Posts tagged "release" | Rust Blog

Announcing Rust 1.99.1

2026-10-15T00:00:00+00:00

The Rust team has published a new point release of Rust, 1.99.1. Rust is a programming language that is empowering everyone to build reliable and efficient software.

If you have a previous version of Rust installed via rustup, getting Rust 1.99.1 is as easy as:

rustup update stable

If you don't have it already, you can get rustup from the appropriate page on our website.

What's in 1.99.1

Rust 1.99.1 fixes the following regressions from prior releases:

Missing symbol wcslen: Some Rust targets were getting link errors for missing wcslen, and that function is now present in Rust's compiler-builtins library as a fallback.

The LLVM loop-idiom-wcslen pass may introduce calls to wcslen as an optimization, and some Rust targets did not have that function readily available in libc or elsewhere. The UEFI targets in particular were broken for any project using std, as some of these calls were introduced in the precompiled standard library, but the issue was also reproducible for similar user code patterns.
Miscompilation of FFI bool return values on x86_64: Rust functions returning bool through FFI could leave bits 1-7 of the return register unspecified, causing callers to observe raw values other than 0 or 1. This return type is now marked for zero-extension again, as required by the ABI.
rust-lld failed to load libLLVM on macOS: This linker could fail to run if the compiler was invoked without the rustup proxy, as there was no direct setting for the appropriate library search path. Now rust-lld is built with an rpath entry for the directory containing libLLVM.dylib.

If you'd like to help us out by testing future releases, you might consider using the beta (rustup default beta) and nightly (rustup default nightly) channels locally and in your CI. Please report any bugs you might come across!

Contributors to 1.99.1

Many people came together to create Rust 1.99.1. We couldn't have done it without all of you. Thanks!

Announcing Rust 1.99.0

2026-10-01T00:00:00+00:00

The Rust team is happy to announce a new version of Rust, 1.99.0. Rust is a programming language empowering everyone to build reliable and efficient software.

If you have a previous version of Rust installed via rustup, you can get 1.99.0 with:

$ rustup update stable

If you don't have it already, you can get rustup from the appropriate page on our website, and check out the detailed release notes for 1.99.0.

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 any bugs you might come across!

What's in 1.99.0 stable

extern "C" variadics

Rust 1.99.0 stabilizes defining C-ABI variadic functions with "C" and "C-unwind" ABIs. Variadic functions defined this way use a variable argument list (...) and accept an arbitrary number of arguments. Rust could already call externally-defined variadic functions (e.g., libc::printf). With Rust 1.99, these functions can now be written in Rust itself:

/// SAFETY: must be called with (at least) 2 i32 arguments.
unsafe extern "C" fn sum(mut args: ...) -> i32 {
    // SAFETY: guaranteed by the caller.
    let a = unsafe { args.next_arg::<i32>() };
    let b = unsafe { args.next_arg::<i32>() };
    a + b
}

fn foo() -> i32 {
    unsafe { sum(0i32, 2i32) }
}

The type of ... is VaList, which is ABI-compatible with the C va_list type across targets. What types can be read from a VaList is guarded by the VaArgSafe trait.

For more details on c-variadic functions, see the Reference. This release also stabilizes support for defining naked variadic functions with non-"C" ABIs, which must be written via inline assembly.

Layout information from raw pointers

This release settles the safety requirements for retrieving the size and alignment on raw pointers to both Sized (trivially safe, already possible on stable) and non-Sized types.

This is done by stabilizing three functions:

Layout::for_value_raw
mem::size_of_val_raw
mem::align_of_val_raw

Recommend against round-trip unleaking after `Box::leak`

While there are no changes to the language semantics in Rust 1.99, we have updated the documentation on Box::leak to recommend against patterns that later deallocate that memory. This was done because such code was found to have problematic interactions with current and future potential compiler optimizations, and is especially problematic with the upcoming stabilization of custom allocators. Instead, Box::into_non_null or Box::into_raw should be preferred.

This guidance also applies to other leak functions in the standard library.

