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+# NEWS for Ruby 3.2.0
+
+This document is a list of user-visible feature changes
+since the **3.1.0** release, except for bug fixes.
+
+Note that each entry is kept to a minimum, see links for details.
+
+## Language changes
+
+* Anonymous rest and keyword rest arguments can now be passed as
+ arguments, instead of just used in method parameters.
+ [[Feature #18351]]
+
+ ```ruby
+ def foo(*)
+ bar(*)
+ end
+ def baz(**)
+ quux(**)
+ end
+ ```
+
+* A proc that accepts a single positional argument and keywords will
+ no longer autosplat. [[Bug #18633]]
+
+ ```ruby
+ 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:
+
+ ```ruby
+ 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:
+
+ ```ruby
+ 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]]
+
+ ```ruby
+ def target(**kw)
+ end
+
+ # 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)
+ target(*args)
+ end
+
+ ruby2_keywords def foo(*args)
+ bar(*args)
+ end
+
+ foo(k: 1)
+ ```
+
+## Core classes updates
+
+Note: We're only listing outstanding class updates.
+
+* Fiber
+
+ * Introduce Fiber.[] and Fiber.[]= for inheritable fiber storage.
+ Introduce Fiber#storage and Fiber#storage= (experimental) for
+ getting and resetting the current storage. Introduce
+ `Fiber.new(storage:)` for setting the storage when creating a
+ fiber. [[Feature #19078]]
+
+ Existing Thread and Fiber local variables can be tricky to use.
+ Thread-local variables are shared between all fibers, making it
+ hard to isolate, while Fiber-local variables can be hard to
+ share. It is often desirable to define unit of execution
+ ("execution context") such that some state is shared between all
+ fibers and threads created in that context. This is what Fiber
+ storage provides.
+
+ ```ruby
+ def log(message)
+ puts "#{Fiber[:request_id]}: #{message}"
+ end
+
+ def handle_requests
+ while request = read_request
+ Fiber.schedule do
+ Fiber[:request_id] = SecureRandom.uuid
+
+ request.messages.each do |message|
+ Fiber.schedule do
+ log("Handling #{message}") # Log includes inherited request_id.
+ end
+ end
+ end
+ end
+ end
+ ```
+
+ You should generally consider Fiber storage for any state which
+ you want to be shared implicitly between all fibers and threads
+ created in a given context, e.g. a connection pool, a request
+ id, a logger level, environment variables, configuration, etc.
+
+* Fiber::Scheduler
+
+ * Introduce `Fiber::Scheduler#io_select` for non-blocking IO.select.
+ [[Feature #19060]]
+
+* IO
+
+ * Introduce IO#timeout= and IO#timeout which can cause
+ IO::TimeoutError to be raised if a blocking operation exceeds the
+ specified timeout. [[Feature #18630]]
+
+ ```ruby
+ STDIN.timeout = 1
+ STDIN.read # => Blocking operation timed out! (IO::TimeoutError)
+ ```
+
+ * Introduce `IO.new(..., path:)` and promote `File#path` to `IO#path`.
+ [[Feature #19036]]
+
+* Class
+
+ * Class#attached_object, which returns the object for which
+ the receiver is the singleton class. Raises TypeError if the
+ receiver is not a singleton class.
