Ruby 3.2.0 Preview 2 Released

We are pleased to announce the release of Ruby 3.2.0-preview2. Ruby 3.2 adds many features and performance improvements.

WASI based WebAssembly support

This is an initial port of WASI based WebAssembly support. This enables a CRuby binary to be available on Web browser, Serverless Edge environment, and other WebAssembly/WASI embedders. Currently this port passes basic and bootstrap test suites not using Thread API.


WebAssembly (Wasm) is originally introduced to run programs safely and fast in web browsers. But its objective - running programs efficinently with security on various environment - is long wanted not only by web but also by general applications.

WASI (The WebAssembly System Interface) is designed for such use cases. Though such applications need to communicate with operating systems, WebAssembly runs on a virtual machine which didn’t have a system interface. WASI standardizes it.

WebAssembly/WASI Support in Ruby intends to leverage those projects. It enables Ruby developers to write applications which runs on such promised platform.

Use case

This support encourages developers can utilize CRuby in WebAssembly environment. An example use case of it is TryRuby playground’s CRuby support. Now you can try original CRuby in your web browser.

Technical points

Today’s WASI and WebAssembly itself has some missing features to implement Fiber, exception, and GC because it’s still evolving and also for security reasons. So CRuby fills the gap by using Asyncify, which is a binary transformation technique to control execution in userland.

In addition, we built a VFS on top of WASI so that we can easily pack Ruby apps into a single .wasm file. This makes distribution of Ruby apps a bit easier.

Related links

Regexp timeout

A timeout feature for Regexp matching is introduced.

Regexp.timeout = 1.0

/^a*b?a*$/ =~ "a" * 50000 + "x"
#=> Regexp::TimeoutError is raised in one second

It is known that Regexp matching may take unexpectedly long. If your code attempts to match an possibly inefficient Regexp against an untrusted input, an attacker may exploit it for efficient Denial of Service (so-called Regular expression DoS, or ReDoS).

The risk of DoS can be prevented or significantly mitigated by configuring Regexp.timeout according to the requirements of your Ruby application. Please try it out in your application and welcome your feedback.

Note that Regexp.timeout is a global configuration. If you want to use different timeout settings for some special Regexps, you may want to use timeout keyword for

Regexp.timeout = 1.0

# This regexp has no timeout
long_time_re ="^a*b?a*$", timeout: nil)

long_time_re =~ "a" * 50000 + "x" # never interrupted

The original proposal is

Other Notable New Features

No longer bundle 3rd party sources

  • We no longer bundle 3rd party sources like libyaml, libffi.

    • libyaml source has been removed from psych. You may need to install libyaml-dev with Ubuntu/Debian platform. The package name is different each platforms.

    • libffi will be removed from fiddle at preview2


  • Anonymous rest and keyword rest arguments can now be passed as arguments, instead of just used in method parameters. [Feature #18351]

      def foo(*)
      def baz(**)
  • A proc that accepts a single positional argument and keywords will no longer autosplat. [Bug #18633]

    proc{|a, **k| a}.call([1, 2])
    # Ruby 3.1 and before
    # => 1
    # Ruby 3.2 and after
    # => [1, 2]
  • Constant assignment evaluation order for constants set on explicit objects has been made consistent with single attribute assignment evaluation order. With this code:

      foo::BAR = baz

    foo is now called before baz. Similarly, for multiple assignments to constants, left-to-right evaluation order is used. With this code:

        foo1::BAR1, foo2::BAR2 = baz1, baz2

    The following evaluation order is now used:

    1. foo1
    2. foo2
    3. baz1
    4. baz2

    [Bug #15928]

  • Find pattern is no longer experimental. [Feature #18585]

