Ruby 2.6.0-preview3 Released

We are pleased to announce the release of Ruby 2.6.0-preview3.

Ruby 2.6.0-preview3 is the third preview toward Ruby 2.6.0. This preview3 is released to test new features before coming Release Candidate.


Ruby 2.6 introduces an initial implementation of JIT (Just-in-time) compiler.

JIT compiler aims to improve performance of any Ruby program execution. Unlike ordinary JIT compilers for other languages, Ruby’s JIT compiler does JIT compilation in a unique way, which prints C code to a disk and spawns common C compiler process to generate native code. See also: MJIT organization by Vladimir Makarov.

How to use: Just specify --jit in command line or $RUBYOPT environment variable. Specifying --jit-verbose=1 allows to print basic information of ongoing JIT compilation. See ruby --help for other options.

The main purpose of this JIT release is to provide a chance to check if it works for your platform and to find out security risks before the 2.6 release. JIT compiler is supported when Ruby is built by GCC, Clang, or Microsoft VC++, which needs to be available on runtime. Otherwise you can’t use it for now.

As of Ruby 2.6.0 preview3, we achieved 1.7x faster performance than Ruby 2.5 on CPU-intensive non-trivial benchmark workload called Optcarrot We’re going to improve the performance on memory-intensive workload like Rails application as well.

Stay tuned for the new age of Ruby’s performance.

RubyVM::AST [Experimental]

Ruby 2.6 introduces RubyVM::AST module.

This module has parse method which parses a given ruby code of string and returns AST (Abstract Syntax Tree) nodes, and parse_file method which parses a given ruby code file and returns AST nodes. RubyVM::AST::Node class is also introduced. You can get location information and children nodes from Node objects. This feature is experimental. Compatibility of the structure of AST nodes are not guaranteed.

New Features

  • Add a new alias then to Kernel#yield_self. [Feature #14594]

  • else without rescue now causes a syntax error. [EXPERIMENTAL]

  • constant names may start with a non-ASCII capital letter. [Feature #13770]

  • endless range [Feature #12912]

    An endless range, (1..), is introduced. It works as it has no end. This shows typical use cases:

    ary[1..]                          # identical to ary[1..-1] without magical -1
    (1..).each {|index| ... }         # infinite loop from index 1 {|elem, index| ... } # ary.each.with_index(1) { ... }
  • Add Binding#source_location. [Feature #14230]

    This method returns the source location of binding, a 2-element array of __FILE__ and __LINE__. Traditionally, the same information could be retrieved by eval("[__FILE__, __LINE__]", binding), but we are planning to change this behavior so that Kernel#eval ignores binding’s source location [Bug #4352]. So, users should use this newly-introduced method instead of Kernel#eval.

  • Add :exception option to let Kernel.#system raise error instead of returning false. [Feature #14386]

Performance improvements

  • Speedup Proc#call because we don’t need to care about $SAFE any more. [Feature #14318]

    With lc_fizzbuzz benchmark which uses Proc#call so many times we can measure x1.4 improvements [Bug #10212].

  • Speedup where block is passed block parameter. [Feature #14330]

    Ruby 2.5 improves block passing performance. [Feature #14045] Additionally, Ruby 2.6 improves the performance of passed block calling. With micro-benchmark we can observe x2.6 improvement.

  • Transient Heap (theap) is introduced. [Bug #14858] [Feature #14989] theap is managed heap for short-living memory objects which are pointed by specific classes (Array, Hash, Object, and Struct). For example, making small and short-living Hash object is x2 faster. With rdoc benchmark, we observed 6-7% performance improvement.

Other notable changes since 2.5

  • $SAFE is a process global state and we can set 0 again. [Feature #14250]

  • Passing safe_level to is deprecated. trim_mode and eoutvar arguments are changed to keyword arguments. [Feature #14256]

  • Merge RubyGems 3.0.0.beta2. --ri and --rdoc options was removed. Please use --document and --no-document options instead of them.

  • Merge Bundler as Default gems.

See NEWS or the commit logs for details.

With those changes, 6474 files changed, 171888 insertions(+), 46617 deletions(-) since Ruby 2.5.0!

Enjoy programming with Ruby 2.6.0-preview3!



    SIZE:   17071670 bytes
    SHA1:   67836fda11fa91e0b988a6cc07989fbceda025b4
    SHA256: 60243e3bd9661e37675009ab66ba63beacf5dec748885b9b93916909f965f27a
    SHA512: 877278cd6e9b947f5bb6ed78136efb232dcc9c5c218b7236576171e7c3cd7f6b7d10d07d8402014a14aba1fcd1913a4370f0725c561ead41d8a3fe92029f7f76

    SIZE:   21537655 bytes
    SHA1:   45f3c90dfffe03b746f21f24152666e361cbb41a
    SHA256: 9152af9e700349dcfa2eec196dd91587d42d70a6837fa2c415ebba1167587be1
    SHA512: 335de36cf56706326f4acc4bbd35be01e0ac5fff30d0a69b2e1630ba4c78f0e711822d1623d0099a517c824b154917d2f60be192dfb143a422cf1d17b38e1183

    SIZE:   14973451 bytes
    SHA1:   5f2df5d8c5a3888ccb915d36a3532ba32cda8791
    SHA256: 1f09a2ac1ab26721923cbf4b9302a66d36bb302dc45e72112b41d6fccc5b5931
    SHA512: d1693625723796e8902f3e4c4fae444f2912af9173489f7cf18c99db2a217afc971b082fce7089e39f8edd54d762d2b4e72843c8306ed29b05ccb15ac03dbb5b

    SIZE:   12291692 bytes
    SHA1:   7f8216247745215e9645568e7a02140f9a029b31
    SHA256: 9856d9e0e32df9e5cdf01928eec363d037f1a76dab2abbf828170647beaf64fe
    SHA512: b4d3b17ecf96272c43cd7518c0b54dee63fc1150ad143e1d9c9d708506fe78676c80eb96cc47b8d46d1128bd483a53f16c944963a03d1f99f00131b74714df7b