+ [[Feature #12084]]
+
+ ```ruby
+ class Foo; end
+
+ Foo.singleton_class.attached_object #=> Foo
+ Foo.new.singleton_class.attached_object #=> #<Foo:0x000000010491a370>
+ Foo.attached_object #=> TypeError: `Foo' is not a singleton class
+ nil.singleton_class.attached_object #=> TypeError: `NilClass' is not a singleton class
+ ```
+
+* Data
+
+ * New core class to represent simple immutable value object. The class is
+ similar to Struct and partially shares an implementation, but has more
+ lean and strict API. [[Feature #16122]]
+
+ ```ruby
+ Measure = Data.define(:amount, :unit)
+ distance = Measure.new(100, 'km') #=> #<data Measure amount=100, unit="km">
+ weight = Measure.new(amount: 50, unit: 'kg') #=> #<data Measure amount=50, unit="kg">
+ weight.with(amount: 40) #=> #<data Measure amount=40, unit="kg">
+ weight.amount #=> 50
+ weight.amount = 40 #=> NoMethodError: undefined method `amount='
+ ```
+
+* Encoding
+
+ * Encoding#replicate has been deprecated and will be removed in 3.3. [[Feature #18949]]
+ * The dummy `Encoding::UTF_16` and `Encoding::UTF_32` encodings no longer
+ try to dynamically guess the endian based on a byte order mark.
+ Use `Encoding::UTF_16BE`/`UTF_16LE` and `Encoding::UTF_32BE`/`UTF_32LE` instead.
+ This change speeds up getting the encoding of a String. [[Feature #18949]]
+ * Limit maximum encoding set size by 256.
+ If exceeding maximum size, `EncodingError` will be raised. [[Feature #18949]]
+
+* Enumerator
+
+ * Enumerator.product has been added. Enumerator::Product is the implementation. [[Feature #18685]]
+
+* Exception
+
+ * Exception#detailed_message has been added.
+ The default error printer calls this method on the Exception object
+ instead of #message. [[Feature #18564]]
+
+* 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]]
+
+* Integer
+
+ * Integer#ceildiv has been added. [[Feature #18809]]
+
+* Kernel
+
+ * Kernel#binding raises RuntimeError if called from a non-Ruby frame
+ (such as a method defined in C). [[Bug #18487]]
+
+* MatchData
+
+ * MatchData#byteoffset has been added. [[Feature #13110]]
+ * MatchData#deconstruct has been added. [[Feature #18821]]
+ * MatchData#deconstruct_keys has been added. [[Feature #18821]]
+
+* Module
+
+ * Module.used_refinements has been added. [[Feature #14332]]
+ * Module#refinements has been added. [[Feature #12737]]
+ * Module#const_added has been added. [[Feature #17881]]
+ * Module#undefined_instance_methods has been added. [[Feature #12655]]
+
+* Proc
+
+ * Proc#dup returns an instance of subclass. [[Bug #17545]]
+ * Proc#parameters now accepts lambda keyword. [[Feature #15357]]
+
+* Process
+ * Added `RLIMIT_NPTS` constant to FreeBSD platform
+
+* Regexp
+
+ * The cache-based optimization is introduced.
+ Many (but not all) Regexp matching is now in linear time, which
+ will prevent regular expression denial of service (ReDoS)
+ vulnerability. [[Feature #19104]]
+
+ * Regexp.linear_time? is introduced. [[Feature #19194]]
+
+ * Regexp.new now supports passing the regexp flags not only as an Integer,
+ but also as a String. Unknown flags raise ArgumentError.
+ Otherwise, anything other than `true`, `false`, `nil` or Integer will be warned.
+ [[Feature #18788]]
+
+ * Regexp.timeout= has been added. Also, Regexp.new new supports timeout keyword.
+ See [[Feature #17837]]
+
+* Refinement
+
+ * Refinement#refined_class has been added. [[Feature #12737]]
+
+* RubyVM::AbstractSyntaxTree
+
+ * Add `error_tolerant` option for `parse`, `parse_file` and `of`. [[Feature #19013]]
+ With this option
+
+ 1. SyntaxError is suppressed
+ 2. AST is returned for invalid input
+ 3. `end` is complemented when a parser reaches to the end of input but `end` is insufficient
+ 4. `end` is treated as keyword based on indent
+
+ ```ruby
+ # Without error_tolerant option
+ root = RubyVM::AbstractSyntaxTree.parse(<<~RUBY)
+ def m
+ a = 10
+ if
+ end
+ RUBY
+ # => <internal:ast>:33:in `parse': syntax error, unexpected `end' (SyntaxError)
+
+ # With error_tolerant option
+ root = RubyVM::AbstractSyntaxTree.parse(<<~RUBY, error_tolerant: true)
+ def m
+ a = 10
+ if
+ end
+ RUBY
+ p root # => #<RubyVM::AbstractSyntaxTree::Node:SCOPE@1:0-4:3>
+
+ # `end` is treated as keyword based on indent
+ root = RubyVM::AbstractSyntaxTree.parse(<<~RUBY, error_tolerant: true)
+ module Z
+ class Foo
+ foo.
