[ruby-core:115351] Ruby 3.3.0-preview3 Released

We are pleased to announce the release of Ruby 3.3.0-preview3. Ruby
3.3 adds a new parser named Prism, uses Lrama as a parser generator,
adds a new pure-Ruby JIT compiler named RJIT, and many performance
improvements especially YJIT.

## Prism

* Introduced [the Prism parser](https://github.com/ruby/prism) as a default gem
    * Prism is a portable, error tolerant, and maintainable recursive
descent parser for the Ruby language
* Prism is production ready and actively maintained, you can use it in
place of Ripper
    * There is [extensive
documentation](https://ruby.github.io/prism/) on how to use Prism
    * Prism is both a C library that will be used internally by CRuby
and a Ruby gem that can be used by any tooling which needs to parse
Ruby code
    * Notable methods in the Prism API are:
        * `Prism.parse(source)` which returns the AST as part of a ParseResult
        * `Prism.dump(source, filepath)` which returns the serialized
AST as a String
        * `Prism.parse_comments(source)` which returns the comments
* You can make pull requests or issues directly on [the Prism
repository](https://github.com/ruby/prism) if you are interested in
contributing

## Use Lrama instead of Bison

* Replace Bison with [Lrama LALR parser
generator](https://github.com/yui-knk/lrama) [Feature
#19637](https://bugs.ruby-lang.org/issues/19637)
  * If you have interest, please see [The future vision of Ruby
Parser](https://rubykaigi.org/2023/presentations/spikeolaf.html)
  * Lrama internal parser is replaced with LR parser generated by Racc
for maintainability
  * Parameterizing Rules `(?, *, +)` are supported, it will be used in
Ruby parse.y

## RJIT

* Introduced a pure-Ruby JIT compiler RJIT and replaced MJIT.
  * RJIT supports only x86-64 architecture on Unix platforms.
  * Unlike MJIT, it doesn't require a C compiler at runtime.
* RJIT exists only for experimental purposes.
  * You should keep using YJIT in production.
* If you are interested in developing JIT for Ruby, please check out
[k0kubun's presentation on Day 3 of
RubyKaigi](https://rubykaigi.org/2023/presentations/k0kubun.html#day3).

## YJIT

* Major performance improvements over 3.2
  * Support for splat and rest arguments has been improved.
  * Registers are allocated for stack operations of the virtual machine.
  * More calls with optional arguments are compiled.
  * Exception handlers are also compiled.
  * Instance variables no longer exit to the interpreter
    with megamorphic object shapes.
  * Unsupported call types no longer exit to the interpreter.
  * `Integer#!=`, `String#!=`, `Kernel#block_given?`, `Kernel#is_a?`,
    `Kernel#instance_of?`, `Module#===` are specially optimized.
  * Now more than 3x faster than the interpreter on optcarrot!
* Significantly improved memory usage over 3.2
    * Metadata for compiled code uses a lot less memory.
    * Generate more compact code on ARM64
* Compilation speed is now slightly faster than 3.2.
* Add `RubyVM::YJIT.enable` that can enable YJIT at run-time
  * You can start YJIT without modifying command-line arguments or
environment variables.
  * This can also be used to enable YJIT only once your application is
    done booting. `--yjit-disable` can be used if you want to use other
    YJIT options while disabling YJIT at boot.
* Option to disable code GC and treat `--yjit-exec-mem-size` as a hard limit
  * Can produce better copy-on-write behavior on servers using unicorn
and forking
* `ratio_in_yjit` stat produced by `--yjit-stats` is now avaiable in
release builds,
  a special stats or dev build is no longer required to access most stats.
* Exit tracing option now supports sampling
  * `--trace-exits-sample-rate=N`
* `--yjit-perf` is added to facilitate profiling with Linux perf.
* More thorough testing and multiple bug fixes