  • Methods taking a rest parameter (like *args) and wishing to delegate keyword arguments through foo(*args) must now be marked with ruby2_keywords (if not already the case). In other words, all methods wishing to delegate keyword arguments through *args must now be marked with ruby2_keywords, with no exception. This will make it easier to transition to other ways of delegation once a library can require Ruby 3+. Previously, the ruby2_keywords flag was kept if the receiving method took *args, but this was a bug and an inconsistency. A good technique to find the potentially-missing ruby2_keywords is to run the test suite, for where it fails find the last method which must receive keyword arguments, use puts nil, caller, nil there, and check each method/block on the call chain which must delegate keywords is correctly marked as ruby2_keywords. [Bug #18625] [Bug #16466]

      def target(**kw)
      # Accidentally worked without ruby2_keywords in Ruby 2.7-3.1, ruby2_keywords
      # needed in 3.2+. Just like (*args, **kwargs) or (...) would be needed on
      # both #foo and #bar when migrating away from ruby2_keywords.
      ruby2_keywords def bar(*args)
      ruby2_keywords def foo(*args)
      foo(k: 1)

Performance improvements


  • Support arm64 / aarch64 on UNIX platforms.
  • Building YJIT requires Rust 1.58.1+. [Feature #18481]

Other notable changes since 3.1

  • Hash
    • Hash#shift now always returns nil if the hash is empty, instead of returning the default value or calling the default proc. [Bug #16908]
  • MatchData
  • Module
  • Proc
  • Refinement
  • Set
    • Set is now available as a builtin class without the need for require "set". [Feature #16989] It is currently autoloaded via the Set constant or a call to Enumerable#to_set.
  • String
    • String#byteindex and String#byterindex have been added. [Feature #13110]
    • Update Unicode to Version 14.0.0 and Emoji Version 14.0. [Feature #18037] (also applies to Regexp)
    • String#bytesplice has been added. [Feature #18598]
  • Struct
    • A Struct class can also be initialized with keyword arguments without keyword_init: true on [Feature #16806]

Compatibility issues

Note: Excluding feature bug fixes.

Removed constants

The following deprecated constants are removed.

Removed methods

The following deprecated methods are removed.

Stdlib compatibility issues

  • Psych no longer bundles libyaml sources. Users need to install the libyaml library themselves via the package system. [Feature #18571]

C API updates

Removed C APIs

The following deprecated APIs are removed.

  • rb_cData variable.
  • “taintedness” and “trustedness” functions. [Feature #16131]

Standard libraries updates

  • The following default gem are updated.

    • TBD
  • The following bundled gems are updated.

    • TBD
  • The following default gems are now bundled gems. You need to add the following libraries to Gemfile under the bundler environment.

    • TBD

See NEWS or commit logs for more details.

With those changes, 2393 files changed, 168931 insertions(+), 113411 deletions(-) since Ruby 3.1.0!



    SIZE: 19816780
    SHA1: 2106c77fc1600daf41ae137ecc4cf7937e27f67f
    SHA256: 8a78fd7a221b86032f96f25c1d852954c94d193b9d21388a9b434e160b7ed891
    SHA512: 5e9ddcb1a43cff449b0062cc716bfb80a9ebbb14a1b063f34005e2998c2c5033badb44e882232db9b2fceda9376f6615986e983511fda2575d60894752b605cc

    SIZE: 14578112
    SHA1: 538b3ea4dc0d99f60f8bd6f71e65a56ceeb41c18
    SHA256: 01fac0929dccdabc0686c1109da6c187897a401da9ff8851242befa92f7fd430
    SHA512: 0f4cc919284fdfa1a42b6381760d1b3a4660da4b0fcdd2adf01ea04a425548b3c5ac090866915675db73964a1055090e54dd97cf4628cbb69403e541c71c28ff

    SIZE: 24150109
    SHA1: 69ffffc52cad626166f73f21f25c29c9d73fe0e8
    SHA256: 67f9ad3110be1975b3ce547c0a6e2c910dfc1945fd6e9bb1bd340568897c6554
    SHA512: 1447e099e7a8da0ff206fda6f4e466640d6e86e9da8148315ab0154684b1fd22c02c0022b5a2f4d3fc00103b4e8cef8e35a770174921fd8c6abeca9ad41c1818

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.