+ end
+
+ def bar
+ end
+ end
+ RUBY
+ p root.children[-1].children[-1].children[-1].children[-2..-1]
+ # => [#<RubyVM::AbstractSyntaxTree::Node:CLASS@2:2-4:5>, #<RubyVM::AbstractSyntaxTree::Node:DEFN@6:2-7:5>]
+ ```
+
+ * Add `keep_tokens` option for `parse`, `parse_file` and `of`. Add `#tokens` and `#all_tokens`
+ for RubyVM::AbstractSyntaxTree::Node [[Feature #19070]]
+
+ ```ruby
+ root = RubyVM::AbstractSyntaxTree.parse("x = 1 + 2", keep_tokens: true)
+ root.tokens # => [[0, :tIDENTIFIER, "x", [1, 0, 1, 1]], [1, :tSP, " ", [1, 1, 1, 2]], ...]
+ root.tokens.map{_1[2]}.join # => "x = 1 + 2"
+ ```
+
+* Set
+
+ * Set is now available as a built-in 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]]
+ * String#dedup has been added as an alias to String#-@. [[Feature #18595]]
+
+* Struct
+
+ * A Struct class can also be initialized with keyword arguments
+ without `keyword_init: true` on Struct.new [[Feature #16806]]
+
+ ```ruby
+ Post = Struct.new(:id, :name)
+ Post.new(1, "hello") #=> #<struct Post id=1, name="hello">
+ # From Ruby 3.2, the following code also works without keyword_init: true.
+ Post.new(id: 1, name: "hello") #=> #<struct Post id=1, name="hello">
+ ```
+
+* Thread
+
+ * Thread.each_caller_location is added. [[Feature #16663]]
+
+* Thread::Queue
+
+ * Thread::Queue#pop(timeout: sec) is added. [[Feature #18774]]
+
+* Thread::SizedQueue
+
+ * Thread::SizedQueue#pop(timeout: sec) is added. [[Feature #18774]]
+ * Thread::SizedQueue#push(timeout: sec) is added. [[Feature #18944]]
+
+* Time
+
+ * Time#deconstruct_keys is added, allowing to use Time instances
+ in pattern-matching expressions [[Feature #19071]]
+
+ * Time.new now can parse a string like generated by Time#inspect
+ and return a Time instance based on the given argument.
+ [[Feature #18033]]
+
+* SyntaxError
+ * SyntaxError#path has been added. [[Feature #19138]]
+
+* TracePoint
+
+ * TracePoint#binding now returns `nil` for `c_call`/`c_return` TracePoints.
+ [[Bug #18487]]
+ * TracePoint#enable `target_thread` keyword argument now defaults to the
+ current thread if a block is given and `target` and `target_line` keyword
+ arguments are not passed. [[Bug #16889]]
+
+* UnboundMethod
+
+ * `UnboundMethod#==` returns `true` if the actual method is same. For example,
+ `String.instance_method(:object_id) == Array.instance_method(:object_id)`
+ returns `true`. [[Feature #18798]]
+
+ * `UnboundMethod#inspect` does not show the receiver of `instance_method`.
+ For example `String.instance_method(:object_id).inspect` returns
+ `"#<UnboundMethod: Kernel#object_id()>"`
+ (was `"#<UnboundMethod: String(Kernel)#object_id()>"`).
