| 
 | 1 | ++++  | 
 | 2 | +path = "2025/10/30/Rust-1.91.0"  | 
 | 3 | +title = "Announcing Rust 1.91.0"  | 
 | 4 | +authors = ["The Rust Release Team"]  | 
 | 5 | +aliases = ["releases/1.91.0"]  | 
 | 6 | + | 
 | 7 | +[extra]  | 
 | 8 | +release = true  | 
 | 9 | ++++  | 
 | 10 | + | 
 | 11 | +The Rust team is happy to announce a new version of Rust, 1.91.0. Rust is a programming language empowering everyone to build reliable and efficient software.  | 
 | 12 | + | 
 | 13 | +If you have a previous version of Rust installed via `rustup`, you can get 1.91.0 with:  | 
 | 14 | + | 
 | 15 | +```console  | 
 | 16 | +$ rustup update stable  | 
 | 17 | +```  | 
 | 18 | + | 
 | 19 | +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 1.91.0](https://doc.rust-lang.org/stable/releases.html#version-1910-2025-10-30).  | 
 | 20 | + | 
 | 21 | +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!  | 
 | 22 | + | 
 | 23 | +## What's in 1.91.0 stable  | 
 | 24 | + | 
 | 25 | +### `aarch64-pc-windows-msvc` is now a Tier 1 platform  | 
 | 26 | + | 
 | 27 | +The Rust compiler supports [a wide variety of targets][platform-support], but  | 
 | 28 | +the Rust Team can't provide the same level of support for all of them. To  | 
 | 29 | +clearly mark how supported each target is, we use a tiering system:  | 
 | 30 | + | 
 | 31 | +* Tier 3 targets are technically supported by the compiler, but we don't check  | 
 | 32 | +  whether their code build or passes the tests, and we don't provide any  | 
 | 33 | +  prebuilt binaries as part of our releases.  | 
 | 34 | +* Tier 2 targets are guaranteed to build and we provide prebuilt binaries, but  | 
 | 35 | +  we don't execute the test suite on those platforms: the produced binaries  | 
 | 36 | +  might not work or might have bugs.  | 
 | 37 | +* Tier 1 targets provide the highest support guarantee, and we run the full  | 
 | 38 | +  suite on those platforms for every change merged in the compiler. Prebuilt  | 
 | 39 | +  binaries are also available.  | 
 | 40 | + | 
 | 41 | +Rust 1.91.0 promotes the `aarch64-pc-windows-msvc` target to Tier 1 support,  | 
 | 42 | +bringing our highest guarantees to users of 64-bit ARM systems running Windows.  | 
 | 43 | + | 
 | 44 | +### Add lint against dangling raw pointers from local variables  | 
 | 45 | + | 
 | 46 | +While Rust's borrow checking prevents dangling references from being returned, it doesn't  | 
 | 47 | +track raw pointers. With this release, we are adding a warn-by-default lint on raw  | 
 | 48 | +pointers to local variables being returned from functions. For example, code like this:  | 
 | 49 | + | 
 | 50 | +```rust  | 
 | 51 | +fn f() -> *const u8 {  | 
 | 52 | +    let x = 0;  | 
 | 53 | +    &x  | 
 | 54 | +}  | 
 | 55 | +```  | 
 | 56 | + | 
 | 57 | +will now produce a lint:  | 
 | 58 | + | 
 | 59 | +```  | 
 | 60 | +warning: a dangling pointer will be produced because the local variable `x` will be dropped  | 
 | 61 | + --> src/lib.rs:3:5  | 
 | 62 | +  |  | 
 | 63 | +1 | fn f() -> *const u8 {  | 
 | 64 | +  |           --------- return type of the function is `*const u8`  | 
 | 65 | +2 |     let x = 0;  | 
 | 66 | +  |         - `x` is part the function and will be dropped at the end of the function  | 
 | 67 | +3 |     &x  | 
 | 68 | +  |     ^^  | 
 | 69 | +  |  | 
 | 70 | +  = note: pointers do not have a lifetime; after returning, the `u8` will be deallocated  | 
 | 71 | +    at the end of the function because nothing is referencing it as far as the type system is  | 
 | 72 | +    concerned  | 
