Ruby 3.2.0 RC 1 Released

We are pleased to announce the release of Ruby 3.2.0-rc1. 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 a Web browser, a Serverless Edge environment, or other kinds of WebAssembly/WASI embedders. Currently this port passes basic and bootstrap test suites not using the Thread API.


WebAssembly (Wasm) was originally introduced to run programs safely and fast in web browsers. But its objective - running programs efficiently with security on various environment - is long wanted not only for 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 run on such promised platforms.

Use case

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

Technical points

Today’s WASI and WebAssembly itself is missing some 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 improvements against ReDoS

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

We have introduced two improvements that significantly mitigate ReDoS.

Improved Regexp matching algorithm

Since Ruby 3.2, Regexp’s matching algorithm has been greatly improved by using a memoization technique.

# This match takes 10 sec. in Ruby 3.1, and 0.003 sec. in Ruby 3.2

/^a*b?a*$/ =~ "a" * 50000 + "x"

The improved matching algorithm allows most Regexp matching (about 90% in our experiments) to be completed in linear time.

(For preview users: this optimization may consume memory proportional to the input length for each match. We expect no practical problems to arise because this memory allocation is usually delayed, and a normal Regexp match should consume at most 10 times as much memory as the input length. If you run out of memory when matching Regexps in a real-world application, please report it.)

The original proposal is

Regexp timeout

The optimization above cannot be applied to some kind of regular expressions, such as those including advanced features (e.g., back-references or look-around), or with a huge fixed number of repetitions. As a fallback measure, a timeout feature for Regexp matches is also introduced.

Regexp.timeout = 1.0

/^a*b?a*()\1$/ =~ "a" * 50000 + "x"
#=> Regexp::TimeoutError is raised in one second

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 the timeout keyword for

Regexp.timeout = 1.0

# This regexp has no timeout
long_time_re ='^a*b?a*()\1$', timeout: Float::INFINITY)

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

The original proposal is

Other Notable New Features


  • The feature of syntax_suggest (formerly dead_end) is integrated into Ruby. This helps you find the position of errors such as missing or superfluous ends, to get you back on your way faster, such as in the following example:

    Unmatched `end', missing keyword (`do', `def`, `if`, etc.) ?
      1  class Dog
    > 2    defbark
    > 4    end
      5  end

    [Feature #18159]


  • Now it points at the relevant argument(s) for TypeError and ArgumentError
test.rb:2:in `+': nil can't be coerced into Integer (TypeError)

sum = ary[0] + ary[1]


  • 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]

  • The 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 potentially missing ruby2_keywords is to run the test suite, find the last method which must receive keyword arguments for each place where the test suite fails, and use puts nil, caller, nil there. Then check that each method/block on the call chain which must delegate keywords is correctly marked with 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


  • YJIT now supports both x86-64 and arm64/aarch64 CPUs on Linux, MacOS, BSD and other UNIX platforms.
    • This release brings support for Mac M1/M2, AWS Graviton and Raspberry Pi 4 ARM64 processors.
  • Building YJIT requires Rust 1.58.0+. [Feature #18481]
    • In order to ensure that CRuby is built with YJIT, please install rustc >= 1.58.0 and run ./configure with --enable-yjit.
    • Please reach out to the YJIT team should you run into any issues.
  • Physical memory for JIT code is lazily allocated. Unlike Ruby 3.1, the RSS of a Ruby process is minimized because virtual memory pages allocated by --yjit-exec-mem-size will not be mapped to physical memory pages until actually utilized by JIT code.
  • Introduce Code GC that frees all code pages when the memory consumption by JIT code reaches --yjit-exec-mem-size.
    • RubyVM::YJIT.runtime_stats returns Code GC metrics in addition to existing inline_code_size and outlined_code_size keys: code_gc_count, live_page_count, freed_page_count, and freed_code_size.
  • Most of the statistics produced by RubyVM::YJIT.runtime_stats are now available in release builds.
    • Simply run ruby with --yjit-stats to compute stats (incurs some run-time overhead).
  • YJIT is now optimized to take advantage of object shapes. [Feature #18776]
  • Take advantage of finer-grained constant invalidation to invalidate less code when defining new constants. [Feature #18589]


  • The MJIT compiler is re-implemented in Ruby as a standard library mjit.
  • MJIT compiler is executed under a forked Ruby process instead of doing it in a native thread called MJIT worker. [[Feature #18968]]
    • As a result, Microsoft Visual Studio (MSWIN) is no longer supported.
  • MinGW is no longer supported. [[Feature #18824]]
  • Rename --mjit-min-calls to --mjit-call-threshold.
  • Change default --mjit-max-cache back from 10000 to 100.


  • Bundler 2.4 now uses PubGrub resolver instead of Molinillo.