+
+* GC
+
+ * Expose `need_major_gc` via `GC.latest_gc_info`. [GH-6791]
+
+* ObjectSpace
+
+ * `ObjectSpace.dump_all` dump shapes as well. [GH-6868]
+
+## Stdlib updates
+
+* Bundler
+
+ * Bundler now uses [PubGrub] resolver instead of [Molinillo] for performance improvement.
+ * Add --ext=rust support to bundle gem for creating simple gems with Rust extensions.
+ [[GH-rubygems-6149]]
+ * Make cloning git repos faster [[GH-rubygems-4475]]
+
+* RubyGems
+
+ * Add mswin support for cargo builder. [[GH-rubygems-6167]]
+
+* CGI
+
+ * `CGI.escapeURIComponent` and `CGI.unescapeURIComponent` are added.
+ [[Feature #18822]]
+
+* Coverage
+
+ * `Coverage.setup` now accepts `eval: true`. By this, `eval` and related methods are
+ able to generate code coverage. [[Feature #19008]]
+
+ * `Coverage.supported?(mode)` enables detection of what coverage modes are
+ supported. [[Feature #19026]]
+
+* Date
+
+ * Added `Date#deconstruct_keys` and `DateTime#deconstruct_keys` same as [[Feature #19071]]
+
+* ERB
+
+ * `ERB::Util.html_escape` is made faster than `CGI.escapeHTML`.
+ * It no longer allocates a String object when no character needs to be escaped.
+ * It skips calling `#to_s` method when an argument is already a String.
+ * `ERB::Escape.html_escape` is added as an alias to `ERB::Util.html_escape`,
+ which has not been monkey-patched by Rails.
+ * `ERB::Util.url_encode` is made faster using `CGI.escapeURIComponent`.
+ * `-S` option is removed from `erb` command.
+
+* FileUtils
+
+ * Add FileUtils.ln_sr method and `relative:` option to FileUtils.ln_s.
+ [[Feature #18925]]
+
+* IRB
+
+ * debug.gem integration commands have been added: `debug`, `break`, `catch`,
+ `next`, `delete`, `step`, `continue`, `finish`, `backtrace`, `info`
+ * They work even if you don't have `gem "debug"` in your Gemfile.
+ * See also: [What's new in Ruby 3.2's IRB?](https://st0012.dev/whats-new-in-ruby-3-2-irb)
+ * More Pry-like commands and features have been added.
+ * `edit` and `show_cmds` (like Pry's `help`) are added.
+ * `ls` takes `-g` or `-G` option to filter out outputs.
+ * `show_source` is aliased from `$` and accepts unquoted inputs.
+ * `whereami` is aliased from `@`.
+
+* Net::Protocol
+
+ * Improve `Net::BufferedIO` performance. [[GH-net-protocol-14]]
+
+* Pathname
+
+ * Added `Pathname#lutime`. [[GH-pathname-20]]
+
+* Socket
+
+ * Added the following constants for supported platforms.
+ * `SO_INCOMING_CPU`
+ * `SO_INCOMING_NAPI_ID`
+ * `SO_RTABLE`
+ * `SO_SETFIB`
+ * `SO_USER_COOKIE`
+ * `TCP_KEEPALIVE`
+ * `TCP_CONNECTION_INFO`
+
+* SyntaxSuggest
+
+ * The feature of `syntax_suggest` formerly `dead_end` is integrated in Ruby.
+ [[Feature #18159]]
+
+* UNIXSocket
+
+ * Add support for UNIXSocket on Windows. Emulate anonymous sockets. Add
+ support for File.socket? and File::Stat#socket? where possible.
+ [[Feature #19135]]
+
+* The following default gems are updated.