Stabilized APIs

IntoIterator for Box<[T; N]>
IntoIterator for &Box<[T; N]>
IntoIterator for &mut Box<[T; N]>
VecDeque::retain_back
core::ffi::VaList
Box::into_non_null
Box::from_non_null
Vec::into_parts
Vec::from_parts
core::mem::size_of_val_raw
core::mem::align_of_val_raw
core::alloc::Layout::for_value_raw
String::from_utf8_lossy_owned
string::FromUtf8Error::into_utf8_lossy
FusedIterator for StepBy<I>
std::fs::set_times
std::fs::set_times_nofollow

Other changes

Check out everything that changed in Rust, Cargo, and Clippy.

Contributors to 1.99.0

Many people came together to create Rust 1.99.0. We couldn't have done it without all of you. Thanks!

Announcing Rust 1.98.1

2026-09-03T00:00:00+00:00

The Rust team has published a new point release of Rust, 1.98.1. Rust is a programming language that is empowering everyone to build reliable and efficient software.

If you have a previous version of Rust installed via rustup, getting Rust 1.98.1 is as easy as:

rustup update stable

If you don't have it already, you can get rustup from the appropriate page on our website.

What's in 1.98.1

Rust 1.98.1 fixes a miscompilation in vtable generation.

In Rust 1.98.0, in some circumstances, rustc would incorrectly generate a trait object vtable with a null pointer where a function pointer should be. This leads to undefined behavior in the emitted code. In some cases this may 'just' cause segfaults due to the null pointer being loaded, but it is possible for it to be justification for arbitrary effects (as is typical for UB).

Contributors to 1.98.1

Many people came together to create Rust 1.98.1. We couldn't have done it without all of you. Thanks!

Announcing Rust 1.98.0

2026-08-20T00:00:00+00:00

The Rust team is happy to announce a new version of Rust, 1.98.0. Rust is a programming language empowering everyone to build reliable and efficient software.

If you have a previous version of Rust installed via rustup, you can get 1.98.0 with:

$ rustup update stable

If you don't have it already, you can get rustup from the appropriate page on our website, and check out the detailed release notes for 1.98.0.

What's in 1.98.0 stable

Algebraic floating-point methods

The floating-point types f32 and f64 now have "algebraic" methods for addition, subtraction, multiplication, division, and remainder. These allow optimizations on these operations using the algebraic properties of real numbers, even though these properties do not hold with the limitations of floating-point representations. The exact set of optimizations is not specified, but may be similar to the kind of optimization you would see with the -ffast-math option in other languages.

For example, floating-point addition is not associative, so a sum like a + b + c + d must be evaluated in the left-associative order in which it is parsed, like ((a + b) + c) + d. If you write the same sum as a chain of algebraic_add calls, then the compiler is free to reorder it, perhaps like (a + b) + (c + d) to evaluate the partial sums simultaneously. Broader loop-vectorization is often enabled by using these algebraic methods as well.

These methods are non-deterministic, since the compiler is free to choose different optimizations, but they never cause undefined behavior. See the library documentation and the original API change proposal for more details.

Buffered integer formatting

All of the primitive integer types now have a format_into method that takes a &mut NumBuffer<Self> parameter, which is a buffer that is large enough to hold the decimal format of any value of that type. The buffer itself is opaque, but the method returns the formatted &str with a lifetime borrowed from that buffer.

This method also bypasses much of the dynamic dispatch that you would get with buffered write! formatting, which can be a boon to performance. The itoa-benchmark repo now shows that format_into performs similarly to itoa itself, so this could serve as a standard replacement for that dependency and others like it.

Fix interaction between `ManuallyDrop` and `Box`

Prior to Rust 1.96.0, there was a bug in the Rust compiler, which made the following code undefined behavior:

let mut x = ManuallyDrop::new(Box::new(1));
unsafe { ManuallyDrop::drop(&mut x) };
let x = x; // UB!

This is because the compiler considers it undefined behavior to move a Box that has been dropped (deallocated), and ManuallyDrop used to propagate that, such that moving ManuallyDrop<Box<_>> where the box has been dropped would also be considered UB.

In Rust 1.96.0 we fixed this, so this code was no longer UB. In this release we have updated the ManuallyDrop documentation, providing a stable guarantee that this code will continue to not be UB in the future. See ManuallyDrop docs and the related RFC 3336 for more information.