 | 73 | +  = note: `#[warn(dangling_pointers_from_locals)]` on by default  | 
 | 74 | +```  | 
 | 75 | + | 
 | 76 | +Note that the code above is not itself unsafe, as it doesn't perform any dangerous  | 
 | 77 | +operations itself. Only dereferencing the raw pointer would be unsafe. We expect future  | 
 | 78 | +releases of Rust to add more functionality helping authors to safely interact with raw  | 
 | 79 | +pointers, and unsafe code more generally.  | 
 | 80 | + | 
 | 81 | +### Stabilized APIs  | 
 | 82 | + | 
 | 83 | +- [`Path::file_prefix`](https://doc.rust-lang.org/stable/std/path/struct.Path.html#method.file_prefix)  | 
 | 84 | +- [`AtomicPtr::fetch_ptr_add`](https://doc.rust-lang.org/stable/std/sync/atomic/struct.AtomicPtr.html#method.fetch_ptr_add)  | 
 | 85 | +- [`AtomicPtr::fetch_ptr_sub`](https://doc.rust-lang.org/stable/std/sync/atomic/struct.AtomicPtr.html#method.fetch_ptr_sub)  | 
 | 86 | +- [`AtomicPtr::fetch_byte_add`](https://doc.rust-lang.org/stable/std/sync/atomic/struct.AtomicPtr.html#method.fetch_byte_add)  | 
 | 87 | +- [`AtomicPtr::fetch_byte_sub`](https://doc.rust-lang.org/stable/std/sync/atomic/struct.AtomicPtr.html#method.fetch_byte_sub)  | 
 | 88 | +- [`AtomicPtr::fetch_or`](https://doc.rust-lang.org/stable/std/sync/atomic/struct.AtomicPtr.html#method.fetch_or)  | 
 | 89 | +- [`AtomicPtr::fetch_and`](https://doc.rust-lang.org/stable/std/sync/atomic/struct.AtomicPtr.html#method.fetch_and)  | 
 | 90 | +- [`AtomicPtr::fetch_xor`](https://doc.rust-lang.org/stable/std/sync/atomic/struct.AtomicPtr.html#method.fetch_xor)  | 
 | 91 | +- [`{integer}::strict_add`](https://doc.rust-lang.org/stable/std/primitive.u32.html#method.strict_add)  | 
 | 92 | +- [`{integer}::strict_sub`](https://doc.rust-lang.org/stable/std/primitive.u32.html#method.strict_sub)  | 
 | 93 | +- [`{integer}::strict_mul`](https://doc.rust-lang.org/stable/std/primitive.u32.html#method.strict_mul)  | 
 | 94 | +- [`{integer}::strict_div`](https://doc.rust-lang.org/stable/std/primitive.u32.html#method.strict_div)  | 
 | 95 | +- [`{integer}::strict_div_euclid`](https://doc.rust-lang.org/stable/std/primitive.u32.html#method.strict_div_euclid)  | 
 | 96 | +- [`{integer}::strict_rem`](https://doc.rust-lang.org/stable/std/primitive.u32.html#method.strict_rem)  | 
 | 97 | +- [`{integer}::strict_rem_euclid`](https://doc.rust-lang.org/stable/std/primitive.u32.html#method.strict_rem_euclid)  | 
 | 98 | +- [`{integer}::strict_neg`](https://doc.rust-lang.org/stable/std/primitive.u32.html#method.strict_neg)  | 
 | 99 | +- [`{integer}::strict_shl`](https://doc.rust-lang.org/stable/std/primitive.u32.html#method.strict_shl)  | 
 | 100 | +- [`{integer}::strict_shr`](https://doc.rust-lang.org/stable/std/primitive.u32.html#method.strict_shr)  | 
 | 101 | +- [`{integer}::strict_pow`](https://doc.rust-lang.org/stable/std/primitive.u32.html#method.strict_pow)  | 
 | 102 | +- [`i{N}::strict_add_unsigned`](https://doc.rust-lang.org/stable/std/primitive.i32.html#method.strict_add_unsigned)  | 
 | 103 | +- [`i{N}::strict_sub_unsigned`](https://doc.rust-lang.org/stable/std/primitive.i32.html#method.strict_sub_unsigned)  | 
 | 104 | +- [`i{N}::strict_abs`](https://doc.rust-lang.org/stable/std/primitive.i32.html#method.strict_abs)  | 
 | 105 | +- [`u{N}::strict_add_signed`](https://doc.rust-lang.org/stable/std/primitive.u32.html#method.strict_add_signed)  | 
 | 106 | +- [`u{N}::strict_sub_signed`](https://doc.rust-lang.org/stable/std/primitive.u32.html#method.strict_sub_signed)  | 
 | 107 | +- [`PanicHookInfo::payload_as_str`](https://doc.rust-lang.org/stable/std/panic/struct.PanicHookInfo.html#method.payload_as_str)  | 