+
+ * RubyGems 3.4.1
+ * abbrev 0.1.1
+ * benchmark 0.2.1
+ * bigdecimal 3.1.3
+ * bundler 2.4.1
+ * cgi 0.3.6
+ * csv 3.2.6
+ * date 3.3.3
+ * delegate 0.3.0
+ * did_you_mean 1.6.3
+ * digest 3.1.1
+ * drb 2.1.1
+ * english 0.7.2
+ * erb 4.0.2
+ * error_highlight 0.5.1
+ * etc 1.4.2
+ * fcntl 1.0.2
+ * fiddle 1.1.1
+ * fileutils 1.7.0
+ * forwardable 1.3.3
+ * getoptlong 0.2.0
+ * io-console 0.6.0
+ * io-nonblock 0.2.0
+ * io-wait 0.3.0
+ * ipaddr 1.2.5
+ * irb 1.6.2
+ * json 2.6.3
+ * logger 1.5.3
+ * mutex_m 0.1.2
+ * net-http 0.3.2
+ * net-protocol 0.2.1
+ * nkf 0.1.2
+ * open-uri 0.3.0
+ * open3 0.1.2
+ * openssl 3.1.0
+ * optparse 0.3.1
+ * ostruct 0.5.5
+ * pathname 0.2.1
+ * pp 0.4.0
+ * pstore 0.1.2
+ * psych 5.0.1
+ * racc 1.6.2
+ * rdoc 6.5.0
+ * readline-ext 0.1.5
+ * reline 0.3.2
+ * resolv 0.2.2
+ * resolv-replace 0.1.1
+ * securerandom 0.2.2
+ * set 1.0.3
+ * stringio 3.0.4
+ * strscan 3.0.5
+ * syntax_suggest 1.0.2
+ * syslog 0.1.1
+ * tempfile 0.1.3
+ * time 0.2.1
+ * timeout 0.3.1
+ * tmpdir 0.1.3
+ * tsort 0.1.1
+ * un 0.2.1
+ * uri 0.12.0
+ * weakref 0.1.2
+ * win32ole 1.8.9
+ * yaml 0.2.1
+ * zlib 3.0.0
+
+* The following bundled gems are updated.
+
+ * minitest 5.16.3
+ * power_assert 2.0.3
+ * test-unit 3.5.7
+ * net-ftp 0.2.0
+ * net-imap 0.3.4
+ * net-pop 0.1.2
+ * net-smtp 0.3.3
+ * rbs 2.8.2
+ * typeprof 0.21.3
+ * debug 1.7.1
+
+See GitHub releases like [GitHub Releases of Logger](https://github.com/ruby/logger/releases) or changelog for details of the default gems or bundled gems.
+
+## Supported platforms
+
+* WebAssembly/WASI is added. See [wasm/README.md] and [ruby.wasm] for more details. [[Feature #18462]]
+
+## Compatibility issues
+
+* `String#to_c` currently treat a sequence of underscores as an end of Complex
+ string. [[Bug #19087]]
+
+* Now `ENV.clone` raises `TypeError` as well as `ENV.dup` [[Bug #17767]]
+
+### Removed constants
+
+The following deprecated constants are removed.
+
+* `Fixnum` and `Bignum` [[Feature #12005]]
+* `Random::DEFAULT` [[Feature #17351]]
+* `Struct::Group`
+* `Struct::Passwd`
+
+### Removed methods
+
+The following deprecated methods are removed.
+
+* `Dir.exists?` [[Feature #17391]]
+* `File.exists?` [[Feature #17391]]
+* `Kernel#=~` [[Feature #15231]]
+* `Kernel#taint`, `Kernel#untaint`, `Kernel#tainted?`
+ [[Feature #16131]]
+* `Kernel#trust`, `Kernel#untrust`, `Kernel#untrusted?`
+ [[Feature #16131]]
+* `Method#public?`, `Method#private?`, `Method#protected?`,
+ `UnboundMethod#public?`, `UnboundMethod#private?`, `UnboundMethod#protected?`
+ [[Bug #18729]] [[Bug #18751]] [[Bug #18435]]
+
+### Source code incompatibility of extension libraries
+
+* Extension libraries provide PRNG, subclasses of Random, need updates.