Stabilized APIs

str::substr_range
[T]::subslice_range
core::fmt::NumBuffer
<{integer}>::format_into
Send/Sync for std::process::CommandArgs
{fN}::algebraic_add
{fN}::algebraic_sub
{fN}::algebraic_mul
{fN}::algebraic_div
{fN}::algebraic_rem
NonZero<{integer}>::from_str_radix
String::from_utf16le
String::from_utf16le_lossy
String::from_utf16be
String::from_utf16be_lossy
[T]::strip_circumfix
str::strip_circumfix
Atomic<T>::from_mut
Atomic<T>::get_mut_slice
Atomic<T>::from_mut_slice
std::range::legacy

Other changes

Check out everything that changed in Rust, Cargo, and Clippy.

Contributors to 1.98.0

Many people came together to create Rust 1.98.0. We couldn't have done it without all of you. Thanks!

Announcing Rust 1.97.1

2026-07-16T00:00:00+00:00

The Rust team has published a new point release of Rust, 1.97.1. Rust is a programming language that is empowering everyone to build reliable and efficient software.

If you have a previous version of Rust installed via rustup, getting Rust 1.97.1 is as easy as:

rustup update stable

If you don't have it already, you can get rustup from the appropriate page on our website.

What's in 1.97.1

Rust 1.97.1 fixes a miscompilation in an LLVM optimization.

We have backported both an LLVM fix and a disable of the underlying change in Rust 1.97.0 of Rust's generated IR that increased the likelihood of this happening. However, note that the underlying miscompilation has been present since at least Rust 1.87.

If you'd like to help us out by testing future releases, you might consider running your code's CI or locally using the beta channel (rustup default beta) or the nightly channel (rustup default nightly). Please report any bugs you might come across!

Contributors to 1.97.1

Many people came together to create Rust 1.97.1. We couldn't have done it without all of you. Thanks!

Announcing Rust 1.97.0

2026-07-09T00:00:00+00:00

The Rust team is happy to announce a new version of Rust, 1.97.0. Rust is a programming language empowering everyone to build reliable and efficient software.

If you have a previous version of Rust installed via rustup, you can get 1.97.0 with:

$ rustup update stable

If you don't have it already, you can get rustup from the appropriate page on our website, and check out the detailed release notes for 1.97.0.

What's in 1.97.0 stable

Symbol mangling v0 enabled by default

When Rust is compiled into object files and binaries, each item (functions, statics, etc) must have a globally unique "symbol" identifying it. To avoid conflicts when linking together different Rust programs, Rust mangles the original name of items to include additional context such as the module path, defining crate, generics, and more. Historically, this mangling was based on the Itanium ABI, also (sometimes) used by C++.

The new mangling scheme resolves a number of drawbacks from the previous one:

Generic parameter instantiations preserve their values, rather than being tracked solely behind a hash
Inconsistencies: not all parts used the Itanium ABI, meaning that custom demangling was still necessary

Since Rust 1.59, the compiler has supported opting into a Rust-specific mangling scheme via -Csymbol-mangling-version=v0. Since November 2025, this scheme has been enabled by default on nightly, and 1.97 is now enabling it on stable Rust. The legacy mangling scheme can only be enabled on nightly, and the current plan is to fully remove it.

See the previous blog post for more details.

Cargo support for denying warnings

It's common practice to deny warnings in CI. Historically, doing so is typically done through RUSTFLAGS=-Dwarnings. With Rust 1.97, Cargo controls how warnings interact with build success: either silencing them (via allow level), rendering without failing (default, warn), or denying them (via deny).

As a result of Cargo configuration determining the behavior, using this feature doesn't invalidate the underlying build cache, meaning that it's easy to temporarily opt-in. For example, if warnings are adding unwanted noise while working through fixing errors after a refactor, you can run CARGO_BUILD_WARNINGS=allow cargo check, temporarily silencing them.

In CI, jobs can instead set CARGO_BUILD_WARNINGS=deny to deny warnings. This can be combined with --keep-going to collect all errors and warnings rather than stopping on the first failing package.

See the documentation for more details.

Linker output no longer hidden by default

rustc invokes a linker on behalf of users. Historically, rustc has silenced linker output by default if the link completes successfully. This can mask real problems, though, so in Rust 1.97 we are enabling linker messages by default. These are emitted as a warning lint, for example:

warning: linker stderr: ignoring deprecated linker optimization setting '1'
  |
  = note: `#[warn(linker_messages)]` on by default

Common linker messages that have been diagnosed as false positives or intentional behavior are filtered out by rustc. Several defects have already been fixed as a result of no longer hiding this output on nightly.