 | 108 | +- [`core::iter::chain`](https://doc.rust-lang.org/stable/core/iter/fn.chain.html)  | 
 | 109 | +- [`u{N}::checked_signed_diff`](https://doc.rust-lang.org/stable/std/primitive.u16.html#method.checked_signed_diff)  | 
 | 110 | +- [`core::array::repeat`](https://doc.rust-lang.org/stable/core/array/fn.repeat.html)  | 
 | 111 | +- [`PathBuf::add_extension`](https://doc.rust-lang.org/stable/std/path/struct.PathBuf.html#method.add_extension)  | 
 | 112 | +- [`PathBuf::with_added_extension`](https://doc.rust-lang.org/stable/std/path/struct.PathBuf.html#method.with_added_extension)  | 
 | 113 | +- [`Duration::from_mins`](https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.from_mins)  | 
 | 114 | +- [`Duration::from_hours`](https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.from_hours)  | 
 | 115 | +- [`impl PartialEq<str> for PathBuf`](https://doc.rust-lang.org/stable/std/path/struct.PathBuf.html#impl-PartialEq%3Cstr%3E-for-PathBuf)  | 
 | 116 | +- [`impl PartialEq<String> for PathBuf`](https://doc.rust-lang.org/stable/std/path/struct.PathBuf.html#impl-PartialEq%3CString%3E-for-PathBuf)  | 
 | 117 | +- [`impl PartialEq<str> for Path`](https://doc.rust-lang.org/stable/std/path/struct.Path.html#impl-PartialEq%3Cstr%3E-for-Path)  | 
 | 118 | +- [`impl PartialEq<String> for Path`](https://doc.rust-lang.org/stable/std/path/struct.Path.html#impl-PartialEq%3CString%3E-for-Path)  | 
 | 119 | +- [`impl PartialEq<PathBuf> for String`](https://doc.rust-lang.org/nightly/std/string/struct.String.html#impl-PartialEq%3CPathBuf%3E-for-String)  | 
 | 120 | +- [`impl PartialEq<Path> for String`](https://doc.rust-lang.org/nightly/std/string/struct.String.html#impl-PartialEq%3CPath%3E-for-String)  | 
 | 121 | +- [`impl PartialEq<PathBuf> for str`](https://doc.rust-lang.org/nightly/std/primitive.str.html#impl-PartialEq%3CPathBuf%3E-for-str)  | 
 | 122 | +- [`impl PartialEq<Path> for str`](https://doc.rust-lang.org/nightly/std/primitive.str.html#impl-PartialEq%3CPath%3E-for-str)  | 
 | 123 | +- [`Ipv4Addr::from_octets`](https://doc.rust-lang.org/stable/std/net/struct.Ipv4Addr.html#method.from_octets)  | 
 | 124 | +- [`Ipv6Addr::from_octets`](https://doc.rust-lang.org/stable/std/net/struct.Ipv6Addr.html#method.from_octets)  | 
 | 125 | +- [`Ipv6Addr::from_segments`](https://doc.rust-lang.org/stable/std/net/struct.Ipv6Addr.html#method.from_segments)  | 
 | 126 | +- [`impl<T> Default for Pin<Box<T>> where Box<T>: Default, T: ?Sized`](https://doc.rust-lang.org/stable/std/default/trait.Default.html#impl-Default-for-Pin%3CBox%3CT%3E%3E)  | 
 | 127 | +- [`impl<T> Default for Pin<Rc<T>> where Rc<T>: Default, T: ?Sized`](https://doc.rust-lang.org/stable/std/default/trait.Default.html#impl-Default-for-Pin%3CRc%3CT%3E%3E)  | 
 | 128 | +- [`impl<T> Default for Pin<Arc<T>> where Arc<T>: Default, T: ?Sized`](https://doc.rust-lang.org/stable/std/default/trait.Default.html#impl-Default-for-Pin%3CArc%3CT%3E%3E)  | 
 | 129 | +- [`Cell::as_array_of_cells`](https://doc.rust-lang.org/stable/std/cell/struct.Cell.html#method.as_array_of_cells)  | 
 | 130 | +- [`u{N}::carrying_add`](https://doc.rust-lang.org/stable/std/primitive.u64.html#method.carrying_add)  | 
 | 131 | +- [`u{N}::borrowing_sub`](https://doc.rust-lang.org/stable/std/primitive.u64.html#method.borrowing_sub)  | 
 | 132 | +- [`u{N}::carrying_mul`](https://doc.rust-lang.org/stable/std/primitive.u64.html#method.carrying_mul)  | 
 | 133 | +- [`u{N}::carrying_mul_add`](https://doc.rust-lang.org/stable/std/primitive.u64.html#method.carrying_mul_add)  | 