+ See [PRNG update] below for more information. [[Bug #19100]]
+
+### Error printer
+
+* Ruby no longer escapes control characters and backslashes in an
+ error message. [[Feature #18367]]
+
+### Constant lookup when defining a class/module
+
+* When defining a class/module directly under the Object class by class/module
+ statement, if there is already a class/module defined by `Module#include`
+ with the same name, the statement was handled as "open class" in Ruby 3.1 or before.
+ Since Ruby 3.2, a new class is defined instead. [[Feature #18832]]
+
+## Stdlib compatibility issues
+
+* Psych no longer bundles libyaml sources.
+ And also Fiddle no longer bundles libffi sources.
+ Users need to install the libyaml/libffi library themselves via the package
+ manager like apt, yum, brew, etc.
+
+ Psych and fiddle supported the static build with specific version of libyaml
+ and libffi sources. You can build psych with libyaml-0.2.5 like this.
+
+ ```bash
+ $ ./configure --with-libyaml-source-dir=/path/to/libyaml-0.2.5
+ ```
+
+ And you can build fiddle with libffi-3.4.4 like this.
+
+ ```bash
+ $ ./configure --with-libffi-source-dir=/path/to/libffi-3.4.4
+ ```
+
+ [[Feature #18571]]
+
+* Check cookie name/path/domain characters in `CGI::Cookie`. [[CVE-2021-33621]]
+
+* `URI.parse` return empty string in host instead of nil. [[sec-156615]]
+
+## C API updates
+
+### Updated C APIs
+
+The following APIs are updated.
+
+* PRNG update
+
+ `rb_random_interface_t` in ruby/random.h updated and versioned.
+ Extension libraries which use this interface and built for older
+ versions need to rebuild with adding `init_int32` function.
+
+### Added C APIs
+
+* `VALUE rb_hash_new_capa(long capa)` was added to created hashes with the desired capacity.
+* `rb_internal_thread_add_event_hook` and `rb_internal_thread_add_event_hook` were added to instrument threads scheduling.
+ The following events are available:
+ * `RUBY_INTERNAL_THREAD_EVENT_STARTED`
+ * `RUBY_INTERNAL_THREAD_EVENT_READY`
+ * `RUBY_INTERNAL_THREAD_EVENT_RESUMED`
+ * `RUBY_INTERNAL_THREAD_EVENT_SUSPENDED`
+ * `RUBY_INTERNAL_THREAD_EVENT_EXITED`
+* `rb_debug_inspector_current_depth` and `rb_debug_inspector_frame_depth` are added for debuggers.
+
+### Removed C APIs
+
+The following deprecated APIs are removed.
+
+* `rb_cData` variable.
+* "taintedness" and "trustedness" functions. [[Feature #16131]]
+
+## Implementation improvements
+
+* Fixed several race conditions in Kernel#autoload. [[Bug #18782]]
+* Cache invalidation for expressions referencing constants is now
+ more fine-grained. `RubyVM.stat(:global_constant_state)` was
+ removed because it was closely tied to the previous caching scheme
+ where setting any constant invalidates all caches in the system.
+ New keys, `:constant_cache_invalidations` and `:constant_cache_misses`,
+ were introduced to help with use cases for `:global_constant_state`.
+ [[Feature #18589]]
+* The cache-based optimization for Regexp matching is introduced.
+ [[Feature #19104]]
+* [Variable Width Allocation](https://shopify.engineering/ruby-variable-width-allocation)
+ is now enabled by default. [[Feature #18239]]
+* Added a new instance variable caching mechanism, called object shapes, which
+ improves inline cache hits for most objects and allows us to generate very
+ efficient JIT code. Objects whose instance variables are defined in a
+ consistent order will see the most performance benefits.