Note that currently, linker_messages is a special lint that is not affected by the warnings lint group. This is intentional as rustc generally doesn't control linker output as precisely, and it's not uncommon for output to only appear on some platforms. If you are seeing what you think is a false positive output from the linker, please file an issue.

To silence the warning in the mean time, you can configure the lint level to allow. This can be done through Cargo.toml by adding a lints section like this:

[lints.rust]
linker_messages = "allow"

Stabilized APIs

Default for RepeatN
Copy for ffi::FromBytesUntilNulError
Send for std::fs::File on UEFI
<{integer}>::isolate_highest_one
<{integer}>::isolate_lowest_one
<{integer}>::highest_one
<{integer}>::lowest_one
<{uN}>::bit_width
NonZero<{integer}>::isolate_highest_one
NonZero<{integer}>::isolate_lowest_one
NonZero<{integer}>::highest_one
NonZero<{integer}>::lowest_one
NonZero<{uN}>::bit_width

These previously stable APIs are now stable in const contexts:

char::is_control

Other changes

Check out everything that changed in Rust, Cargo, and Clippy.

Contributors to 1.97.0

Many people came together to create Rust 1.97.0. We couldn't have done it without all of you. Thanks!

Announcing Rust 1.96.1

2026-06-30T00:00:00+00:00

The Rust team has published a new point release of Rust, 1.96.1. Rust is a programming language that is empowering everyone to build reliable and efficient software.

If you have a previous version of Rust installed via rustup, getting Rust 1.96.1 is as easy as:

rustup update stable

If you don't have it already, you can get rustup from the appropriate page on our website.

What's in 1.96.1

Rust 1.96.1 fixes:

Missing retries / timeouts in Cargo's HTTP client
Miscompilation in a MIR optimization

It also fixes three CVEs affecting libssh2 (which is compiled into Cargo):

CVE-2025-15661
CVE-2026-55199
CVE-2026-55200

Contributors to 1.96.1

Many people came together to create Rust 1.96.1. We couldn't have done it without all of you. Thanks!

Announcing Rust 1.96.0

2026-05-28T00:00:00+00:00

The Rust team is happy to announce a new version of Rust, 1.96.0. Rust is a programming language empowering everyone to build reliable and efficient software.

If you have a previous version of Rust installed via rustup, you can get 1.96.0 with:

$ rustup update stable

If you don't have it already, you can get rustup from the appropriate page on our website, and check out the detailed release notes for 1.96.0.

What's in 1.96.0 stable

New `Range*` types

Many users expect Range and related core::ops types to be Copy, but this is not the case: they implement Iterator directly, and it is a footgun to implement both Iterator and Copy on the same type so this has been avoided. RFC3550 proposed a set of replacement range types that implement IntoIterator rather than Iterator, meaning they can also be Copy. The standard library portion of that RFC is now stable, introducing:

core::range::Range
core::range::RangeFrom
core::range::RangeInclusive
Associated iterators

A Rust version in the near future will also add core::range::RangeFull and core::range::RangeTo as re-exports from core::ops (these do not implement Iterator and already implement Copy), and core::range::legacy::* as the new home for the current ranges. Range syntax like 0..1 still produces the legacy types for now, but will be updated to core::range types in a future edition.

With these stabilizations, it is now possible to store slice accessors in Copy types without splitting start and end:

use core::range::Range;

#[derive(Clone, Copy)]
pub struct Span(Range<usize>);

impl Span {
    pub fn of(self, s: &str) -> &str {
        &s[self.0]
    }
}

The new RangeInclusive also makes its fields public, unlike the legacy version which avoided exposing the exhausted iterator state. This isn't a concern with the new type since it must be converted to begin iteration.

Library authors should consider making use of impl RangeBounds in public API, which accepts both legacy and new range types. If a concrete type is needed, prefer using new ranges as this will eventually become the default.

Assert matching patterns

The new macros assert_matches! and debug_assert_matches! check that a value matches a given pattern, panicking with a Debug representation of the value otherwise. These are essentially the same as assert!(matches!(..)) and debug_assert!(matches!(..)), but the printed value improves the possibility of diagnosing the failure.

