---
layout: news_post
title: "Ruby 3.4.0 Released"
author: "naruse"
translator:
date: 2024-12-12 00:00:00 +0000
lang: en
---

{% assign release = site.data.releases | where: "version", "3.4.0" | first %}
We are pleased to announce the release of Ruby {{ release.version }}.

## Message from Matz

## Prism

Switch the default parser from parse.y to Prism. [[Feature #20564]]

To use the conventional parser, use the command-line argument `--parser=parse.y`.

## Modular GC

* Alternative garbage collector (GC) implementations can be loaded dynamically
through the modular garbage collector feature. To enable this feature,
configure Ruby with `--with-modular-gc` at build time. GC libraries can be
loaded at runtime using the environment variable `RUBY_GC_LIBRARY`.
[[Feature #20351]]

* Ruby's built-in garbage collector has been split into a separate file at
`gc/default/default.c` and interacts with Ruby using an API defined in
`gc/gc_impl.h`. The built-in garbage collector can now also be built as a
library using `make modular-gc MODULAR_GC=default` and enabled using the
environment variable `RUBY_GC_LIBRARY=default`. [[Feature #20470]]

* An experimental GC library is provided based on [MMTk](https://www.mmtk.io/).
This GC library can be built using `make modular-gc MODULAR_GC=mmtk` and
enabled using the environment variable `RUBY_GC_LIBRARY=mmtk`. This requires
the Rust toolchain on the build machine. [[Feature #20860]]

## The socket library now features Happy Eyeballs Version 2 (RFC 8305)

The socket library now features [Happy Eyeballs Version 2 (RFC 8305)](https://datatracker.ietf.org/doc/html/rfc8305), the latest standardized version of a widely adopted approach for better connectivity in many programming languages, in `TCPSocket.new` (`TCPSocket.open`) and `Socket.tcp`.
This improvement enables Ruby to provide efficient and reliable network connections, adapted to modern internet environments.

Until Ruby 3.3, these methods performed name resolution and connection attempts serially. With this algorithm, they now operate as follows:

1. Performs IPv6 and IPv4 name resolution concurrently
2. Attempt connections to the resolved IP addresses, prioritizing IPv6, with parallel attempts staggered at 250ms intervals
3. Return the first successful connection while canceling any others

This ensures minimized connection delays, even if a specific protocol or IP address is delayed or unavailable.
This feature is enabled by default, so additional configuration is not required to use it. To disable it globally, set the environment variable `RUBY_TCP_NO_FAST_FALLBACK=1` or call `Socket.tcp_fast_fallback=false`. Or to disable it on a per-method basis, use the keyword argument `fast_fallback: false`.

## YJIT

### TL;DR

* Better performance on most benchmarks on both x86-64 and arm64 platforms.
* Reduced memory usage of compilation metadata
* Multiple bug fixes. YJIT is now even more robust and better tested.

### New features

* Add unified memory limit via `--yjit-mem-size` command-line option (default 128MiB)
which tracks total YJIT memory usage and is more intuitive than the
old `--yjit-exec-mem-size`.
* More statistics now always available via `RubyVM::YJIT.runtime_stats`
* Add compilation log to track what gets compiled via `--yjit-log`
* Tail of the log also available at run-time via `RubyVM::YJIT.log`
* Add support for shareable consts in multi-ractor mode
* Can now trace counted exits with `--yjit-trace-exits=COUNTER`

### New optimizations

* Compressed context reduces memory needed to store YJIT metadata
* Improved allocator with ability to allocate registers for local variables
* When YJIT is enabled, use more Core primitives written in Ruby:
* `Array#each`, `Array#select`, `Array#map` rewritten in Ruby for better performance [[Feature #20182]].
* Ability to inline small/trivial methods such as:
* Empty methods
* Methods returning a constant
* Methods returning `self`
* Methods directly returning an argument
* Specialized codegen for many more runtime methods
* Optimize `String#getbyte`, `String#setbyte` and other string methods
* Optimize bitwise operations to speed up low-level bit/byte manipulation
* Various other incremental optimizations

## Language changes

* `it` is added to reference a block parameter. [[Feature #18980]]

* String literals in files without a `frozen_string_literal` comment now emit a deprecation warning
when they are mutated.
These warnings can be enabled with `-W:deprecated` or by setting `Warning[:deprecated] = true`.
To disable this change, you can run Ruby with the `--disable-frozen-string-literal`
command line argument. [[Feature #20205]]

* Keyword splatting `nil` when calling methods is now supported.
`**nil` is treated similarly to `**{}`, passing no keywords,
and not calling any conversion methods. [[Bug #20064]]

* Block passing is no longer allowed in index. [[Bug #19918]]

* Keyword arguments are no longer allowed in index. [[Bug #20218]]

* The toplevel name `::Ruby` is reserved now, and the definition will be warned when `Warning[:deprecated]`. [[Feature #20884]]

## Core classes updates

Note: We're only listing notable updates of Core class.

