NEWS.md

NEWS for Ruby 3.3.0

This document is a list of user-visible feature changes since the 3.2.0 release, except for bug fixes.

Note that each entry is kept to a minimum, see links for details.

Language changes

Command line options

• A new performance warning category was introduced. They are not displayed by default even in verbose mode. Turn them on with -W:performance or Warning[:performance] = true. [Feature #19538]

• A new RUBY_CRASH_REPORT environment variable was introduced to allow redirecting Ruby crash reports to a file or sub command. See the BUG REPORT ENVIRONMENT section of the ruby manpage for further details. [Feature #19790]

Core classes updates

Note: We're only listing outstanding class updates.

• Array

  • Array#pack now raises ArgumentError for unknown directives. [Bug #19150]

• Dir

  • Dir.for_fd added for returning a Dir object for the directory specified by the provided directory file descriptor. [Feature #19347]
  • Dir.fchdir added for changing the directory to the directory specified by the provided directory file descriptor. [Feature #19347]
  • Dir#chdir added for changing the directory to the directory specified by the provided Dir object. [Feature #19347]

• MatchData

  • MatchData#named_captures now accepts optional symbolize_names keyword. [Feature #19591]

• Module

  • Module#set_temporary_name added for setting a temporary name for a module. [Feature #19521]

• ObjectSpace::WeakKeyMap

  • New core class to build collections with weak references. The class use equality semantic to lookup keys like a regular hash, but it doesn't hold strong references on the keys. [Feature #18498]

• ObjectSpace::WeakMap

  • ObjectSpace::WeakMap#delete was added to eagerly clear weak map entries. [Feature #19561]

• Proc

  • Now Proc#dup and Proc#clone call #initialize_dup and #initialize_clone hooks respectively. [Feature #19362]

• Process

  • New Process.warmup method that notify the Ruby virtual machine that the boot sequence is finished, and that now is a good time to optimize the application. This is useful for long-running applications. The actual optimizations performed are entirely implementation-specific and may change in the future without notice. [Feature #18885]

• Process::Status

  • Process::Status#& and Process::Status#>> are deprecated. [Bug #19868]

• Queue

  • Queue#freeze now raises TypeError. [Bug #17146]

• Range

  • Range#reverse_each can now process beginless ranges with an Integer endpoint. [Feature #18515]
  • Range#reverse_each now raises TypeError for endless ranges. [Feature #18551]

• Refinement

  • Add Refinement#target as an alternative of Refinement#refined_class. Refinement#refined_class is deprecated and will be removed in Ruby 3.4. [Feature #19714]

• SizedQueue

  • SizedQueue#freeze now raises TypeError. [Bug #17146]

• String

  • String#unpack now raises ArgumentError for unknown directives. [Bug #19150]
  • String#bytesplice now accepts new arguments index/length or range of the source string to be copied. [Feature #19314]

• TracePoint

  • TracePoint supports rescue event. When the raised exception was rescued, the TracePoint will fire the hook. rescue event only supports Ruby-level rescue. [Feature #19572]

Stdlib updates

• RubyGems and Bundler warn if users require gem that is scheduled to become the bundled gems in the future version of Ruby. [Feature #19351] [Feature #19776] [Feature #19843]

  Targeted libraries are:

  • abbrev
  • base64
  • bigdecimal
  • csv
  • drb
  • getoptlong
  • mutex_m
  • nkf
  • observer
  • racc
  • resolv-replace
  • rinda
  • syslog

• Socket#recv and Socket#recv_nonblock returns nil instead of an empty string on closed connections. Socket#recvmsg and Socket#recvmsg_nonblock returns nil instead of an empty packet on closed connections. [Bug #19012]

• Random::Formatter#alphanumeric is extended to accept optional chars keyword argument. [Feature #18183]

The following default gem is added.

• prism 0.18.0

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 0.4.1
• 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.1
• irb 1.10.1
• json 2.7.1
• 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 6.6.1
• reline 0.4.0
• rinda 0.2.0
• securerandom 0.3.0
• shellwords 0.2.0
• singleton 0.2.0
• stringio 3.1.1
• strscan 3.0.8
• syntax_suggest 1.1.0
• tempfile 0.2.1
• 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 0.4.7
• net-smtp 0.4.0
• rbs 3.3.2
• typeprof 0.21.8
• debug 1.8.0

See GitHub releases like Logger or changelog for details of the default gems or bundled gems.