These new macros have not been added to the standard prelude, because they would collide with popular third-party crates that provide macros with the same name. Instead, they should be manually imported from core or std before use.

use core::assert_matches;

/// [Random Number](https://xkcd.com/221/)
fn get_random_number() -> u32 {
    // chosen by a fair dice roll.
    // guaranteed to be random.
    4
}

fn main() {
    assert_matches!(get_random_number(), 1..=6);
}

Changes to WebAssembly targets

WebAssembly targets no longer pass --allow-undefined to the linker which means that undefined symbols when linking are now a linker error instead of being converted to WebAssembly imports from the "env" module. This change prevents modules from linking unless all linking-related symbols are defined to catch bugs earlier and prevent accidental issues with symbol naming or similar.

Undefined linking-related symbols are often indicative of build-time related bugs or misconfiguration. If, however, the old behavior is intended then it can be re-enabled with RUSTFLAGS=-Clink-arg=--allow-undefined or by editing the source code and using #[link(wasm_import_module = "env")] on the block defining the symbol.

This change was previously announced on this blog, and now takes effect in Rust 1.96.

Two Cargo advisories

Rust 1.96 contains fixes for two vulnerabilities for users of third-party registries.

CVE-2026-5223 is a medium severity vulnerability regarding extraction of crate tarballs with symlinks.
CVE-2026-5222 is a low severity vulnerability regarding authentication with normalized URLs.

Users of crates.io are not affected by either vulnerability.

Other changes

Check out everything that changed in Rust, Cargo, and Clippy.

Contributors to 1.96.0

Many people came together to create Rust 1.96.0. We couldn't have done it without all of you. Thanks!

Announcing Rust 1.95.0

2026-04-16T00:00:00+00:00

The Rust team is happy to announce a new version of Rust, 1.95.0. Rust is a programming language empowering everyone to build reliable and efficient software.

If you have a previous version of Rust installed via rustup, you can get 1.95.0 with:

$ rustup update stable

If you don't have it already, you can get rustup from the appropriate page on our website, and check out the detailed release notes for 1.95.0.

What's in 1.95.0 stable

`cfg_select!`

Rust 1.95 introduces a cfg_select! macro that acts roughly similar to a compile-time match on cfgs. This fulfills the same purpose as the popular cfg-if crate, although with a different syntax. cfg_select! expands to the right-hand side of the first arm whose configuration predicate evaluates to true. Some examples:

cfg_select! {
    unix => {
        fn foo() { /* unix specific functionality */ }
    }
    target_pointer_width = "32" => {
        fn foo() { /* non-unix, 32-bit functionality */ }
    }
    _ => {
        fn foo() { /* fallback implementation */ }
    }
}

let is_windows_str = cfg_select! {
    windows => "windows",
    _ => "not windows",
};

if-let guards in matches

Rust 1.88 stabilized let chains. Rust 1.95 brings that capability into match expressions, allowing for conditionals based on pattern matching.

match value {
    Some(x) if let Ok(y) = compute(x) => {
        // Both `x` and `y` are available here
        println!("{}, {}", x, y);
    }
    _ => {}
}

Note that the compiler will not currently consider the patterns matched in if let guards as part of the exhaustiveness evaluation of the overall match, just like if guards.

Stabilized APIs

MaybeUninit<[T; N]>: From<[MaybeUninit<T>; N]>
MaybeUninit<[T; N]>: AsRef<[MaybeUninit<T>; N]>
MaybeUninit<[T; N]>: AsRef<[MaybeUninit<T>]>
MaybeUninit<[T; N]>: AsMut<[MaybeUninit<T>; N]>
MaybeUninit<[T; N]>: AsMut<[MaybeUninit<T>]>
[MaybeUninit<T>; N]: From<MaybeUninit<[T; N]>>
Cell<[T; N]>: AsRef<[Cell<T>; N]>
Cell<[T; N]>: AsRef<[Cell<T>]>
Cell<[T]>: AsRef<[Cell<T>]>
bool: TryFrom<{integer}>
AtomicPtr::update
AtomicPtr::try_update
AtomicBool::update
AtomicBool::try_update
AtomicIn::update
AtomicIn::try_update
AtomicUn::update
AtomicUn::try_update
cfg_select!
mod core::range
core::range::RangeInclusive
core::range::RangeInclusiveIter
core::hint::cold_path
<*const T>::as_ref_unchecked
<*mut T>::as_ref_unchecked
<*mut T>::as_mut_unchecked
Vec::push_mut
Vec::insert_mut
VecDeque::push_front_mut
VecDeque::push_back_mut
VecDeque::insert_mut
LinkedList::push_front_mut
LinkedList::push_back_mut
Layout::dangling_ptr
Layout::repeat
Layout::repeat_packed
Layout::extend_packed