+ [[Feature #18776]]
+* Speed up marking instruction sequences by using a bitmap to find "markable"
+ objects. This change results in faster major collections.
+ [[Feature #18875]]
+
+## JIT
+
+### YJIT
+
+* YJIT is no longer experimental
+ * Has been tested on production workloads for over a year and proven to be quite stable.
+* 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.
+* Building YJIT now requires Rust 1.58.0+. [[Feature #18481]]
+ * In order to ensure that CRuby is built with YJIT, please install `rustc` >= 1.58.0
+ before running `./configure`
+ * 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 and dump 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 default `--yjit-exec-mem-size` is changed to 64 (MiB).
+* The default `--yjit-call-threshold` is changed to 30.
+
+### MJIT
+
+* The MJIT compiler is re-implemented in Ruby as `ruby_vm/mjit/compiler`.
+* 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.
+
+[Feature #12005]: https://bugs.ruby-lang.org/issues/12005
+[Feature #12084]: https://bugs.ruby-lang.org/issues/12084
+[Feature #12655]: https://bugs.ruby-lang.org/issues/12655
+[Feature #12737]: https://bugs.ruby-lang.org/issues/12737
+[Feature #13110]: https://bugs.ruby-lang.org/issues/13110
+[Feature #14332]: https://bugs.ruby-lang.org/issues/14332
+[Feature #15231]: https://bugs.ruby-lang.org/issues/15231
+[Feature #15357]: https://bugs.ruby-lang.org/issues/15357
+[Bug #15928]: https://bugs.ruby-lang.org/issues/15928
+[Feature #16122]: https://bugs.ruby-lang.org/issues/16122
+[Feature #16131]: https://bugs.ruby-lang.org/issues/16131
+[Bug #16466]: https://bugs.ruby-lang.org/issues/16466
+[Feature #16663]: https://bugs.ruby-lang.org/issues/16663
+[Feature #16806]: https://bugs.ruby-lang.org/issues/16806
+[Bug #16889]: https://bugs.ruby-lang.org/issues/16889
+[Bug #16908]: https://bugs.ruby-lang.org/issues/16908
+[Feature #16989]: https://bugs.ruby-lang.org/issues/16989
+[Feature #17351]: https://bugs.ruby-lang.org/issues/17351
+[Feature #17391]: https://bugs.ruby-lang.org/issues/17391
+[Bug #17545]: https://bugs.ruby-lang.org/issues/17545
+[Bug #17767]: https://bugs.ruby-lang.org/issues/17767
+[Feature #17837]: https://bugs.ruby-lang.org/issues/17837
+[Feature #17881]: https://bugs.ruby-lang.org/issues/17881
+[Feature #18033]: https://bugs.ruby-lang.org/issues/18033
+[Feature #18159]: https://bugs.ruby-lang.org/issues/18159
+[Feature #18239]: https://bugs.ruby-lang.org/issues/18239#note-17
+[Feature #18351]: https://bugs.ruby-lang.org/issues/18351
+[Feature #18367]: https://bugs.ruby-lang.org/issues/18367
+[Bug #18435]: https://bugs.ruby-lang.org/issues/18435
+[Feature #18462]: https://bugs.ruby-lang.org/issues/18462
+[Feature #18481]: https://bugs.ruby-lang.org/issues/18481
+[Bug #18487]: https://bugs.ruby-lang.org/issues/18487
+[Feature #18564]: https://bugs.ruby-lang.org/issues/18564
+[Feature #18571]: https://bugs.ruby-lang.org/issues/18571
+[Feature #18585]: https://bugs.ruby-lang.org/issues/18585
+[Feature #18589]: https://bugs.ruby-lang.org/issues/18589