* Exception

* `Exception#set_backtrace` now accepts an array of `Thread::Backtrace::Location`.
`Kernel#raise`, `Thread#raise` and `Fiber#raise` also accept this new format. [[Feature #13557]]

* GC

* GC.config added to allow setting configuration variables on the Garbage
Collector. [[Feature #20443]]

* GC configuration parameter `rgengc_allow_full_mark` introduced. When `false`
GC will only mark young objects. Default is `true`. [[Feature #20443]]

* Ractor

* `require` in Ractor is allowed. The requiring process will be run on
the main Ractor.
`Ractor._require(feature)` is added to run requiring process on the
main Ractor.
[[Feature #20627]]

* Ractor.main? is added. [[Feature #20627]]

* Ractor.[] and Ractor.[]= are added to access the ractor local storage
of the current Ractor. [[Feature #20715]]

* `Ractor.store_if_absent(key){ init }` is added to initialize ractor local
variables in thread-safty. [[Feature #20875]]

* Range

* `Range#size` now raises `TypeError` if the range is not iterable. [[Misc #18984]]

## Standard Library updates

Note: We're only listing notable updates of Standard librarires.

* RubyGems
* Add --attestation option to gem push. It enabled to store signature to [sigstore.dev]

* Bundler
* Add a lockfile_checksums configuration to include checksums in fresh lockfiles
* Add bundle lock --add-checksums to add checksums to an existing lockfile

* JSON

* Performance improvements of `JSON.parse` about 1.5 times faster than json-2.7.x.

* Tempfile

* The keyword argument `anonymous: true` is implemented for Tempfile.create.
`Tempfile.create(anonymous: true)` removes the created temporary file immediately.
So applications don't need to remove the file.
[[Feature #20497]]

* win32/sspi.rb

* This library is now extracted from the Ruby repository to [ruby/net-http-sspi].
[[Feature #20775]]

## Compatibility issues

Note: Excluding feature bug fixes.

* Error messages and backtrace displays have been changed.
* Use a single quote instead of a backtick as a opening quote. [[Feature #16495]]
* Display a class name before a method name (only when the class has a permanent name). [[Feature #19117]]
* `Kernel#caller`, `Thread::Backtrace::Location`'s methods, etc. are also changed accordingly.

  Old:
  test.rb:1:in `foo': undefined method `time' for an instance of Integer
          from test.rb:2:in `<main>'

  New:
  test.rb:1:in 'Object#foo': undefined method 'time' for an instance of Integer
          from test.rb:2:in '<main>'

* Hash#inspect rendering have been changed. [[Bug #20433]]

* Symbol keys are displayed using the modern symbol key syntax: `"{user: 1}"`
* Other keys now have spaces around `=>`: `'{"user" => 1}'`, while previously they didn't: `'{"user"=>1}'`

* Kernel#Float() now accepts a decimal string with decimal part omitted. [[Feature #20705]]

  Float("1.")    #=> 1.0 (previously, an ArgumentError was raised)
  Float("1.E-1") #=> 0.1 (previously, an ArgumentError was raised)

* String#to_f now accepts a decimal string with decimal part omitted. Note that the result changes when an exponent is specified. [[Feature #20705]]

  "1.".to_f    #=> 1.0
  "1.E-1".to_f #=> 0.1 (previously, 1.0 was returned)

* Object#singleton_method now returns methods in modules prepended to or included in the
receiver's singleton class. [[Bug #20620]]

  o = Object.new
  o.extend(Module.new{def a = 1})
  o.singleton_method(:a).call #=> 1

* Refinement#refined_class has been removed. [[Feature #19714]]

## Standard library compatibility issues

* DidYouMean

* `DidYouMean::SPELL_CHECKERS[]=` and `DidYouMean::SPELL_CHECKERS.merge!` are removed.

* Net::HTTP

* Removed the following deprecated constants:
* `Net::HTTP::ProxyMod`
* `Net::NetPrivate::HTTPRequest`
* `Net::HTTPInformationCode`
* `Net::HTTPSuccessCode`
* `Net::HTTPRedirectionCode`
* `Net::HTTPRetriableCode`
* `Net::HTTPClientErrorCode`
* `Net::HTTPFatalErrorCode`
* `Net::HTTPServerErrorCode`
* `Net::HTTPResponseReceiver`
* `Net::HTTPResponceReceiver`

These constants were deprecated from 2012.

