We are pleased to announce the release of Ruby 2.6.0.
It introduces a number of new features and performance improvements,
most notably:
* A new JIT compiler.
* The `RubyVM::AbstractSyntaxTree` module.
## JIT [Experimental]
Ruby 2.6 introduces an initial implementation of a JIT (Just-In-Time) compiler.
The JIT compiler aims to improve the performance of Ruby programs.
Unlike traditional JIT compilers which operate in-process, Ruby's JIT
compiler writes out C code to disk and spawns a common C compiler to
generate native code. For more details about it, see the [MJIT
organization by Vladimir
Makarov](https://bugs.ruby-lang.org/projects/ruby/wiki/MJIT#MJIT-organization).
In order to enable the JIT compiler, specify `--jit` on the command
line or in the `$RUBYOPT` environment variable. Specifying
`--jit-verbose=1` will cause the JIT compiler to print additional
information. Read the output of `ruby --help` or [the
documentation](https://bugs.ruby-lang.org/projects/ruby/wiki/MJIT#Basic-usage)
for other options.
The JIT compiler is supported when Ruby is built by GCC, Clang, or
Microsoft VC++, which needs to be available at runtime.
As of Ruby 2.6.0, we have achieved [1.7x faster
performance](https://gist.github.com/k0kubun/d7f54d96f8e501bbbc78b927640f4208)
compared to Ruby 2.5 on a CPU-intensive, non-trivial benchmark called
[Optcarrot](https://github.com/mame/optcarrot). However, it is still
experimental and many other memory-intensive workloads like Rails
might not benefit from it at the moment. For more details, see [Ruby
2.6 JIT - Progress and
Future](https://medium.com/@k0kubun/ruby-2-6-jit-progress-and-future-84e0a830ecbf).
Stay tuned for the new age of Ruby's performance.
## `RubyVM::AbstractSyntaxTree` [Experimental]
Ruby 2.6 introduces the `RubyVM::AbstractSyntaxTree` module. **Future
compatibility of this module is not guaranteed**.
This module has a `parse` method, which parses the given string as
Ruby code and returns the AST (Abstract Syntax Tree) nodes of the
code. The `parse_file` method opens and parses the given file as Ruby
code and returns AST nodes.
The `RubyVM::AbstractSyntaxTree::Node` class is also introduced. You
can get source location and children nodes from `Node` objects. This
feature is experimental.
## Other Notable New Features
* Add an alias of `Kernel#yield_self` named `#then`. [[Feature
#14594]](https://bugs.ruby-lang.org/issues/14594)
* Constant names may start with a non-ASCII capital letter. [[Feature
#13770]](https://bugs.ruby-lang.org/issues/13770)
* Introduce endless ranges. [[Feature
#12912]](https://bugs.ruby-lang.org/issues/12912)
An endless range, `(1..)`, works as if it has no end. Here are some
typical use cases:
ary[1..] # identical to ary[1..-1]
without magical -1
(1..).each {|index| ... } # enumerates values starting
from index 1
ary.zip(1..) {|elem, index| ... } # ary.each.with_index(1) { ... }
* Add `Enumerable#chain` and `Enumerator#+` [[Feature
#15144]](https://bugs.ruby-lang.org/issues/15144)
* Add function composition operators `<<` and `>>` to `Proc` and
`Method`. [[Feature #6284]](https://bugs.ruby-lang.org/issues/6284)
f = proc{|x| x + 2}
g = proc{|x| x * 3}
(f << g).call(3) # -> 11; identical to f(g(3))
(f >> g).call(3) # -> 15; identical to g(f(3))
* Add `Binding#source_location`. [[Feature
#14230]](https://bugs.ruby-lang.org/issues/14230)
This method returns the source location of the binding, a 2-element
array of `__FILE__` and `__LINE__`. Technically speaking, this is
identical to `eval("[__FILE__, __LINE__]", binding)`. However, we are
planning to change this behavior so that `Kernel#eval` ignores
binding's source location [[Bug
#4352]](https://bugs.ruby-lang.org/issues/4352). As such, it is
recommended to use `Binding#source_location` instead of `Kernel#eval`.
* Add an `exception:` option to `Kernel#system` which causes it to
raise an exception on failure instead of returning `false`. [[Feature
#14386]](https://bugs.ruby-lang.org/issues/14386)
* Add a oneshot mode to `Coverage`
[[Feature#15022]](https://bugs.ruby-lang.org/issues/15022)
* This mode checks "whether each line was executed at least once or
not", instead of "how many times each line was executed". A hook for
each line is fired only once, and once it is fired the hook flag will
be removed, i.e., it runs with zero overhead.
* Add `oneshot_lines:` keyword argument to Coverage.start.