These previously stable APIs are now stable in const contexts:

fmt::from_fn
ControlFlow::is_break
ControlFlow::is_continue

Destabilized JSON target specs

Rust 1.95 removes support on stable for passing a custom target specification to rustc. This should not affect any Rust users using a fully stable toolchain, as building the standard library (including just core) already required using nightly-only features.

We're also gathering use cases for custom targets on the tracking issue as we consider whether some form of this feature should eventually be stabilized.

Other changes

Check out everything that changed in Rust, Cargo, and Clippy.

Contributors to 1.95.0

Many people came together to create Rust 1.95.0. We couldn't have done it without all of you. Thanks!

Announcing Rust 1.94.1

2026-03-26T00:00:00+00:00

The Rust team has published a new point release of Rust, 1.94.1. Rust is a programming language that is empowering everyone to build reliable and efficient software.

If you have a previous version of Rust installed via rustup, getting Rust 1.94.1 is as easy as:

rustup update stable

If you don't have it already, you can get rustup from the appropriate page on our website.

What's in 1.94.1

Rust 1.94.1 resolves three regressions that were introduced in the 1.94.0 release.

Fix std::thread::spawn on wasm32-wasip1-threads
Remove new methods added to std::os::windows::fs::OpenOptionsExt The new methods were unstable, but the trait itself is not sealed and so cannot be extended with non-default methods.
Clippy: fix ICE in match_same_arms
Cargo: downgrade curl-sys to 0.4.83 This fixes certificate validation error for some users on some versions of FreeBSD. See this issue for more details.

And a security fix:

Cargo: Update tar to 0.4.45 This resolves CVE-2026-33055 and CVE-2026-33056. Users of crates.io are not affected. See blog for more details.

Contributors to 1.94.1

Many people came together to create Rust 1.94.1. We couldn't have done it without all of you. Thanks!

Posts tagged "release" | Rust Blog

Announcing Rust 1.99.1

What's in 1.99.1

Contributors to 1.99.1

Announcing Rust 1.99.0

What's in 1.99.0 stable

extern "C" variadics

Layout information from raw pointers

Recommend against round-trip unleaking after Box::leak

Stabilized APIs

Other changes

Contributors to 1.99.0

Announcing Rust 1.98.1

What's in 1.98.1

Contributors to 1.98.1

Announcing Rust 1.98.0

What's in 1.98.0 stable

Algebraic floating-point methods

Buffered integer formatting

Fix interaction between ManuallyDrop and Box

Stabilized APIs

Other changes

Contributors to 1.98.0

Announcing Rust 1.97.1

What's in 1.97.1

Contributors to 1.97.1

Announcing Rust 1.97.0

What's in 1.97.0 stable

Symbol mangling v0 enabled by default

Cargo support for denying warnings

Linker output no longer hidden by default

Stabilized APIs

Other changes

Contributors to 1.97.0

Announcing Rust 1.96.1

What's in 1.96.1

Contributors to 1.96.1

Announcing Rust 1.96.0

What's in 1.96.0 stable

New Range* types

Assert matching patterns

Changes to WebAssembly targets

Stabilized APIs

Two Cargo advisories

Other changes

Contributors to 1.96.0

Announcing Rust 1.95.0

What's in 1.95.0 stable

cfg_select!

if-let guards in matches

Stabilized APIs

Destabilized JSON target specs

Other changes

Contributors to 1.95.0

Announcing Rust 1.94.1

What's in 1.94.1

Contributors to 1.94.1

Recommend against round-trip unleaking after `Box::leak`

Fix interaction between `ManuallyDrop` and `Box`

New `Range*` types

`cfg_select!`