    • PubGrub is the next generation solving algorithm used by pub package manager for the Dart programming language.
    • You may get different resolution result after this change. Please report such cases to RubyGems/Bundler issues
  • RubyGems still uses Molinillo resolver in Ruby 3.2. We plan to replace it with PubGrub in the future.

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
  • RubyVM::AbstractSyntaxTree
    • Add error_tolerant option for parse, parse_file and of. [[Feature #19013]]
  • 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 15.0.0 and Emoji Version 15.0. [Feature #18639] (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

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 for each platform.

    • Bundled libffi source is also removed from fiddle

  • Psych and fiddle supported static builds with specific versions of libyaml and libffi sources. You can build psych with libyaml-0.2.5 like this:

      $ ./configure --with-libyaml-source-dir=/path/to/libyaml-0.2.5

    And you can build fiddle with libffi-3.4.4 like this:

      $ ./configure --with-libffi-source-dir=/path/to/libffi-3.4.4

    [Feature #18571]

C API updates

Updated C APIs

The following APIs are updated.

  • PRNG update rb_random_interface_t updated and versioned. Extension libraries which use this interface and built for older versions. Also init_int32 function needs to be defined.

Removed C APIs

The following deprecated APIs are removed.

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

Standard library updates

  • The following default gems are updated.
    • RubyGems
    • benchmark 0.2.1
    • bigdecimal 3.1.3
    • bundler
    • cgi 0.3.6
    • date 3.3.0
    • delegate 0.3.0
    • did_you_mean 1.6.2
    • digest 3.1.1
    • drb 2.1.1
    • erb 4.0.2
    • error_highlight 0.5.1
    • etc 1.4.1
    • fcntl 1.0.2
    • fiddle 1.1.1
    • fileutils 1.7.0
    • forwardable 1.3.3
    • getoptlong 0.2.0
    • io-console 0.5.11
    • io-nonblock 0.2.0
    • io-wait 0.3.0.pre
    • ipaddr 1.2.5
    • irb 1.5.1
    • json 2.6.2
    • logger 1.5.2
    • mutex_m 0.1.2
    • net-http 0.3.1
    • net-protocol 0.2.0
    • nkf 0.1.2
    • open-uri 0.3.0
    • openssl 3.1.0.pre
    • optparse 0.3.0
    • ostruct 0.5.5
    • pathname 0.2.1
    • pp 0.4.0
    • pstore 0.1.2
    • psych 5.0.0
    • racc 1.6.1
    • rdoc 6.5.0
    • reline 0.3.1
    • resolv 0.2.2
    • securerandom 0.2.1
    • set 1.0.3
    • stringio 3.0.3
    • syntax_suggest 1.0.1
    • timeout 0.3.1
    • tmpdir 0.1.3
    • tsort 0.1.1
    • un 0.2.1
    • uri 0.12.0
    • win32ole 1.8.9
    • zlib 3.0.0
  • The following bundled gems are updated.
    • minitest 5.16.3
    • power_assert 2.0.2
    • test-unit 3.5.5
    • net-ftp 0.2.0
    • net-imap 0.3.1
    • net-pop 0.1.2
    • net-smtp 0.3.3
    • rbs 2.8.1
    • typeprof 0.21.3
    • debug 1.7.0

See NEWS or commit logs for more details.

With those changes, 2846 files changed, 203950 insertions(+), 127153 deletions(-) since Ruby 3.1.0!



    SIZE: 20253652
    SHA1: 9b45af61ef1ae3c21ab88d7c9e30b80060116ac3
    SHA256: 3bb9760c1ac1b66416aaa4899809f6ccd010e57038eaaeca19a383fd56275dac
    SHA512: 798157d785ebae94cb128d3c134fa35e0e90c654972e531cb6562823042f3fb68a270226f7b1cf0c42572ef2b1488a1a3e44f88389ad2a6f9ca4b280a2a8e759

    SIZE: 14934012
    SHA1: 5576e304786d466410f27a345dc1cb66f2c773f6
    SHA256: 0d45b3af14e84337882a2021235a091ae5dcfc0baaf31dccc479b71d96dd07bc
    SHA512: d38fcb1e09eb9984f3b2347e65ae7406129c2578d068a25d33b5b4f021ec3b567a9abe56c2acbec6d07a3c2b4bc7b485dbd330cbfbb3a96350f60a2bb94d016e

    SIZE: 24473024
    SHA1: 8fdc85363ce61e0b8f04da36e709d49028d04a75
    SHA256: 7ff32473be108534548e401aaa9092c37a27f73323ea4091c33901c714c87ee5
    SHA512: 07adf6a9c89fdcf420e7b131f40f2b1f4aca036aa6f28539ade26ca552f84a75e0698f77a8b774d2ea52b8c756c4982ef319bda5afa786c081a31dd9873c5ef7

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.