* Add `stop:` and `clear:` keyword arguments to Coverage.result. If
`clear` is true, it clears the counters to zero. If `stop` is true,
it disables coverage measurement.
* Coverage.line_stub is a simple helper function that creates the
"stub" of line coverage from a given source code.
* Add `FileUtils#cp_lr`. It works just like cp_r but links instead of
copies. [[Feature #4189]](https://bugs.ruby-lang.org/issues/4189)
## Performance improvements
* Speed up `Proc#call` by removing the temporary allocation for `$SAFE`.
[[Feature #14318]](https://bugs.ruby-lang.org/issues/14318)
We have observed a 1.4x peformance improvement in the `lc_fizzbuzz`
benchmark that calls `Proc#call` numerous times. [[Bug
#10212]](https://bugs.ruby-lang.org/issues/10212)
* Speed up `block.call` when `block` is passed in as a block
parameter. [[Feature #14330]](https://bugs.ruby-lang.org/issues/14330)
Combined with improvements around block handling introduced in Ruby
2.5, block evaluation now performs 2.6x faster in a micro-benchmark in
Ruby 2.6. [[Feature #14045]](https://bugs.ruby-lang.org/issues/14045)
* Transient Heap (`theap`) is introduced. [[Bug
#14858]](https://bugs.ruby-lang.org/issues/14858) [[Feature
#14989]](https://bugs.ruby-lang.org/issues/14989)
`theap` is managed heap for short-living memory objects which are
pointed by specific classes (`Array`, `Hash`, `Object`, and `Struct`).
Making small and short-living Hash object is 2x faster. With rdoc
benchmark, we observed 6-7% performance improvement.
* Native implementations (`arm32`, `arm64`, `ppc64le`, `win32`,
`win64`, `x86`, `amd64`) of coroutines to improve context switching
performance of Fiber significantly. [[Feature
#14739]](https://bugs.ruby-lang.org/issues/14739)
`Fiber.yield` and `Fiber#resume` is about 5x faster on 64-bit Linux.
Fiber intensive programs can expect up to 5% improvement overall.
## Other notable changes since 2.5
* `$SAFE` is now a process global state and it can be set back to `0`.
[[Feature #14250]](https://bugs.ruby-lang.org/issues/14250)
* Passing `safe_level` to `ERB.new` is deprecated. `trim_mode` and
`eoutvar` arguments have been changed to keyword arguments. [[Feature
#14256]](https://bugs.ruby-lang.org/issues/14256)
* Unicode support is updated to version 11. We have plans to add
support Unicode version 12 and 12.1 in a future TEENY release of Ruby
2.6. This will include support for the [new Japenese
era](http://blog.unicode.org/2018/09/new-japanese-era.html).
* Merge RubyGems 3.0.1. The `--ri` and `--rdoc` options have been
removed. Please use `--document` and `--no-document` options instead.
* [Bundler](https://github.com/bundler/bundler) is now installed as a
default gem.
* In exception handling blocks, `else` without `rescue` now causes a
syntax error. [EXPERIMENTAL][[Feature
#14606]](https://bugs.ruby-lang.org/issues/14606)
See [NEWS](https://github.com/ruby/ruby/blob/v2_6_0/NEWS) or [commit
logs](https://github.com/ruby/ruby/compare/v2_5_0...v2_6_0) for more
details.
With those changes, [6376 files changed, 227364 insertions(+), 51599
deletions(-)](https://github.com/ruby/ruby/compare/v2_5_0...v2_6_0)
since Ruby 2.5.0!
Merry Christmas, Happy Holidays, and enjoy programming with Ruby 2.6!
## Download
* <https://cache.ruby-lang.org/pub/ruby/2.6/ruby-2.6.0.tar.gz>
SIZE: 16687800 bytes
SHA1: c95f4e86e21390270dad3ebb94491fd42ee2ce69
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* <https://cache.ruby-lang.org/pub/ruby/2.6/ruby-2.6.0.zip>
SIZE: 20582054 bytes
SHA1: a804e63d18da12107e1d101918a3d8f4c5462a27
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* <https://cache.ruby-lang.org/pub/ruby/2.6/ruby-2.6.0.tar.bz2>
SIZE: 14585856 bytes
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SHA256: c89ca663ad9a6238f4b1ec4d04c7dff630560c6e6eca6d30857c4d394f01a599
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* <https://cache.ruby-lang.org/pub/ruby/2.6/ruby-2.6.0.tar.xz>
SIZE: 11918536 bytes
SHA1: 9ddaeba3505d2855460c8c653159fc0ac8928c0f
SHA256: acb00f04374899ba8ee74bbbcb9b35c5c6b1fd229f1876554ee76f0f1710ff5f
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