Ruby 2.6.0-preview2 Released

Posted by naruse on 31 May 2018

We are pleased to announce the release of Ruby 2.6.0-preview2.

Ruby 2.6.0-preview2 is the second preview toward Ruby 2.6.0. This preview2 is released earlier than usual because it includes an important new feature, JIT.

JIT

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. Currently JIT compiler is supported only when Ruby is built by gcc or clang and the compiler is available on runtime. Otherwise you can’t use it for now.

As of 2.6.0-preview2, we’re just preparing infrastructure for JIT and very few optimizations are implemented. You can measure some of potential improvements in micro benchmarks with this release, but it is NOT ready for benchmarking final performance of Ruby’s JIT compiler, especially for larger programs like Rails applications.

We’re going to implement method iniling in JIT compiler, which is expected to increase Ruby’s performance in order of magnitude. Also, we’re planning to increase the supported platforms, and the next plan is to support Visual Studio.

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
ary.zip(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 block.call 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.

Other notable changes since 2.5

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

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

  • Merge RubyGems 3.0.0.beta1

See NEWS or the commit logs for details.

With those changes, 4699 files changed, 45744 insertions(+), 30885 deletions(-) since Ruby 2.5.0!

Enjoy programming with Ruby 2.6.0-preview2!

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