Supported platforms

Compatibility issues

• Subprocess creation/forking via the following file open methods is deprecated. [Feature #19630]

  • Kernel#open
  • URI.open
  • IO.binread
  • IO.foreach
  • IO.readlines
  • IO.read
  • IO.write

• When given a non-lambda, non-literal block, Kernel#lambda with now raises ArgumentError instead of returning it unmodified. These usages have been issuing warnings under the Warning[:deprecated] category since Ruby 3.0.0. [Feature #19777]

• The RUBY_GC_HEAP_INIT_SLOTS environment variable has been deprecated and removed. Environment variables RUBY_GC_HEAP_%d_INIT_SLOTS should be used instead. [Feature #19785]

Stdlib compatibility issues

• racc is promoted to bundled gems.
  • You need to add racc to your Gemfile if you use racc under bundler environment.
• 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

Implementation improvements

• defined?(@ivar) is optimized with Object Shapes.
• Name resolution such as Socket.getaddrinfo can now be interrupted. [Feature #19965]

GC

• Major performance improvements over 3.2
  • Young objects referenced by old objects are no longer immediately promoted to the old generation. This significantly reduces the frequency of major GC collections. [Feature #19678]
  • A new REMEMBERED_WB_UNPROTECTED_OBJECTS_LIMIT_RATIO tuning variable was introduced to control the number of unprotected objects cause a major GC collection to trigger. The default is set to 0.01 (1%). This significantly reduces the frequency of major GC collection. [Feature #19571]
  • Write Barriers were implemented for many core types that were missing them, notably Time, Enumerator, MatchData, Method, File::Stat, BigDecimal and several others. This significantly reduces minor GC collection time and major GC collection frequency.
  • Most core classes are now using Variable Width Allocation, notably Hash, Time, Thread::Backtrace, Thread::Backtrace::Location, File::Stat, Method. This makes these classes faster to allocate and free, use less memory and reduce heap fragmentation.

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 later
  • 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.
• Code GC now disabled by default, with --yjit-exec-mem-size treated as a hard limit
  • Can produce better copy-on-write behavior on forking web servers such as unicorn
  • Use the --yjit-code-gc option to automatically run code GC when YJIT reaches the size limit
• ratio_in_yjit stat produced by --yjit-stats is now available 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
• More thorough testing and multiple bug fixes
• --yjit-stats=quiet is added to avoid printing stats on exit.
• --yjit-perf is added to facilitate profiling with Linux perf.

MJIT

• MJIT is removed.
  • --disable-jit-support is removed. Consider using --disable-yjit --disable-rjit instead.

RJIT

• Introduced a pure-Ruby JIT compiler RJIT.
  • 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.

M:N Thread scheduler

• M:N Thread scheduler is introduced. [Feature #19842]
  • Background: Ruby 1.8 and before, M:1 thread scheduler (M Ruby threads with 1 native thread. Called as User level threads or Green threads) is used. Ruby 1.9 and later, 1:1 thread scheduler (1 Ruby thread with 1 native thread). M:1 threads takes lower resources compare with 1:1 threads because it needs only 1 native threads. However it is difficult to support context switching for all of blocking operation so 1:1 threads are employed from Ruby 1.9. M:N thread scheduler uses N native threads for M Ruby threads (N is small number in general). It doesn't need same number of native threads as Ruby threads (similar to the M:1 thread scheduler). Also our M:N threads supports blocking operations well same as 1:1 threads. See the ticket for more details. Our M:N thread scheduler refers on the goroutine scheduler in the Go language.
  • In a ractor, only 1 thread can run in a same time because of implementation. Therefore, applications that use only one Ractor (most applications) M:N thread scheduler works as M:1 thread scheduler with further extension from Ruby 1.8.
  • M:N thread scheduler can introduce incompatibility for C-extensions, so it is disabled by default on the main Ractors. RUBY_MN_THREADS=1 environment variable will enable it. On non-main Ractors, M:N thread scheduler is enabled (and can not disable it now).
  • N (the number of native threads) can be specified with RUBY_MAX_CPU environment variable. The default is 8. Note that more than N native threads are used to support many kind of blocking operations.