+[Feature #18595]: https://bugs.ruby-lang.org/issues/18595
+[Feature #18598]: https://bugs.ruby-lang.org/issues/18598
+[Bug #18625]: https://bugs.ruby-lang.org/issues/18625
+[Feature #18630]: https://bugs.ruby-lang.org/issues/18630
+[Bug #18633]: https://bugs.ruby-lang.org/issues/18633
+[Feature #18639]: https://bugs.ruby-lang.org/issues/18639
+[Feature #18685]: https://bugs.ruby-lang.org/issues/18685
+[Bug #18729]: https://bugs.ruby-lang.org/issues/18729
+[Bug #18751]: https://bugs.ruby-lang.org/issues/18751
+[Feature #18774]: https://bugs.ruby-lang.org/issues/18774
+[Feature #18776]: https://bugs.ruby-lang.org/issues/18776
+[Bug #18782]: https://bugs.ruby-lang.org/issues/18782
+[Feature #18788]: https://bugs.ruby-lang.org/issues/18788
+[Feature #18798]: https://bugs.ruby-lang.org/issues/18798
+[Feature #18809]: https://bugs.ruby-lang.org/issues/18809
+[Feature #18821]: https://bugs.ruby-lang.org/issues/18821
+[Feature #18822]: https://bugs.ruby-lang.org/issues/18822
+[Feature #18824]: https://bugs.ruby-lang.org/issues/18824
+[Feature #18832]: https://bugs.ruby-lang.org/issues/18832
+[Feature #18875]: https://bugs.ruby-lang.org/issues/18875
+[Feature #18925]: https://bugs.ruby-lang.org/issues/18925
+[Feature #18944]: https://bugs.ruby-lang.org/issues/18944
+[Feature #18949]: https://bugs.ruby-lang.org/issues/18949
+[Feature #18968]: https://bugs.ruby-lang.org/issues/18968
+[Feature #19008]: https://bugs.ruby-lang.org/issues/19008
+[Feature #19013]: https://bugs.ruby-lang.org/issues/19013
+[Feature #19026]: https://bugs.ruby-lang.org/issues/19026
+[Feature #19036]: https://bugs.ruby-lang.org/issues/19036
+[Feature #19060]: https://bugs.ruby-lang.org/issues/19060
+[Feature #19070]: https://bugs.ruby-lang.org/issues/19070
+[Feature #19071]: https://bugs.ruby-lang.org/issues/19071
+[Feature #19078]: https://bugs.ruby-lang.org/issues/19078
+[Bug #19087]: https://bugs.ruby-lang.org/issues/19087
+[Bug #19100]: https://bugs.ruby-lang.org/issues/19100
+[Feature #19104]: https://bugs.ruby-lang.org/issues/19104
+[Feature #19135]: https://bugs.ruby-lang.org/issues/19135
+[Feature #19138]: https://bugs.ruby-lang.org/issues/19138
+[Feature #19194]: https://bugs.ruby-lang.org/issues/19194
+[Molinillo]: https://github.com/CocoaPods/Molinillo
+[PubGrub]: https://github.com/jhawthorn/pub_grub
+[GH-net-protocol-14]: https://github.com/ruby/net-protocol/pull/14
+[GH-pathname-20]: https://github.com/ruby/pathname/pull/20
+[GH-6791]: https://github.com/ruby/ruby/pull/6791
+[GH-6868]: https://github.com/ruby/ruby/pull/6868
+[GH-rubygems-4475]: https://github.com/rubygems/rubygems/pull/4475
+[GH-rubygems-6149]: https://github.com/rubygems/rubygems/pull/6149
+[GH-rubygems-6167]: https://github.com/rubygems/rubygems/pull/6167
+[sec-156615]: https://hackerone.com/reports/156615
+[CVE-2021-33621]: https://www.ruby-lang.org/en/news/2022/11/22/http-response-splitting-in-cgi-cve-2021-33621/
+[wasm/README.md]: https://github.com/ruby/ruby/blob/master/wasm/README.md
+[ruby.wasm]: https://github.com/ruby/ruby.wasm