[ruby-core:90547] Ruby 2.6.0-rc2 Released

From: "NARUSE, Yui" <naruse@...>
Date: 2018-12-15 13:13:56 UTC
List: ruby-core #90547
We are pleased to announce the release of Ruby 2.6.0-rc2.

Ruby 2.6.0-rc2 is the second release candidate of Ruby 2.6.0.
RC2 is released to test bundled Bundler 1.17 instead of 2.0.
It introduces some new features and performance improvements, for example:

## 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](https://github.com/vnmakarov/ruby/tree/rtl_mjit_branch#mjit-organization).

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-rc2, we achieved 1.7x faster performance than Ruby
2.5 on CPU-intensive non-trivial benchmark workload called Optcarrot
<https://gist.github.com/k0kubun/d7f54d96f8e501bbbc78b927640f4208>.
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::AbstractSyntaxTree [Experimental]

Ruby 2.6 introduces `RubyVM::AbstractSyntaxTree` 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::AbstractSyntaxTree::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]](https://bugs.ruby-lang.org/issues/14594)

* `else` without `rescue` now causes a syntax error.
[EXPERIMENTAL][[Feature
#14606]](https://bugs.ruby-lang.org/issues/14606)

* constant names may start with a non-ASCII capital letter. [[Feature
#13770]](https://bugs.ruby-lang.org/issues/13770)

* endless range [[Feature #12912]](https://bugs.ruby-lang.org/issues/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| ... }         # inifinite loop from index 1
      ary.zip(1..) {|elem, index| ... } # ary.each.with_index(1) { ... }

* Add `Binding#source_location`.  [[Feature
#14230]](https://bugs.ruby-lang.org/issues/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]](https://bugs.ruby-lang.org/issues/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]](https://bugs.ruby-lang.org/issues/14386)

* add the oneshot mode
[[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 at most once, and after it is fired the hook flag
is 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, which is a simple helper function that creates
the "stub" of line coverage from a given source code.

* `FileUtils#cp_lr`.  [[Feature #4189]](https://bugs.ruby-lang.org/issues/4189)

## Performance improvements

* Speedup `Proc#call` because we don't need to care about `$SAFE` any more.
  [[Feature #14318]](https://bugs.ruby-lang.org/issues/14318)

  With `lc_fizzbuzz` benchmark which uses `Proc#call` so many times we
can measure
  x1.4 improvements [[Bug #10212]](https://bugs.ruby-lang.org/issues/10212).

* Speedup `block.call` where `block` is passed block parameter.
[[Feature #14330]](https://bugs.ruby-lang.org/issues/14330)

  Ruby 2.5 improves block passing performance. [[Feature
#14045]](https://bugs.ruby-lang.org/issues/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]](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). 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]](https://bugs.ruby-lang.org/issues/14250)

* Passing `safe_level` to `ERB.new` is deprecated. `trim_mode` and
`eoutvar` arguments are changed to keyword arguments. [[Feature
#14256]](https://bugs.ruby-lang.org/issues/14256)

* Supported Unicode version is updated to 11. It is planed to update
12 and 12.1 in future TEENY releases of Ruby 2.6.

* Merge RubyGems 3.0.0.beta3. `--ri` and `--rdoc` options was removed.
Please use `--document` and `--no-document` options instead of them.

* Merge [Bundler](https://github.com/bundler/bundler) as Default gems.

See [NEWS](https://github.com/ruby/ruby/blob/v2_6_0_rc2/NEWS)
or [commit logs](https://github.com/ruby/ruby/compare/v2_5_0...v2_6_0_rc2)
for details.

With those changes,
[6411 files changed, 228864 insertions(+), 97600
deletions(-)](https://github.com/ruby/ruby/compare/v2_5_0...v2_6_0_rc2)
since Ruby 2.5.0!

Enjoy programming with Ruby 2.6.0-rc2!

## Download

* <https://cache.ruby-lang.org/pub/ruby/2.6/ruby-2.6.0-rc2.tar.gz>

      SIZE:   16723556 bytes
      SHA1:   a4d7f8c8c3584a60fe1a57d03d80162361fe3c78
      SHA256: 9c0245e96379246040f1fd0978f8e447e7f47cdccbdaffdb83302a995276b62b
      SHA512: 789f608f93db6e12835911f3105d9abe2fabb67cd22dc3bafdff38716ac56974925738e7f7788ebef5bdf67b6fd91f84a4ee78a3e5d072cfc8ee0972de737b08
* <https://cache.ruby-lang.org/pub/ruby/2.6/ruby-2.6.0-rc2.zip>

      SIZE:   20643747 bytes
      SHA1:   c1a2898949d929dd952880f1c1c2bac2ef2609b4
      SHA256: e8a446cf1f2ffc14483604de0a5e12c2578dd2f672ae87798ca2bbb9b7b73899
      SHA512: 2d06feae13f485f5da59574672b14d03881ed532d652648f94e2435f5d81df623b5ef532b8ba8e0b9bc4ee6baf7c0328a5610eab753a9020a0fea2673254c76c
* <https://cache.ruby-lang.org/pub/ruby/2.6/ruby-2.6.0-rc2.tar.bz2>

      SIZE:   14581998 bytes
      SHA1:   94bbee97de4955e67effb7f512c58300617a3a09
      SHA256: b3d03e471e3136f43bb948013d4f4974abb63d478e8ff7ec2741b22750a3ec50
      SHA512: 9bfbe83fd3699b71bae2350801d8c967eb128e79b62a9d36fc0f011b83c53cab28a280939f4cc9f0a28f9bf02dce8eea30866ca4d06480dc44289400abf580ba
* <https://cache.ruby-lang.org/pub/ruby/2.6/ruby-2.6.0-rc2.tar.xz>

      SIZE:   11908088 bytes
      SHA1:   13a7f06d832dc28989e3e4321490a6ba528ed023
      SHA256: d620b3d87b3190867304067f3ce77f5305f7ec1b2e73b09c17710c97c028986d
      SHA512: a3dc43c0bc70dfdb9ff0d18b5b9797bbf332524f5d3bbb7940cf4e32286ca715808acfd11ebf3cdbe358a2466b7c6b5be3a7a784af7eb95c071fe1f8b4ab1261

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