 | 134 | +- [`BTreeMap::extract_if`](https://doc.rust-lang.org/stable/std/collections/struct.BTreeMap.html#method.extract_if)  | 
 | 135 | +- [`BTreeSet::extract_if`](https://doc.rust-lang.org/stable/std/collections/struct.BTreeSet.html#method.extract_if)  | 
 | 136 | +- [`impl Debug for windows::ffi::EncodeWide<'_>`](https://doc.rust-lang.org/stable/std/os/windows/ffi/struct.EncodeWide.html#impl-Debug-for-EncodeWide%3C'_%3E)  | 
 | 137 | +- [`str::ceil_char_boundary`](https://doc.rust-lang.org/stable/std/primitive.str.html#method.ceil_char_boundary)  | 
 | 138 | +- [`str::floor_char_boundary`](https://doc.rust-lang.org/stable/std/primitive.str.html#method.floor_char_boundary)  | 
 | 139 | +- [`impl Sum for Saturating<u{N}>`](https://doc.rust-lang.org/stable/std/num/struct.Saturating.html#impl-Sum-for-Saturating%3Cu32%3E)  | 
 | 140 | +- [`impl Sum<&u{N}> for Saturating<u{N}>`](https://doc.rust-lang.org/stable/std/num/struct.Saturating.html#impl-Sum%3C%26Saturating%3Cu32%3E%3E-for-Saturating%3Cu32%3E)  | 
 | 141 | +- [`impl Product for Saturating<u{N}>`](https://doc.rust-lang.org/stable/std/num/struct.Saturating.html#impl-Product-for-Saturating%3Cu32%3E)  | 
 | 142 | +- [`impl Product<&u{N}> for Saturating<u{N}>`](https://doc.rust-lang.org/stable/std/num/struct.Saturating.html#impl-Product%3C%26Saturating%3Cu32%3E%3E-for-Saturating%3Cu32%3E)  | 
 | 143 | + | 
 | 144 | +These previously stable APIs are now stable in const contexts:  | 
 | 145 | + | 
 | 146 | +- [`<[T; N]>::each_ref`](https://doc.rust-lang.org/stable/std/primitive.array.html#method.each_ref)  | 
 | 147 | +- [`<[T; N]>::each_mut`](https://doc.rust-lang.org/stable/std/primitive.array.html#method.each_mut)  | 
 | 148 | +- [`OsString::new`](https://doc.rust-lang.org/stable/std/ffi/struct.OsString.html#method.new)  | 
 | 149 | +- [`PathBuf::new`](https://doc.rust-lang.org/stable/std/path/struct.PathBuf.html#method.new)  | 
 | 150 | +- [`TypeId::of`](https://doc.rust-lang.org/stable/std/any/struct.TypeId.html#method.of)  | 
 | 151 | +- [`ptr::with_exposed_provenance`](https://doc.rust-lang.org/stable/std/ptr/fn.with_exposed_provenance.html)  | 
 | 152 | +- [`ptr::with_exposed_provenance_mut`](https://doc.rust-lang.org/stable/std/ptr/fn.with_exposed_provenance_mut.html)  | 
 | 153 | + | 
 | 154 | +### Platform Support  | 
 | 155 | + | 
 | 156 | +- [Promote `aarch64-pc-windows-msvc` to Tier 1](https://github.com/rust-lang/rust/pull/145682)  | 
 | 157 | +- [Promote `aarch64-pc-windows-gnullvm` and `x86_64-pc-windows-gnullvm` to Tier 2 with host tools.](https://github.com/rust-lang/rust/pull/143031)  | 
 | 158 | +  Note: llvm-tools and MSI installers are missing but will be added in future releases.  | 
 | 159 | + | 
 | 160 | +Refer to Rust’s [platform support page][platform-support] for more information on Rust’s tiered platform support.  | 
 | 161 | + | 
 | 162 | +### Other changes  | 
 | 163 | + | 
 | 164 | +Check out everything that changed in [Rust](https://github.com/rust-lang/rust/releases/tag/1.91.0), [Cargo](https://doc.rust-lang.org/nightly/cargo/CHANGELOG.html#cargo-191-2025-10-30), and [Clippy](https://github.com/rust-lang/rust-clippy/blob/master/CHANGELOG.md#rust-191).  | 
 | 165 | + | 
 | 166 | +## Contributors to 1.91.0  | 
 | 167 | + | 
 | 168 | +Many people came together to create Rust 1.91.0. We couldn't have done it without all of you. [Thanks!](https://thanks.rust-lang.org/rust/1.91.0/)  | 
 | 169 | + | 
 | 170 | +[platform-support]: https://doc.rust-lang.org/rustc/platform-support.html  | 
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