### M:N thread scheduler

* M:N thread scheduler was introduced. [[Feature
#19842]](https://bugs.ruby-lang.org/issues/19842)
  * M Ruby threads are managed by N native threads (OS threads) so the
thread creation and management cost are reduced.
  * It can break C-extension compatibility so that M:N thread
scheduler is disabled on the main Ractor by default.
      * `RUBY_MN_THREADS=1` environment variable enables M:N threads
on the main Ractor.
      * M:N threads are enabled on non-main Ractors.
  * `RUBY_MAX_CPU=n` environment variable sets maximum number of `N`
(maximum number of native threads). The default value is 8.
      * Since only one Ruby thread per Ractor can run at the same
time, the number of native threads will be used, which is the smaller
of the number specified in `RUBY_MAX_CPU` and the number of running
Ractors. So that single Ractor applications (most of applications)
will use 1 native thread.
      * To support blocking operations, more than `N` native threads
can be used.

## Other Notable New Features



### Language



## Performance improvements

* `defined?(@ivar)` is optimized with Object Shapes.
* Name resolution such as `Socket.getaddrinfo` can now be interrupted
(in environments where pthreads are available). [Feature
#19965](https://bugs.ruby-lang.org/issues/19965)
  * For this purpose, a pthread is now created whenever calling
getaddrinfo or getnameinfo. This incurs some overhead in name
resolution (about 2.5x in our experiments). We do not expect the name
resolution overhead to be a problem for most applications, but if you
observe such, or if you see unexpected affects that you believe are
due to this change, please report them.
* Environment variable
`RUBY_GC_HEAP_REMEMBERED_WB_UNPROTECTED_OBJECTS_LIMIT_RATIO` has been
added. [Feature #19571](https://bugs.ruby-lang.org/issues/19571)
* Children of old objects are no longer immedately promoted to the old
generation in the garbage collector. [Feature
#19678](https://bugs.ruby-lang.org/issues/19678)
* Support for weak references has been added to the garbage collector.
[Feature #19783](https://bugs.ruby-lang.org/issues/19783)

## Other notable changes since 3.2

### IRB

IRB has received several enhancements, including but not limited to:

- Advanced `irb:rdbg` integration that provides an equivalent
debugging experience to `pry-byebug`
([doc](https://github.com/ruby/irb#debugging-with-irb)).
- Pager support for `ls`, `show_source` and `show_cmds` commands.
- More accurate and helpful information provided by the `ls` and
`show_source` commands.
- Experimental autocompletion using type analysis
([doc](https://github.com/ruby/irb#type-based-completion)).
- It is now possible to change the font color and font style in the
completion dialog by a newly introduced class Reline::Face
([doc](https://github.com/ruby/ruby/blob/master/doc/reline/face.md))

In addition, IRB has also undergone extensive refactoring and received
dozens of bug fixes to facilitate easier future enhancements.

## Compatibility issues

Note: Excluding feature bug fixes.

### Removed constants

The following deprecated constants are removed.



### Removed methods

The following deprecated methods are removed.

### Removed environment variables

The following deprecated methods are removed.

* Environment variable `RUBY_GC_HEAP_INIT_SLOTS` has been deprecated
and is a no-op. Please use environment variables
`RUBY_GC_HEAP_{0,1,2,3,4}_INIT_SLOTS` instead. [Feature
#19785](https://bugs.ruby-lang.org/issues/19785)

## Stdlib compatibility issues

### `ext/readline` is retired

* We have `reline` that is pure Ruby implementation compatible with
`ext/readline` API. We rely on `reline` in the future. If you need to
use `ext/readline`, you can install `ext/readline` via rubygems.org
with `gem install readline-ext`.
* We no longer need to install libraries like `libreadline` or `libedit`.

## C API updates

### Updated C APIs

The following APIs are updated.



### Removed C APIs

The following deprecated APIs are removed.



## Standard library updates

RubyGems and Bundler warn if users require gem that is scheduled to
become the bundled gems in the future version of Ruby.

Targeted libraries are:
  * abbrev
  * base64
  * bigdecimal
  * csv
  * drb
  * getoptlong
  * mutex_m
  * nkf
  * observer
  * racc
  * resolv-replace
  * rinda
  * syslog

The following default gem is added.

