</ref> to reduce the sizes of structures in memory, for better memory alignment and efficiency.{{sfn|Gjengset|2021|p=22}}

== Adoption ==

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[[Discord]], an [[instant messaging]] software company, rewrote parts of its system in Rust for increased performance in 2020. In the same year, Dropbox announced that its [[file synchronization]] had been rewritten in Rust. [[Facebook]] ([[Meta Platforms|Meta]]) used Rust to redesign its system that manages source code for internal projects.<ref name="MITTechReview" />

In the 20242025 [[Stack Overflow]] Developer Survey, 1214.68% of respondents had recently done extensive development in Rust.<ref name="SO-20242025-survey">{{Cite web |title=20242025 Stack Overflow Developer Survey – Technology |url=https://survey.stackoverflow.co/20242025/technology |access-date=20242025-1108-2809 |website=[[Stack Overflow]]}}</ref> The survey named Rust the "most admired programming language" annually from 2016 to 20242025 (inclusive), as measured by the number of existing developers interested in continuing to work in the language.<ref>{{Cite web |last=Claburn |first=Thomas |date=2022-06-23 |title=Linus Torvalds says Rust is coming to the Linux kernel |url=https://www.theregister.com/2022/06/23/linus_torvalds_rust_linux_kernel/ |access-date=2022-07-15 |website=[[The Register]] |language=en |archive-date=2022-07-28 |archive-url=https://web.archive.org/web/20220728221531/https://www.theregister.com/2022/06/23/linus_torvalds_rust_linux_kernel/ |url-status=live }}</ref>{{refn|group=note|That is, among respondents who have done "extensive development work [with Rust] in over the past year" (1214.68%), Rust had the largest percentage who also expressed interest to "work in [Rust] over the next year" (8272.24%).<ref name="SO-20242025-survey"/>}} In 20242025, 2829.72% of developers not currently working in Rust expressed an interest in doing so.<ref name="SO-20242025-survey" />

[[DARPA]] has a project TRACTOR (Translating All C to Rust) automatically translating C to Rust using techniques such as static analysis, dynamic analysis, and large language models.<ref>{{cite web |last1=Wallach |first1=Dan |title=TRACTOR: Translating All C to Rust |url=https://www.darpa.mil/research/programs/translating-all-c-to-rust |publisher=[[DARPA]] |access-date=3 August 2025}}</ref>

== In academic research ==

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Rust's safety and performance have been investigated in [[programming language theory]] research.<ref>{{Cite journal |last1=Jung |first1=Ralf |last2=Jourdan |first2=Jacques-Henri |last3=Krebbers |first3=Robbert |last4=Dreyer |first4=Derek |date=2017-12-27 |title=RustBelt: securing the foundations of the Rust programming language |url=https://dl.acm.org/doi/10.1145/3158154 |journal=Proceedings of the ACM on Programming Languages |language=en |volume=2 |issue=POPL |pages=1–34 |doi=10.1145/3158154 |issn=2475-1421|hdl=21.11116/0000-0003-34C6-3 |hdl-access=free }}</ref><ref name="UnsafeRustUse"/><ref>{{Cite journal |last1=Popescu |first1=Natalie |last2=Xu |first2=Ziyang |last3=Apostolakis |first3=Sotiris |last4=August |first4=David I. |last5=Levy |first5=Amit |date=2021-10-20 |title=Safer at any speed: automatic context-aware safety enhancement for Rust |journal=Proceedings of the ACM on Programming Languages |language=en |volume=5 |issue=OOPSLA |pages=1–23 |doi=10.1145/3485480 |issn=2475-1421|doi-access=free }}</ref>

Rust's applicability to writing research software has been examined in other fields. A journal article published to ''[[Proceedings of the International Astronomical Union]]'' used Rust to simulate multi-planet systems.<ref name=ResearchSoftware1>{{Cite journal |last1=Blanco-Cuaresma |first1=Sergi |last2=Bolmont |first2=Emeline |date=2017-05-30 |title=What can the programming language Rust do for astrophysics? |url=https://www.cambridge.org/core/journals/proceedings-of-the-international-astronomical-union/article/what-can-the-programming-language-rust-do-for-astrophysics/B51B6DF72B7641F2352C05A502F3D881 |journal=[[Proceedings of the International Astronomical Union]] |language=en |volume=12 |issue=S325 |pages=341–344 |doi=10.1017/S1743921316013168 |arxiv=1702.02951 |bibcode=2017IAUS..325..341B |s2cid=7857871 |issn=1743-9213 |archive-date=2022-06-25 |access-date=2022-06-25 |archive-url=https://web.archive.org/web/20220625140128/https://www.cambridge.org/core/journals/proceedings-of-the-international-astronomical-union/article/what-can-the-programming-language-rust-do-for-astrophysics/B51B6DF72B7641F2352C05A502F3D881 |url-status=live }}</ref> An article published in ''[[Nature (journal)|Nature]]'' shared stories of bioinformaticians using Rust.<ref name="Nature"/> Both articles found that Rust has advantages for its performance and safety, and cited the [[learning curve]] as being a primary drawback to its adoption.<ref name=ResearchSoftware1/><ref name="Nature"/>