* Timeout

* Reject negative values for Timeout.timeout. [[Bug #20795]]

* URI

* Switched default parser to RFC 3986 compliant from RFC 2396 compliant.
[[Bug #19266]]

## C API updates

* `rb_newobj` and `rb_newobj_of` (and corresponding macros `RB_NEWOBJ`, `RB_NEWOBJ_OF`, `NEWOBJ`, `NEWOBJ_OF`) have been removed. [[Feature #20265]]
* Removed deprecated function `rb_gc_force_recycle`. [[Feature #18290]]

## Miscellaneous changes

* Passing a block to a method which doesn't use the passed block will show
a warning on verbose mode (`-w`).
[[Feature #15554]]

* Redefining some core methods that are specially optimized by the interpeter
and JIT like `String.freeze` or `Integer#+` now emits a performance class
warning (`-W:performance` or `Warning[:performance] = true`).
[[Feature #20429]]

See [NEWS](https://github.com/ruby/ruby/blob/{{ release.tag }}/NEWS.md)
or [commit logs](https://github.com/ruby/ruby/compare/v3_3_0...{{ release.tag }})
for more details.

With those changes, [{{ release.stats.files_changed }} files changed, {{ release.stats.insertions }} insertions(+), {{ release.stats.deletions }} deletions(-)](https://github.com/ruby/ruby/compare/v3_3_0...{{ release.tag }}#file_bucket)
since Ruby 3.3.0!

## Download

* <{{ release.url.gz }}>

SIZE: {{ release.size.gz }}
SHA1: {{ release.sha1.gz }}
SHA256: {{ release.sha256.gz }}
SHA512: {{ release.sha512.gz }}

* <{{ release.url.xz }}>

SIZE: {{ release.size.xz }}
SHA1: {{ release.sha1.xz }}
SHA256: {{ release.sha256.xz }}
SHA512: {{ release.sha512.xz }}

* <{{ release.url.zip }}>

SIZE: {{ release.size.zip }}
SHA1: {{ release.sha1.zip }}
SHA256: {{ release.sha256.zip }}
SHA512: {{ release.sha512.zip }}

## What is Ruby

Ruby was first developed by Matz (Yukihiro Matsumoto) in 1993,
and is now developed as Open Source. It runs on multiple platforms
and is used all over the world especially for web development.

[Feature #13557]: https://bugs.ruby-lang.org/issues/13557
[Feature #15554]: https://bugs.ruby-lang.org/issues/15554
[Feature #16495]: https://bugs.ruby-lang.org/issues/16495
[Feature #18290]: https://bugs.ruby-lang.org/issues/18290
[Feature #18980]: https://bugs.ruby-lang.org/issues/18980
[Misc #18984]: https://bugs.ruby-lang.org/issues/18984
[Feature #19117]: https://bugs.ruby-lang.org/issues/19117
[Bug #19266]: https://bugs.ruby-lang.org/issues/19266
[Feature #19714]: https://bugs.ruby-lang.org/issues/19714
[Bug #19918]: https://bugs.ruby-lang.org/issues/19918
[Bug #20064]: https://bugs.ruby-lang.org/issues/20064
[Feature #20182]: https://bugs.ruby-lang.org/issues/20182
[Feature #20205]: https://bugs.ruby-lang.org/issues/20205
[Bug #20218]: https://bugs.ruby-lang.org/issues/20218
[Feature #20265]: https://bugs.ruby-lang.org/issues/20265
[Feature #20351]: https://bugs.ruby-lang.org/issues/20351
[Feature #20429]: https://bugs.ruby-lang.org/issues/20429
[Feature #20443]: https://bugs.ruby-lang.org/issues/20443
[Feature #20470]: https://bugs.ruby-lang.org/issues/20470
[Feature #20497]: https://bugs.ruby-lang.org/issues/20497
[Feature #20564]: https://bugs.ruby-lang.org/issues/20564
[Bug #20620]: https://bugs.ruby-lang.org/issues/20620
[Feature #20627]: https://bugs.ruby-lang.org/issues/20627
[Feature #20705]: https://bugs.ruby-lang.org/issues/20705
[Feature #20715]: https://bugs.ruby-lang.org/issues/20715
[Feature #20775]: https://bugs.ruby-lang.org/issues/20775
[Bug #20795]: https://bugs.ruby-lang.org/issues/20795
[Feature #20860]: https://bugs.ruby-lang.org/issues/20860
[Feature #20875]: https://bugs.ruby-lang.org/issues/20875
[Feature #20884]: https://bugs.ruby-lang.org/issues/20884
[sigstore.dev]: sigstore.dev
[ruby/net-http-sspi]: https://github.com/ruby/net-http-sspi