* prism 0.15.1

The following default gems are updated.

* RubyGems 3.5.0.dev
* base64 0.2.0
* benchmark 0.3.0
* bigdecimal 3.1.5
* bundler 2.5.0.dev
* cgi 0.4.0
* csv 3.2.8
* date 3.3.4
* delegate 0.3.1
* drb 2.2.0
* english 0.8.0
* erb 4.0.3
* etc 1.4.3.dev.1
* fcntl 1.1.0
* fiddle 1.1.2
* fileutils 1.7.2
* find 0.2.0
* getoptlong 0.2.1
* io-console 0.6.1.dev
* irb 1.8.3
* logger 1.6.0
* mutex_m 0.2.0
* net-http 0.4.0
* net-protocol 0.2.2
* nkf 0.1.3
* observer 0.1.2
* open-uri 0.4.0
* open3 0.2.0
* openssl 3.2.0
* optparse 0.4.0
* ostruct 0.6.0
* pathname 0.3.0
* pp 0.5.0
* prettyprint 0.2.0
* pstore 0.1.3
* psych 5.1.1.1
* rdoc 6.6.0
* reline 0.3.9
* rinda 0.2.0
* securerandom 0.3.0
* shellwords 0.2.0
* singleton 0.2.0
* stringio 3.0.9
* strscan 3.0.7
* syntax_suggest 1.1.0
* tempfile 0.2.0
* time 0.3.0
* timeout 0.4.1
* tmpdir 0.2.0
* tsort 0.2.0
* un 0.3.0
* uri 0.13.0
* weakref 0.1.3
* win32ole 1.8.10
* yaml 0.3.0
* zlib 3.1.0

The following bundled gem is promoted from default gems.

* racc 1.7.3

The following bundled gems are updated.

* minitest 5.20.0
* rake 13.1.0
* test-unit 3.6.1
* rexml 3.2.6
* rss 0.3.0
* net-imap 0.4.4
* net-smtp 0.4.0
* rbs 3.2.2
* typeprof 0.21.8
* debug 1.8.0

See GitHub releases like [Logger](https://github.com/ruby/logger/releases) or
changelog for details of the default gems or bundled gems.

See [NEWS](https://github.com/ruby/ruby/blob/v3_3_0_preview3/NEWS.md)
or [commit logs](https://github.com/ruby/ruby/compare/v3_2_0...v3_3_0_preview3)
for more details.

With those changes, [5207 files changed, 284820 insertions(+), 174773
deletions(-)](https://github.com/ruby/ruby/compare/v3_2_0...v3_3_0_preview3#file_bucket)
since Ruby 3.2.0!


## Download

* <https://cache.ruby-lang.org/pub/ruby/3.3/ruby-3.3.0-preview3.tar.gz>

      SIZE: 21550473
      SHA1: 2811f191d66dffee0206771873bd990857ae4ed6
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* <https://cache.ruby-lang.org/pub/ruby/3.3/ruby-3.3.0-preview3.tar.xz>

      SIZE: 15970144
      SHA1: 496600612605f8ebeb955255e98bac73a4cbc045
      SHA256: f79afcf122dc7d04fe26cfa4436b9c488b21766fc54b0d2dfb2ba41cd0cdd355
      SHA512: d7ab0d703e7884efd31045933409cd68fac1d9941963537ccc8e309ca7c8bee8500a68182135acba22cbdbf4a8ae99f39bf7f0925273eb4fbc3728c0c1ba0c19

* <https://cache.ruby-lang.org/pub/ruby/3.3/ruby-3.3.0-preview3.zip>

      SIZE: 26618303
      SHA1: 6a13e08c7e484d42037c1e2c87c5d0e220f893a0
      SHA256: c35bf637a647c2f60148368ffb374db5c258570911794f46b6dfdb98ebfe95d9
      SHA512: c4ef2cdcdadeb85ad1d42aedc97f9f3d609b3b01eea2319451cf92c81bd31ae8129b7c91fc68571469dd888c01ea0f48f73234b965db17f6a87404ca382f7794

## 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.
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