== Community ==

[[File:Rustacean-orig-noshadow.svg|alt=A bright orange crab icon|thumb|Some Rust users refer to themselves as Rustaceans (similar to the word [[crustacean]]) and have adopted an orange crab, Ferris, as their unofficial mascot.{{sfn|Klabnik|Nichols|2019|p=4}}<ref>{{cite web |title=Getting Started |url=https://www.rust-lang.org/learn/get-started#ferris |website=The Rust Programming Language |access-date=11 October 2020 |archive-date=1 November 2020 |archive-url=https://web.archive.org/web/20201101145703/https://www.rust-lang.org/learn/get-started#ferris |url-status=live}}</ref>]]

According to the ''[[MIT Technology Review]]'', the Rust community has been seen as "unusually friendly" to newcomers and particularly attracted people from the [[queer community]], partly due to its [[code of conduct]] which outlined a set of expectations for Rust community members to follow.<ref name="MITTechReview"/> Inclusiveness of the community has been cited as an important factor for some Rust developers.<ref name="Nature"/> Demographic data on the community has been collected and published by the Rust official blog.<ref name=StateOfRustSurvey2024>{{Cite web |title=2024 State of Rust Survey Results {{!}} Rust Blog |url=https://blog.rust-lang.org/2025/02/13/2024-State-Of-Rust-Survey-results.html |access-date=2025-04-06 |website=blog.rustRust-lang.org Blog |language=en}}</ref>

According to [[GitHub]]'s ''State of the Octoverse'' project, the Rust community grew by 50.5% in 2022, making it one of the fastest growing communities,<ref>{{Cite web |title=The top programming languages |url=https://octoverse.github.com/2022/top-programming-languages |access-date=2025-06-25 |website=The State of the Octoverse |language=en-gb}}</ref> though not one of the 10 largest communities as of 2024.<ref>{{Cite web |last=Staff |first=GitHub |date=2024-10-29 |title=Octoverse: AI leads Python to top language as the number of global developers surges |url=https://github.blog/news-insights/octoverse/octoverse-2024/ |access-date=2025-06-25 |website=The GitHub Blog |language=en-US}}</ref>

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=== Rust Foundation ===

{{Infobox organization

| name = Rust Foundation

| logo = Rust Foundation logo.png

| formation = {{Start date and age|2021|02|08}}

| founders = {{unbulleted list|[[Amazon Web Services]]|[[Google]]|[[Huawei]]|[[Microsoft]]|[[Mozilla Foundation]]}}

| type = [[Nonprofit organization]]

| location_country = [[United States]]

| leader_title = [[Chairperson]]

| leader_name = Shane Miller

| leader_title2 = [[Executive Director]]

| leader_name2 = Rebecca Rumbul

| website = {{URL|https://foundation.rust-lang.org}}

}}

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=== Book sources ===

{{refbegin}}

* {{Cite book |last=Gjengset |first=Jon |url=https://www.worldcat.org/oclc/1277511986 |title=Rust for Rustaceans |date=2021 |publisher=No Starch Press |isbn=9781718501850 |edition=1st |oclc=1277511986 |language=en}}

* {{Cite book|last1=Klabnik|first1=Steve|url=https://books.google.com/books?id=0Vv6DwAAQBAJ|title=The Rust Programming Language (Covers Rust 2018)|last2=Nichols|first2=Carol|date=2019-08-12|publisher=No Starch Press|isbn=978-1-7185-0044-0|language=en}}

* {{Cite book|last1=Blandy|first1=Jim|last2=Orendorff|first2=Jason|last3=Tindall|first3=Leonora F. S.|url=https://www.worldcat.org/oclc/1289839504|date=2021|edition=2nd|title=Programming Rust: Fast, Safe Systems Development|publisher=O'Reilly Media|isbn=978-1-4920-5254-8 |language=en|oclc=1289839504}}

* {{Cite book|last1=McNamara|first1=Tim|url=https://www.worldcat.org/oclc/1153044639|title=Rust in Action|oclc=1153044639|date=2021|publisher=Manning Publications|isbn=978-1-6172-9455-6|language=en}}

* {{Cite book |last1=Klabnik |first1=Steve |last2=Nichols |first2=Carol |url=https://www.worldcat.org/oclc/1363816350 |title=The Rust programming language |date=2023 |publisher=No Starch Press |isbn=978-1-7185-0310-6 |edition=2nd |oclc=1363816350}}

{{refend}}

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[[Category:Rust (programming language)| ]]

[[Category:Compiled programming languages]]

[[Category:Concurrent programming languages]]

[[Category:Free and open source compilers]]

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<!-- Hidden categories below -->

[[Category:Articles with example Rust code]]

[[Category:Compiled programming languages]]